Hindawi Publishing CorporationJournal of RoboticsVolume 2013 Article ID 741359 15 pageshttpdxdoiorg1011552013741359

Research ArticleA Bioinspired 10 DOF Wearable Powered ArmExoskeleton for Rehabilitation

Soumya Kanti Manna and Subhasis Bhaumik

School of Mechatronics amp Robotics Bengal Engineering amp Science University Shibpur Howrah 711103 India

Correspondence should be addressed to Soumya Kanti Manna soumyakantimidgmailcom

Received 31 May 2013 Revised 7 October 2013 Accepted 8 October 2013

Academic Editor Oliver Sawodny

Copyright copy 2013 S K Manna and S BhaumikThis is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in anymedium provided the originalwork is properly cited

The developed exoskeleton device (Exorn) has ten degrees of freedom to control joints starting from shoulder griddle to wrist toprovide better redundancy portability and flexibility to the human armmotion A 3D conceptual model is being designed to makethe system wearable by human arm All the joints are simple revolute joints with desired motion limit A Simulink model of thehuman arm is being developedwith propermass and length to determine proper torque required for actuating those joints Forwardkinematics of the whole system has been formulated for getting desired dexterous workspace A proper and simple GraphicalUser Interface (GUI) and the required embedded system have been designed for providing physiotherapy lessons to the patientsIn the literature review it has been found that researchers have generally ignored the motion of shoulder griddle Here we haveimplemented those motions in our design It has also been found that people have taken elbow pronation and supinationmotion asa part of shoulder internal and external rotation though bothmotions are quite different A predefined resolvedmotion rate controlstructure with independent joint control is used so that all movements can be controlled in a predefined way

1 Introduction

It is seen that a major stroke is viewed by more than halfof those at risk as being worse than death Paralysis iscaused due to complete loss of muscle function In bothcases patients have stiff muscles which restrict them fromany physical movement of the affected part Even the patientssuffering from spinal cord injury or several nerve diseasesmay also lose their muscle strength gradually Accordingto Krakauer [1] the degree of improvement at 6 monthsis best predicted by the motor deficit at 1 month despitestandard rehabilitative interventions in the ensuing 5monthsIt is already proved that if they are under the process ofrehabilitation for several months after stroke their activerange of motion as well as muscle strength can increasesignificantly The training includes all the orthopedic andneurological lessons so that it is effective to the humanmuscletreatment The rehabilitation training is generally performedby a physiotherapist but the duration of the training is notadequate due to the fatigue of the therapist It is observed thata physiotherapist can perform the training for 8ndash10 hours aday and can provide service to 2 to 3 patients at a very high

costTheymay even omit certain exercises which are essentialto the patients The person also does not get repetitive andaccurate movement sessions in case of a manual interactionConsidering time cost repeatability reproducibility andaccuracy robotically assisted rehabilitation process is farbetter than human assisted training process Several assistivedevices like ARMin MEDARM and SMA are already beingdeveloped for the rehabilitation process But each one of themhas several advantages and disadvantages The purpose ofExorn is to provide maximum degree of freedom so that thedevice becomes as redundant as human hand and can providebetter rehabilitation process in future

2 The Literature Review

Until now two types of design are being proposed First oneis an exoskeleton structure connected to a base platformfrom where all the actuators are being controlled taking theplatform as a reference Second one is a portable structurewearable by a human First one is a bulky system like ARMin[2] MEDARM [3] and Sarcos Master Arm [4] where themotion is stable but it cannot be effective as an assistive

2 Journal of Robotics

device for the paralyzed people Also there is a problem ofmisalignment of the system with the human hand at thetime of joint movement due to which there is a possibilityof injury [5] In some design the number of degree offreedom is restricted to certain directions [6] It will omitcertain necessary movements which are very much neededfor the proper rehabilitation process including solder griddlemovement Hydraulic and pneumatic actuatorsdevices likeNEUROExos [7] have a big cylinder and pump connectedwith it to provide actuation signal This kind of system isimpossible to relocate with the human movement to makesystem portable

Mistry et al have already carried out experiments onjoint space force field trajectories [4] to estimate kinematicsand dynamics of the human arm with several trails in caseof 3D movement of the human arm Parallel manipulatorshave a problem of high stiffness and range of motion withseveral restrictions In case of a serial manipulator if theoffset between actuators is less then it acts like a joint withseveral DOFs Yang et al control puma manipulator usingarm exoskeleton because control system is quite the same forboth the cases [9] Pneumatic and hydraulic system are usedfor actuation electroactive polymer (EAP) has been used forhaptic device Ball et al have developed actuation systemusing cables which in reverse increases the stiffness factor by10 to 12 [6] So it is expected that motor driven system shouldbe used to make the exoskeleton robot simple Researchersare also trying to control the actuation through EMG sensorsusing fuzzy algorithm [10] Generally impedance control isusually implemented in which the Cartesian forces appliedat the joint are converted into joint torque commands usingthe Jacobian [1] matrixThemain disadvantage of impedancecontrol is that good force replication requires compensationof the natural dynamics of the exoskeleton such as gravityloading and drives frictions The Exoskeleton Arm-Master[12] and the L-EXOS Exoskeleton [13] are classic examples ofexoskeletons that use this approach An alternative approachof joint control is called ldquoadmittancerdquo control which is pri-marily used to controlmanipulators used as large reach hapticdevices However it has the major drawback of instability forhigh admittance (low impedance) which is the opposite ofimpedance control [14] The Sensor Arm [15] is an exampleof an exoskeleton implementing this approach

3 Mechanical Model

The whole structure is made of Perspex which is lighter inweight and much hardy than any other similar materialHigh torque DC geared motor is used for controlling thejoint movements of shoulder griddle glenohumeral jointand elbow joint for gross positioning For the motion ofwrist joint small BLDC servo motor is being used for finepositioning Gear drives are made of Nylon 101 materialAs there are some joint limitations because of mechanicalconstraints it cannot give the same motion as human jointrange as shown in Table 1 In few locations suspensors areused to sustain any jerk and to incorporate the variationof link Human joint of two or more degrees of freedom is

Figure 1 Total exoskeleton system

Figure 2 Manufacturing model of exoskeleton

being replaced by serial manipulator with several actuatorsThe offset between those actuators is less so that it can actlike a single joint actuator with several degrees of freedomThe axis of rotation of human joint has been considered forplacement of the actuators In this model the length of upperarm and forearm supporting link can be varied according tothe different human arm length The CAD model of Exornand manufactured model are shown in Figures 1 and 2 Theother parts of exoskeleton structure and its manufacturedmodels are shown in Figures 3 4 5 6 7 8 9 and 10 Fromthose given figures the design of any particular joint modelcan be analyzed

Shoulder griddle is one of the vital joints with two degreesof freedom Actuator 1 is used for giving the elevation anddepressionmotion in vertical direction and actuator 2 is usedfor scapular abduction and adduction in horizontal directionFor elevation and depression screw nut mechanism is beingused Glenohumeral joint is a ball-socket joint having threedegrees of freedom The actuators required for giving themotion to this joint are shown in Figure 5 Actuators 3 toactuator 5 are DC motors used for three different rotationsActuator 6 is a BLDC motor used for shoulder internal andexternal rotation One hollow cylindrical spur gear mesheswith a small pinion gear which is driven by actuator 6The length between shoulder joint and elbow is changeableActuator 7 is a DC motor used for controlling elbow flexionand extension as shown in Figure 7 The same kind oftechnique is applied for forearm pronation and supination asthat happened in the case of shoulder internal and externalrotation A suspensor is attached to upper portion of elbowjoint to make it jerk-free and incorporate the change in armlength Wrist joint has two degrees of freedom in two planes

Journal of Robotics 3

Scapular abduction and adduction

Horizontal abduction and adduction

Elevation and depression of shoulder griddle

Conversion of rotational motion into linear motion

through screw jack

Actuator 2Suspensor

Actuator 1

Figure 3 Shoulder griddle joint model

Scapular abduction and adduction

Horizontalabduction and

adduction

Conversion of rotational motion into linear motion through screw jack

Actuator 1

DC geared motor

Figure 4 Manufactured model of shoulder griddle

(A) Horizontal abduction and adduction(B) Vertical abduction and adduction(C) Forward flexion and extension(D) External and internal rotation

Actuator 3

Actuator 4Actuator 5

Actuator 6

Adjustment for variable upper arm length

Suspensor

A

BC

D

Figure 5 Glenohumeral joint model

adduction

DC geared motor used for forward flexion and

DC geared motor used for vertical abduction and

Variable adjustable upper arm structure

extension

Figure 6 Manufactured model of glenohumeral joint

Adjustment for variable upper arm length

Shoulder external and internal rotation

Elbow flexion and extension

Hand rest for forearm

Suspensor

Actuator 7

Figure 7 Elbow joint model

Actuators 9 and 10 are used for providing thosemotions Herewe can see that all the actuators are dedicated to give themotion in all directions according to the differentmovementsof human arm as shown in Figure 11

Weight of the Prototype 5 kg

Specification of the DC Geared Motor

Weightmdash500 gm

Speedmdash10 rpm

Torquemdash100 kg-cm at 4 ampere (Max)

Specification of BLDC Motor

Company-Faulhaber

Weightmdash500 gm

Speedmdash10 rpm

Torquemdash100 kg-cm at 4 ampere (Max)

Gears are made up of Nylon 101 Structures are usedfor twisting moment at human elbow and wrist with thehelp of gear arrangement which provide better flexibility andstrength

4 Journal of Robotics

Gear arrangement for shoulder external and internal rotation

DC geared motor for elbow flexion and

BLDC motor

Suspensor

Forearm structure

extension

Figure 8 Manufactured model of elbow joint

Adjustment for variable forearm

Elbow pronation and supination

Palm flexion and extension

Palm radial andulnar deviation

Actuator 8

Actuator 9

Actuator 10

Hand rest

length

Figure 9 Wrist joint model

Specification of Nylon 101

Tensile strength 79289709Nm2

Mass density 1150Kgm3

Elastic modulus 1000000000Nm2

Yield strength 60000000Nm2

Turn ratio at the elbow joint 35 8Turn ratio at wrist joint 15 4

At the shoulder joint bush is used to provide the supportto the joint motor axis It is made up of brass to reducethe wear and tear between perspex and motor spindle Onecylindrical rod of the same material moves inside the bushand provides the support to the other end of structure at thetime of joint flexion and extension

The whole body of Exorn is made up of perspex It ishardy and elastic It gives less weight in respect to aluminumPerplex sheet is cut into different pieces and attached witheach other through industrial gum and nut (M4 thread)Three different thickness perspex sheets have been used forthe structureHigherwidth is used at the arm structure to givebetter support and the lower one is used for hand structure

Type 1mdashWidth 5mmType 2mdashWidth 10mmType 3mdashWidth 20mm

BLDC motor used for elbow pronation and supination

BLDC motor used for palm flexion

BLDC motor used for palm radial and

ulnar deviation

Hand rest

and extension

Figure 10 Manufactured model of wrist joint

Specification of Perspex (TM) GS Acrylic Cast Sheet

Tensile strength 75000000Nm2

Density 1190Kgm3

Size of the Exoskeleton The size of the exoskeleton (approxi-mately 9673 cm) has been taken as per the standard length ofa human arm and it can be varied from person to person

Length of shoulder griddle 0129119867Length of upper arm 0186119867Length of forearm 0146119867Length of hand 0108119867

Here 119867 is defined as the height of the human arm and ifwe consider the height of a standard human as 170 cm thelength will be approximately 9673 cm Obviously the lengthof human arm is different from person to person But as wehave made a physical system we have taken the standardlength But the system has a provision so that it is wearable toall the people of variable arm lengthwhich has been discussedin the portion of mechanical model

4 Kinematic Analysis of Exorn

Kinematic model of Exorn is designed according to theanthropometric data of standard human arm The mechani-cal structure is such that it can align with human arm and canprovide the desirable joint motion Some mechanical barrieris located to restrict the joint from hyperextension Here theforward kinematics of the whole system is discussed whichprovides the end point position and orientation due to severaljointmotions It is basically acting as a seriesmanipulatorThekinematic relation of a manipulator is represented by = 119869 120579

Journal of Robotics 5

Elevation

Depression

Extension

Flexion

Abduction

Adduction

Flexion

Extension

Horizontal abduction

Horizontaladduction

Lateral

Medical rotation

Flexion

ExtensionSupination Pronation

Extension

Flexion

Ulnar deviation Radial deviation0

0

0

0

0

0

0 0

0

0

0∘

15∘

15∘

40∘ 180∘

180∘

135∘

20∘

20∘

20∘

45∘

45∘

60∘60∘

80∘

80∘

10∘

80∘ 90∘

140∘

Figure 11 Different motions of human arm

is the119898 dimensional vector specifying the task velocityof end effector 120579 is 119899 dimensional vector representing thejoint velocity 119869 is the119898 by 119899 Jacobianmatrix For a redundantmanipulator 119899 is always greater than 119898 Here the kinematicredundancy is 3

41 D-HParameter of the 3DModel To do kinematic analysisof the whole system it is essential to derive D-H parameterof the whole system The coordinate system of the wholestructure is shown in Figure 12 The coordinate structure ofthe exoskeleton system is based on 3D conceptual modelof Exorn D-H parameters of the structure are shown inTable 2 It is essential to calculate the position and orientationof the end point in 3D space with respect to the referencecoordinate

42 Transformation Matrix Generation For getting the posi-tion and orientation of the end point of Exorn systemhomogeneous transformation matrix is considered Eachhomogeneous transformation matrix was calculated for theposition and orientation of present frame with respect to theprevious frame It is a 4 times 4 matrix The column 119894minus1119889

119894is

position of the end point and 119894minus1119877119894is the orientation of end

point in 3D space The transformation matrix is 119894minus1119860119894

119894minus1119860119894= [

119894minus1119877119894

119894minus1

119889119894

0 1]

4times4

(1)

The homogeneous matrix is being explained as119894minus1119860119894= 119863119911119894minus1119889119894

lowast 119877119911119894minus1120579119894

lowast 119863119909119894minus1119886119894

lowast 119877119909119894minus1120572119894

=

[[[

[

cos 120579119894minus sin 120579

119894cos120572119894

sin 120579119894sin120572119894

119886119894cos 120579119894

sin 120579119894

cos 120579119894cos120572119894minus cos 120579

119894sin120572119894119886119894sin 120579119894

0 sin120572119894

cos120572119894

119889119894

0 0 0 1

]]]

]

119894minus1119889119894= [

[

119886119894cos 120579119894

119886119894sin 120579119894

119889119894

]

]

119894minus1119877119894= [

[

cos 120579119894minus sin 120579

119894cos120572119894

sin 120579119894sin120572119894

sin 120579119894

cos 120579119894cos120572119894minus cos 120579

119894sin120572119894

0 sin120572119894

cos120572119894

]

]

(2)

For calculating the homogeneous matrix due to 10 degrees offreedom the 10 homogeneous matrixes are been multipliedsequentially The final matrix is 119879 which is represented as

119879 =01198601times11198602times21198603times31198604times41198605sdot sdot sdot times911986010 (3)

The calculation can be made easy by dividing the totalmultiplication into two parts such that 119879 =

01198605times511986011 As

it is a 10 DOF system Finally 119879 matrix of the end point ofExorn is represented with respect to reference and its upper 3values of last column are position vector of end point relatedto world frame

6 Journal of Robotics

a1a2

a3

a4

a5

a7

d2

d3

d5

d6

d7

d8d9

d10

x1x2

x3

x4

x5

x6

x7

x8

x9x10

x11

y1

y2

y3y4

y6

y7

y8

y9

y10y11

z2

z3

z4z5

z6

z7

z8

z9

z10 z11

Figure 12 Coordinate system of 3D model

5 Simulation Model of Human Arm

A human armmodel is being made in Simulink to determinethe required torque to move a joint The length of upperarm lower arm and hand is considered according to theanthropometric data of standard human arm The inertiamatrix of each segment is determined according to the massof that segment and length of the centre of gravity fromthe proximal end as per Table 3 In Simulink it is possibleto provide motions in terms of velocity to joint actuatorand from the joint sensor torque level change is notedThe Simulink model of human arm is shown in Figure 13Maximum amount of torque is needed to move those jointswhich are in vertical direction Here only joint motionrelated to shoulder elbow and wrist flexion and extensionis considered Next those internal and external rotations are

Table 1 Comparative study between joints of human arm andExorn

Actuatornumber Movement Human joint

range (Deg)Exorn range

(deg)Shoulder griddle movements

Actuator 1 Elevation 40 30Depression 10 10

Actuator 2 Scapular abduction 20 20Scapular adduction 15 15

Shoulder joint movements

Actuator 3 Horizontal abduction 135 90Horizontal adduction 45 45

Actuator 4 Vertical abduction 180 160Vertical adduction 20 0

Actuator 5 Forward flexion 180 90Forward extension 60 60

Actuator 6 External rotation 90 90Internal rotation 20 20

Elbow joint movements

Actuator 7 Elbow flexion 140 120Elbow extension 0 0

Actuator 8 Forearm pronation 90 90Forearm supination 80 80

Wrist joint movements

Actuator 9 Palm radial deviation 15 10palm ulnar deviation 45 30

Actuator 10 Palm flexion 80 80Palm extension 80 80

Table 2 D-H parameter of Exorn

119886119894(cm) 120572

119894(deg) 119889

119894(cm) 120579

119894(deg)

10 90 0 Θ1

12 0 5 Θ2

6 90 2 Θ3

3 minus90 0 Θ4

31 0 minus25 Θ5

0 90 6 Θ6

3 0 35 Θ7

0 90 25 Θ8

0 minus90 4 Θ9

0 0 8 Θ10

being taken care of In exoskeleton system those motionscannot be controlled from the fixed end due to its twistingtypeTherefore the end effector should be rotatedwith respectto fixed end

The Simulink blocks used for making the human armmodel are shown in Figures 14 and 15 A joint actuator blockis connected to provide the actuation signal and joint sensorblock is attached to measure the computed torque In orderto make a joint with several DOFs several bodies of zeromass and zero length with actuator block of different axis of

Journal of Robotics 7

(a) (b)

Figure 13 (a) Simulink model of human hand (b) human hand position at zero position

Conn1Conn1

Conn1Conn1

Conn2 Conn2

Conn2

Conn2

Conn3

Conn3

Conn3

Conn4

Conn4Conn5

Out1

Out1

Out2

Out3

Out3Out2

Ground Weld Body2

To workspace

To workspace1

To workspace2

Subsystem

Subsystem3 Subsystem6 Subsystem9

Shoulder joint Elbow jointWrist joint

Display3 Display9 Display12

Finger

In1 out1 In1 out1 In1 out1

CS1 CS17

x

y

z

B F

Figure 14 Human arm model in Simulink

rotations are connected Here in Figure 15 body 1 and body2 have zero length and zero mass Only body 3 is the actualbody It is under every human arm joint Body sensor isattached at the end point to get points in 3D space at the timeof motion

6 Embedded System

A PC based control system is being developed to provideparticular orthopedic lesson First of all command signalfrom PC is transmitted to the master controller Mastercontroller activates those joints which are needed to achievethe desired motion It sends the command bits in a packagethrough serial communication Enable signal is being sent to

all the local controllers but only few are being activated as percommand with the help of multiprocessor communicationtechnique All the motor controllers are connected in adaisy chain network that means 119879

119909and 119877

119909pins of master

controller are connected to all 119877119909and 119879

119909pins of each

controller respectively Each controller has a particular nodeas an activating signal When the master controller sends theactivation signal the particular motor controller with thatparticular node is activated

The interfacing circuit between microcontroller andmotor driver is shown in Figures 16(a) and 16(b) Driver IChas 4 input pins and 2 enable pins Here all the inputs pins andenable pins are connecting to port 0 and port 1 Here all theenable pins are sorted and connected through one port pin

8 Journal of Robotics

CS1 CS15 CS1 CS15 CS1 CS15B F B FB F1

12

2

3

Conn2 Conn3Body1 Body2 Body3

Out1Out2 Out3

Signal2Signal2Signal2

Revolute1 Revolute2 Revolute3

Joint actuatorJoint actuator1 Joint actuator2Joint sensor1 Joint sensor2 Joint sensor3

Shoulder vertical motion Shoulder forward flexion Shoulder horizontal motion

Figure 15 Block diagram below each human joint

(a)

Junction circuit 1P89V51RD2 7805 IC

7805 IC Max232DB-9

DB-9

Local controller for DC motor

Local controller for BLDC motor

DC motor driver circuit

Junction circuit 2

7805 IC

IN 4007L298

(b)

Figure 16 (a) Schematic design of interfacing circuit between microcontroller and motor driver (b) Developed interfacing circuit ofmicrocontroller

In this case all the enable pins become activated at one timeSo the motion of motor can be controlled by changing driverinputsThose inputs are amplified from 5V to 12V to run themotor in clockwise and anticlockwise manner (Figure 17) Asshown in the figure one dedicated 7805 IC (Voltage regulator)is connected tomicrocontroller for 5V power supply A serialIC MAX232 is connected to the microcontroller to convert

the RS232rsquos signals to TTL voltage levels that is acceptable to8051 microcontroller 119879

119909and 119877

119909pins

A bidirectional H bridgeDC motor control circuit isshown in Figures 17(a) and 17(b) The circuit is based onthe IC L298 from ST Microelectronics L298 It is a dual fullbridge driver that has a wide operating voltage range andcan handle load currents up to 3A The IC also features low

Journal of Robotics 9

Out In

sum

sum

MT2

100120583F

1 120583F

1 120583F

10120583F

CN5

CN6

1K 1K

1K1K

L298

REF7805

D1

D2

D3

D4

D5

D6 D7

D8

D9D10

D11 D12

R1 R2

R3R4

C1

C2

C3C4

(a)

Motor driver L298

H bridge driver

Power supply

(b)

Figure 17 (a) Schematic design of motor driver circuit (b) Developed motor driver circuit

Table 3 Segment mass and lengths of human arm [8]

Segment Segment masstotal body mass Centre of masssegment length Radius of gyrationsegment lengthProximal Distal CM Proximal Distal

Hand 0006 0506 0494 0297 0587 0577Forearm 0016 0430 0570 0303 0526 0647Upperarm 0028 0436 0564 0322 0542 0645Forearm and Hand 0022 0682 0318 0468 0827 0565Total arm 0050 0530 0470 0368 0645 0596

saturation voltage and over temperature protection In thecircuit diodes D1 to D8 are protection diodesThe state of themotor depends on the logic level of the pins 5 6 and 7 and10 11 and 12 and it is described in the table shown below thecircuit diagram

The diodes D1 to D4 and D5 to D8 provide a safer pathfor the back emf from the motor to dissipate and thus itprotects the corresponding bipolar transistors from damageThe input pins from motor driver are being connected tothe microcontroller port pins When the enable pins of thedriver pin are active then the input signal of the motor driveris amplified to 12 volt and sent to the motor According tothe configuration of port pins motor moves in clockwise oranticlockwise direction

In case of BLDCmotor controller every controller has itsparticular node for distinguishing one from the other It ispossible to control the speed of the motor either by varyingthe voltage supplied to it or by sending the serial command toit The speed of the motor is controlled by sending a string ofcommand to the BLDCmotor controller serially Also there isan encoder inside the BLDCmotor for getting the angle valuesimultaneously in a feedback loop

All the supply voltages are being bypassed through thosejunction circuits Actually all voltage sources are being sortedA 7812 IC voltage regulator is used to convert the 24Vinto 12V DC supply When the diode connected in junctioncircuit is in forward bias it sends the power supply to alldriver circuits but in the opposite case current from driver

10 Journal of Robotics

No

Serial communication configuration

Command comes from PC

GUI open

Serial port start

Serial port configuration

Commands send to the BLDC controller

Interrupt control

Select direction

Select BLDC motor

Send command to motor

Serial portclose

Select speed

DC motor controller

Motor moves

Formation of command package

Can be applied for all motors

SBUF Move motor 1 clockwise

SBUF Move motor 1 anticlockwise

SBUF Move motor 1 stop

Yes

Yes

Yes

No

No

CWCC

= A

= B

= X

Figure 18 Flow chart for PC based control

circuit cannot be sent to the controller circuit The flow chart(Figure 18) is showing the logic behind the algorithm

7 Graphical User Interface Model of Exorn v1

A proper Graphical User Interface (Figure 19) has beendeveloped for controlling all the motions serially through PCbased system It is being designed in Microsoft visual studioplatformThewholeGUImodel is divided into four divisionsFirst one is the configuration of serial communication whereuser has to select the particular COM port and baud rateIt has two buttons for opening and closing of COM portAfter opening of COM port any command can be sent to

the serial portThere are three divisions regarding themotionof human joint for proper treatment Here only one controlcan be selected out of three options Selection of one optionwill freeze the others The flow chart behind the GUI modelis shown in Figure 20

71 Orthopedic Lessons There are some movements whichare generally prescribed by different doctors for strokepatients for different problems All the motions are stored inmemory After selecting somemotion the patient presses thestart button and a command will be sent through serially fortaking proper action It will be updated with time accordingto orthopedic doctor advice

Journal of Robotics 11

Figure 19 GUI model

Serial communication and

configuration

Orthopaedic lessonsIsolateral exercises Angle oriented control

M1

Select BAUD

Select COM port

SpeedCW

CC

M2 Speed CW

CC

SpeedCW

CC

Arm movement

Elbow movement

Forearm movement

Wrist movement

Elevation and depression of shoulder griddle

Scapular abduction and adduction of shoulder griddle

Horizontal abduction and adduction of shoulder joint

Flexion and extension of wrist

M10

Figure 20 Flow chart of GUI model

72 Isolateral Exercises In isolateral exercises there are somepredefined exercises which are standard motions of all jointsof human arm Patients can follow those exercises so that theirmuscle rigidity becomes less After each selection a commandis being sent serially to master controller Master controlleralways takes care of proper actions

73 Angle Oriented Control In this configuration each jointis controlled in clockwise or anticlockwise manner withdifferent speedMore than one joint can be governed throughitWhen user selects jointmotions then a frame of commandbit serially sends with a start and stop bit to distinguish

between different commands User has to write the requiredspeed beside the box of direction of rotation In case twomotions are contradictory then the controller does not allowthat motion It is already preprogrammed in the controller

8 Predefined Control System

It is a predefined control (Figure 21) Already a vast scheduleof exercise modules is to be loaded in the memory Whensomeone wants to perform a task it is being sent to thecontroller through a manual switch or PC Master controllerwill generate a reference trajectory for that particular task

12 Journal of Robotics

PCandGUI

Master controller

Local controller

1H bridge

circuitDriver L298

Feedback

Exorn joint 1

Local controller

10H bridge circuit

Driver L298

Feedback

Exorn joint 10

Inverse kinematics

Forward kinematics

1205751205791

12057512057910

120575x

x

xd

120579

12057910

1205791

jminus1

Figure 21 Independent joint control system

0 20 40 60 80 100

0

2

4

6

8

10

Time (s)

Torque versus time

minus2

minus4

Com

pute

d to

rque

(N-m

)

Figure 22 Joint torque graph at shoulder due to flexion andextension

Then it is being sent to the local controller which takes careof that particular trajectory Always there is feedback loopconnected between the system and the master controllerWith the help of resolved motion rate control (Whitney 72)approach each joint can be controlled in an independent wayAccording to forward kinematics the kinematic model can beexpressed using the equation

120575119909 = 119869 (120579) 120575120579 (4)

Outside the singularities the inverse kinematics can beexpressed as

120575120579 = 119869minus1(120579) 120575119909 (5)

0 20 40 60 80 100 120

0

05

1

15

2

25

minus05

minus1

minus15

minus2

Time (s)

Torque versus time

Com

pute

d to

rque

(N-m

)

Figure 23 Joint torque graph at elbow due to elbow flexion andextension

There is a relation between task space and joint space Herethe current position at some angle 120579 can be expressed as

119909 = 119891 (120579) (6)

The desired location in 3D space is defined as 119909119889 So error

between current and desired position can be expressed as

120575119909 = 119909119889minus 119909

120575120579 = 119869minus1(120579) 120575119909

(7)

The next 120579 will be expressed as 1205791015840 = 120579 + 120575120579 In this way 120579value can be increased or decreased in an iterative way so that

Journal of Robotics 13

0 10 20 30 40 50 60 70 80 90005

01

015

02

025

03

035

04

045

Time (s)

Torque versus time

Com

pute

d to

rque

(N-m

)

Figure 24 Joint torque graph at wrist due to flexion and extension

0 10 20 30 40 50 60

0

1

2

3

4

5

6

minus1

minus2

minus3

times10minus3

Time (s)

Torque versus time

Com

pute

d to

rque

(N-m

)

Figure 25 Joint torque graph at elbow due to shoulder internal andexternal rotation

the desired location can be reached The error betweendesired location and current location can be compared usingforward kinematics in a feedback loop

In case of finding inverse kinematics there is a problem ofsingularity So we are imposing damped least square methodfor calculating the inverse kinematics The damped leastsquares solutions are intended to ensure a well-conditionedmatrix for the solution algorithmwhile limiting the size of thesolution vector 120575120579 This is done by adding a diagonal matrix120572119868 to the matrix 119869119869119879 The approximate solution of dampedleast squares method can be expressed as 120575120579 = 119869

+120575119909 where

119869+ can be expressed as the equation given below

119869+= 119869119879(119869119869119879+ 120572119868)minus1

120572 ge 0 (8)

0 20 40 60 80 100 120

0

2

4

6

minus2

minus4

minus6

times10minus3

Time (s)

Torque versus time

Com

pute

d to

rque

(N-m

)

Figure 26 Joint torque graph at wrist due to elbow pronation andsupination

When this equation is used then the solution satisfies

min120575120579

120575119909 minus 1198691205751205792+ 12057221205751205792 (9)

where sdot denotes the Euclidean norm For 120572 = 0 the dampedleast squares solution will become pseudoinverse solutionThen the Jacobian inversematrix will be 119869lowast where 119869lowast becomeexpressed as 119869119879(119869119869119879)minus1

In the damped least squares method the size of errorin the task space is weighed against the size of the resultingsolution For a given 120575119909 the size of the solution vector isdecreased by increasing 120572 However this is done at theexpense of using an approximate solution As 120572 increases sodoes the size of the error in the task space A large 120572 hasthe other benefit of ensuring a well-conditioned matrix forinversion It has been shown that the condition number 119870of the matrix 119875 equiv (119869119869

119879+ 120572119868) is 119870 = (120590

2

1+ 120572)(120590

2

119898+ 120572)

Here 1205901ge 1205902ge 1205903sdot sdot sdot ge 120590

119898ge 0 are the singular values of

the Jacobian matrix It can be seen in this equation that 119870is made arbitrarily close to 1 by increasing 120572 thus ensuringa well-conditioned matrix for inversion even in a singularconfiguration where 120590

119898= 0 Simply stated if one is willing

to give up the exactness of the solution then the size of thejoint rate can be reduced and a well-conditioned matrix forinversion can be ensured by increasing 120572

9 Simulation Results of Torque Level ofGeneral Human Arm

Maximum amount of torque is required to actuate humanjoints in vertical direction Here in Figure 25 the torqueneeded to twist the elbow with respect to shoulder joint isshown Figure 26 is showing the same kind ofmotion in wrist

14 Journal of Robotics

0 200 400 600 800 1000 12000500

1000

0500

1000

minus500

minus1000

minus500

minus1000

(a)

20

20

0

0

minus20

minus20

minus40

minus40

40

minus60

minus60

minus80 500

minus50

x

y z

Untitled fit 1x versus z y

(b)

Figure 27 (a) Outer region covered by Exorn (b) Workspace covered by Exorn

0

minus10

minus20

minus30

minus40

minus5040

3020

100minus10

minus20 0 1020 30

40 5060

70

Figure 28 Motion due to shoulder griddle

006

004

002

0

minus0020

001

002

003

004

005002

0 minus002 minus004minus006 minus008

minus01

Figure 29 Motion due to shoulder griddle glenohumerals andelbow joint movement

joint with respect to the elbow Figures 22 23 24 25 and26 will show torque variation in different joints in verticaldirection because of proper actuation signal From thosebelow graphs max and min torque for joint actuator can bedetermined because it is very much essential to select propermotor

006

004

002

0

minus0020

minus002minus004

minus006minus008

minus010

002

004

006

008

Figure 30 Motion due to shoulder joint and elbow joint movementin vertical direction

003

002

001

0

minus001

minus002

minus0030 minus002 minus004 minus006 minus008 minus01

0

001

002

003

Figure 31 Motion due to glenohumeral joint and elbow jointmovement in horizontal direction

10 Workspace Calculation and Motion due toForward Kinematics

For calculating the workspace of the robotic system aMATLAB code of nested for loop of all DOFs is being takenwith the joint range It will plot all the reachable points ofarm exoskeleton in 3D space Figure 27 is showing the outer

Journal of Robotics 15

region covered by human hand Figures 28 29 30 and 31 areshowing themotion of exoskeletonmodel due to several jointmovements

11 Conclusion

From the above discussion it may be concluded that thedeveloped system is useful for rehabilitation Comparisonsbetween human jointrsquos range and that of Exorn are alreadytabulated in Table 1 and the ranges are quite the same for boththe cases If the portable mechanical structure is attached tothe human arm it can be used as an assistive device for theparalyzed people The 3D model of exoskeleton is alreadybeing developed The model has been fabricated With thehelp of the GUI all the motions can be controlled throughserial communication The developed prototype is underworking condition We would like to build the real system sothat patient can be benefitted

References

[1] J W Krakauer ldquoArm function after stroke from physiology torecoveryrdquo Seminars in Neurology vol 25 no 4 pp 384ndash3952005

[2] T Nef and R Riener ldquoARMinmdashdesign of a novel arm reha-bilitation robotrdquo in Proceedings of the IEEE 9th InternationalConference on Rehabilitation Robotics (ICORR rsquo05) pp 57ndash60July 2005

[3] S J Ball I E Brown and S H Scott ldquoMEDARM a rehabilita-tion robot with 5DOF at the shoulder complexrdquo in Proceedingsof the IEEEASME International Conference on Advanced Intel-ligent Mechatronics (AIM rsquo07) September 2007

[4] M Mistry P Mohajerian and S Schaal ldquoArm movementexperiments with joint space force fields using an exoskeletonrobotrdquo in Proceedings of the IEEE 9th International Conferenceon Rehabilitation Robotics (ICORR rsquo05) pp 408ndash413 July 2005

[5] A Schiele and F C T van der Helm ldquoKinematic design toimprove ergonomics in human machine interactionrdquo IEEETransactions on Neural System and Rehabilitation vol 14 no4 pp 1534ndash4320 2006

[6] S J Ball I E Brown and S H Scott ldquoA planar 3DOF roboticexoskeleton for rehabilitation and assessmentrdquo in Proceedingsof the 29th Annual International Conference of IEEE-EMBSEngineering in Medicine and Biology Society (EMBC rsquo07) pp4024ndash4027 August 2007

[7] I Sardellitti E Cattin S Roccella et al ldquoDescription char-acterization and assessment of a bio-inspired shoulder joint-first link robot for neuro-robotic applicationsrdquo in Proceedings ofthe 1st IEEERAS-EMBS International Conference on BiomedicalRobotics andBiomechatronics (BioRob rsquo06) pp 112ndash117 February2006

[8] Source-winter Biomechanics and Motor Control of HumanMotion ISBN-978-0470398180 2010

[9] C-J Yang B Niu J-F Zhang and Y Chen ldquoDifferent structurebased control system of the PUMA manipulator with an armexoskeletonrdquo in Proceedings of the IEEE Conference on RoboticsAutomation and Mechatronics pp 572ndash577 December 2004

[10] K Kiguchi T Tanaka K Watanabe and T Fukuda ldquoExoskele-ton for human upper-limb motion supportrdquo in Proceedings ofthe IEEE International Conference on Robotics and Automationpp 2206ndash2211 September 2003

[11] T H Massie and K J Salisbury ldquoPHANToM haptic interfacea device for probing virtual objectsrdquo in Proceedings of theInternational Mechanical Engineering Congress and Expositionpp 295ndash299 November 1994

[12] CCarignan andKCleary ldquoClosed-loop force control for hapticsimulation of virtual environmentsrdquo The Electronic Journal ofHaptics Research vol 2 no 2 pp 1ndash14 2000

[13] A Frisoli F Rocchi S Marcheschi A Dettori F Salsedo andM Bergamasco ldquoA new force-feedback arm exoskeleton forhaptic interaction in virtual environmentsrdquo in Proceedings ofthe First Joint Eurohaptics Conference and Symposium on HapticInterfaces for Virtual Environment and Teleoperator Systems pp195ndash201 2005

[14] D Lawrence ldquoImpedance control stability properties in com-mon implementationsrdquo in Proceedings of the IEEE InternationalConference on Robotics and Automation pp 1185ndash1190 1988

[15] A Nakai Y Kunii H Hashimoto and F Harashima ldquoArmtype haptic human interface sensor armrdquo in Proceedings of theInternational Conference on Artificial Reality and Tele-Existence(ICAT) pp 77ndash84 Tokyo Japan December 1997

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DistributedSensor Networks

International Journal of

2 Journal of Robotics

device for the paralyzed people Also there is a problem ofmisalignment of the system with the human hand at thetime of joint movement due to which there is a possibilityof injury [5] In some design the number of degree offreedom is restricted to certain directions [6] It will omitcertain necessary movements which are very much neededfor the proper rehabilitation process including solder griddlemovement Hydraulic and pneumatic actuatorsdevices likeNEUROExos [7] have a big cylinder and pump connectedwith it to provide actuation signal This kind of system isimpossible to relocate with the human movement to makesystem portable

Mistry et al have already carried out experiments onjoint space force field trajectories [4] to estimate kinematicsand dynamics of the human arm with several trails in caseof 3D movement of the human arm Parallel manipulatorshave a problem of high stiffness and range of motion withseveral restrictions In case of a serial manipulator if theoffset between actuators is less then it acts like a joint withseveral DOFs Yang et al control puma manipulator usingarm exoskeleton because control system is quite the same forboth the cases [9] Pneumatic and hydraulic system are usedfor actuation electroactive polymer (EAP) has been used forhaptic device Ball et al have developed actuation systemusing cables which in reverse increases the stiffness factor by10 to 12 [6] So it is expected that motor driven system shouldbe used to make the exoskeleton robot simple Researchersare also trying to control the actuation through EMG sensorsusing fuzzy algorithm [10] Generally impedance control isusually implemented in which the Cartesian forces appliedat the joint are converted into joint torque commands usingthe Jacobian [1] matrixThemain disadvantage of impedancecontrol is that good force replication requires compensationof the natural dynamics of the exoskeleton such as gravityloading and drives frictions The Exoskeleton Arm-Master[12] and the L-EXOS Exoskeleton [13] are classic examples ofexoskeletons that use this approach An alternative approachof joint control is called ldquoadmittancerdquo control which is pri-marily used to controlmanipulators used as large reach hapticdevices However it has the major drawback of instability forhigh admittance (low impedance) which is the opposite ofimpedance control [14] The Sensor Arm [15] is an exampleof an exoskeleton implementing this approach

3 Mechanical Model

The whole structure is made of Perspex which is lighter inweight and much hardy than any other similar materialHigh torque DC geared motor is used for controlling thejoint movements of shoulder griddle glenohumeral jointand elbow joint for gross positioning For the motion ofwrist joint small BLDC servo motor is being used for finepositioning Gear drives are made of Nylon 101 materialAs there are some joint limitations because of mechanicalconstraints it cannot give the same motion as human jointrange as shown in Table 1 In few locations suspensors areused to sustain any jerk and to incorporate the variationof link Human joint of two or more degrees of freedom is

Figure 1 Total exoskeleton system

Figure 2 Manufacturing model of exoskeleton

being replaced by serial manipulator with several actuatorsThe offset between those actuators is less so that it can actlike a single joint actuator with several degrees of freedomThe axis of rotation of human joint has been considered forplacement of the actuators In this model the length of upperarm and forearm supporting link can be varied according tothe different human arm length The CAD model of Exornand manufactured model are shown in Figures 1 and 2 Theother parts of exoskeleton structure and its manufacturedmodels are shown in Figures 3 4 5 6 7 8 9 and 10 Fromthose given figures the design of any particular joint modelcan be analyzed

Shoulder griddle is one of the vital joints with two degreesof freedom Actuator 1 is used for giving the elevation anddepressionmotion in vertical direction and actuator 2 is usedfor scapular abduction and adduction in horizontal directionFor elevation and depression screw nut mechanism is beingused Glenohumeral joint is a ball-socket joint having threedegrees of freedom The actuators required for giving themotion to this joint are shown in Figure 5 Actuators 3 toactuator 5 are DC motors used for three different rotationsActuator 6 is a BLDC motor used for shoulder internal andexternal rotation One hollow cylindrical spur gear mesheswith a small pinion gear which is driven by actuator 6The length between shoulder joint and elbow is changeableActuator 7 is a DC motor used for controlling elbow flexionand extension as shown in Figure 7 The same kind oftechnique is applied for forearm pronation and supination asthat happened in the case of shoulder internal and externalrotation A suspensor is attached to upper portion of elbowjoint to make it jerk-free and incorporate the change in armlength Wrist joint has two degrees of freedom in two planes

Journal of Robotics 3

Scapular abduction and adduction

Horizontal abduction and adduction

Elevation and depression of shoulder griddle

Conversion of rotational motion into linear motion

through screw jack

Actuator 2Suspensor

Actuator 1

Figure 3 Shoulder griddle joint model

Scapular abduction and adduction

Horizontalabduction and

adduction

Conversion of rotational motion into linear motion through screw jack

Actuator 1

DC geared motor

Figure 4 Manufactured model of shoulder griddle

(A) Horizontal abduction and adduction(B) Vertical abduction and adduction(C) Forward flexion and extension(D) External and internal rotation

Actuator 3

Actuator 4Actuator 5

Actuator 6

Adjustment for variable upper arm length

Suspensor

A

BC

D

Figure 5 Glenohumeral joint model

adduction

DC geared motor used for forward flexion and

DC geared motor used for vertical abduction and

Variable adjustable upper arm structure

extension

Figure 6 Manufactured model of glenohumeral joint

Adjustment for variable upper arm length

Shoulder external and internal rotation

Elbow flexion and extension

Hand rest for forearm

Suspensor

Actuator 7

Figure 7 Elbow joint model

Actuators 9 and 10 are used for providing thosemotions Herewe can see that all the actuators are dedicated to give themotion in all directions according to the differentmovementsof human arm as shown in Figure 11

Weight of the Prototype 5 kg

Specification of the DC Geared Motor

Weightmdash500 gm

Speedmdash10 rpm

Torquemdash100 kg-cm at 4 ampere (Max)

Specification of BLDC Motor

Company-Faulhaber

Weightmdash500 gm

Speedmdash10 rpm

Torquemdash100 kg-cm at 4 ampere (Max)

Gears are made up of Nylon 101 Structures are usedfor twisting moment at human elbow and wrist with thehelp of gear arrangement which provide better flexibility andstrength

4 Journal of Robotics

Gear arrangement for shoulder external and internal rotation

DC geared motor for elbow flexion and

BLDC motor

Suspensor

Forearm structure

extension

Figure 8 Manufactured model of elbow joint

Adjustment for variable forearm

Elbow pronation and supination

Palm flexion and extension

Palm radial andulnar deviation

Actuator 8

Actuator 9

Actuator 10

Hand rest

length

Figure 9 Wrist joint model

Specification of Nylon 101

Tensile strength 79289709Nm2

Mass density 1150Kgm3

Elastic modulus 1000000000Nm2

Yield strength 60000000Nm2

Turn ratio at the elbow joint 35 8Turn ratio at wrist joint 15 4

At the shoulder joint bush is used to provide the supportto the joint motor axis It is made up of brass to reducethe wear and tear between perspex and motor spindle Onecylindrical rod of the same material moves inside the bushand provides the support to the other end of structure at thetime of joint flexion and extension

The whole body of Exorn is made up of perspex It ishardy and elastic It gives less weight in respect to aluminumPerplex sheet is cut into different pieces and attached witheach other through industrial gum and nut (M4 thread)Three different thickness perspex sheets have been used forthe structureHigherwidth is used at the arm structure to givebetter support and the lower one is used for hand structure

Type 1mdashWidth 5mmType 2mdashWidth 10mmType 3mdashWidth 20mm

BLDC motor used for elbow pronation and supination

BLDC motor used for palm flexion

BLDC motor used for palm radial and

ulnar deviation

Hand rest

and extension

Figure 10 Manufactured model of wrist joint

Specification of Perspex (TM) GS Acrylic Cast Sheet

Tensile strength 75000000Nm2

Density 1190Kgm3

Size of the Exoskeleton The size of the exoskeleton (approxi-mately 9673 cm) has been taken as per the standard length ofa human arm and it can be varied from person to person

Length of shoulder griddle 0129119867Length of upper arm 0186119867Length of forearm 0146119867Length of hand 0108119867

Here 119867 is defined as the height of the human arm and ifwe consider the height of a standard human as 170 cm thelength will be approximately 9673 cm Obviously the lengthof human arm is different from person to person But as wehave made a physical system we have taken the standardlength But the system has a provision so that it is wearable toall the people of variable arm lengthwhich has been discussedin the portion of mechanical model

4 Kinematic Analysis of Exorn

Kinematic model of Exorn is designed according to theanthropometric data of standard human arm The mechani-cal structure is such that it can align with human arm and canprovide the desirable joint motion Some mechanical barrieris located to restrict the joint from hyperextension Here theforward kinematics of the whole system is discussed whichprovides the end point position and orientation due to severaljointmotions It is basically acting as a seriesmanipulatorThekinematic relation of a manipulator is represented by = 119869 120579

Journal of Robotics 5

Elevation

Depression

Extension

Flexion

Abduction

Adduction

Flexion

Extension

Horizontal abduction

Horizontaladduction

Lateral

Medical rotation

Flexion

ExtensionSupination Pronation

Extension

Flexion

Ulnar deviation Radial deviation0

0

0

0

0

0

0 0

0

0

0∘

15∘

15∘

40∘ 180∘

180∘

135∘

20∘

20∘

20∘

45∘

45∘

60∘60∘

80∘

80∘

10∘

80∘ 90∘

140∘

Figure 11 Different motions of human arm

is the119898 dimensional vector specifying the task velocityof end effector 120579 is 119899 dimensional vector representing thejoint velocity 119869 is the119898 by 119899 Jacobianmatrix For a redundantmanipulator 119899 is always greater than 119898 Here the kinematicredundancy is 3

41 D-HParameter of the 3DModel To do kinematic analysisof the whole system it is essential to derive D-H parameterof the whole system The coordinate system of the wholestructure is shown in Figure 12 The coordinate structure ofthe exoskeleton system is based on 3D conceptual modelof Exorn D-H parameters of the structure are shown inTable 2 It is essential to calculate the position and orientationof the end point in 3D space with respect to the referencecoordinate

42 Transformation Matrix Generation For getting the posi-tion and orientation of the end point of Exorn systemhomogeneous transformation matrix is considered Eachhomogeneous transformation matrix was calculated for theposition and orientation of present frame with respect to theprevious frame It is a 4 times 4 matrix The column 119894minus1119889

119894is

position of the end point and 119894minus1119877119894is the orientation of end

point in 3D space The transformation matrix is 119894minus1119860119894

119894minus1119860119894= [

119894minus1119877119894

119894minus1

119889119894

0 1]

4times4

(1)

The homogeneous matrix is being explained as119894minus1119860119894= 119863119911119894minus1119889119894

lowast 119877119911119894minus1120579119894

lowast 119863119909119894minus1119886119894

lowast 119877119909119894minus1120572119894

=

[[[

[

cos 120579119894minus sin 120579

119894cos120572119894

sin 120579119894sin120572119894

119886119894cos 120579119894

sin 120579119894

cos 120579119894cos120572119894minus cos 120579

119894sin120572119894119886119894sin 120579119894

0 sin120572119894

cos120572119894

119889119894

0 0 0 1

]]]

]

119894minus1119889119894= [

[

119886119894cos 120579119894

119886119894sin 120579119894

119889119894

]

]

119894minus1119877119894= [

[

cos 120579119894minus sin 120579

119894cos120572119894

sin 120579119894sin120572119894

sin 120579119894

cos 120579119894cos120572119894minus cos 120579

119894sin120572119894

0 sin120572119894

cos120572119894

]

]

(2)

For calculating the homogeneous matrix due to 10 degrees offreedom the 10 homogeneous matrixes are been multipliedsequentially The final matrix is 119879 which is represented as

119879 =01198601times11198602times21198603times31198604times41198605sdot sdot sdot times911986010 (3)

The calculation can be made easy by dividing the totalmultiplication into two parts such that 119879 =

01198605times511986011 As

it is a 10 DOF system Finally 119879 matrix of the end point ofExorn is represented with respect to reference and its upper 3values of last column are position vector of end point relatedto world frame

6 Journal of Robotics

a1a2

a3

a4

a5

a7

d2

d3

d5

d6

d7

d8d9

d10

x1x2

x3

x4

x5

x6

x7

x8

x9x10

x11

y1

y2

y3y4

y6

y7

y8

y9

y10y11

z2

z3

z4z5

z6

z7

z8

z9

z10 z11

Figure 12 Coordinate system of 3D model

5 Simulation Model of Human Arm

A human armmodel is being made in Simulink to determinethe required torque to move a joint The length of upperarm lower arm and hand is considered according to theanthropometric data of standard human arm The inertiamatrix of each segment is determined according to the massof that segment and length of the centre of gravity fromthe proximal end as per Table 3 In Simulink it is possibleto provide motions in terms of velocity to joint actuatorand from the joint sensor torque level change is notedThe Simulink model of human arm is shown in Figure 13Maximum amount of torque is needed to move those jointswhich are in vertical direction Here only joint motionrelated to shoulder elbow and wrist flexion and extensionis considered Next those internal and external rotations are

Table 1 Comparative study between joints of human arm andExorn

Actuatornumber Movement Human joint

range (Deg)Exorn range

(deg)Shoulder griddle movements

Actuator 1 Elevation 40 30Depression 10 10

Actuator 2 Scapular abduction 20 20Scapular adduction 15 15

Shoulder joint movements

Actuator 3 Horizontal abduction 135 90Horizontal adduction 45 45

Actuator 4 Vertical abduction 180 160Vertical adduction 20 0

Actuator 5 Forward flexion 180 90Forward extension 60 60

Actuator 6 External rotation 90 90Internal rotation 20 20

Elbow joint movements

Actuator 7 Elbow flexion 140 120Elbow extension 0 0

Actuator 8 Forearm pronation 90 90Forearm supination 80 80

Wrist joint movements

Actuator 9 Palm radial deviation 15 10palm ulnar deviation 45 30

Actuator 10 Palm flexion 80 80Palm extension 80 80

Table 2 D-H parameter of Exorn

119886119894(cm) 120572

119894(deg) 119889

119894(cm) 120579

119894(deg)

10 90 0 Θ1

12 0 5 Θ2

6 90 2 Θ3

3 minus90 0 Θ4

31 0 minus25 Θ5

0 90 6 Θ6

3 0 35 Θ7

0 90 25 Θ8

0 minus90 4 Θ9

0 0 8 Θ10

being taken care of In exoskeleton system those motionscannot be controlled from the fixed end due to its twistingtypeTherefore the end effector should be rotatedwith respectto fixed end

The Simulink blocks used for making the human armmodel are shown in Figures 14 and 15 A joint actuator blockis connected to provide the actuation signal and joint sensorblock is attached to measure the computed torque In orderto make a joint with several DOFs several bodies of zeromass and zero length with actuator block of different axis of

Journal of Robotics 7

(a) (b)

Figure 13 (a) Simulink model of human hand (b) human hand position at zero position

Conn1Conn1

Conn1Conn1

Conn2 Conn2

Conn2

Conn2

Conn3

Conn3

Conn3

Conn4

Conn4Conn5

Out1

Out1

Out2

Out3

Out3Out2

Ground Weld Body2

To workspace

To workspace1

To workspace2

Subsystem

Subsystem3 Subsystem6 Subsystem9

Shoulder joint Elbow jointWrist joint

Display3 Display9 Display12

Finger

In1 out1 In1 out1 In1 out1

CS1 CS17

x

y

z

B F

Figure 14 Human arm model in Simulink

rotations are connected Here in Figure 15 body 1 and body2 have zero length and zero mass Only body 3 is the actualbody It is under every human arm joint Body sensor isattached at the end point to get points in 3D space at the timeof motion

6 Embedded System

A PC based control system is being developed to provideparticular orthopedic lesson First of all command signalfrom PC is transmitted to the master controller Mastercontroller activates those joints which are needed to achievethe desired motion It sends the command bits in a packagethrough serial communication Enable signal is being sent to

all the local controllers but only few are being activated as percommand with the help of multiprocessor communicationtechnique All the motor controllers are connected in adaisy chain network that means 119879

119909and 119877

119909pins of master

controller are connected to all 119877119909and 119879

119909pins of each

controller respectively Each controller has a particular nodeas an activating signal When the master controller sends theactivation signal the particular motor controller with thatparticular node is activated

The interfacing circuit between microcontroller andmotor driver is shown in Figures 16(a) and 16(b) Driver IChas 4 input pins and 2 enable pins Here all the inputs pins andenable pins are connecting to port 0 and port 1 Here all theenable pins are sorted and connected through one port pin

8 Journal of Robotics

CS1 CS15 CS1 CS15 CS1 CS15B F B FB F1

12

2

3

Conn2 Conn3Body1 Body2 Body3

Out1Out2 Out3

Signal2Signal2Signal2

Revolute1 Revolute2 Revolute3

Joint actuatorJoint actuator1 Joint actuator2Joint sensor1 Joint sensor2 Joint sensor3

Shoulder vertical motion Shoulder forward flexion Shoulder horizontal motion

Figure 15 Block diagram below each human joint

(a)

Junction circuit 1P89V51RD2 7805 IC

7805 IC Max232DB-9

DB-9

Local controller for DC motor

Local controller for BLDC motor

DC motor driver circuit

Junction circuit 2

7805 IC

IN 4007L298

(b)

Figure 16 (a) Schematic design of interfacing circuit between microcontroller and motor driver (b) Developed interfacing circuit ofmicrocontroller

In this case all the enable pins become activated at one timeSo the motion of motor can be controlled by changing driverinputsThose inputs are amplified from 5V to 12V to run themotor in clockwise and anticlockwise manner (Figure 17) Asshown in the figure one dedicated 7805 IC (Voltage regulator)is connected tomicrocontroller for 5V power supply A serialIC MAX232 is connected to the microcontroller to convert

the RS232rsquos signals to TTL voltage levels that is acceptable to8051 microcontroller 119879

119909and 119877

119909pins

A bidirectional H bridgeDC motor control circuit isshown in Figures 17(a) and 17(b) The circuit is based onthe IC L298 from ST Microelectronics L298 It is a dual fullbridge driver that has a wide operating voltage range andcan handle load currents up to 3A The IC also features low

Journal of Robotics 9

Out In

sum

sum

MT2

100120583F

1 120583F

1 120583F

10120583F

CN5

CN6

1K 1K

1K1K

L298

REF7805

D1

D2

D3

D4

D5

D6 D7

D8

D9D10

D11 D12

R1 R2

R3R4

C1

C2

C3C4

(a)

Motor driver L298

H bridge driver

Power supply

(b)

Figure 17 (a) Schematic design of motor driver circuit (b) Developed motor driver circuit

Table 3 Segment mass and lengths of human arm [8]

Segment Segment masstotal body mass Centre of masssegment length Radius of gyrationsegment lengthProximal Distal CM Proximal Distal

Hand 0006 0506 0494 0297 0587 0577Forearm 0016 0430 0570 0303 0526 0647Upperarm 0028 0436 0564 0322 0542 0645Forearm and Hand 0022 0682 0318 0468 0827 0565Total arm 0050 0530 0470 0368 0645 0596

saturation voltage and over temperature protection In thecircuit diodes D1 to D8 are protection diodesThe state of themotor depends on the logic level of the pins 5 6 and 7 and10 11 and 12 and it is described in the table shown below thecircuit diagram

The diodes D1 to D4 and D5 to D8 provide a safer pathfor the back emf from the motor to dissipate and thus itprotects the corresponding bipolar transistors from damageThe input pins from motor driver are being connected tothe microcontroller port pins When the enable pins of thedriver pin are active then the input signal of the motor driveris amplified to 12 volt and sent to the motor According tothe configuration of port pins motor moves in clockwise oranticlockwise direction

In case of BLDCmotor controller every controller has itsparticular node for distinguishing one from the other It ispossible to control the speed of the motor either by varyingthe voltage supplied to it or by sending the serial command toit The speed of the motor is controlled by sending a string ofcommand to the BLDCmotor controller serially Also there isan encoder inside the BLDCmotor for getting the angle valuesimultaneously in a feedback loop

All the supply voltages are being bypassed through thosejunction circuits Actually all voltage sources are being sortedA 7812 IC voltage regulator is used to convert the 24Vinto 12V DC supply When the diode connected in junctioncircuit is in forward bias it sends the power supply to alldriver circuits but in the opposite case current from driver

10 Journal of Robotics

No

Serial communication configuration

Command comes from PC

GUI open

Serial port start

Serial port configuration

Commands send to the BLDC controller

Interrupt control

Select direction

Select BLDC motor

Send command to motor

Serial portclose

Select speed

DC motor controller

Motor moves

Formation of command package

Can be applied for all motors

SBUF Move motor 1 clockwise

SBUF Move motor 1 anticlockwise

SBUF Move motor 1 stop

Yes

Yes

Yes

No

No

CWCC

= A

= B

= X

Figure 18 Flow chart for PC based control

circuit cannot be sent to the controller circuit The flow chart(Figure 18) is showing the logic behind the algorithm

7 Graphical User Interface Model of Exorn v1

A proper Graphical User Interface (Figure 19) has beendeveloped for controlling all the motions serially through PCbased system It is being designed in Microsoft visual studioplatformThewholeGUImodel is divided into four divisionsFirst one is the configuration of serial communication whereuser has to select the particular COM port and baud rateIt has two buttons for opening and closing of COM portAfter opening of COM port any command can be sent to

the serial portThere are three divisions regarding themotionof human joint for proper treatment Here only one controlcan be selected out of three options Selection of one optionwill freeze the others The flow chart behind the GUI modelis shown in Figure 20

71 Orthopedic Lessons There are some movements whichare generally prescribed by different doctors for strokepatients for different problems All the motions are stored inmemory After selecting somemotion the patient presses thestart button and a command will be sent through serially fortaking proper action It will be updated with time accordingto orthopedic doctor advice

Journal of Robotics 11

Figure 19 GUI model

Serial communication and

configuration

Orthopaedic lessonsIsolateral exercises Angle oriented control

M1

Select BAUD

Select COM port

SpeedCW

CC

M2 Speed CW

CC

SpeedCW

CC

Arm movement

Elbow movement

Forearm movement

Wrist movement

Elevation and depression of shoulder griddle

Scapular abduction and adduction of shoulder griddle

Horizontal abduction and adduction of shoulder joint

Flexion and extension of wrist

M10

Figure 20 Flow chart of GUI model

72 Isolateral Exercises In isolateral exercises there are somepredefined exercises which are standard motions of all jointsof human arm Patients can follow those exercises so that theirmuscle rigidity becomes less After each selection a commandis being sent serially to master controller Master controlleralways takes care of proper actions

73 Angle Oriented Control In this configuration each jointis controlled in clockwise or anticlockwise manner withdifferent speedMore than one joint can be governed throughitWhen user selects jointmotions then a frame of commandbit serially sends with a start and stop bit to distinguish

between different commands User has to write the requiredspeed beside the box of direction of rotation In case twomotions are contradictory then the controller does not allowthat motion It is already preprogrammed in the controller

8 Predefined Control System

It is a predefined control (Figure 21) Already a vast scheduleof exercise modules is to be loaded in the memory Whensomeone wants to perform a task it is being sent to thecontroller through a manual switch or PC Master controllerwill generate a reference trajectory for that particular task

12 Journal of Robotics

PCandGUI

Master controller

Local controller

1H bridge

circuitDriver L298

Feedback

Exorn joint 1

Local controller

10H bridge circuit

Driver L298

Feedback

Exorn joint 10

Inverse kinematics

Forward kinematics

1205751205791

12057512057910

120575x

x

xd

120579

12057910

1205791

jminus1

Figure 21 Independent joint control system

0 20 40 60 80 100

0

2

4

6

8

10

Time (s)

Torque versus time

minus2

minus4

Com

pute

d to

rque

(N-m

)

Figure 22 Joint torque graph at shoulder due to flexion andextension

Then it is being sent to the local controller which takes careof that particular trajectory Always there is feedback loopconnected between the system and the master controllerWith the help of resolved motion rate control (Whitney 72)approach each joint can be controlled in an independent wayAccording to forward kinematics the kinematic model can beexpressed using the equation

120575119909 = 119869 (120579) 120575120579 (4)

Outside the singularities the inverse kinematics can beexpressed as

120575120579 = 119869minus1(120579) 120575119909 (5)

0 20 40 60 80 100 120

0

05

1

15

2

25

minus05

minus1

minus15

minus2

Time (s)

Torque versus time

Com

pute

d to

rque

(N-m

)

Figure 23 Joint torque graph at elbow due to elbow flexion andextension

There is a relation between task space and joint space Herethe current position at some angle 120579 can be expressed as

119909 = 119891 (120579) (6)

The desired location in 3D space is defined as 119909119889 So error

between current and desired position can be expressed as

120575119909 = 119909119889minus 119909

120575120579 = 119869minus1(120579) 120575119909

(7)

The next 120579 will be expressed as 1205791015840 = 120579 + 120575120579 In this way 120579value can be increased or decreased in an iterative way so that

Journal of Robotics 13

0 10 20 30 40 50 60 70 80 90005

01

015

02

025

03

035

04

045

Time (s)

Torque versus time

Com

pute

d to

rque

(N-m

)

Figure 24 Joint torque graph at wrist due to flexion and extension

0 10 20 30 40 50 60

0

1

2

3

4

5

6

minus1

minus2

minus3

times10minus3

Time (s)

Torque versus time

Com

pute

d to

rque

(N-m

)

Figure 25 Joint torque graph at elbow due to shoulder internal andexternal rotation

the desired location can be reached The error betweendesired location and current location can be compared usingforward kinematics in a feedback loop

In case of finding inverse kinematics there is a problem ofsingularity So we are imposing damped least square methodfor calculating the inverse kinematics The damped leastsquares solutions are intended to ensure a well-conditionedmatrix for the solution algorithmwhile limiting the size of thesolution vector 120575120579 This is done by adding a diagonal matrix120572119868 to the matrix 119869119869119879 The approximate solution of dampedleast squares method can be expressed as 120575120579 = 119869

+120575119909 where

119869+ can be expressed as the equation given below

119869+= 119869119879(119869119869119879+ 120572119868)minus1

120572 ge 0 (8)

0 20 40 60 80 100 120

0

2

4

6

minus2

minus4

minus6

times10minus3

Time (s)

Torque versus time

Com

pute

d to

rque

(N-m

)

Figure 26 Joint torque graph at wrist due to elbow pronation andsupination

When this equation is used then the solution satisfies

min120575120579

120575119909 minus 1198691205751205792+ 12057221205751205792 (9)

where sdot denotes the Euclidean norm For 120572 = 0 the dampedleast squares solution will become pseudoinverse solutionThen the Jacobian inversematrix will be 119869lowast where 119869lowast becomeexpressed as 119869119879(119869119869119879)minus1

In the damped least squares method the size of errorin the task space is weighed against the size of the resultingsolution For a given 120575119909 the size of the solution vector isdecreased by increasing 120572 However this is done at theexpense of using an approximate solution As 120572 increases sodoes the size of the error in the task space A large 120572 hasthe other benefit of ensuring a well-conditioned matrix forinversion It has been shown that the condition number 119870of the matrix 119875 equiv (119869119869

119879+ 120572119868) is 119870 = (120590

2

1+ 120572)(120590

2

119898+ 120572)

Here 1205901ge 1205902ge 1205903sdot sdot sdot ge 120590

119898ge 0 are the singular values of

the Jacobian matrix It can be seen in this equation that 119870is made arbitrarily close to 1 by increasing 120572 thus ensuringa well-conditioned matrix for inversion even in a singularconfiguration where 120590

119898= 0 Simply stated if one is willing

to give up the exactness of the solution then the size of thejoint rate can be reduced and a well-conditioned matrix forinversion can be ensured by increasing 120572

9 Simulation Results of Torque Level ofGeneral Human Arm

Maximum amount of torque is required to actuate humanjoints in vertical direction Here in Figure 25 the torqueneeded to twist the elbow with respect to shoulder joint isshown Figure 26 is showing the same kind ofmotion in wrist

14 Journal of Robotics

0 200 400 600 800 1000 12000500

1000

0500

1000

minus500

minus1000

minus500

minus1000

(a)

20

20

0

0

minus20

minus20

minus40

minus40

40

minus60

minus60

minus80 500

minus50

x

y z

Untitled fit 1x versus z y

(b)

Figure 27 (a) Outer region covered by Exorn (b) Workspace covered by Exorn

0

minus10

minus20

minus30

minus40

minus5040

3020

100minus10

minus20 0 1020 30

40 5060

70

Figure 28 Motion due to shoulder griddle

006

004

002

0

minus0020

001

002

003

004

005002

0 minus002 minus004minus006 minus008

minus01

Figure 29 Motion due to shoulder griddle glenohumerals andelbow joint movement

joint with respect to the elbow Figures 22 23 24 25 and26 will show torque variation in different joints in verticaldirection because of proper actuation signal From thosebelow graphs max and min torque for joint actuator can bedetermined because it is very much essential to select propermotor

006

004

002

0

minus0020

minus002minus004

minus006minus008

minus010

002

004

006

008

Figure 30 Motion due to shoulder joint and elbow joint movementin vertical direction

003

002

001

0

minus001

minus002

minus0030 minus002 minus004 minus006 minus008 minus01

0

001

002

003

Figure 31 Motion due to glenohumeral joint and elbow jointmovement in horizontal direction

10 Workspace Calculation and Motion due toForward Kinematics

For calculating the workspace of the robotic system aMATLAB code of nested for loop of all DOFs is being takenwith the joint range It will plot all the reachable points ofarm exoskeleton in 3D space Figure 27 is showing the outer

Journal of Robotics 15

region covered by human hand Figures 28 29 30 and 31 areshowing themotion of exoskeletonmodel due to several jointmovements

11 Conclusion

From the above discussion it may be concluded that thedeveloped system is useful for rehabilitation Comparisonsbetween human jointrsquos range and that of Exorn are alreadytabulated in Table 1 and the ranges are quite the same for boththe cases If the portable mechanical structure is attached tothe human arm it can be used as an assistive device for theparalyzed people The 3D model of exoskeleton is alreadybeing developed The model has been fabricated With thehelp of the GUI all the motions can be controlled throughserial communication The developed prototype is underworking condition We would like to build the real system sothat patient can be benefitted

References

[1] J W Krakauer ldquoArm function after stroke from physiology torecoveryrdquo Seminars in Neurology vol 25 no 4 pp 384ndash3952005

[2] T Nef and R Riener ldquoARMinmdashdesign of a novel arm reha-bilitation robotrdquo in Proceedings of the IEEE 9th InternationalConference on Rehabilitation Robotics (ICORR rsquo05) pp 57ndash60July 2005

[3] S J Ball I E Brown and S H Scott ldquoMEDARM a rehabilita-tion robot with 5DOF at the shoulder complexrdquo in Proceedingsof the IEEEASME International Conference on Advanced Intel-ligent Mechatronics (AIM rsquo07) September 2007

[4] M Mistry P Mohajerian and S Schaal ldquoArm movementexperiments with joint space force fields using an exoskeletonrobotrdquo in Proceedings of the IEEE 9th International Conferenceon Rehabilitation Robotics (ICORR rsquo05) pp 408ndash413 July 2005

[5] A Schiele and F C T van der Helm ldquoKinematic design toimprove ergonomics in human machine interactionrdquo IEEETransactions on Neural System and Rehabilitation vol 14 no4 pp 1534ndash4320 2006

[6] S J Ball I E Brown and S H Scott ldquoA planar 3DOF roboticexoskeleton for rehabilitation and assessmentrdquo in Proceedingsof the 29th Annual International Conference of IEEE-EMBSEngineering in Medicine and Biology Society (EMBC rsquo07) pp4024ndash4027 August 2007

[7] I Sardellitti E Cattin S Roccella et al ldquoDescription char-acterization and assessment of a bio-inspired shoulder joint-first link robot for neuro-robotic applicationsrdquo in Proceedings ofthe 1st IEEERAS-EMBS International Conference on BiomedicalRobotics andBiomechatronics (BioRob rsquo06) pp 112ndash117 February2006

[8] Source-winter Biomechanics and Motor Control of HumanMotion ISBN-978-0470398180 2010

[9] C-J Yang B Niu J-F Zhang and Y Chen ldquoDifferent structurebased control system of the PUMA manipulator with an armexoskeletonrdquo in Proceedings of the IEEE Conference on RoboticsAutomation and Mechatronics pp 572ndash577 December 2004

[10] K Kiguchi T Tanaka K Watanabe and T Fukuda ldquoExoskele-ton for human upper-limb motion supportrdquo in Proceedings ofthe IEEE International Conference on Robotics and Automationpp 2206ndash2211 September 2003

[11] T H Massie and K J Salisbury ldquoPHANToM haptic interfacea device for probing virtual objectsrdquo in Proceedings of theInternational Mechanical Engineering Congress and Expositionpp 295ndash299 November 1994

[12] CCarignan andKCleary ldquoClosed-loop force control for hapticsimulation of virtual environmentsrdquo The Electronic Journal ofHaptics Research vol 2 no 2 pp 1ndash14 2000

[13] A Frisoli F Rocchi S Marcheschi A Dettori F Salsedo andM Bergamasco ldquoA new force-feedback arm exoskeleton forhaptic interaction in virtual environmentsrdquo in Proceedings ofthe First Joint Eurohaptics Conference and Symposium on HapticInterfaces for Virtual Environment and Teleoperator Systems pp195ndash201 2005

[14] D Lawrence ldquoImpedance control stability properties in com-mon implementationsrdquo in Proceedings of the IEEE InternationalConference on Robotics and Automation pp 1185ndash1190 1988

[15] A Nakai Y Kunii H Hashimoto and F Harashima ldquoArmtype haptic human interface sensor armrdquo in Proceedings of theInternational Conference on Artificial Reality and Tele-Existence(ICAT) pp 77ndash84 Tokyo Japan December 1997

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Journal of Robotics 3

Scapular abduction and adduction

Horizontal abduction and adduction

Elevation and depression of shoulder griddle

Conversion of rotational motion into linear motion

through screw jack

Actuator 2Suspensor

Actuator 1

Figure 3 Shoulder griddle joint model

Scapular abduction and adduction

Horizontalabduction and

adduction

Conversion of rotational motion into linear motion through screw jack

Actuator 1

DC geared motor

Figure 4 Manufactured model of shoulder griddle

(A) Horizontal abduction and adduction(B) Vertical abduction and adduction(C) Forward flexion and extension(D) External and internal rotation

Actuator 3

Actuator 4Actuator 5

Actuator 6

Adjustment for variable upper arm length

Suspensor

A

BC

D

Figure 5 Glenohumeral joint model

adduction

DC geared motor used for forward flexion and

DC geared motor used for vertical abduction and

Variable adjustable upper arm structure

extension

Figure 6 Manufactured model of glenohumeral joint

Adjustment for variable upper arm length

Shoulder external and internal rotation

Elbow flexion and extension

Hand rest for forearm

Suspensor

Actuator 7

Figure 7 Elbow joint model

Actuators 9 and 10 are used for providing thosemotions Herewe can see that all the actuators are dedicated to give themotion in all directions according to the differentmovementsof human arm as shown in Figure 11

Weight of the Prototype 5 kg

Specification of the DC Geared Motor

Weightmdash500 gm

Speedmdash10 rpm

Torquemdash100 kg-cm at 4 ampere (Max)

Specification of BLDC Motor

Company-Faulhaber

Weightmdash500 gm

Speedmdash10 rpm

Torquemdash100 kg-cm at 4 ampere (Max)

Gears are made up of Nylon 101 Structures are usedfor twisting moment at human elbow and wrist with thehelp of gear arrangement which provide better flexibility andstrength

4 Journal of Robotics

Gear arrangement for shoulder external and internal rotation

DC geared motor for elbow flexion and

BLDC motor

Suspensor

Forearm structure

extension

Figure 8 Manufactured model of elbow joint

Adjustment for variable forearm

Elbow pronation and supination

Palm flexion and extension

Palm radial andulnar deviation

Actuator 8

Actuator 9

Actuator 10

Hand rest

length

Figure 9 Wrist joint model

Specification of Nylon 101

Tensile strength 79289709Nm2

Mass density 1150Kgm3

Elastic modulus 1000000000Nm2

Yield strength 60000000Nm2

Turn ratio at the elbow joint 35 8Turn ratio at wrist joint 15 4

At the shoulder joint bush is used to provide the supportto the joint motor axis It is made up of brass to reducethe wear and tear between perspex and motor spindle Onecylindrical rod of the same material moves inside the bushand provides the support to the other end of structure at thetime of joint flexion and extension

The whole body of Exorn is made up of perspex It ishardy and elastic It gives less weight in respect to aluminumPerplex sheet is cut into different pieces and attached witheach other through industrial gum and nut (M4 thread)Three different thickness perspex sheets have been used forthe structureHigherwidth is used at the arm structure to givebetter support and the lower one is used for hand structure

Type 1mdashWidth 5mmType 2mdashWidth 10mmType 3mdashWidth 20mm

BLDC motor used for elbow pronation and supination

BLDC motor used for palm flexion

BLDC motor used for palm radial and

ulnar deviation

Hand rest

and extension

Figure 10 Manufactured model of wrist joint

Specification of Perspex (TM) GS Acrylic Cast Sheet

Tensile strength 75000000Nm2

Density 1190Kgm3

Size of the Exoskeleton The size of the exoskeleton (approxi-mately 9673 cm) has been taken as per the standard length ofa human arm and it can be varied from person to person

Length of shoulder griddle 0129119867Length of upper arm 0186119867Length of forearm 0146119867Length of hand 0108119867

Here 119867 is defined as the height of the human arm and ifwe consider the height of a standard human as 170 cm thelength will be approximately 9673 cm Obviously the lengthof human arm is different from person to person But as wehave made a physical system we have taken the standardlength But the system has a provision so that it is wearable toall the people of variable arm lengthwhich has been discussedin the portion of mechanical model

4 Kinematic Analysis of Exorn

Kinematic model of Exorn is designed according to theanthropometric data of standard human arm The mechani-cal structure is such that it can align with human arm and canprovide the desirable joint motion Some mechanical barrieris located to restrict the joint from hyperextension Here theforward kinematics of the whole system is discussed whichprovides the end point position and orientation due to severaljointmotions It is basically acting as a seriesmanipulatorThekinematic relation of a manipulator is represented by = 119869 120579

Journal of Robotics 5

Elevation

Depression

Extension

Flexion

Abduction

Adduction

Flexion

Extension

Horizontal abduction

Horizontaladduction

Lateral

Medical rotation

Flexion

ExtensionSupination Pronation

Extension

Flexion

Ulnar deviation Radial deviation0

0

0

0

0

0

0 0

0

0

0∘

15∘

15∘

40∘ 180∘

180∘

135∘

20∘

20∘

20∘

45∘

45∘

60∘60∘

80∘

80∘

10∘

80∘ 90∘

140∘

Figure 11 Different motions of human arm

is the119898 dimensional vector specifying the task velocityof end effector 120579 is 119899 dimensional vector representing thejoint velocity 119869 is the119898 by 119899 Jacobianmatrix For a redundantmanipulator 119899 is always greater than 119898 Here the kinematicredundancy is 3

41 D-HParameter of the 3DModel To do kinematic analysisof the whole system it is essential to derive D-H parameterof the whole system The coordinate system of the wholestructure is shown in Figure 12 The coordinate structure ofthe exoskeleton system is based on 3D conceptual modelof Exorn D-H parameters of the structure are shown inTable 2 It is essential to calculate the position and orientationof the end point in 3D space with respect to the referencecoordinate

42 Transformation Matrix Generation For getting the posi-tion and orientation of the end point of Exorn systemhomogeneous transformation matrix is considered Eachhomogeneous transformation matrix was calculated for theposition and orientation of present frame with respect to theprevious frame It is a 4 times 4 matrix The column 119894minus1119889

119894is

position of the end point and 119894minus1119877119894is the orientation of end

point in 3D space The transformation matrix is 119894minus1119860119894

119894minus1119860119894= [

119894minus1119877119894

119894minus1

119889119894

0 1]

4times4

(1)

The homogeneous matrix is being explained as119894minus1119860119894= 119863119911119894minus1119889119894

lowast 119877119911119894minus1120579119894

lowast 119863119909119894minus1119886119894

lowast 119877119909119894minus1120572119894

=

[[[

[

cos 120579119894minus sin 120579

119894cos120572119894

sin 120579119894sin120572119894

119886119894cos 120579119894

sin 120579119894

cos 120579119894cos120572119894minus cos 120579

119894sin120572119894119886119894sin 120579119894

0 sin120572119894

cos120572119894

119889119894

0 0 0 1

]]]

]

119894minus1119889119894= [

[

119886119894cos 120579119894

119886119894sin 120579119894

119889119894

]

]

119894minus1119877119894= [

[

cos 120579119894minus sin 120579

119894cos120572119894

sin 120579119894sin120572119894

sin 120579119894

cos 120579119894cos120572119894minus cos 120579

119894sin120572119894

0 sin120572119894

cos120572119894

]

]

(2)

For calculating the homogeneous matrix due to 10 degrees offreedom the 10 homogeneous matrixes are been multipliedsequentially The final matrix is 119879 which is represented as

119879 =01198601times11198602times21198603times31198604times41198605sdot sdot sdot times911986010 (3)

The calculation can be made easy by dividing the totalmultiplication into two parts such that 119879 =

01198605times511986011 As

it is a 10 DOF system Finally 119879 matrix of the end point ofExorn is represented with respect to reference and its upper 3values of last column are position vector of end point relatedto world frame

6 Journal of Robotics

a1a2

a3

a4

a5

a7

d2

d3

d5

d6

d7

d8d9

d10

x1x2

x3

x4

x5

x6

x7

x8

x9x10

x11

y1

y2

y3y4

y6

y7

y8

y9

y10y11

z2

z3

z4z5

z6

z7

z8

z9

z10 z11

Figure 12 Coordinate system of 3D model

5 Simulation Model of Human Arm

A human armmodel is being made in Simulink to determinethe required torque to move a joint The length of upperarm lower arm and hand is considered according to theanthropometric data of standard human arm The inertiamatrix of each segment is determined according to the massof that segment and length of the centre of gravity fromthe proximal end as per Table 3 In Simulink it is possibleto provide motions in terms of velocity to joint actuatorand from the joint sensor torque level change is notedThe Simulink model of human arm is shown in Figure 13Maximum amount of torque is needed to move those jointswhich are in vertical direction Here only joint motionrelated to shoulder elbow and wrist flexion and extensionis considered Next those internal and external rotations are

Table 1 Comparative study between joints of human arm andExorn

Actuatornumber Movement Human joint

range (Deg)Exorn range

(deg)Shoulder griddle movements

Actuator 1 Elevation 40 30Depression 10 10

Actuator 2 Scapular abduction 20 20Scapular adduction 15 15

Shoulder joint movements

Actuator 3 Horizontal abduction 135 90Horizontal adduction 45 45

Actuator 4 Vertical abduction 180 160Vertical adduction 20 0

Actuator 5 Forward flexion 180 90Forward extension 60 60

Actuator 6 External rotation 90 90Internal rotation 20 20

Elbow joint movements

Actuator 7 Elbow flexion 140 120Elbow extension 0 0

Actuator 8 Forearm pronation 90 90Forearm supination 80 80

Wrist joint movements

Actuator 9 Palm radial deviation 15 10palm ulnar deviation 45 30

Actuator 10 Palm flexion 80 80Palm extension 80 80

Table 2 D-H parameter of Exorn

119886119894(cm) 120572

119894(deg) 119889

119894(cm) 120579

119894(deg)

10 90 0 Θ1

12 0 5 Θ2

6 90 2 Θ3

3 minus90 0 Θ4

31 0 minus25 Θ5

0 90 6 Θ6

3 0 35 Θ7

0 90 25 Θ8

0 minus90 4 Θ9

0 0 8 Θ10

being taken care of In exoskeleton system those motionscannot be controlled from the fixed end due to its twistingtypeTherefore the end effector should be rotatedwith respectto fixed end

The Simulink blocks used for making the human armmodel are shown in Figures 14 and 15 A joint actuator blockis connected to provide the actuation signal and joint sensorblock is attached to measure the computed torque In orderto make a joint with several DOFs several bodies of zeromass and zero length with actuator block of different axis of

Journal of Robotics 7

(a) (b)

Figure 13 (a) Simulink model of human hand (b) human hand position at zero position

Conn1Conn1

Conn1Conn1

Conn2 Conn2

Conn2

Conn2

Conn3

Conn3

Conn3

Conn4

Conn4Conn5

Out1

Out1

Out2

Out3

Out3Out2

Ground Weld Body2

To workspace

To workspace1

To workspace2

Subsystem

Subsystem3 Subsystem6 Subsystem9

Shoulder joint Elbow jointWrist joint

Display3 Display9 Display12

Finger

In1 out1 In1 out1 In1 out1

CS1 CS17

x

y

z

B F

Figure 14 Human arm model in Simulink

rotations are connected Here in Figure 15 body 1 and body2 have zero length and zero mass Only body 3 is the actualbody It is under every human arm joint Body sensor isattached at the end point to get points in 3D space at the timeof motion

6 Embedded System

A PC based control system is being developed to provideparticular orthopedic lesson First of all command signalfrom PC is transmitted to the master controller Mastercontroller activates those joints which are needed to achievethe desired motion It sends the command bits in a packagethrough serial communication Enable signal is being sent to

all the local controllers but only few are being activated as percommand with the help of multiprocessor communicationtechnique All the motor controllers are connected in adaisy chain network that means 119879

119909and 119877

119909pins of master

controller are connected to all 119877119909and 119879

119909pins of each

controller respectively Each controller has a particular nodeas an activating signal When the master controller sends theactivation signal the particular motor controller with thatparticular node is activated

The interfacing circuit between microcontroller andmotor driver is shown in Figures 16(a) and 16(b) Driver IChas 4 input pins and 2 enable pins Here all the inputs pins andenable pins are connecting to port 0 and port 1 Here all theenable pins are sorted and connected through one port pin

8 Journal of Robotics

CS1 CS15 CS1 CS15 CS1 CS15B F B FB F1

12

2

3

Conn2 Conn3Body1 Body2 Body3

Out1Out2 Out3

Signal2Signal2Signal2

Revolute1 Revolute2 Revolute3

Joint actuatorJoint actuator1 Joint actuator2Joint sensor1 Joint sensor2 Joint sensor3

Shoulder vertical motion Shoulder forward flexion Shoulder horizontal motion

Figure 15 Block diagram below each human joint

(a)

Junction circuit 1P89V51RD2 7805 IC

7805 IC Max232DB-9

DB-9

Local controller for DC motor

Local controller for BLDC motor

DC motor driver circuit

Junction circuit 2

7805 IC

IN 4007L298

(b)

Figure 16 (a) Schematic design of interfacing circuit between microcontroller and motor driver (b) Developed interfacing circuit ofmicrocontroller

In this case all the enable pins become activated at one timeSo the motion of motor can be controlled by changing driverinputsThose inputs are amplified from 5V to 12V to run themotor in clockwise and anticlockwise manner (Figure 17) Asshown in the figure one dedicated 7805 IC (Voltage regulator)is connected tomicrocontroller for 5V power supply A serialIC MAX232 is connected to the microcontroller to convert

the RS232rsquos signals to TTL voltage levels that is acceptable to8051 microcontroller 119879

119909and 119877

119909pins

A bidirectional H bridgeDC motor control circuit isshown in Figures 17(a) and 17(b) The circuit is based onthe IC L298 from ST Microelectronics L298 It is a dual fullbridge driver that has a wide operating voltage range andcan handle load currents up to 3A The IC also features low

Journal of Robotics 9

Out In

sum

sum

MT2

100120583F

1 120583F

1 120583F

10120583F

CN5

CN6

1K 1K

1K1K

L298

REF7805

D1

D2

D3

D4

D5

D6 D7

D8

D9D10

D11 D12

R1 R2

R3R4

C1

C2

C3C4

(a)

Motor driver L298

H bridge driver

Power supply

(b)

Figure 17 (a) Schematic design of motor driver circuit (b) Developed motor driver circuit

Table 3 Segment mass and lengths of human arm [8]

Segment Segment masstotal body mass Centre of masssegment length Radius of gyrationsegment lengthProximal Distal CM Proximal Distal

Hand 0006 0506 0494 0297 0587 0577Forearm 0016 0430 0570 0303 0526 0647Upperarm 0028 0436 0564 0322 0542 0645Forearm and Hand 0022 0682 0318 0468 0827 0565Total arm 0050 0530 0470 0368 0645 0596

saturation voltage and over temperature protection In thecircuit diodes D1 to D8 are protection diodesThe state of themotor depends on the logic level of the pins 5 6 and 7 and10 11 and 12 and it is described in the table shown below thecircuit diagram

The diodes D1 to D4 and D5 to D8 provide a safer pathfor the back emf from the motor to dissipate and thus itprotects the corresponding bipolar transistors from damageThe input pins from motor driver are being connected tothe microcontroller port pins When the enable pins of thedriver pin are active then the input signal of the motor driveris amplified to 12 volt and sent to the motor According tothe configuration of port pins motor moves in clockwise oranticlockwise direction

In case of BLDCmotor controller every controller has itsparticular node for distinguishing one from the other It ispossible to control the speed of the motor either by varyingthe voltage supplied to it or by sending the serial command toit The speed of the motor is controlled by sending a string ofcommand to the BLDCmotor controller serially Also there isan encoder inside the BLDCmotor for getting the angle valuesimultaneously in a feedback loop

All the supply voltages are being bypassed through thosejunction circuits Actually all voltage sources are being sortedA 7812 IC voltage regulator is used to convert the 24Vinto 12V DC supply When the diode connected in junctioncircuit is in forward bias it sends the power supply to alldriver circuits but in the opposite case current from driver

10 Journal of Robotics

No

Serial communication configuration

Command comes from PC

GUI open

Serial port start

Serial port configuration

Commands send to the BLDC controller

Interrupt control

Select direction

Select BLDC motor

Send command to motor

Serial portclose

Select speed

DC motor controller

Motor moves

Formation of command package

Can be applied for all motors

SBUF Move motor 1 clockwise

SBUF Move motor 1 anticlockwise

SBUF Move motor 1 stop

Yes

Yes

Yes

No

No

CWCC

= A

= B

= X

Figure 18 Flow chart for PC based control

circuit cannot be sent to the controller circuit The flow chart(Figure 18) is showing the logic behind the algorithm

7 Graphical User Interface Model of Exorn v1

A proper Graphical User Interface (Figure 19) has beendeveloped for controlling all the motions serially through PCbased system It is being designed in Microsoft visual studioplatformThewholeGUImodel is divided into four divisionsFirst one is the configuration of serial communication whereuser has to select the particular COM port and baud rateIt has two buttons for opening and closing of COM portAfter opening of COM port any command can be sent to

the serial portThere are three divisions regarding themotionof human joint for proper treatment Here only one controlcan be selected out of three options Selection of one optionwill freeze the others The flow chart behind the GUI modelis shown in Figure 20

71 Orthopedic Lessons There are some movements whichare generally prescribed by different doctors for strokepatients for different problems All the motions are stored inmemory After selecting somemotion the patient presses thestart button and a command will be sent through serially fortaking proper action It will be updated with time accordingto orthopedic doctor advice

Journal of Robotics 11

Figure 19 GUI model

Serial communication and

configuration

Orthopaedic lessonsIsolateral exercises Angle oriented control

M1

Select BAUD

Select COM port

SpeedCW

CC

M2 Speed CW

CC

SpeedCW

CC

Arm movement

Elbow movement

Forearm movement

Wrist movement

Elevation and depression of shoulder griddle

Scapular abduction and adduction of shoulder griddle

Horizontal abduction and adduction of shoulder joint

Flexion and extension of wrist

M10

Figure 20 Flow chart of GUI model

72 Isolateral Exercises In isolateral exercises there are somepredefined exercises which are standard motions of all jointsof human arm Patients can follow those exercises so that theirmuscle rigidity becomes less After each selection a commandis being sent serially to master controller Master controlleralways takes care of proper actions

73 Angle Oriented Control In this configuration each jointis controlled in clockwise or anticlockwise manner withdifferent speedMore than one joint can be governed throughitWhen user selects jointmotions then a frame of commandbit serially sends with a start and stop bit to distinguish

between different commands User has to write the requiredspeed beside the box of direction of rotation In case twomotions are contradictory then the controller does not allowthat motion It is already preprogrammed in the controller

8 Predefined Control System

It is a predefined control (Figure 21) Already a vast scheduleof exercise modules is to be loaded in the memory Whensomeone wants to perform a task it is being sent to thecontroller through a manual switch or PC Master controllerwill generate a reference trajectory for that particular task

12 Journal of Robotics

PCandGUI

Master controller

Local controller

1H bridge

circuitDriver L298

Feedback

Exorn joint 1

Local controller

10H bridge circuit

Driver L298

Feedback

Exorn joint 10

Inverse kinematics

Forward kinematics

1205751205791

12057512057910

120575x

x

xd

120579

12057910

1205791

jminus1

Figure 21 Independent joint control system

0 20 40 60 80 100

0

2

4

6

8

10

Time (s)

Torque versus time

minus2

minus4

Com

pute

d to

rque

(N-m

)

Figure 22 Joint torque graph at shoulder due to flexion andextension

Then it is being sent to the local controller which takes careof that particular trajectory Always there is feedback loopconnected between the system and the master controllerWith the help of resolved motion rate control (Whitney 72)approach each joint can be controlled in an independent wayAccording to forward kinematics the kinematic model can beexpressed using the equation

120575119909 = 119869 (120579) 120575120579 (4)

Outside the singularities the inverse kinematics can beexpressed as

120575120579 = 119869minus1(120579) 120575119909 (5)

0 20 40 60 80 100 120

0

05

1

15

2

25

minus05

minus1

minus15

minus2

Time (s)

Torque versus time

Com

pute

d to

rque

(N-m

)

Figure 23 Joint torque graph at elbow due to elbow flexion andextension

There is a relation between task space and joint space Herethe current position at some angle 120579 can be expressed as

119909 = 119891 (120579) (6)

The desired location in 3D space is defined as 119909119889 So error

between current and desired position can be expressed as

120575119909 = 119909119889minus 119909

120575120579 = 119869minus1(120579) 120575119909

(7)

The next 120579 will be expressed as 1205791015840 = 120579 + 120575120579 In this way 120579value can be increased or decreased in an iterative way so that

Journal of Robotics 13

0 10 20 30 40 50 60 70 80 90005

01

015

02

025

03

035

04

045

Time (s)

Torque versus time

Com

pute

d to

rque

(N-m

)

Figure 24 Joint torque graph at wrist due to flexion and extension

0 10 20 30 40 50 60

0

1

2

3

4

5

6

minus1

minus2

minus3

times10minus3

Time (s)

Torque versus time

Com

pute

d to

rque

(N-m

)

Figure 25 Joint torque graph at elbow due to shoulder internal andexternal rotation

the desired location can be reached The error betweendesired location and current location can be compared usingforward kinematics in a feedback loop

In case of finding inverse kinematics there is a problem ofsingularity So we are imposing damped least square methodfor calculating the inverse kinematics The damped leastsquares solutions are intended to ensure a well-conditionedmatrix for the solution algorithmwhile limiting the size of thesolution vector 120575120579 This is done by adding a diagonal matrix120572119868 to the matrix 119869119869119879 The approximate solution of dampedleast squares method can be expressed as 120575120579 = 119869

+120575119909 where

119869+ can be expressed as the equation given below

119869+= 119869119879(119869119869119879+ 120572119868)minus1

120572 ge 0 (8)

0 20 40 60 80 100 120

0

2

4

6

minus2

minus4

minus6

times10minus3

Time (s)

Torque versus time

Com

pute

d to

rque

(N-m

)

Figure 26 Joint torque graph at wrist due to elbow pronation andsupination

When this equation is used then the solution satisfies

min120575120579

120575119909 minus 1198691205751205792+ 12057221205751205792 (9)

where sdot denotes the Euclidean norm For 120572 = 0 the dampedleast squares solution will become pseudoinverse solutionThen the Jacobian inversematrix will be 119869lowast where 119869lowast becomeexpressed as 119869119879(119869119869119879)minus1

In the damped least squares method the size of errorin the task space is weighed against the size of the resultingsolution For a given 120575119909 the size of the solution vector isdecreased by increasing 120572 However this is done at theexpense of using an approximate solution As 120572 increases sodoes the size of the error in the task space A large 120572 hasthe other benefit of ensuring a well-conditioned matrix forinversion It has been shown that the condition number 119870of the matrix 119875 equiv (119869119869

119879+ 120572119868) is 119870 = (120590

2

1+ 120572)(120590

2

119898+ 120572)

Here 1205901ge 1205902ge 1205903sdot sdot sdot ge 120590

119898ge 0 are the singular values of

the Jacobian matrix It can be seen in this equation that 119870is made arbitrarily close to 1 by increasing 120572 thus ensuringa well-conditioned matrix for inversion even in a singularconfiguration where 120590

119898= 0 Simply stated if one is willing

to give up the exactness of the solution then the size of thejoint rate can be reduced and a well-conditioned matrix forinversion can be ensured by increasing 120572

9 Simulation Results of Torque Level ofGeneral Human Arm

Maximum amount of torque is required to actuate humanjoints in vertical direction Here in Figure 25 the torqueneeded to twist the elbow with respect to shoulder joint isshown Figure 26 is showing the same kind ofmotion in wrist

14 Journal of Robotics

0 200 400 600 800 1000 12000500

1000

0500

1000

minus500

minus1000

minus500

minus1000

(a)

20

20

0

0

minus20

minus20

minus40

minus40

40

minus60

minus60

minus80 500

minus50

x

y z

Untitled fit 1x versus z y

(b)

Figure 27 (a) Outer region covered by Exorn (b) Workspace covered by Exorn

0

minus10

minus20

minus30

minus40

minus5040

3020

100minus10

minus20 0 1020 30

40 5060

70

Figure 28 Motion due to shoulder griddle

006

004

002

0

minus0020

001

002

003

004

005002

0 minus002 minus004minus006 minus008

minus01

Figure 29 Motion due to shoulder griddle glenohumerals andelbow joint movement

joint with respect to the elbow Figures 22 23 24 25 and26 will show torque variation in different joints in verticaldirection because of proper actuation signal From thosebelow graphs max and min torque for joint actuator can bedetermined because it is very much essential to select propermotor

006

004

002

0

minus0020

minus002minus004

minus006minus008

minus010

002

004

006

008

Figure 30 Motion due to shoulder joint and elbow joint movementin vertical direction

003

002

001

0

minus001

minus002

minus0030 minus002 minus004 minus006 minus008 minus01

0

001

002

003

Figure 31 Motion due to glenohumeral joint and elbow jointmovement in horizontal direction

10 Workspace Calculation and Motion due toForward Kinematics

For calculating the workspace of the robotic system aMATLAB code of nested for loop of all DOFs is being takenwith the joint range It will plot all the reachable points ofarm exoskeleton in 3D space Figure 27 is showing the outer

Journal of Robotics 15

region covered by human hand Figures 28 29 30 and 31 areshowing themotion of exoskeletonmodel due to several jointmovements

11 Conclusion

From the above discussion it may be concluded that thedeveloped system is useful for rehabilitation Comparisonsbetween human jointrsquos range and that of Exorn are alreadytabulated in Table 1 and the ranges are quite the same for boththe cases If the portable mechanical structure is attached tothe human arm it can be used as an assistive device for theparalyzed people The 3D model of exoskeleton is alreadybeing developed The model has been fabricated With thehelp of the GUI all the motions can be controlled throughserial communication The developed prototype is underworking condition We would like to build the real system sothat patient can be benefitted

References

[1] J W Krakauer ldquoArm function after stroke from physiology torecoveryrdquo Seminars in Neurology vol 25 no 4 pp 384ndash3952005

[2] T Nef and R Riener ldquoARMinmdashdesign of a novel arm reha-bilitation robotrdquo in Proceedings of the IEEE 9th InternationalConference on Rehabilitation Robotics (ICORR rsquo05) pp 57ndash60July 2005

[3] S J Ball I E Brown and S H Scott ldquoMEDARM a rehabilita-tion robot with 5DOF at the shoulder complexrdquo in Proceedingsof the IEEEASME International Conference on Advanced Intel-ligent Mechatronics (AIM rsquo07) September 2007

[4] M Mistry P Mohajerian and S Schaal ldquoArm movementexperiments with joint space force fields using an exoskeletonrobotrdquo in Proceedings of the IEEE 9th International Conferenceon Rehabilitation Robotics (ICORR rsquo05) pp 408ndash413 July 2005

[5] A Schiele and F C T van der Helm ldquoKinematic design toimprove ergonomics in human machine interactionrdquo IEEETransactions on Neural System and Rehabilitation vol 14 no4 pp 1534ndash4320 2006

[6] S J Ball I E Brown and S H Scott ldquoA planar 3DOF roboticexoskeleton for rehabilitation and assessmentrdquo in Proceedingsof the 29th Annual International Conference of IEEE-EMBSEngineering in Medicine and Biology Society (EMBC rsquo07) pp4024ndash4027 August 2007

[7] I Sardellitti E Cattin S Roccella et al ldquoDescription char-acterization and assessment of a bio-inspired shoulder joint-first link robot for neuro-robotic applicationsrdquo in Proceedings ofthe 1st IEEERAS-EMBS International Conference on BiomedicalRobotics andBiomechatronics (BioRob rsquo06) pp 112ndash117 February2006

[8] Source-winter Biomechanics and Motor Control of HumanMotion ISBN-978-0470398180 2010

[9] C-J Yang B Niu J-F Zhang and Y Chen ldquoDifferent structurebased control system of the PUMA manipulator with an armexoskeletonrdquo in Proceedings of the IEEE Conference on RoboticsAutomation and Mechatronics pp 572ndash577 December 2004

[10] K Kiguchi T Tanaka K Watanabe and T Fukuda ldquoExoskele-ton for human upper-limb motion supportrdquo in Proceedings ofthe IEEE International Conference on Robotics and Automationpp 2206ndash2211 September 2003

[11] T H Massie and K J Salisbury ldquoPHANToM haptic interfacea device for probing virtual objectsrdquo in Proceedings of theInternational Mechanical Engineering Congress and Expositionpp 295ndash299 November 1994

[12] CCarignan andKCleary ldquoClosed-loop force control for hapticsimulation of virtual environmentsrdquo The Electronic Journal ofHaptics Research vol 2 no 2 pp 1ndash14 2000

[13] A Frisoli F Rocchi S Marcheschi A Dettori F Salsedo andM Bergamasco ldquoA new force-feedback arm exoskeleton forhaptic interaction in virtual environmentsrdquo in Proceedings ofthe First Joint Eurohaptics Conference and Symposium on HapticInterfaces for Virtual Environment and Teleoperator Systems pp195ndash201 2005

[14] D Lawrence ldquoImpedance control stability properties in com-mon implementationsrdquo in Proceedings of the IEEE InternationalConference on Robotics and Automation pp 1185ndash1190 1988

[15] A Nakai Y Kunii H Hashimoto and F Harashima ldquoArmtype haptic human interface sensor armrdquo in Proceedings of theInternational Conference on Artificial Reality and Tele-Existence(ICAT) pp 77ndash84 Tokyo Japan December 1997

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4 Journal of Robotics

Gear arrangement for shoulder external and internal rotation

DC geared motor for elbow flexion and

BLDC motor

Suspensor

Forearm structure

extension

Figure 8 Manufactured model of elbow joint

Adjustment for variable forearm

Elbow pronation and supination

Palm flexion and extension

Palm radial andulnar deviation

Actuator 8

Actuator 9

Actuator 10

Hand rest

length

Figure 9 Wrist joint model

Specification of Nylon 101

Tensile strength 79289709Nm2

Mass density 1150Kgm3

Elastic modulus 1000000000Nm2

Yield strength 60000000Nm2

Turn ratio at the elbow joint 35 8Turn ratio at wrist joint 15 4

At the shoulder joint bush is used to provide the supportto the joint motor axis It is made up of brass to reducethe wear and tear between perspex and motor spindle Onecylindrical rod of the same material moves inside the bushand provides the support to the other end of structure at thetime of joint flexion and extension

The whole body of Exorn is made up of perspex It ishardy and elastic It gives less weight in respect to aluminumPerplex sheet is cut into different pieces and attached witheach other through industrial gum and nut (M4 thread)Three different thickness perspex sheets have been used forthe structureHigherwidth is used at the arm structure to givebetter support and the lower one is used for hand structure

Type 1mdashWidth 5mmType 2mdashWidth 10mmType 3mdashWidth 20mm

BLDC motor used for elbow pronation and supination

BLDC motor used for palm flexion

BLDC motor used for palm radial and

ulnar deviation

Hand rest

and extension

Figure 10 Manufactured model of wrist joint

Specification of Perspex (TM) GS Acrylic Cast Sheet

Tensile strength 75000000Nm2

Density 1190Kgm3

Size of the Exoskeleton The size of the exoskeleton (approxi-mately 9673 cm) has been taken as per the standard length ofa human arm and it can be varied from person to person

Length of shoulder griddle 0129119867Length of upper arm 0186119867Length of forearm 0146119867Length of hand 0108119867

Here 119867 is defined as the height of the human arm and ifwe consider the height of a standard human as 170 cm thelength will be approximately 9673 cm Obviously the lengthof human arm is different from person to person But as wehave made a physical system we have taken the standardlength But the system has a provision so that it is wearable toall the people of variable arm lengthwhich has been discussedin the portion of mechanical model

4 Kinematic Analysis of Exorn

Kinematic model of Exorn is designed according to theanthropometric data of standard human arm The mechani-cal structure is such that it can align with human arm and canprovide the desirable joint motion Some mechanical barrieris located to restrict the joint from hyperextension Here theforward kinematics of the whole system is discussed whichprovides the end point position and orientation due to severaljointmotions It is basically acting as a seriesmanipulatorThekinematic relation of a manipulator is represented by = 119869 120579

Journal of Robotics 5

Elevation

Depression

Extension

Flexion

Abduction

Adduction

Flexion

Extension

Horizontal abduction

Horizontaladduction

Lateral

Medical rotation

Flexion

ExtensionSupination Pronation

Extension

Flexion

Ulnar deviation Radial deviation0

0

0

0

0

0

0 0

0

0

0∘

15∘

15∘

40∘ 180∘

180∘

135∘

20∘

20∘

20∘

45∘

45∘

60∘60∘

80∘

80∘

10∘

80∘ 90∘

140∘

Figure 11 Different motions of human arm

is the119898 dimensional vector specifying the task velocityof end effector 120579 is 119899 dimensional vector representing thejoint velocity 119869 is the119898 by 119899 Jacobianmatrix For a redundantmanipulator 119899 is always greater than 119898 Here the kinematicredundancy is 3

41 D-HParameter of the 3DModel To do kinematic analysisof the whole system it is essential to derive D-H parameterof the whole system The coordinate system of the wholestructure is shown in Figure 12 The coordinate structure ofthe exoskeleton system is based on 3D conceptual modelof Exorn D-H parameters of the structure are shown inTable 2 It is essential to calculate the position and orientationof the end point in 3D space with respect to the referencecoordinate

42 Transformation Matrix Generation For getting the posi-tion and orientation of the end point of Exorn systemhomogeneous transformation matrix is considered Eachhomogeneous transformation matrix was calculated for theposition and orientation of present frame with respect to theprevious frame It is a 4 times 4 matrix The column 119894minus1119889

119894is

position of the end point and 119894minus1119877119894is the orientation of end

point in 3D space The transformation matrix is 119894minus1119860119894

119894minus1119860119894= [

119894minus1119877119894

119894minus1

119889119894

0 1]

4times4

(1)

The homogeneous matrix is being explained as119894minus1119860119894= 119863119911119894minus1119889119894

lowast 119877119911119894minus1120579119894

lowast 119863119909119894minus1119886119894

lowast 119877119909119894minus1120572119894

=

[[[

[

cos 120579119894minus sin 120579

119894cos120572119894

sin 120579119894sin120572119894

119886119894cos 120579119894

sin 120579119894

cos 120579119894cos120572119894minus cos 120579

119894sin120572119894119886119894sin 120579119894

0 sin120572119894

cos120572119894

119889119894

0 0 0 1

]]]

]

119894minus1119889119894= [

[

119886119894cos 120579119894

119886119894sin 120579119894

119889119894

]

]

119894minus1119877119894= [

[

cos 120579119894minus sin 120579

119894cos120572119894

sin 120579119894sin120572119894

sin 120579119894

cos 120579119894cos120572119894minus cos 120579

119894sin120572119894

0 sin120572119894

cos120572119894

]

]

(2)

For calculating the homogeneous matrix due to 10 degrees offreedom the 10 homogeneous matrixes are been multipliedsequentially The final matrix is 119879 which is represented as

119879 =01198601times11198602times21198603times31198604times41198605sdot sdot sdot times911986010 (3)

The calculation can be made easy by dividing the totalmultiplication into two parts such that 119879 =

01198605times511986011 As

it is a 10 DOF system Finally 119879 matrix of the end point ofExorn is represented with respect to reference and its upper 3values of last column are position vector of end point relatedto world frame

6 Journal of Robotics

a1a2

a3

a4

a5

a7

d2

d3

d5

d6

d7

d8d9

d10

x1x2

x3

x4

x5

x6

x7

x8

x9x10

x11

y1

y2

y3y4

y6

y7

y8

y9

y10y11

z2

z3

z4z5

z6

z7

z8

z9

z10 z11

Figure 12 Coordinate system of 3D model

5 Simulation Model of Human Arm

A human armmodel is being made in Simulink to determinethe required torque to move a joint The length of upperarm lower arm and hand is considered according to theanthropometric data of standard human arm The inertiamatrix of each segment is determined according to the massof that segment and length of the centre of gravity fromthe proximal end as per Table 3 In Simulink it is possibleto provide motions in terms of velocity to joint actuatorand from the joint sensor torque level change is notedThe Simulink model of human arm is shown in Figure 13Maximum amount of torque is needed to move those jointswhich are in vertical direction Here only joint motionrelated to shoulder elbow and wrist flexion and extensionis considered Next those internal and external rotations are

Table 1 Comparative study between joints of human arm andExorn

Actuatornumber Movement Human joint

range (Deg)Exorn range

(deg)Shoulder griddle movements

Actuator 1 Elevation 40 30Depression 10 10

Actuator 2 Scapular abduction 20 20Scapular adduction 15 15

Shoulder joint movements

Actuator 3 Horizontal abduction 135 90Horizontal adduction 45 45

Actuator 4 Vertical abduction 180 160Vertical adduction 20 0

Actuator 5 Forward flexion 180 90Forward extension 60 60

Actuator 6 External rotation 90 90Internal rotation 20 20

Elbow joint movements

Actuator 7 Elbow flexion 140 120Elbow extension 0 0

Actuator 8 Forearm pronation 90 90Forearm supination 80 80

Wrist joint movements

Actuator 9 Palm radial deviation 15 10palm ulnar deviation 45 30

Actuator 10 Palm flexion 80 80Palm extension 80 80

Table 2 D-H parameter of Exorn

119886119894(cm) 120572

119894(deg) 119889

119894(cm) 120579

119894(deg)

10 90 0 Θ1

12 0 5 Θ2

6 90 2 Θ3

3 minus90 0 Θ4

31 0 minus25 Θ5

0 90 6 Θ6

3 0 35 Θ7

0 90 25 Θ8

0 minus90 4 Θ9

0 0 8 Θ10

being taken care of In exoskeleton system those motionscannot be controlled from the fixed end due to its twistingtypeTherefore the end effector should be rotatedwith respectto fixed end

The Simulink blocks used for making the human armmodel are shown in Figures 14 and 15 A joint actuator blockis connected to provide the actuation signal and joint sensorblock is attached to measure the computed torque In orderto make a joint with several DOFs several bodies of zeromass and zero length with actuator block of different axis of

Journal of Robotics 7

(a) (b)

Figure 13 (a) Simulink model of human hand (b) human hand position at zero position

Conn1Conn1

Conn1Conn1

Conn2 Conn2

Conn2

Conn2

Conn3

Conn3

Conn3

Conn4

Conn4Conn5

Out1

Out1

Out2

Out3

Out3Out2

Ground Weld Body2

To workspace

To workspace1

To workspace2

Subsystem

Subsystem3 Subsystem6 Subsystem9

Shoulder joint Elbow jointWrist joint

Display3 Display9 Display12

Finger

In1 out1 In1 out1 In1 out1

CS1 CS17

x

y

z

B F

Figure 14 Human arm model in Simulink

rotations are connected Here in Figure 15 body 1 and body2 have zero length and zero mass Only body 3 is the actualbody It is under every human arm joint Body sensor isattached at the end point to get points in 3D space at the timeof motion

6 Embedded System

A PC based control system is being developed to provideparticular orthopedic lesson First of all command signalfrom PC is transmitted to the master controller Mastercontroller activates those joints which are needed to achievethe desired motion It sends the command bits in a packagethrough serial communication Enable signal is being sent to

all the local controllers but only few are being activated as percommand with the help of multiprocessor communicationtechnique All the motor controllers are connected in adaisy chain network that means 119879

119909and 119877

119909pins of master

controller are connected to all 119877119909and 119879

119909pins of each

controller respectively Each controller has a particular nodeas an activating signal When the master controller sends theactivation signal the particular motor controller with thatparticular node is activated

The interfacing circuit between microcontroller andmotor driver is shown in Figures 16(a) and 16(b) Driver IChas 4 input pins and 2 enable pins Here all the inputs pins andenable pins are connecting to port 0 and port 1 Here all theenable pins are sorted and connected through one port pin

8 Journal of Robotics

CS1 CS15 CS1 CS15 CS1 CS15B F B FB F1

12

2

3

Conn2 Conn3Body1 Body2 Body3

Out1Out2 Out3

Signal2Signal2Signal2

Revolute1 Revolute2 Revolute3

Joint actuatorJoint actuator1 Joint actuator2Joint sensor1 Joint sensor2 Joint sensor3

Shoulder vertical motion Shoulder forward flexion Shoulder horizontal motion

Figure 15 Block diagram below each human joint

(a)

Junction circuit 1P89V51RD2 7805 IC

7805 IC Max232DB-9

DB-9

Local controller for DC motor

Local controller for BLDC motor

DC motor driver circuit

Junction circuit 2

7805 IC

IN 4007L298

(b)

Figure 16 (a) Schematic design of interfacing circuit between microcontroller and motor driver (b) Developed interfacing circuit ofmicrocontroller

In this case all the enable pins become activated at one timeSo the motion of motor can be controlled by changing driverinputsThose inputs are amplified from 5V to 12V to run themotor in clockwise and anticlockwise manner (Figure 17) Asshown in the figure one dedicated 7805 IC (Voltage regulator)is connected tomicrocontroller for 5V power supply A serialIC MAX232 is connected to the microcontroller to convert

the RS232rsquos signals to TTL voltage levels that is acceptable to8051 microcontroller 119879

119909and 119877

119909pins

A bidirectional H bridgeDC motor control circuit isshown in Figures 17(a) and 17(b) The circuit is based onthe IC L298 from ST Microelectronics L298 It is a dual fullbridge driver that has a wide operating voltage range andcan handle load currents up to 3A The IC also features low

Journal of Robotics 9

Out In

sum

sum

MT2

100120583F

1 120583F

1 120583F

10120583F

CN5

CN6

1K 1K

1K1K

L298

REF7805

D1

D2

D3

D4

D5

D6 D7

D8

D9D10

D11 D12

R1 R2

R3R4

C1

C2

C3C4

(a)

Motor driver L298

H bridge driver

Power supply

(b)

Figure 17 (a) Schematic design of motor driver circuit (b) Developed motor driver circuit

Table 3 Segment mass and lengths of human arm [8]

Segment Segment masstotal body mass Centre of masssegment length Radius of gyrationsegment lengthProximal Distal CM Proximal Distal

Hand 0006 0506 0494 0297 0587 0577Forearm 0016 0430 0570 0303 0526 0647Upperarm 0028 0436 0564 0322 0542 0645Forearm and Hand 0022 0682 0318 0468 0827 0565Total arm 0050 0530 0470 0368 0645 0596

saturation voltage and over temperature protection In thecircuit diodes D1 to D8 are protection diodesThe state of themotor depends on the logic level of the pins 5 6 and 7 and10 11 and 12 and it is described in the table shown below thecircuit diagram

The diodes D1 to D4 and D5 to D8 provide a safer pathfor the back emf from the motor to dissipate and thus itprotects the corresponding bipolar transistors from damageThe input pins from motor driver are being connected tothe microcontroller port pins When the enable pins of thedriver pin are active then the input signal of the motor driveris amplified to 12 volt and sent to the motor According tothe configuration of port pins motor moves in clockwise oranticlockwise direction

In case of BLDCmotor controller every controller has itsparticular node for distinguishing one from the other It ispossible to control the speed of the motor either by varyingthe voltage supplied to it or by sending the serial command toit The speed of the motor is controlled by sending a string ofcommand to the BLDCmotor controller serially Also there isan encoder inside the BLDCmotor for getting the angle valuesimultaneously in a feedback loop

All the supply voltages are being bypassed through thosejunction circuits Actually all voltage sources are being sortedA 7812 IC voltage regulator is used to convert the 24Vinto 12V DC supply When the diode connected in junctioncircuit is in forward bias it sends the power supply to alldriver circuits but in the opposite case current from driver

10 Journal of Robotics

No

Serial communication configuration

Command comes from PC

GUI open

Serial port start

Serial port configuration

Commands send to the BLDC controller

Interrupt control

Select direction

Select BLDC motor

Send command to motor

Serial portclose

Select speed

DC motor controller

Motor moves

Formation of command package

Can be applied for all motors

SBUF Move motor 1 clockwise

SBUF Move motor 1 anticlockwise

SBUF Move motor 1 stop

Yes

Yes

Yes

No

No

CWCC

= A

= B

= X

Figure 18 Flow chart for PC based control

circuit cannot be sent to the controller circuit The flow chart(Figure 18) is showing the logic behind the algorithm

7 Graphical User Interface Model of Exorn v1

A proper Graphical User Interface (Figure 19) has beendeveloped for controlling all the motions serially through PCbased system It is being designed in Microsoft visual studioplatformThewholeGUImodel is divided into four divisionsFirst one is the configuration of serial communication whereuser has to select the particular COM port and baud rateIt has two buttons for opening and closing of COM portAfter opening of COM port any command can be sent to

the serial portThere are three divisions regarding themotionof human joint for proper treatment Here only one controlcan be selected out of three options Selection of one optionwill freeze the others The flow chart behind the GUI modelis shown in Figure 20

71 Orthopedic Lessons There are some movements whichare generally prescribed by different doctors for strokepatients for different problems All the motions are stored inmemory After selecting somemotion the patient presses thestart button and a command will be sent through serially fortaking proper action It will be updated with time accordingto orthopedic doctor advice

Journal of Robotics 11

Figure 19 GUI model

Serial communication and

configuration

Orthopaedic lessonsIsolateral exercises Angle oriented control

M1

Select BAUD

Select COM port

SpeedCW

CC

M2 Speed CW

CC

SpeedCW

CC

Arm movement

Elbow movement

Forearm movement

Wrist movement

Elevation and depression of shoulder griddle

Scapular abduction and adduction of shoulder griddle

Horizontal abduction and adduction of shoulder joint

Flexion and extension of wrist

M10

Figure 20 Flow chart of GUI model

72 Isolateral Exercises In isolateral exercises there are somepredefined exercises which are standard motions of all jointsof human arm Patients can follow those exercises so that theirmuscle rigidity becomes less After each selection a commandis being sent serially to master controller Master controlleralways takes care of proper actions

73 Angle Oriented Control In this configuration each jointis controlled in clockwise or anticlockwise manner withdifferent speedMore than one joint can be governed throughitWhen user selects jointmotions then a frame of commandbit serially sends with a start and stop bit to distinguish

between different commands User has to write the requiredspeed beside the box of direction of rotation In case twomotions are contradictory then the controller does not allowthat motion It is already preprogrammed in the controller

8 Predefined Control System

It is a predefined control (Figure 21) Already a vast scheduleof exercise modules is to be loaded in the memory Whensomeone wants to perform a task it is being sent to thecontroller through a manual switch or PC Master controllerwill generate a reference trajectory for that particular task

12 Journal of Robotics

PCandGUI

Master controller

Local controller

1H bridge

circuitDriver L298

Feedback

Exorn joint 1

Local controller

10H bridge circuit

Driver L298

Feedback

Exorn joint 10

Inverse kinematics

Forward kinematics

1205751205791

12057512057910

120575x

x

xd

120579

12057910

1205791

jminus1

Figure 21 Independent joint control system

0 20 40 60 80 100

0

2

4

6

8

10

Time (s)

Torque versus time

minus2

minus4

Com

pute

d to

rque

(N-m

)

Figure 22 Joint torque graph at shoulder due to flexion andextension

Then it is being sent to the local controller which takes careof that particular trajectory Always there is feedback loopconnected between the system and the master controllerWith the help of resolved motion rate control (Whitney 72)approach each joint can be controlled in an independent wayAccording to forward kinematics the kinematic model can beexpressed using the equation

120575119909 = 119869 (120579) 120575120579 (4)

Outside the singularities the inverse kinematics can beexpressed as

120575120579 = 119869minus1(120579) 120575119909 (5)

0 20 40 60 80 100 120

0

05

1

15

2

25

minus05

minus1

minus15

minus2

Time (s)

Torque versus time

Com

pute

d to

rque

(N-m

)

Figure 23 Joint torque graph at elbow due to elbow flexion andextension

There is a relation between task space and joint space Herethe current position at some angle 120579 can be expressed as

119909 = 119891 (120579) (6)

The desired location in 3D space is defined as 119909119889 So error

between current and desired position can be expressed as

120575119909 = 119909119889minus 119909

120575120579 = 119869minus1(120579) 120575119909

(7)

The next 120579 will be expressed as 1205791015840 = 120579 + 120575120579 In this way 120579value can be increased or decreased in an iterative way so that

Journal of Robotics 13

0 10 20 30 40 50 60 70 80 90005

01

015

02

025

03

035

04

045

Time (s)

Torque versus time

Com

pute

d to

rque

(N-m

)

Figure 24 Joint torque graph at wrist due to flexion and extension

0 10 20 30 40 50 60

0

1

2

3

4

5

6

minus1

minus2

minus3

times10minus3

Time (s)

Torque versus time

Com

pute

d to

rque

(N-m

)

Figure 25 Joint torque graph at elbow due to shoulder internal andexternal rotation

the desired location can be reached The error betweendesired location and current location can be compared usingforward kinematics in a feedback loop

In case of finding inverse kinematics there is a problem ofsingularity So we are imposing damped least square methodfor calculating the inverse kinematics The damped leastsquares solutions are intended to ensure a well-conditionedmatrix for the solution algorithmwhile limiting the size of thesolution vector 120575120579 This is done by adding a diagonal matrix120572119868 to the matrix 119869119869119879 The approximate solution of dampedleast squares method can be expressed as 120575120579 = 119869

+120575119909 where

119869+ can be expressed as the equation given below

119869+= 119869119879(119869119869119879+ 120572119868)minus1

120572 ge 0 (8)

0 20 40 60 80 100 120

0

2

4

6

minus2

minus4

minus6

times10minus3

Time (s)

Torque versus time

Com

pute

d to

rque

(N-m

)

Figure 26 Joint torque graph at wrist due to elbow pronation andsupination

When this equation is used then the solution satisfies

min120575120579

120575119909 minus 1198691205751205792+ 12057221205751205792 (9)

where sdot denotes the Euclidean norm For 120572 = 0 the dampedleast squares solution will become pseudoinverse solutionThen the Jacobian inversematrix will be 119869lowast where 119869lowast becomeexpressed as 119869119879(119869119869119879)minus1

In the damped least squares method the size of errorin the task space is weighed against the size of the resultingsolution For a given 120575119909 the size of the solution vector isdecreased by increasing 120572 However this is done at theexpense of using an approximate solution As 120572 increases sodoes the size of the error in the task space A large 120572 hasthe other benefit of ensuring a well-conditioned matrix forinversion It has been shown that the condition number 119870of the matrix 119875 equiv (119869119869

119879+ 120572119868) is 119870 = (120590

2

1+ 120572)(120590

2

119898+ 120572)

Here 1205901ge 1205902ge 1205903sdot sdot sdot ge 120590

119898ge 0 are the singular values of

the Jacobian matrix It can be seen in this equation that 119870is made arbitrarily close to 1 by increasing 120572 thus ensuringa well-conditioned matrix for inversion even in a singularconfiguration where 120590

119898= 0 Simply stated if one is willing

to give up the exactness of the solution then the size of thejoint rate can be reduced and a well-conditioned matrix forinversion can be ensured by increasing 120572

9 Simulation Results of Torque Level ofGeneral Human Arm

Maximum amount of torque is required to actuate humanjoints in vertical direction Here in Figure 25 the torqueneeded to twist the elbow with respect to shoulder joint isshown Figure 26 is showing the same kind ofmotion in wrist

14 Journal of Robotics

0 200 400 600 800 1000 12000500

1000

0500

1000

minus500

minus1000

minus500

minus1000

(a)

20

20

0

0

minus20

minus20

minus40

minus40

40

minus60

minus60

minus80 500

minus50

x

y z

Untitled fit 1x versus z y

(b)

Figure 27 (a) Outer region covered by Exorn (b) Workspace covered by Exorn

0

minus10

minus20

minus30

minus40

minus5040

3020

100minus10

minus20 0 1020 30

40 5060

70

Figure 28 Motion due to shoulder griddle

006

004

002

0

minus0020

001

002

003

004

005002

0 minus002 minus004minus006 minus008

minus01

Figure 29 Motion due to shoulder griddle glenohumerals andelbow joint movement

joint with respect to the elbow Figures 22 23 24 25 and26 will show torque variation in different joints in verticaldirection because of proper actuation signal From thosebelow graphs max and min torque for joint actuator can bedetermined because it is very much essential to select propermotor

006

004

002

0

minus0020

minus002minus004

minus006minus008

minus010

002

004

006

008

Figure 30 Motion due to shoulder joint and elbow joint movementin vertical direction

003

002

001

0

minus001

minus002

minus0030 minus002 minus004 minus006 minus008 minus01

0

001

002

003

Figure 31 Motion due to glenohumeral joint and elbow jointmovement in horizontal direction

10 Workspace Calculation and Motion due toForward Kinematics

For calculating the workspace of the robotic system aMATLAB code of nested for loop of all DOFs is being takenwith the joint range It will plot all the reachable points ofarm exoskeleton in 3D space Figure 27 is showing the outer

Journal of Robotics 15

region covered by human hand Figures 28 29 30 and 31 areshowing themotion of exoskeletonmodel due to several jointmovements

11 Conclusion

From the above discussion it may be concluded that thedeveloped system is useful for rehabilitation Comparisonsbetween human jointrsquos range and that of Exorn are alreadytabulated in Table 1 and the ranges are quite the same for boththe cases If the portable mechanical structure is attached tothe human arm it can be used as an assistive device for theparalyzed people The 3D model of exoskeleton is alreadybeing developed The model has been fabricated With thehelp of the GUI all the motions can be controlled throughserial communication The developed prototype is underworking condition We would like to build the real system sothat patient can be benefitted

References

[1] J W Krakauer ldquoArm function after stroke from physiology torecoveryrdquo Seminars in Neurology vol 25 no 4 pp 384ndash3952005

[2] T Nef and R Riener ldquoARMinmdashdesign of a novel arm reha-bilitation robotrdquo in Proceedings of the IEEE 9th InternationalConference on Rehabilitation Robotics (ICORR rsquo05) pp 57ndash60July 2005

[3] S J Ball I E Brown and S H Scott ldquoMEDARM a rehabilita-tion robot with 5DOF at the shoulder complexrdquo in Proceedingsof the IEEEASME International Conference on Advanced Intel-ligent Mechatronics (AIM rsquo07) September 2007

[4] M Mistry P Mohajerian and S Schaal ldquoArm movementexperiments with joint space force fields using an exoskeletonrobotrdquo in Proceedings of the IEEE 9th International Conferenceon Rehabilitation Robotics (ICORR rsquo05) pp 408ndash413 July 2005

[5] A Schiele and F C T van der Helm ldquoKinematic design toimprove ergonomics in human machine interactionrdquo IEEETransactions on Neural System and Rehabilitation vol 14 no4 pp 1534ndash4320 2006

[6] S J Ball I E Brown and S H Scott ldquoA planar 3DOF roboticexoskeleton for rehabilitation and assessmentrdquo in Proceedingsof the 29th Annual International Conference of IEEE-EMBSEngineering in Medicine and Biology Society (EMBC rsquo07) pp4024ndash4027 August 2007

[7] I Sardellitti E Cattin S Roccella et al ldquoDescription char-acterization and assessment of a bio-inspired shoulder joint-first link robot for neuro-robotic applicationsrdquo in Proceedings ofthe 1st IEEERAS-EMBS International Conference on BiomedicalRobotics andBiomechatronics (BioRob rsquo06) pp 112ndash117 February2006

[8] Source-winter Biomechanics and Motor Control of HumanMotion ISBN-978-0470398180 2010

[9] C-J Yang B Niu J-F Zhang and Y Chen ldquoDifferent structurebased control system of the PUMA manipulator with an armexoskeletonrdquo in Proceedings of the IEEE Conference on RoboticsAutomation and Mechatronics pp 572ndash577 December 2004

[10] K Kiguchi T Tanaka K Watanabe and T Fukuda ldquoExoskele-ton for human upper-limb motion supportrdquo in Proceedings ofthe IEEE International Conference on Robotics and Automationpp 2206ndash2211 September 2003

[11] T H Massie and K J Salisbury ldquoPHANToM haptic interfacea device for probing virtual objectsrdquo in Proceedings of theInternational Mechanical Engineering Congress and Expositionpp 295ndash299 November 1994

[12] CCarignan andKCleary ldquoClosed-loop force control for hapticsimulation of virtual environmentsrdquo The Electronic Journal ofHaptics Research vol 2 no 2 pp 1ndash14 2000

[13] A Frisoli F Rocchi S Marcheschi A Dettori F Salsedo andM Bergamasco ldquoA new force-feedback arm exoskeleton forhaptic interaction in virtual environmentsrdquo in Proceedings ofthe First Joint Eurohaptics Conference and Symposium on HapticInterfaces for Virtual Environment and Teleoperator Systems pp195ndash201 2005

[14] D Lawrence ldquoImpedance control stability properties in com-mon implementationsrdquo in Proceedings of the IEEE InternationalConference on Robotics and Automation pp 1185ndash1190 1988

[15] A Nakai Y Kunii H Hashimoto and F Harashima ldquoArmtype haptic human interface sensor armrdquo in Proceedings of theInternational Conference on Artificial Reality and Tele-Existence(ICAT) pp 77ndash84 Tokyo Japan December 1997

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International Journal of

Journal of Robotics 5

Elevation

Depression

Extension

Flexion

Abduction

Adduction

Flexion

Extension

Horizontal abduction

Horizontaladduction

Lateral

Medical rotation

Flexion

ExtensionSupination Pronation

Extension

Flexion

Ulnar deviation Radial deviation0

0

0

0

0

0

0 0

0

0

0∘

15∘

15∘

40∘ 180∘

180∘

135∘

20∘

20∘

20∘

45∘

45∘

60∘60∘

80∘

80∘

10∘

80∘ 90∘

140∘

Figure 11 Different motions of human arm

is the119898 dimensional vector specifying the task velocityof end effector 120579 is 119899 dimensional vector representing thejoint velocity 119869 is the119898 by 119899 Jacobianmatrix For a redundantmanipulator 119899 is always greater than 119898 Here the kinematicredundancy is 3

41 D-HParameter of the 3DModel To do kinematic analysisof the whole system it is essential to derive D-H parameterof the whole system The coordinate system of the wholestructure is shown in Figure 12 The coordinate structure ofthe exoskeleton system is based on 3D conceptual modelof Exorn D-H parameters of the structure are shown inTable 2 It is essential to calculate the position and orientationof the end point in 3D space with respect to the referencecoordinate

42 Transformation Matrix Generation For getting the posi-tion and orientation of the end point of Exorn systemhomogeneous transformation matrix is considered Eachhomogeneous transformation matrix was calculated for theposition and orientation of present frame with respect to theprevious frame It is a 4 times 4 matrix The column 119894minus1119889

119894is

position of the end point and 119894minus1119877119894is the orientation of end

point in 3D space The transformation matrix is 119894minus1119860119894

119894minus1119860119894= [

119894minus1119877119894

119894minus1

119889119894

0 1]

4times4

(1)

The homogeneous matrix is being explained as119894minus1119860119894= 119863119911119894minus1119889119894

lowast 119877119911119894minus1120579119894

lowast 119863119909119894minus1119886119894

lowast 119877119909119894minus1120572119894

=

[[[

[

cos 120579119894minus sin 120579

119894cos120572119894

sin 120579119894sin120572119894

119886119894cos 120579119894

sin 120579119894

cos 120579119894cos120572119894minus cos 120579

119894sin120572119894119886119894sin 120579119894

0 sin120572119894

cos120572119894

119889119894

0 0 0 1

]]]

]

119894minus1119889119894= [

[

119886119894cos 120579119894

119886119894sin 120579119894

119889119894

]

]

119894minus1119877119894= [

[

cos 120579119894minus sin 120579

119894cos120572119894

sin 120579119894sin120572119894

sin 120579119894

cos 120579119894cos120572119894minus cos 120579

119894sin120572119894

0 sin120572119894

cos120572119894

]

]

(2)

For calculating the homogeneous matrix due to 10 degrees offreedom the 10 homogeneous matrixes are been multipliedsequentially The final matrix is 119879 which is represented as

119879 =01198601times11198602times21198603times31198604times41198605sdot sdot sdot times911986010 (3)

The calculation can be made easy by dividing the totalmultiplication into two parts such that 119879 =

01198605times511986011 As

it is a 10 DOF system Finally 119879 matrix of the end point ofExorn is represented with respect to reference and its upper 3values of last column are position vector of end point relatedto world frame

6 Journal of Robotics

a1a2

a3

a4

a5

a7

d2

d3

d5

d6

d7

d8d9

d10

x1x2

x3

x4

x5

x6

x7

x8

x9x10

x11

y1

y2

y3y4

y6

y7

y8

y9

y10y11

z2

z3

z4z5

z6

z7

z8

z9

z10 z11

Figure 12 Coordinate system of 3D model

5 Simulation Model of Human Arm

A human armmodel is being made in Simulink to determinethe required torque to move a joint The length of upperarm lower arm and hand is considered according to theanthropometric data of standard human arm The inertiamatrix of each segment is determined according to the massof that segment and length of the centre of gravity fromthe proximal end as per Table 3 In Simulink it is possibleto provide motions in terms of velocity to joint actuatorand from the joint sensor torque level change is notedThe Simulink model of human arm is shown in Figure 13Maximum amount of torque is needed to move those jointswhich are in vertical direction Here only joint motionrelated to shoulder elbow and wrist flexion and extensionis considered Next those internal and external rotations are

Table 1 Comparative study between joints of human arm andExorn

Actuatornumber Movement Human joint

range (Deg)Exorn range

(deg)Shoulder griddle movements

Actuator 1 Elevation 40 30Depression 10 10

Actuator 2 Scapular abduction 20 20Scapular adduction 15 15

Shoulder joint movements

Actuator 3 Horizontal abduction 135 90Horizontal adduction 45 45

Actuator 4 Vertical abduction 180 160Vertical adduction 20 0

Actuator 5 Forward flexion 180 90Forward extension 60 60

Actuator 6 External rotation 90 90Internal rotation 20 20

Elbow joint movements

Actuator 7 Elbow flexion 140 120Elbow extension 0 0

Actuator 8 Forearm pronation 90 90Forearm supination 80 80

Wrist joint movements

Actuator 9 Palm radial deviation 15 10palm ulnar deviation 45 30

Actuator 10 Palm flexion 80 80Palm extension 80 80

Table 2 D-H parameter of Exorn

119886119894(cm) 120572

119894(deg) 119889

119894(cm) 120579

119894(deg)

10 90 0 Θ1

12 0 5 Θ2

6 90 2 Θ3

3 minus90 0 Θ4

31 0 minus25 Θ5

0 90 6 Θ6

3 0 35 Θ7

0 90 25 Θ8

0 minus90 4 Θ9

0 0 8 Θ10

being taken care of In exoskeleton system those motionscannot be controlled from the fixed end due to its twistingtypeTherefore the end effector should be rotatedwith respectto fixed end

The Simulink blocks used for making the human armmodel are shown in Figures 14 and 15 A joint actuator blockis connected to provide the actuation signal and joint sensorblock is attached to measure the computed torque In orderto make a joint with several DOFs several bodies of zeromass and zero length with actuator block of different axis of

Journal of Robotics 7

(a) (b)

Figure 13 (a) Simulink model of human hand (b) human hand position at zero position

Conn1Conn1

Conn1Conn1

Conn2 Conn2

Conn2

Conn2

Conn3

Conn3

Conn3

Conn4

Conn4Conn5

Out1

Out1

Out2

Out3

Out3Out2

Ground Weld Body2

To workspace

To workspace1

To workspace2

Subsystem

Subsystem3 Subsystem6 Subsystem9

Shoulder joint Elbow jointWrist joint

Display3 Display9 Display12

Finger

In1 out1 In1 out1 In1 out1

CS1 CS17

x

y

z

B F

Figure 14 Human arm model in Simulink

rotations are connected Here in Figure 15 body 1 and body2 have zero length and zero mass Only body 3 is the actualbody It is under every human arm joint Body sensor isattached at the end point to get points in 3D space at the timeof motion

6 Embedded System

A PC based control system is being developed to provideparticular orthopedic lesson First of all command signalfrom PC is transmitted to the master controller Mastercontroller activates those joints which are needed to achievethe desired motion It sends the command bits in a packagethrough serial communication Enable signal is being sent to

all the local controllers but only few are being activated as percommand with the help of multiprocessor communicationtechnique All the motor controllers are connected in adaisy chain network that means 119879

119909and 119877

119909pins of master

controller are connected to all 119877119909and 119879

119909pins of each

controller respectively Each controller has a particular nodeas an activating signal When the master controller sends theactivation signal the particular motor controller with thatparticular node is activated

The interfacing circuit between microcontroller andmotor driver is shown in Figures 16(a) and 16(b) Driver IChas 4 input pins and 2 enable pins Here all the inputs pins andenable pins are connecting to port 0 and port 1 Here all theenable pins are sorted and connected through one port pin

8 Journal of Robotics

CS1 CS15 CS1 CS15 CS1 CS15B F B FB F1

12

2

3

Conn2 Conn3Body1 Body2 Body3

Out1Out2 Out3

Signal2Signal2Signal2

Revolute1 Revolute2 Revolute3

Joint actuatorJoint actuator1 Joint actuator2Joint sensor1 Joint sensor2 Joint sensor3

Shoulder vertical motion Shoulder forward flexion Shoulder horizontal motion

Figure 15 Block diagram below each human joint

(a)

Junction circuit 1P89V51RD2 7805 IC

7805 IC Max232DB-9

DB-9

Local controller for DC motor

Local controller for BLDC motor

DC motor driver circuit

Junction circuit 2

7805 IC

IN 4007L298

(b)

Figure 16 (a) Schematic design of interfacing circuit between microcontroller and motor driver (b) Developed interfacing circuit ofmicrocontroller

In this case all the enable pins become activated at one timeSo the motion of motor can be controlled by changing driverinputsThose inputs are amplified from 5V to 12V to run themotor in clockwise and anticlockwise manner (Figure 17) Asshown in the figure one dedicated 7805 IC (Voltage regulator)is connected tomicrocontroller for 5V power supply A serialIC MAX232 is connected to the microcontroller to convert

the RS232rsquos signals to TTL voltage levels that is acceptable to8051 microcontroller 119879

119909and 119877

119909pins

A bidirectional H bridgeDC motor control circuit isshown in Figures 17(a) and 17(b) The circuit is based onthe IC L298 from ST Microelectronics L298 It is a dual fullbridge driver that has a wide operating voltage range andcan handle load currents up to 3A The IC also features low

Journal of Robotics 9

Out In

sum

sum

MT2

100120583F

1 120583F

1 120583F

10120583F

CN5

CN6

1K 1K

1K1K

L298

REF7805

D1

D2

D3

D4

D5

D6 D7

D8

D9D10

D11 D12

R1 R2

R3R4

C1

C2

C3C4

(a)

Motor driver L298

H bridge driver

Power supply

(b)

Figure 17 (a) Schematic design of motor driver circuit (b) Developed motor driver circuit

Table 3 Segment mass and lengths of human arm [8]

Segment Segment masstotal body mass Centre of masssegment length Radius of gyrationsegment lengthProximal Distal CM Proximal Distal

Hand 0006 0506 0494 0297 0587 0577Forearm 0016 0430 0570 0303 0526 0647Upperarm 0028 0436 0564 0322 0542 0645Forearm and Hand 0022 0682 0318 0468 0827 0565Total arm 0050 0530 0470 0368 0645 0596

saturation voltage and over temperature protection In thecircuit diodes D1 to D8 are protection diodesThe state of themotor depends on the logic level of the pins 5 6 and 7 and10 11 and 12 and it is described in the table shown below thecircuit diagram

The diodes D1 to D4 and D5 to D8 provide a safer pathfor the back emf from the motor to dissipate and thus itprotects the corresponding bipolar transistors from damageThe input pins from motor driver are being connected tothe microcontroller port pins When the enable pins of thedriver pin are active then the input signal of the motor driveris amplified to 12 volt and sent to the motor According tothe configuration of port pins motor moves in clockwise oranticlockwise direction

In case of BLDCmotor controller every controller has itsparticular node for distinguishing one from the other It ispossible to control the speed of the motor either by varyingthe voltage supplied to it or by sending the serial command toit The speed of the motor is controlled by sending a string ofcommand to the BLDCmotor controller serially Also there isan encoder inside the BLDCmotor for getting the angle valuesimultaneously in a feedback loop

All the supply voltages are being bypassed through thosejunction circuits Actually all voltage sources are being sortedA 7812 IC voltage regulator is used to convert the 24Vinto 12V DC supply When the diode connected in junctioncircuit is in forward bias it sends the power supply to alldriver circuits but in the opposite case current from driver

10 Journal of Robotics

No

Serial communication configuration

Command comes from PC

GUI open

Serial port start

Serial port configuration

Commands send to the BLDC controller

Interrupt control

Select direction

Select BLDC motor

Send command to motor

Serial portclose

Select speed

DC motor controller

Motor moves

Formation of command package

Can be applied for all motors

SBUF Move motor 1 clockwise

SBUF Move motor 1 anticlockwise

SBUF Move motor 1 stop

Yes

Yes

Yes

No

No

CWCC

= A

= B

= X

Figure 18 Flow chart for PC based control

circuit cannot be sent to the controller circuit The flow chart(Figure 18) is showing the logic behind the algorithm

7 Graphical User Interface Model of Exorn v1

A proper Graphical User Interface (Figure 19) has beendeveloped for controlling all the motions serially through PCbased system It is being designed in Microsoft visual studioplatformThewholeGUImodel is divided into four divisionsFirst one is the configuration of serial communication whereuser has to select the particular COM port and baud rateIt has two buttons for opening and closing of COM portAfter opening of COM port any command can be sent to

the serial portThere are three divisions regarding themotionof human joint for proper treatment Here only one controlcan be selected out of three options Selection of one optionwill freeze the others The flow chart behind the GUI modelis shown in Figure 20

71 Orthopedic Lessons There are some movements whichare generally prescribed by different doctors for strokepatients for different problems All the motions are stored inmemory After selecting somemotion the patient presses thestart button and a command will be sent through serially fortaking proper action It will be updated with time accordingto orthopedic doctor advice

Journal of Robotics 11

Figure 19 GUI model

Serial communication and

configuration

Orthopaedic lessonsIsolateral exercises Angle oriented control

M1

Select BAUD

Select COM port

SpeedCW

CC

M2 Speed CW

CC

SpeedCW

CC

Arm movement

Elbow movement

Forearm movement

Wrist movement

Elevation and depression of shoulder griddle

Scapular abduction and adduction of shoulder griddle

Horizontal abduction and adduction of shoulder joint

Flexion and extension of wrist

M10

Figure 20 Flow chart of GUI model

72 Isolateral Exercises In isolateral exercises there are somepredefined exercises which are standard motions of all jointsof human arm Patients can follow those exercises so that theirmuscle rigidity becomes less After each selection a commandis being sent serially to master controller Master controlleralways takes care of proper actions

73 Angle Oriented Control In this configuration each jointis controlled in clockwise or anticlockwise manner withdifferent speedMore than one joint can be governed throughitWhen user selects jointmotions then a frame of commandbit serially sends with a start and stop bit to distinguish

between different commands User has to write the requiredspeed beside the box of direction of rotation In case twomotions are contradictory then the controller does not allowthat motion It is already preprogrammed in the controller

8 Predefined Control System

It is a predefined control (Figure 21) Already a vast scheduleof exercise modules is to be loaded in the memory Whensomeone wants to perform a task it is being sent to thecontroller through a manual switch or PC Master controllerwill generate a reference trajectory for that particular task

12 Journal of Robotics

PCandGUI

Master controller

Local controller

1H bridge

circuitDriver L298

Feedback

Exorn joint 1

Local controller

10H bridge circuit

Driver L298

Feedback

Exorn joint 10

Inverse kinematics

Forward kinematics

1205751205791

12057512057910

120575x

x

xd

120579

12057910

1205791

jminus1

Figure 21 Independent joint control system

0 20 40 60 80 100

0

2

4

6

8

10

Time (s)

Torque versus time

minus2

minus4

Com

pute

d to

rque

(N-m

)

Figure 22 Joint torque graph at shoulder due to flexion andextension

Then it is being sent to the local controller which takes careof that particular trajectory Always there is feedback loopconnected between the system and the master controllerWith the help of resolved motion rate control (Whitney 72)approach each joint can be controlled in an independent wayAccording to forward kinematics the kinematic model can beexpressed using the equation

120575119909 = 119869 (120579) 120575120579 (4)

Outside the singularities the inverse kinematics can beexpressed as

120575120579 = 119869minus1(120579) 120575119909 (5)

0 20 40 60 80 100 120

0

05

1

15

2

25

minus05

minus1

minus15

minus2

Time (s)

Torque versus time

Com

pute

d to

rque

(N-m

)

Figure 23 Joint torque graph at elbow due to elbow flexion andextension

There is a relation between task space and joint space Herethe current position at some angle 120579 can be expressed as

119909 = 119891 (120579) (6)

The desired location in 3D space is defined as 119909119889 So error

between current and desired position can be expressed as

120575119909 = 119909119889minus 119909

120575120579 = 119869minus1(120579) 120575119909

(7)

The next 120579 will be expressed as 1205791015840 = 120579 + 120575120579 In this way 120579value can be increased or decreased in an iterative way so that

Journal of Robotics 13

0 10 20 30 40 50 60 70 80 90005

01

015

02

025

03

035

04

045

Time (s)

Torque versus time

Com

pute

d to

rque

(N-m

)

Figure 24 Joint torque graph at wrist due to flexion and extension

0 10 20 30 40 50 60

0

1

2

3

4

5

6

minus1

minus2

minus3

times10minus3

Time (s)

Torque versus time

Com

pute

d to

rque

(N-m

)

Figure 25 Joint torque graph at elbow due to shoulder internal andexternal rotation

the desired location can be reached The error betweendesired location and current location can be compared usingforward kinematics in a feedback loop

In case of finding inverse kinematics there is a problem ofsingularity So we are imposing damped least square methodfor calculating the inverse kinematics The damped leastsquares solutions are intended to ensure a well-conditionedmatrix for the solution algorithmwhile limiting the size of thesolution vector 120575120579 This is done by adding a diagonal matrix120572119868 to the matrix 119869119869119879 The approximate solution of dampedleast squares method can be expressed as 120575120579 = 119869

+120575119909 where

119869+ can be expressed as the equation given below

119869+= 119869119879(119869119869119879+ 120572119868)minus1

120572 ge 0 (8)

0 20 40 60 80 100 120

0

2

4

6

minus2

minus4

minus6

times10minus3

Time (s)

Torque versus time

Com

pute

d to

rque

(N-m

)

Figure 26 Joint torque graph at wrist due to elbow pronation andsupination

When this equation is used then the solution satisfies

min120575120579

120575119909 minus 1198691205751205792+ 12057221205751205792 (9)

where sdot denotes the Euclidean norm For 120572 = 0 the dampedleast squares solution will become pseudoinverse solutionThen the Jacobian inversematrix will be 119869lowast where 119869lowast becomeexpressed as 119869119879(119869119869119879)minus1

In the damped least squares method the size of errorin the task space is weighed against the size of the resultingsolution For a given 120575119909 the size of the solution vector isdecreased by increasing 120572 However this is done at theexpense of using an approximate solution As 120572 increases sodoes the size of the error in the task space A large 120572 hasthe other benefit of ensuring a well-conditioned matrix forinversion It has been shown that the condition number 119870of the matrix 119875 equiv (119869119869

119879+ 120572119868) is 119870 = (120590

2

1+ 120572)(120590

2

119898+ 120572)

Here 1205901ge 1205902ge 1205903sdot sdot sdot ge 120590

119898ge 0 are the singular values of

the Jacobian matrix It can be seen in this equation that 119870is made arbitrarily close to 1 by increasing 120572 thus ensuringa well-conditioned matrix for inversion even in a singularconfiguration where 120590

119898= 0 Simply stated if one is willing

to give up the exactness of the solution then the size of thejoint rate can be reduced and a well-conditioned matrix forinversion can be ensured by increasing 120572

9 Simulation Results of Torque Level ofGeneral Human Arm

Maximum amount of torque is required to actuate humanjoints in vertical direction Here in Figure 25 the torqueneeded to twist the elbow with respect to shoulder joint isshown Figure 26 is showing the same kind ofmotion in wrist

14 Journal of Robotics

0 200 400 600 800 1000 12000500

1000

0500

1000

minus500

minus1000

minus500

minus1000

(a)

20

20

0

0

minus20

minus20

minus40

minus40

40

minus60

minus60

minus80 500

minus50

x

y z

Untitled fit 1x versus z y

(b)

Figure 27 (a) Outer region covered by Exorn (b) Workspace covered by Exorn

0

minus10

minus20

minus30

minus40

minus5040

3020

100minus10

minus20 0 1020 30

40 5060

70

Figure 28 Motion due to shoulder griddle

006

004

002

0

minus0020

001

002

003

004

005002

0 minus002 minus004minus006 minus008

minus01

Figure 29 Motion due to shoulder griddle glenohumerals andelbow joint movement

joint with respect to the elbow Figures 22 23 24 25 and26 will show torque variation in different joints in verticaldirection because of proper actuation signal From thosebelow graphs max and min torque for joint actuator can bedetermined because it is very much essential to select propermotor

006

004

002

0

minus0020

minus002minus004

minus006minus008

minus010

002

004

006

008

Figure 30 Motion due to shoulder joint and elbow joint movementin vertical direction

003

002

001

0

minus001

minus002

minus0030 minus002 minus004 minus006 minus008 minus01

0

001

002

003

Figure 31 Motion due to glenohumeral joint and elbow jointmovement in horizontal direction

10 Workspace Calculation and Motion due toForward Kinematics

For calculating the workspace of the robotic system aMATLAB code of nested for loop of all DOFs is being takenwith the joint range It will plot all the reachable points ofarm exoskeleton in 3D space Figure 27 is showing the outer

Journal of Robotics 15

region covered by human hand Figures 28 29 30 and 31 areshowing themotion of exoskeletonmodel due to several jointmovements

11 Conclusion

From the above discussion it may be concluded that thedeveloped system is useful for rehabilitation Comparisonsbetween human jointrsquos range and that of Exorn are alreadytabulated in Table 1 and the ranges are quite the same for boththe cases If the portable mechanical structure is attached tothe human arm it can be used as an assistive device for theparalyzed people The 3D model of exoskeleton is alreadybeing developed The model has been fabricated With thehelp of the GUI all the motions can be controlled throughserial communication The developed prototype is underworking condition We would like to build the real system sothat patient can be benefitted

References

[1] J W Krakauer ldquoArm function after stroke from physiology torecoveryrdquo Seminars in Neurology vol 25 no 4 pp 384ndash3952005

[2] T Nef and R Riener ldquoARMinmdashdesign of a novel arm reha-bilitation robotrdquo in Proceedings of the IEEE 9th InternationalConference on Rehabilitation Robotics (ICORR rsquo05) pp 57ndash60July 2005

[3] S J Ball I E Brown and S H Scott ldquoMEDARM a rehabilita-tion robot with 5DOF at the shoulder complexrdquo in Proceedingsof the IEEEASME International Conference on Advanced Intel-ligent Mechatronics (AIM rsquo07) September 2007

[4] M Mistry P Mohajerian and S Schaal ldquoArm movementexperiments with joint space force fields using an exoskeletonrobotrdquo in Proceedings of the IEEE 9th International Conferenceon Rehabilitation Robotics (ICORR rsquo05) pp 408ndash413 July 2005

[5] A Schiele and F C T van der Helm ldquoKinematic design toimprove ergonomics in human machine interactionrdquo IEEETransactions on Neural System and Rehabilitation vol 14 no4 pp 1534ndash4320 2006

[6] S J Ball I E Brown and S H Scott ldquoA planar 3DOF roboticexoskeleton for rehabilitation and assessmentrdquo in Proceedingsof the 29th Annual International Conference of IEEE-EMBSEngineering in Medicine and Biology Society (EMBC rsquo07) pp4024ndash4027 August 2007

[7] I Sardellitti E Cattin S Roccella et al ldquoDescription char-acterization and assessment of a bio-inspired shoulder joint-first link robot for neuro-robotic applicationsrdquo in Proceedings ofthe 1st IEEERAS-EMBS International Conference on BiomedicalRobotics andBiomechatronics (BioRob rsquo06) pp 112ndash117 February2006

[8] Source-winter Biomechanics and Motor Control of HumanMotion ISBN-978-0470398180 2010

[9] C-J Yang B Niu J-F Zhang and Y Chen ldquoDifferent structurebased control system of the PUMA manipulator with an armexoskeletonrdquo in Proceedings of the IEEE Conference on RoboticsAutomation and Mechatronics pp 572ndash577 December 2004

[10] K Kiguchi T Tanaka K Watanabe and T Fukuda ldquoExoskele-ton for human upper-limb motion supportrdquo in Proceedings ofthe IEEE International Conference on Robotics and Automationpp 2206ndash2211 September 2003

[11] T H Massie and K J Salisbury ldquoPHANToM haptic interfacea device for probing virtual objectsrdquo in Proceedings of theInternational Mechanical Engineering Congress and Expositionpp 295ndash299 November 1994

[12] CCarignan andKCleary ldquoClosed-loop force control for hapticsimulation of virtual environmentsrdquo The Electronic Journal ofHaptics Research vol 2 no 2 pp 1ndash14 2000

[13] A Frisoli F Rocchi S Marcheschi A Dettori F Salsedo andM Bergamasco ldquoA new force-feedback arm exoskeleton forhaptic interaction in virtual environmentsrdquo in Proceedings ofthe First Joint Eurohaptics Conference and Symposium on HapticInterfaces for Virtual Environment and Teleoperator Systems pp195ndash201 2005

[14] D Lawrence ldquoImpedance control stability properties in com-mon implementationsrdquo in Proceedings of the IEEE InternationalConference on Robotics and Automation pp 1185ndash1190 1988

[15] A Nakai Y Kunii H Hashimoto and F Harashima ldquoArmtype haptic human interface sensor armrdquo in Proceedings of theInternational Conference on Artificial Reality and Tele-Existence(ICAT) pp 77ndash84 Tokyo Japan December 1997

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International Journal of

6 Journal of Robotics

a1a2

a3

a4

a5

a7

d2

d3

d5

d6

d7

d8d9

d10

x1x2

x3

x4

x5

x6

x7

x8

x9x10

x11

y1

y2

y3y4

y6

y7

y8

y9

y10y11

z2

z3

z4z5

z6

z7

z8

z9

z10 z11

Figure 12 Coordinate system of 3D model

5 Simulation Model of Human Arm

A human armmodel is being made in Simulink to determinethe required torque to move a joint The length of upperarm lower arm and hand is considered according to theanthropometric data of standard human arm The inertiamatrix of each segment is determined according to the massof that segment and length of the centre of gravity fromthe proximal end as per Table 3 In Simulink it is possibleto provide motions in terms of velocity to joint actuatorand from the joint sensor torque level change is notedThe Simulink model of human arm is shown in Figure 13Maximum amount of torque is needed to move those jointswhich are in vertical direction Here only joint motionrelated to shoulder elbow and wrist flexion and extensionis considered Next those internal and external rotations are

Table 1 Comparative study between joints of human arm andExorn

Actuatornumber Movement Human joint

range (Deg)Exorn range

(deg)Shoulder griddle movements

Actuator 1 Elevation 40 30Depression 10 10

Actuator 2 Scapular abduction 20 20Scapular adduction 15 15

Shoulder joint movements

Actuator 3 Horizontal abduction 135 90Horizontal adduction 45 45

Actuator 4 Vertical abduction 180 160Vertical adduction 20 0

Actuator 5 Forward flexion 180 90Forward extension 60 60

Actuator 6 External rotation 90 90Internal rotation 20 20

Elbow joint movements

Actuator 7 Elbow flexion 140 120Elbow extension 0 0

Actuator 8 Forearm pronation 90 90Forearm supination 80 80

Wrist joint movements

Actuator 9 Palm radial deviation 15 10palm ulnar deviation 45 30

Actuator 10 Palm flexion 80 80Palm extension 80 80

Table 2 D-H parameter of Exorn

119886119894(cm) 120572

119894(deg) 119889

119894(cm) 120579

119894(deg)

10 90 0 Θ1

12 0 5 Θ2

6 90 2 Θ3

3 minus90 0 Θ4

31 0 minus25 Θ5

0 90 6 Θ6

3 0 35 Θ7

0 90 25 Θ8

0 minus90 4 Θ9

0 0 8 Θ10

being taken care of In exoskeleton system those motionscannot be controlled from the fixed end due to its twistingtypeTherefore the end effector should be rotatedwith respectto fixed end

The Simulink blocks used for making the human armmodel are shown in Figures 14 and 15 A joint actuator blockis connected to provide the actuation signal and joint sensorblock is attached to measure the computed torque In orderto make a joint with several DOFs several bodies of zeromass and zero length with actuator block of different axis of

Journal of Robotics 7

(a) (b)

Figure 13 (a) Simulink model of human hand (b) human hand position at zero position

Conn1Conn1

Conn1Conn1

Conn2 Conn2

Conn2

Conn2

Conn3

Conn3

Conn3

Conn4

Conn4Conn5

Out1

Out1

Out2

Out3

Out3Out2

Ground Weld Body2

To workspace

To workspace1

To workspace2

Subsystem

Subsystem3 Subsystem6 Subsystem9

Shoulder joint Elbow jointWrist joint

Display3 Display9 Display12

Finger

In1 out1 In1 out1 In1 out1

CS1 CS17

x

y

z

B F

Figure 14 Human arm model in Simulink

rotations are connected Here in Figure 15 body 1 and body2 have zero length and zero mass Only body 3 is the actualbody It is under every human arm joint Body sensor isattached at the end point to get points in 3D space at the timeof motion

6 Embedded System

A PC based control system is being developed to provideparticular orthopedic lesson First of all command signalfrom PC is transmitted to the master controller Mastercontroller activates those joints which are needed to achievethe desired motion It sends the command bits in a packagethrough serial communication Enable signal is being sent to

all the local controllers but only few are being activated as percommand with the help of multiprocessor communicationtechnique All the motor controllers are connected in adaisy chain network that means 119879

119909and 119877

119909pins of master

controller are connected to all 119877119909and 119879

119909pins of each

controller respectively Each controller has a particular nodeas an activating signal When the master controller sends theactivation signal the particular motor controller with thatparticular node is activated

The interfacing circuit between microcontroller andmotor driver is shown in Figures 16(a) and 16(b) Driver IChas 4 input pins and 2 enable pins Here all the inputs pins andenable pins are connecting to port 0 and port 1 Here all theenable pins are sorted and connected through one port pin

8 Journal of Robotics

CS1 CS15 CS1 CS15 CS1 CS15B F B FB F1

12

2

3

Conn2 Conn3Body1 Body2 Body3

Out1Out2 Out3

Signal2Signal2Signal2

Revolute1 Revolute2 Revolute3

Joint actuatorJoint actuator1 Joint actuator2Joint sensor1 Joint sensor2 Joint sensor3

Shoulder vertical motion Shoulder forward flexion Shoulder horizontal motion

Figure 15 Block diagram below each human joint

(a)

Junction circuit 1P89V51RD2 7805 IC

7805 IC Max232DB-9

DB-9

Local controller for DC motor

Local controller for BLDC motor

DC motor driver circuit

Junction circuit 2

7805 IC

IN 4007L298

(b)

Figure 16 (a) Schematic design of interfacing circuit between microcontroller and motor driver (b) Developed interfacing circuit ofmicrocontroller

In this case all the enable pins become activated at one timeSo the motion of motor can be controlled by changing driverinputsThose inputs are amplified from 5V to 12V to run themotor in clockwise and anticlockwise manner (Figure 17) Asshown in the figure one dedicated 7805 IC (Voltage regulator)is connected tomicrocontroller for 5V power supply A serialIC MAX232 is connected to the microcontroller to convert

the RS232rsquos signals to TTL voltage levels that is acceptable to8051 microcontroller 119879

119909and 119877

119909pins

A bidirectional H bridgeDC motor control circuit isshown in Figures 17(a) and 17(b) The circuit is based onthe IC L298 from ST Microelectronics L298 It is a dual fullbridge driver that has a wide operating voltage range andcan handle load currents up to 3A The IC also features low

Journal of Robotics 9

Out In

sum

sum

MT2

100120583F

1 120583F

1 120583F

10120583F

CN5

CN6

1K 1K

1K1K

L298

REF7805

D1

D2

D3

D4

D5

D6 D7

D8

D9D10

D11 D12

R1 R2

R3R4

C1

C2

C3C4

(a)

Motor driver L298

H bridge driver

Power supply

(b)

Figure 17 (a) Schematic design of motor driver circuit (b) Developed motor driver circuit

Table 3 Segment mass and lengths of human arm [8]

Segment Segment masstotal body mass Centre of masssegment length Radius of gyrationsegment lengthProximal Distal CM Proximal Distal

Hand 0006 0506 0494 0297 0587 0577Forearm 0016 0430 0570 0303 0526 0647Upperarm 0028 0436 0564 0322 0542 0645Forearm and Hand 0022 0682 0318 0468 0827 0565Total arm 0050 0530 0470 0368 0645 0596

saturation voltage and over temperature protection In thecircuit diodes D1 to D8 are protection diodesThe state of themotor depends on the logic level of the pins 5 6 and 7 and10 11 and 12 and it is described in the table shown below thecircuit diagram

The diodes D1 to D4 and D5 to D8 provide a safer pathfor the back emf from the motor to dissipate and thus itprotects the corresponding bipolar transistors from damageThe input pins from motor driver are being connected tothe microcontroller port pins When the enable pins of thedriver pin are active then the input signal of the motor driveris amplified to 12 volt and sent to the motor According tothe configuration of port pins motor moves in clockwise oranticlockwise direction

In case of BLDCmotor controller every controller has itsparticular node for distinguishing one from the other It ispossible to control the speed of the motor either by varyingthe voltage supplied to it or by sending the serial command toit The speed of the motor is controlled by sending a string ofcommand to the BLDCmotor controller serially Also there isan encoder inside the BLDCmotor for getting the angle valuesimultaneously in a feedback loop

All the supply voltages are being bypassed through thosejunction circuits Actually all voltage sources are being sortedA 7812 IC voltage regulator is used to convert the 24Vinto 12V DC supply When the diode connected in junctioncircuit is in forward bias it sends the power supply to alldriver circuits but in the opposite case current from driver

10 Journal of Robotics

No

Serial communication configuration

Command comes from PC

GUI open

Serial port start

Serial port configuration

Commands send to the BLDC controller

Interrupt control

Select direction

Select BLDC motor

Send command to motor

Serial portclose

Select speed

DC motor controller

Motor moves

Formation of command package

Can be applied for all motors

SBUF Move motor 1 clockwise

SBUF Move motor 1 anticlockwise

SBUF Move motor 1 stop

Yes

Yes

Yes

No

No

CWCC

= A

= B

= X

Figure 18 Flow chart for PC based control

circuit cannot be sent to the controller circuit The flow chart(Figure 18) is showing the logic behind the algorithm

7 Graphical User Interface Model of Exorn v1

A proper Graphical User Interface (Figure 19) has beendeveloped for controlling all the motions serially through PCbased system It is being designed in Microsoft visual studioplatformThewholeGUImodel is divided into four divisionsFirst one is the configuration of serial communication whereuser has to select the particular COM port and baud rateIt has two buttons for opening and closing of COM portAfter opening of COM port any command can be sent to

the serial portThere are three divisions regarding themotionof human joint for proper treatment Here only one controlcan be selected out of three options Selection of one optionwill freeze the others The flow chart behind the GUI modelis shown in Figure 20

71 Orthopedic Lessons There are some movements whichare generally prescribed by different doctors for strokepatients for different problems All the motions are stored inmemory After selecting somemotion the patient presses thestart button and a command will be sent through serially fortaking proper action It will be updated with time accordingto orthopedic doctor advice

Journal of Robotics 11

Figure 19 GUI model

Serial communication and

configuration

Orthopaedic lessonsIsolateral exercises Angle oriented control

M1

Select BAUD

Select COM port

SpeedCW

CC

M2 Speed CW

CC

SpeedCW

CC

Arm movement

Elbow movement

Forearm movement

Wrist movement

Elevation and depression of shoulder griddle

Scapular abduction and adduction of shoulder griddle

Horizontal abduction and adduction of shoulder joint

Flexion and extension of wrist

M10

Figure 20 Flow chart of GUI model

72 Isolateral Exercises In isolateral exercises there are somepredefined exercises which are standard motions of all jointsof human arm Patients can follow those exercises so that theirmuscle rigidity becomes less After each selection a commandis being sent serially to master controller Master controlleralways takes care of proper actions

73 Angle Oriented Control In this configuration each jointis controlled in clockwise or anticlockwise manner withdifferent speedMore than one joint can be governed throughitWhen user selects jointmotions then a frame of commandbit serially sends with a start and stop bit to distinguish

between different commands User has to write the requiredspeed beside the box of direction of rotation In case twomotions are contradictory then the controller does not allowthat motion It is already preprogrammed in the controller

8 Predefined Control System

It is a predefined control (Figure 21) Already a vast scheduleof exercise modules is to be loaded in the memory Whensomeone wants to perform a task it is being sent to thecontroller through a manual switch or PC Master controllerwill generate a reference trajectory for that particular task

12 Journal of Robotics

PCandGUI

Master controller

Local controller

1H bridge

circuitDriver L298

Feedback

Exorn joint 1

Local controller

10H bridge circuit

Driver L298

Feedback

Exorn joint 10

Inverse kinematics

Forward kinematics

1205751205791

12057512057910

120575x

x

xd

120579

12057910

1205791

jminus1

Figure 21 Independent joint control system

0 20 40 60 80 100

0

2

4

6

8

10

Time (s)

Torque versus time

minus2

minus4

Com

pute

d to

rque

(N-m

)

Figure 22 Joint torque graph at shoulder due to flexion andextension

Then it is being sent to the local controller which takes careof that particular trajectory Always there is feedback loopconnected between the system and the master controllerWith the help of resolved motion rate control (Whitney 72)approach each joint can be controlled in an independent wayAccording to forward kinematics the kinematic model can beexpressed using the equation

120575119909 = 119869 (120579) 120575120579 (4)

Outside the singularities the inverse kinematics can beexpressed as

120575120579 = 119869minus1(120579) 120575119909 (5)

0 20 40 60 80 100 120

0

05

1

15

2

25

minus05

minus1

minus15

minus2

Time (s)

Torque versus time

Com

pute

d to

rque

(N-m

)

Figure 23 Joint torque graph at elbow due to elbow flexion andextension

There is a relation between task space and joint space Herethe current position at some angle 120579 can be expressed as

119909 = 119891 (120579) (6)

The desired location in 3D space is defined as 119909119889 So error

between current and desired position can be expressed as

120575119909 = 119909119889minus 119909

120575120579 = 119869minus1(120579) 120575119909

(7)

The next 120579 will be expressed as 1205791015840 = 120579 + 120575120579 In this way 120579value can be increased or decreased in an iterative way so that

Journal of Robotics 13

0 10 20 30 40 50 60 70 80 90005

01

015

02

025

03

035

04

045

Time (s)

Torque versus time

Com

pute

d to

rque

(N-m

)

Figure 24 Joint torque graph at wrist due to flexion and extension

0 10 20 30 40 50 60

0

1

2

3

4

5

6

minus1

minus2

minus3

times10minus3

Time (s)

Torque versus time

Com

pute

d to

rque

(N-m

)

Figure 25 Joint torque graph at elbow due to shoulder internal andexternal rotation

the desired location can be reached The error betweendesired location and current location can be compared usingforward kinematics in a feedback loop

In case of finding inverse kinematics there is a problem ofsingularity So we are imposing damped least square methodfor calculating the inverse kinematics The damped leastsquares solutions are intended to ensure a well-conditionedmatrix for the solution algorithmwhile limiting the size of thesolution vector 120575120579 This is done by adding a diagonal matrix120572119868 to the matrix 119869119869119879 The approximate solution of dampedleast squares method can be expressed as 120575120579 = 119869

+120575119909 where

119869+ can be expressed as the equation given below

119869+= 119869119879(119869119869119879+ 120572119868)minus1

120572 ge 0 (8)

0 20 40 60 80 100 120

0

2

4

6

minus2

minus4

minus6

times10minus3

Time (s)

Torque versus time

Com

pute

d to

rque

(N-m

)

Figure 26 Joint torque graph at wrist due to elbow pronation andsupination

When this equation is used then the solution satisfies

min120575120579

120575119909 minus 1198691205751205792+ 12057221205751205792 (9)

where sdot denotes the Euclidean norm For 120572 = 0 the dampedleast squares solution will become pseudoinverse solutionThen the Jacobian inversematrix will be 119869lowast where 119869lowast becomeexpressed as 119869119879(119869119869119879)minus1

In the damped least squares method the size of errorin the task space is weighed against the size of the resultingsolution For a given 120575119909 the size of the solution vector isdecreased by increasing 120572 However this is done at theexpense of using an approximate solution As 120572 increases sodoes the size of the error in the task space A large 120572 hasthe other benefit of ensuring a well-conditioned matrix forinversion It has been shown that the condition number 119870of the matrix 119875 equiv (119869119869

119879+ 120572119868) is 119870 = (120590

2

1+ 120572)(120590

2

119898+ 120572)

Here 1205901ge 1205902ge 1205903sdot sdot sdot ge 120590

119898ge 0 are the singular values of

the Jacobian matrix It can be seen in this equation that 119870is made arbitrarily close to 1 by increasing 120572 thus ensuringa well-conditioned matrix for inversion even in a singularconfiguration where 120590

119898= 0 Simply stated if one is willing

to give up the exactness of the solution then the size of thejoint rate can be reduced and a well-conditioned matrix forinversion can be ensured by increasing 120572

9 Simulation Results of Torque Level ofGeneral Human Arm

Maximum amount of torque is required to actuate humanjoints in vertical direction Here in Figure 25 the torqueneeded to twist the elbow with respect to shoulder joint isshown Figure 26 is showing the same kind ofmotion in wrist

14 Journal of Robotics

0 200 400 600 800 1000 12000500

1000

0500

1000

minus500

minus1000

minus500

minus1000

(a)

20

20

0

0

minus20

minus20

minus40

minus40

40

minus60

minus60

minus80 500

minus50

x

y z

Untitled fit 1x versus z y

(b)

Figure 27 (a) Outer region covered by Exorn (b) Workspace covered by Exorn

0

minus10

minus20

minus30

minus40

minus5040

3020

100minus10

minus20 0 1020 30

40 5060

70

Figure 28 Motion due to shoulder griddle

006

004

002

0

minus0020

001

002

003

004

005002

0 minus002 minus004minus006 minus008

minus01

Figure 29 Motion due to shoulder griddle glenohumerals andelbow joint movement

joint with respect to the elbow Figures 22 23 24 25 and26 will show torque variation in different joints in verticaldirection because of proper actuation signal From thosebelow graphs max and min torque for joint actuator can bedetermined because it is very much essential to select propermotor

006

004

002

0

minus0020

minus002minus004

minus006minus008

minus010

002

004

006

008

Figure 30 Motion due to shoulder joint and elbow joint movementin vertical direction

003

002

001

0

minus001

minus002

minus0030 minus002 minus004 minus006 minus008 minus01

0

001

002

003

Figure 31 Motion due to glenohumeral joint and elbow jointmovement in horizontal direction

10 Workspace Calculation and Motion due toForward Kinematics

For calculating the workspace of the robotic system aMATLAB code of nested for loop of all DOFs is being takenwith the joint range It will plot all the reachable points ofarm exoskeleton in 3D space Figure 27 is showing the outer

Journal of Robotics 15

region covered by human hand Figures 28 29 30 and 31 areshowing themotion of exoskeletonmodel due to several jointmovements

11 Conclusion

From the above discussion it may be concluded that thedeveloped system is useful for rehabilitation Comparisonsbetween human jointrsquos range and that of Exorn are alreadytabulated in Table 1 and the ranges are quite the same for boththe cases If the portable mechanical structure is attached tothe human arm it can be used as an assistive device for theparalyzed people The 3D model of exoskeleton is alreadybeing developed The model has been fabricated With thehelp of the GUI all the motions can be controlled throughserial communication The developed prototype is underworking condition We would like to build the real system sothat patient can be benefitted

References

[1] J W Krakauer ldquoArm function after stroke from physiology torecoveryrdquo Seminars in Neurology vol 25 no 4 pp 384ndash3952005

[2] T Nef and R Riener ldquoARMinmdashdesign of a novel arm reha-bilitation robotrdquo in Proceedings of the IEEE 9th InternationalConference on Rehabilitation Robotics (ICORR rsquo05) pp 57ndash60July 2005

[3] S J Ball I E Brown and S H Scott ldquoMEDARM a rehabilita-tion robot with 5DOF at the shoulder complexrdquo in Proceedingsof the IEEEASME International Conference on Advanced Intel-ligent Mechatronics (AIM rsquo07) September 2007

[4] M Mistry P Mohajerian and S Schaal ldquoArm movementexperiments with joint space force fields using an exoskeletonrobotrdquo in Proceedings of the IEEE 9th International Conferenceon Rehabilitation Robotics (ICORR rsquo05) pp 408ndash413 July 2005

[5] A Schiele and F C T van der Helm ldquoKinematic design toimprove ergonomics in human machine interactionrdquo IEEETransactions on Neural System and Rehabilitation vol 14 no4 pp 1534ndash4320 2006

[6] S J Ball I E Brown and S H Scott ldquoA planar 3DOF roboticexoskeleton for rehabilitation and assessmentrdquo in Proceedingsof the 29th Annual International Conference of IEEE-EMBSEngineering in Medicine and Biology Society (EMBC rsquo07) pp4024ndash4027 August 2007

[7] I Sardellitti E Cattin S Roccella et al ldquoDescription char-acterization and assessment of a bio-inspired shoulder joint-first link robot for neuro-robotic applicationsrdquo in Proceedings ofthe 1st IEEERAS-EMBS International Conference on BiomedicalRobotics andBiomechatronics (BioRob rsquo06) pp 112ndash117 February2006

[8] Source-winter Biomechanics and Motor Control of HumanMotion ISBN-978-0470398180 2010

[9] C-J Yang B Niu J-F Zhang and Y Chen ldquoDifferent structurebased control system of the PUMA manipulator with an armexoskeletonrdquo in Proceedings of the IEEE Conference on RoboticsAutomation and Mechatronics pp 572ndash577 December 2004

[10] K Kiguchi T Tanaka K Watanabe and T Fukuda ldquoExoskele-ton for human upper-limb motion supportrdquo in Proceedings ofthe IEEE International Conference on Robotics and Automationpp 2206ndash2211 September 2003

[11] T H Massie and K J Salisbury ldquoPHANToM haptic interfacea device for probing virtual objectsrdquo in Proceedings of theInternational Mechanical Engineering Congress and Expositionpp 295ndash299 November 1994

[12] CCarignan andKCleary ldquoClosed-loop force control for hapticsimulation of virtual environmentsrdquo The Electronic Journal ofHaptics Research vol 2 no 2 pp 1ndash14 2000

[13] A Frisoli F Rocchi S Marcheschi A Dettori F Salsedo andM Bergamasco ldquoA new force-feedback arm exoskeleton forhaptic interaction in virtual environmentsrdquo in Proceedings ofthe First Joint Eurohaptics Conference and Symposium on HapticInterfaces for Virtual Environment and Teleoperator Systems pp195ndash201 2005

[14] D Lawrence ldquoImpedance control stability properties in com-mon implementationsrdquo in Proceedings of the IEEE InternationalConference on Robotics and Automation pp 1185ndash1190 1988

[15] A Nakai Y Kunii H Hashimoto and F Harashima ldquoArmtype haptic human interface sensor armrdquo in Proceedings of theInternational Conference on Artificial Reality and Tele-Existence(ICAT) pp 77ndash84 Tokyo Japan December 1997

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DistributedSensor Networks

International Journal of

Journal of Robotics 7

(a) (b)

Figure 13 (a) Simulink model of human hand (b) human hand position at zero position

Conn1Conn1

Conn1Conn1

Conn2 Conn2

Conn2

Conn2

Conn3

Conn3

Conn3

Conn4

Conn4Conn5

Out1

Out1

Out2

Out3

Out3Out2

Ground Weld Body2

To workspace

To workspace1

To workspace2

Subsystem

Subsystem3 Subsystem6 Subsystem9

Shoulder joint Elbow jointWrist joint

Display3 Display9 Display12

Finger

In1 out1 In1 out1 In1 out1

CS1 CS17

x

y

z

B F

Figure 14 Human arm model in Simulink

rotations are connected Here in Figure 15 body 1 and body2 have zero length and zero mass Only body 3 is the actualbody It is under every human arm joint Body sensor isattached at the end point to get points in 3D space at the timeof motion

6 Embedded System

A PC based control system is being developed to provideparticular orthopedic lesson First of all command signalfrom PC is transmitted to the master controller Mastercontroller activates those joints which are needed to achievethe desired motion It sends the command bits in a packagethrough serial communication Enable signal is being sent to

all the local controllers but only few are being activated as percommand with the help of multiprocessor communicationtechnique All the motor controllers are connected in adaisy chain network that means 119879

119909and 119877

119909pins of master

controller are connected to all 119877119909and 119879

119909pins of each

controller respectively Each controller has a particular nodeas an activating signal When the master controller sends theactivation signal the particular motor controller with thatparticular node is activated

The interfacing circuit between microcontroller andmotor driver is shown in Figures 16(a) and 16(b) Driver IChas 4 input pins and 2 enable pins Here all the inputs pins andenable pins are connecting to port 0 and port 1 Here all theenable pins are sorted and connected through one port pin

8 Journal of Robotics

CS1 CS15 CS1 CS15 CS1 CS15B F B FB F1

12

2

3

Conn2 Conn3Body1 Body2 Body3

Out1Out2 Out3

Signal2Signal2Signal2

Revolute1 Revolute2 Revolute3

Joint actuatorJoint actuator1 Joint actuator2Joint sensor1 Joint sensor2 Joint sensor3

Shoulder vertical motion Shoulder forward flexion Shoulder horizontal motion

Figure 15 Block diagram below each human joint

(a)

Junction circuit 1P89V51RD2 7805 IC

7805 IC Max232DB-9

DB-9

Local controller for DC motor

Local controller for BLDC motor

DC motor driver circuit

Junction circuit 2

7805 IC

IN 4007L298

(b)

Figure 16 (a) Schematic design of interfacing circuit between microcontroller and motor driver (b) Developed interfacing circuit ofmicrocontroller

In this case all the enable pins become activated at one timeSo the motion of motor can be controlled by changing driverinputsThose inputs are amplified from 5V to 12V to run themotor in clockwise and anticlockwise manner (Figure 17) Asshown in the figure one dedicated 7805 IC (Voltage regulator)is connected tomicrocontroller for 5V power supply A serialIC MAX232 is connected to the microcontroller to convert

the RS232rsquos signals to TTL voltage levels that is acceptable to8051 microcontroller 119879

119909and 119877

119909pins

A bidirectional H bridgeDC motor control circuit isshown in Figures 17(a) and 17(b) The circuit is based onthe IC L298 from ST Microelectronics L298 It is a dual fullbridge driver that has a wide operating voltage range andcan handle load currents up to 3A The IC also features low

Journal of Robotics 9

Out In

sum

sum

MT2

100120583F

1 120583F

1 120583F

10120583F

CN5

CN6

1K 1K

1K1K

L298

REF7805

D1

D2

D3

D4

D5

D6 D7

D8

D9D10

D11 D12

R1 R2

R3R4

C1

C2

C3C4

(a)

Motor driver L298

H bridge driver

Power supply

(b)

Figure 17 (a) Schematic design of motor driver circuit (b) Developed motor driver circuit

Table 3 Segment mass and lengths of human arm [8]

Segment Segment masstotal body mass Centre of masssegment length Radius of gyrationsegment lengthProximal Distal CM Proximal Distal

Hand 0006 0506 0494 0297 0587 0577Forearm 0016 0430 0570 0303 0526 0647Upperarm 0028 0436 0564 0322 0542 0645Forearm and Hand 0022 0682 0318 0468 0827 0565Total arm 0050 0530 0470 0368 0645 0596

saturation voltage and over temperature protection In thecircuit diodes D1 to D8 are protection diodesThe state of themotor depends on the logic level of the pins 5 6 and 7 and10 11 and 12 and it is described in the table shown below thecircuit diagram

The diodes D1 to D4 and D5 to D8 provide a safer pathfor the back emf from the motor to dissipate and thus itprotects the corresponding bipolar transistors from damageThe input pins from motor driver are being connected tothe microcontroller port pins When the enable pins of thedriver pin are active then the input signal of the motor driveris amplified to 12 volt and sent to the motor According tothe configuration of port pins motor moves in clockwise oranticlockwise direction

In case of BLDCmotor controller every controller has itsparticular node for distinguishing one from the other It ispossible to control the speed of the motor either by varyingthe voltage supplied to it or by sending the serial command toit The speed of the motor is controlled by sending a string ofcommand to the BLDCmotor controller serially Also there isan encoder inside the BLDCmotor for getting the angle valuesimultaneously in a feedback loop

All the supply voltages are being bypassed through thosejunction circuits Actually all voltage sources are being sortedA 7812 IC voltage regulator is used to convert the 24Vinto 12V DC supply When the diode connected in junctioncircuit is in forward bias it sends the power supply to alldriver circuits but in the opposite case current from driver

10 Journal of Robotics

No

Serial communication configuration

Command comes from PC

GUI open

Serial port start

Serial port configuration

Commands send to the BLDC controller

Interrupt control

Select direction

Select BLDC motor

Send command to motor

Serial portclose

Select speed

DC motor controller

Motor moves

Formation of command package

Can be applied for all motors

SBUF Move motor 1 clockwise

SBUF Move motor 1 anticlockwise

SBUF Move motor 1 stop

Yes

Yes

Yes

No

No

CWCC

= A

= B

= X

Figure 18 Flow chart for PC based control

circuit cannot be sent to the controller circuit The flow chart(Figure 18) is showing the logic behind the algorithm

7 Graphical User Interface Model of Exorn v1

A proper Graphical User Interface (Figure 19) has beendeveloped for controlling all the motions serially through PCbased system It is being designed in Microsoft visual studioplatformThewholeGUImodel is divided into four divisionsFirst one is the configuration of serial communication whereuser has to select the particular COM port and baud rateIt has two buttons for opening and closing of COM portAfter opening of COM port any command can be sent to

the serial portThere are three divisions regarding themotionof human joint for proper treatment Here only one controlcan be selected out of three options Selection of one optionwill freeze the others The flow chart behind the GUI modelis shown in Figure 20

71 Orthopedic Lessons There are some movements whichare generally prescribed by different doctors for strokepatients for different problems All the motions are stored inmemory After selecting somemotion the patient presses thestart button and a command will be sent through serially fortaking proper action It will be updated with time accordingto orthopedic doctor advice

Journal of Robotics 11

Figure 19 GUI model

Serial communication and

configuration

Orthopaedic lessonsIsolateral exercises Angle oriented control

M1

Select BAUD

Select COM port

SpeedCW

CC

M2 Speed CW

CC

SpeedCW

CC

Arm movement

Elbow movement

Forearm movement

Wrist movement

Elevation and depression of shoulder griddle

Scapular abduction and adduction of shoulder griddle

Horizontal abduction and adduction of shoulder joint

Flexion and extension of wrist

M10

Figure 20 Flow chart of GUI model

72 Isolateral Exercises In isolateral exercises there are somepredefined exercises which are standard motions of all jointsof human arm Patients can follow those exercises so that theirmuscle rigidity becomes less After each selection a commandis being sent serially to master controller Master controlleralways takes care of proper actions

73 Angle Oriented Control In this configuration each jointis controlled in clockwise or anticlockwise manner withdifferent speedMore than one joint can be governed throughitWhen user selects jointmotions then a frame of commandbit serially sends with a start and stop bit to distinguish

between different commands User has to write the requiredspeed beside the box of direction of rotation In case twomotions are contradictory then the controller does not allowthat motion It is already preprogrammed in the controller

8 Predefined Control System

It is a predefined control (Figure 21) Already a vast scheduleof exercise modules is to be loaded in the memory Whensomeone wants to perform a task it is being sent to thecontroller through a manual switch or PC Master controllerwill generate a reference trajectory for that particular task

12 Journal of Robotics

PCandGUI

Master controller

Local controller

1H bridge

circuitDriver L298

Feedback

Exorn joint 1

Local controller

10H bridge circuit

Driver L298

Feedback

Exorn joint 10

Inverse kinematics

Forward kinematics

1205751205791

12057512057910

120575x

x

xd

120579

12057910

1205791

jminus1

Figure 21 Independent joint control system

0 20 40 60 80 100

0

2

4

6

8

10

Time (s)

Torque versus time

minus2

minus4

Com

pute

d to

rque

(N-m

)

Figure 22 Joint torque graph at shoulder due to flexion andextension

Then it is being sent to the local controller which takes careof that particular trajectory Always there is feedback loopconnected between the system and the master controllerWith the help of resolved motion rate control (Whitney 72)approach each joint can be controlled in an independent wayAccording to forward kinematics the kinematic model can beexpressed using the equation

120575119909 = 119869 (120579) 120575120579 (4)

Outside the singularities the inverse kinematics can beexpressed as

120575120579 = 119869minus1(120579) 120575119909 (5)

0 20 40 60 80 100 120

0

05

1

15

2

25

minus05

minus1

minus15

minus2

Time (s)

Torque versus time

Com

pute

d to

rque

(N-m

)

Figure 23 Joint torque graph at elbow due to elbow flexion andextension

There is a relation between task space and joint space Herethe current position at some angle 120579 can be expressed as

119909 = 119891 (120579) (6)

The desired location in 3D space is defined as 119909119889 So error

between current and desired position can be expressed as

120575119909 = 119909119889minus 119909

120575120579 = 119869minus1(120579) 120575119909

(7)

The next 120579 will be expressed as 1205791015840 = 120579 + 120575120579 In this way 120579value can be increased or decreased in an iterative way so that

Journal of Robotics 13

0 10 20 30 40 50 60 70 80 90005

01

015

02

025

03

035

04

045

Time (s)

Torque versus time

Com

pute

d to

rque

(N-m

)

Figure 24 Joint torque graph at wrist due to flexion and extension

0 10 20 30 40 50 60

0

1

2

3

4

5

6

minus1

minus2

minus3

times10minus3

Time (s)

Torque versus time

Com

pute

d to

rque

(N-m

)

Figure 25 Joint torque graph at elbow due to shoulder internal andexternal rotation

the desired location can be reached The error betweendesired location and current location can be compared usingforward kinematics in a feedback loop

In case of finding inverse kinematics there is a problem ofsingularity So we are imposing damped least square methodfor calculating the inverse kinematics The damped leastsquares solutions are intended to ensure a well-conditionedmatrix for the solution algorithmwhile limiting the size of thesolution vector 120575120579 This is done by adding a diagonal matrix120572119868 to the matrix 119869119869119879 The approximate solution of dampedleast squares method can be expressed as 120575120579 = 119869

+120575119909 where

119869+ can be expressed as the equation given below

119869+= 119869119879(119869119869119879+ 120572119868)minus1

120572 ge 0 (8)

0 20 40 60 80 100 120

0

2

4

6

minus2

minus4

minus6

times10minus3

Time (s)

Torque versus time

Com

pute

d to

rque

(N-m

)

Figure 26 Joint torque graph at wrist due to elbow pronation andsupination

When this equation is used then the solution satisfies

min120575120579

120575119909 minus 1198691205751205792+ 12057221205751205792 (9)

where sdot denotes the Euclidean norm For 120572 = 0 the dampedleast squares solution will become pseudoinverse solutionThen the Jacobian inversematrix will be 119869lowast where 119869lowast becomeexpressed as 119869119879(119869119869119879)minus1

In the damped least squares method the size of errorin the task space is weighed against the size of the resultingsolution For a given 120575119909 the size of the solution vector isdecreased by increasing 120572 However this is done at theexpense of using an approximate solution As 120572 increases sodoes the size of the error in the task space A large 120572 hasthe other benefit of ensuring a well-conditioned matrix forinversion It has been shown that the condition number 119870of the matrix 119875 equiv (119869119869

119879+ 120572119868) is 119870 = (120590

2

1+ 120572)(120590

2

119898+ 120572)

Here 1205901ge 1205902ge 1205903sdot sdot sdot ge 120590

119898ge 0 are the singular values of

the Jacobian matrix It can be seen in this equation that 119870is made arbitrarily close to 1 by increasing 120572 thus ensuringa well-conditioned matrix for inversion even in a singularconfiguration where 120590

119898= 0 Simply stated if one is willing

to give up the exactness of the solution then the size of thejoint rate can be reduced and a well-conditioned matrix forinversion can be ensured by increasing 120572

9 Simulation Results of Torque Level ofGeneral Human Arm

Maximum amount of torque is required to actuate humanjoints in vertical direction Here in Figure 25 the torqueneeded to twist the elbow with respect to shoulder joint isshown Figure 26 is showing the same kind ofmotion in wrist

14 Journal of Robotics

0 200 400 600 800 1000 12000500

1000

0500

1000

minus500

minus1000

minus500

minus1000

(a)

20

20

0

0

minus20

minus20

minus40

minus40

40

minus60

minus60

minus80 500

minus50

x

y z

Untitled fit 1x versus z y

(b)

Figure 27 (a) Outer region covered by Exorn (b) Workspace covered by Exorn

0

minus10

minus20

minus30

minus40

minus5040

3020

100minus10

minus20 0 1020 30

40 5060

70

Figure 28 Motion due to shoulder griddle

006

004

002

0

minus0020

001

002

003

004

005002

0 minus002 minus004minus006 minus008

minus01

Figure 29 Motion due to shoulder griddle glenohumerals andelbow joint movement

joint with respect to the elbow Figures 22 23 24 25 and26 will show torque variation in different joints in verticaldirection because of proper actuation signal From thosebelow graphs max and min torque for joint actuator can bedetermined because it is very much essential to select propermotor

006

004

002

0

minus0020

minus002minus004

minus006minus008

minus010

002

004

006

008

Figure 30 Motion due to shoulder joint and elbow joint movementin vertical direction

003

002

001

0

minus001

minus002

minus0030 minus002 minus004 minus006 minus008 minus01

0

001

002

003

Figure 31 Motion due to glenohumeral joint and elbow jointmovement in horizontal direction

10 Workspace Calculation and Motion due toForward Kinematics

For calculating the workspace of the robotic system aMATLAB code of nested for loop of all DOFs is being takenwith the joint range It will plot all the reachable points ofarm exoskeleton in 3D space Figure 27 is showing the outer

Journal of Robotics 15

region covered by human hand Figures 28 29 30 and 31 areshowing themotion of exoskeletonmodel due to several jointmovements

11 Conclusion

From the above discussion it may be concluded that thedeveloped system is useful for rehabilitation Comparisonsbetween human jointrsquos range and that of Exorn are alreadytabulated in Table 1 and the ranges are quite the same for boththe cases If the portable mechanical structure is attached tothe human arm it can be used as an assistive device for theparalyzed people The 3D model of exoskeleton is alreadybeing developed The model has been fabricated With thehelp of the GUI all the motions can be controlled throughserial communication The developed prototype is underworking condition We would like to build the real system sothat patient can be benefitted

References

[1] J W Krakauer ldquoArm function after stroke from physiology torecoveryrdquo Seminars in Neurology vol 25 no 4 pp 384ndash3952005

[2] T Nef and R Riener ldquoARMinmdashdesign of a novel arm reha-bilitation robotrdquo in Proceedings of the IEEE 9th InternationalConference on Rehabilitation Robotics (ICORR rsquo05) pp 57ndash60July 2005

[3] S J Ball I E Brown and S H Scott ldquoMEDARM a rehabilita-tion robot with 5DOF at the shoulder complexrdquo in Proceedingsof the IEEEASME International Conference on Advanced Intel-ligent Mechatronics (AIM rsquo07) September 2007

[4] M Mistry P Mohajerian and S Schaal ldquoArm movementexperiments with joint space force fields using an exoskeletonrobotrdquo in Proceedings of the IEEE 9th International Conferenceon Rehabilitation Robotics (ICORR rsquo05) pp 408ndash413 July 2005

[5] A Schiele and F C T van der Helm ldquoKinematic design toimprove ergonomics in human machine interactionrdquo IEEETransactions on Neural System and Rehabilitation vol 14 no4 pp 1534ndash4320 2006

[6] S J Ball I E Brown and S H Scott ldquoA planar 3DOF roboticexoskeleton for rehabilitation and assessmentrdquo in Proceedingsof the 29th Annual International Conference of IEEE-EMBSEngineering in Medicine and Biology Society (EMBC rsquo07) pp4024ndash4027 August 2007

[7] I Sardellitti E Cattin S Roccella et al ldquoDescription char-acterization and assessment of a bio-inspired shoulder joint-first link robot for neuro-robotic applicationsrdquo in Proceedings ofthe 1st IEEERAS-EMBS International Conference on BiomedicalRobotics andBiomechatronics (BioRob rsquo06) pp 112ndash117 February2006

[8] Source-winter Biomechanics and Motor Control of HumanMotion ISBN-978-0470398180 2010

[9] C-J Yang B Niu J-F Zhang and Y Chen ldquoDifferent structurebased control system of the PUMA manipulator with an armexoskeletonrdquo in Proceedings of the IEEE Conference on RoboticsAutomation and Mechatronics pp 572ndash577 December 2004

[10] K Kiguchi T Tanaka K Watanabe and T Fukuda ldquoExoskele-ton for human upper-limb motion supportrdquo in Proceedings ofthe IEEE International Conference on Robotics and Automationpp 2206ndash2211 September 2003

[11] T H Massie and K J Salisbury ldquoPHANToM haptic interfacea device for probing virtual objectsrdquo in Proceedings of theInternational Mechanical Engineering Congress and Expositionpp 295ndash299 November 1994

[12] CCarignan andKCleary ldquoClosed-loop force control for hapticsimulation of virtual environmentsrdquo The Electronic Journal ofHaptics Research vol 2 no 2 pp 1ndash14 2000

[13] A Frisoli F Rocchi S Marcheschi A Dettori F Salsedo andM Bergamasco ldquoA new force-feedback arm exoskeleton forhaptic interaction in virtual environmentsrdquo in Proceedings ofthe First Joint Eurohaptics Conference and Symposium on HapticInterfaces for Virtual Environment and Teleoperator Systems pp195ndash201 2005

[14] D Lawrence ldquoImpedance control stability properties in com-mon implementationsrdquo in Proceedings of the IEEE InternationalConference on Robotics and Automation pp 1185ndash1190 1988

[15] A Nakai Y Kunii H Hashimoto and F Harashima ldquoArmtype haptic human interface sensor armrdquo in Proceedings of theInternational Conference on Artificial Reality and Tele-Existence(ICAT) pp 77ndash84 Tokyo Japan December 1997

International Journal of

AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

RoboticsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Active and Passive Electronic Components

Control Scienceand Engineering

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

RotatingMachinery

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

Journal ofEngineeringVolume 2014

Submit your manuscripts athttpwwwhindawicom

VLSI Design

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Shock and Vibration

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawi Publishing Corporation httpwwwhindawicom

Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

SensorsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Navigation and Observation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

DistributedSensor Networks

International Journal of

8 Journal of Robotics

CS1 CS15 CS1 CS15 CS1 CS15B F B FB F1

12

2

3

Conn2 Conn3Body1 Body2 Body3

Out1Out2 Out3

Signal2Signal2Signal2

Revolute1 Revolute2 Revolute3

Joint actuatorJoint actuator1 Joint actuator2Joint sensor1 Joint sensor2 Joint sensor3

Shoulder vertical motion Shoulder forward flexion Shoulder horizontal motion

Figure 15 Block diagram below each human joint

(a)

Junction circuit 1P89V51RD2 7805 IC

7805 IC Max232DB-9

DB-9

Local controller for DC motor

Local controller for BLDC motor

DC motor driver circuit

Junction circuit 2

7805 IC

IN 4007L298

(b)

Figure 16 (a) Schematic design of interfacing circuit between microcontroller and motor driver (b) Developed interfacing circuit ofmicrocontroller

In this case all the enable pins become activated at one timeSo the motion of motor can be controlled by changing driverinputsThose inputs are amplified from 5V to 12V to run themotor in clockwise and anticlockwise manner (Figure 17) Asshown in the figure one dedicated 7805 IC (Voltage regulator)is connected tomicrocontroller for 5V power supply A serialIC MAX232 is connected to the microcontroller to convert

the RS232rsquos signals to TTL voltage levels that is acceptable to8051 microcontroller 119879

119909and 119877

119909pins

A bidirectional H bridgeDC motor control circuit isshown in Figures 17(a) and 17(b) The circuit is based onthe IC L298 from ST Microelectronics L298 It is a dual fullbridge driver that has a wide operating voltage range andcan handle load currents up to 3A The IC also features low

Journal of Robotics 9

Out In

sum

sum

MT2

100120583F

1 120583F

1 120583F

10120583F

CN5

CN6

1K 1K

1K1K

L298

REF7805

D1

D2

D3

D4

D5

D6 D7

D8

D9D10

D11 D12

R1 R2

R3R4

C1

C2

C3C4

(a)

Motor driver L298

H bridge driver

Power supply

(b)

Figure 17 (a) Schematic design of motor driver circuit (b) Developed motor driver circuit

Table 3 Segment mass and lengths of human arm [8]

Segment Segment masstotal body mass Centre of masssegment length Radius of gyrationsegment lengthProximal Distal CM Proximal Distal

Hand 0006 0506 0494 0297 0587 0577Forearm 0016 0430 0570 0303 0526 0647Upperarm 0028 0436 0564 0322 0542 0645Forearm and Hand 0022 0682 0318 0468 0827 0565Total arm 0050 0530 0470 0368 0645 0596

saturation voltage and over temperature protection In thecircuit diodes D1 to D8 are protection diodesThe state of themotor depends on the logic level of the pins 5 6 and 7 and10 11 and 12 and it is described in the table shown below thecircuit diagram

The diodes D1 to D4 and D5 to D8 provide a safer pathfor the back emf from the motor to dissipate and thus itprotects the corresponding bipolar transistors from damageThe input pins from motor driver are being connected tothe microcontroller port pins When the enable pins of thedriver pin are active then the input signal of the motor driveris amplified to 12 volt and sent to the motor According tothe configuration of port pins motor moves in clockwise oranticlockwise direction

In case of BLDCmotor controller every controller has itsparticular node for distinguishing one from the other It ispossible to control the speed of the motor either by varyingthe voltage supplied to it or by sending the serial command toit The speed of the motor is controlled by sending a string ofcommand to the BLDCmotor controller serially Also there isan encoder inside the BLDCmotor for getting the angle valuesimultaneously in a feedback loop

All the supply voltages are being bypassed through thosejunction circuits Actually all voltage sources are being sortedA 7812 IC voltage regulator is used to convert the 24Vinto 12V DC supply When the diode connected in junctioncircuit is in forward bias it sends the power supply to alldriver circuits but in the opposite case current from driver

10 Journal of Robotics

No

Serial communication configuration

Command comes from PC

GUI open

Serial port start

Serial port configuration

Commands send to the BLDC controller

Interrupt control

Select direction

Select BLDC motor

Send command to motor

Serial portclose

Select speed

DC motor controller

Motor moves

Formation of command package

Can be applied for all motors

SBUF Move motor 1 clockwise

SBUF Move motor 1 anticlockwise

SBUF Move motor 1 stop

Yes

Yes

Yes

No

No

CWCC

= A

= B

= X

Figure 18 Flow chart for PC based control

circuit cannot be sent to the controller circuit The flow chart(Figure 18) is showing the logic behind the algorithm

7 Graphical User Interface Model of Exorn v1

A proper Graphical User Interface (Figure 19) has beendeveloped for controlling all the motions serially through PCbased system It is being designed in Microsoft visual studioplatformThewholeGUImodel is divided into four divisionsFirst one is the configuration of serial communication whereuser has to select the particular COM port and baud rateIt has two buttons for opening and closing of COM portAfter opening of COM port any command can be sent to

the serial portThere are three divisions regarding themotionof human joint for proper treatment Here only one controlcan be selected out of three options Selection of one optionwill freeze the others The flow chart behind the GUI modelis shown in Figure 20

71 Orthopedic Lessons There are some movements whichare generally prescribed by different doctors for strokepatients for different problems All the motions are stored inmemory After selecting somemotion the patient presses thestart button and a command will be sent through serially fortaking proper action It will be updated with time accordingto orthopedic doctor advice

Journal of Robotics 11

Figure 19 GUI model

Serial communication and

configuration

Orthopaedic lessonsIsolateral exercises Angle oriented control

M1

Select BAUD

Select COM port

SpeedCW

CC

M2 Speed CW

CC

SpeedCW

CC

Arm movement

Elbow movement

Forearm movement

Wrist movement

Elevation and depression of shoulder griddle

Scapular abduction and adduction of shoulder griddle

Horizontal abduction and adduction of shoulder joint

Flexion and extension of wrist

M10

Figure 20 Flow chart of GUI model

72 Isolateral Exercises In isolateral exercises there are somepredefined exercises which are standard motions of all jointsof human arm Patients can follow those exercises so that theirmuscle rigidity becomes less After each selection a commandis being sent serially to master controller Master controlleralways takes care of proper actions

73 Angle Oriented Control In this configuration each jointis controlled in clockwise or anticlockwise manner withdifferent speedMore than one joint can be governed throughitWhen user selects jointmotions then a frame of commandbit serially sends with a start and stop bit to distinguish

between different commands User has to write the requiredspeed beside the box of direction of rotation In case twomotions are contradictory then the controller does not allowthat motion It is already preprogrammed in the controller

8 Predefined Control System

It is a predefined control (Figure 21) Already a vast scheduleof exercise modules is to be loaded in the memory Whensomeone wants to perform a task it is being sent to thecontroller through a manual switch or PC Master controllerwill generate a reference trajectory for that particular task

12 Journal of Robotics

PCandGUI

Master controller

Local controller

1H bridge

circuitDriver L298

Feedback

Exorn joint 1

Local controller

10H bridge circuit

Driver L298

Feedback

Exorn joint 10

Inverse kinematics

Forward kinematics

1205751205791

12057512057910

120575x

x

xd

120579

12057910

1205791

jminus1

Figure 21 Independent joint control system

0 20 40 60 80 100

0

2

4

6

8

10

Time (s)

Torque versus time

minus2

minus4

Com

pute

d to

rque

(N-m

)

Figure 22 Joint torque graph at shoulder due to flexion andextension

Then it is being sent to the local controller which takes careof that particular trajectory Always there is feedback loopconnected between the system and the master controllerWith the help of resolved motion rate control (Whitney 72)approach each joint can be controlled in an independent wayAccording to forward kinematics the kinematic model can beexpressed using the equation

120575119909 = 119869 (120579) 120575120579 (4)

Outside the singularities the inverse kinematics can beexpressed as

120575120579 = 119869minus1(120579) 120575119909 (5)

0 20 40 60 80 100 120

0

05

1

15

2

25

minus05

minus1

minus15

minus2

Time (s)

Torque versus time

Com

pute

d to

rque

(N-m

)

Figure 23 Joint torque graph at elbow due to elbow flexion andextension

There is a relation between task space and joint space Herethe current position at some angle 120579 can be expressed as

119909 = 119891 (120579) (6)

The desired location in 3D space is defined as 119909119889 So error

between current and desired position can be expressed as

120575119909 = 119909119889minus 119909

120575120579 = 119869minus1(120579) 120575119909

(7)

The next 120579 will be expressed as 1205791015840 = 120579 + 120575120579 In this way 120579value can be increased or decreased in an iterative way so that

Journal of Robotics 13

0 10 20 30 40 50 60 70 80 90005

01

015

02

025

03

035

04

045

Time (s)

Torque versus time

Com

pute

d to

rque

(N-m

)

Figure 24 Joint torque graph at wrist due to flexion and extension

0 10 20 30 40 50 60

0

1

2

3

4

5

6

minus1

minus2

minus3

times10minus3

Time (s)

Torque versus time

Com

pute

d to

rque

(N-m

)

Figure 25 Joint torque graph at elbow due to shoulder internal andexternal rotation

the desired location can be reached The error betweendesired location and current location can be compared usingforward kinematics in a feedback loop

In case of finding inverse kinematics there is a problem ofsingularity So we are imposing damped least square methodfor calculating the inverse kinematics The damped leastsquares solutions are intended to ensure a well-conditionedmatrix for the solution algorithmwhile limiting the size of thesolution vector 120575120579 This is done by adding a diagonal matrix120572119868 to the matrix 119869119869119879 The approximate solution of dampedleast squares method can be expressed as 120575120579 = 119869

+120575119909 where

119869+ can be expressed as the equation given below

119869+= 119869119879(119869119869119879+ 120572119868)minus1

120572 ge 0 (8)

0 20 40 60 80 100 120

0

2

4

6

minus2

minus4

minus6

times10minus3

Time (s)

Torque versus time

Com

pute

d to

rque

(N-m

)

Figure 26 Joint torque graph at wrist due to elbow pronation andsupination

When this equation is used then the solution satisfies

min120575120579

120575119909 minus 1198691205751205792+ 12057221205751205792 (9)

where sdot denotes the Euclidean norm For 120572 = 0 the dampedleast squares solution will become pseudoinverse solutionThen the Jacobian inversematrix will be 119869lowast where 119869lowast becomeexpressed as 119869119879(119869119869119879)minus1

In the damped least squares method the size of errorin the task space is weighed against the size of the resultingsolution For a given 120575119909 the size of the solution vector isdecreased by increasing 120572 However this is done at theexpense of using an approximate solution As 120572 increases sodoes the size of the error in the task space A large 120572 hasthe other benefit of ensuring a well-conditioned matrix forinversion It has been shown that the condition number 119870of the matrix 119875 equiv (119869119869

119879+ 120572119868) is 119870 = (120590

2

1+ 120572)(120590

2

119898+ 120572)

Here 1205901ge 1205902ge 1205903sdot sdot sdot ge 120590

119898ge 0 are the singular values of

the Jacobian matrix It can be seen in this equation that 119870is made arbitrarily close to 1 by increasing 120572 thus ensuringa well-conditioned matrix for inversion even in a singularconfiguration where 120590

119898= 0 Simply stated if one is willing

to give up the exactness of the solution then the size of thejoint rate can be reduced and a well-conditioned matrix forinversion can be ensured by increasing 120572

9 Simulation Results of Torque Level ofGeneral Human Arm

Maximum amount of torque is required to actuate humanjoints in vertical direction Here in Figure 25 the torqueneeded to twist the elbow with respect to shoulder joint isshown Figure 26 is showing the same kind ofmotion in wrist

14 Journal of Robotics

0 200 400 600 800 1000 12000500

1000

0500

1000

minus500

minus1000

minus500

minus1000

(a)

20

20

0

0

minus20

minus20

minus40

minus40

40

minus60

minus60

minus80 500

minus50

x

y z

Untitled fit 1x versus z y

(b)

Figure 27 (a) Outer region covered by Exorn (b) Workspace covered by Exorn

0

minus10

minus20

minus30

minus40

minus5040

3020

100minus10

minus20 0 1020 30

40 5060

70

Figure 28 Motion due to shoulder griddle

006

004

002

0

minus0020

001

002

003

004

005002

0 minus002 minus004minus006 minus008

minus01

Figure 29 Motion due to shoulder griddle glenohumerals andelbow joint movement

joint with respect to the elbow Figures 22 23 24 25 and26 will show torque variation in different joints in verticaldirection because of proper actuation signal From thosebelow graphs max and min torque for joint actuator can bedetermined because it is very much essential to select propermotor

006

004

002

0

minus0020

minus002minus004

minus006minus008

minus010

002

004

006

008

Figure 30 Motion due to shoulder joint and elbow joint movementin vertical direction

003

002

001

0

minus001

minus002

minus0030 minus002 minus004 minus006 minus008 minus01

0

001

002

003

Figure 31 Motion due to glenohumeral joint and elbow jointmovement in horizontal direction

10 Workspace Calculation and Motion due toForward Kinematics

For calculating the workspace of the robotic system aMATLAB code of nested for loop of all DOFs is being takenwith the joint range It will plot all the reachable points ofarm exoskeleton in 3D space Figure 27 is showing the outer

Journal of Robotics 15

region covered by human hand Figures 28 29 30 and 31 areshowing themotion of exoskeletonmodel due to several jointmovements

11 Conclusion

From the above discussion it may be concluded that thedeveloped system is useful for rehabilitation Comparisonsbetween human jointrsquos range and that of Exorn are alreadytabulated in Table 1 and the ranges are quite the same for boththe cases If the portable mechanical structure is attached tothe human arm it can be used as an assistive device for theparalyzed people The 3D model of exoskeleton is alreadybeing developed The model has been fabricated With thehelp of the GUI all the motions can be controlled throughserial communication The developed prototype is underworking condition We would like to build the real system sothat patient can be benefitted

References

[1] J W Krakauer ldquoArm function after stroke from physiology torecoveryrdquo Seminars in Neurology vol 25 no 4 pp 384ndash3952005

[2] T Nef and R Riener ldquoARMinmdashdesign of a novel arm reha-bilitation robotrdquo in Proceedings of the IEEE 9th InternationalConference on Rehabilitation Robotics (ICORR rsquo05) pp 57ndash60July 2005

[3] S J Ball I E Brown and S H Scott ldquoMEDARM a rehabilita-tion robot with 5DOF at the shoulder complexrdquo in Proceedingsof the IEEEASME International Conference on Advanced Intel-ligent Mechatronics (AIM rsquo07) September 2007

[4] M Mistry P Mohajerian and S Schaal ldquoArm movementexperiments with joint space force fields using an exoskeletonrobotrdquo in Proceedings of the IEEE 9th International Conferenceon Rehabilitation Robotics (ICORR rsquo05) pp 408ndash413 July 2005

[5] A Schiele and F C T van der Helm ldquoKinematic design toimprove ergonomics in human machine interactionrdquo IEEETransactions on Neural System and Rehabilitation vol 14 no4 pp 1534ndash4320 2006

[6] S J Ball I E Brown and S H Scott ldquoA planar 3DOF roboticexoskeleton for rehabilitation and assessmentrdquo in Proceedingsof the 29th Annual International Conference of IEEE-EMBSEngineering in Medicine and Biology Society (EMBC rsquo07) pp4024ndash4027 August 2007

[7] I Sardellitti E Cattin S Roccella et al ldquoDescription char-acterization and assessment of a bio-inspired shoulder joint-first link robot for neuro-robotic applicationsrdquo in Proceedings ofthe 1st IEEERAS-EMBS International Conference on BiomedicalRobotics andBiomechatronics (BioRob rsquo06) pp 112ndash117 February2006

[8] Source-winter Biomechanics and Motor Control of HumanMotion ISBN-978-0470398180 2010

[9] C-J Yang B Niu J-F Zhang and Y Chen ldquoDifferent structurebased control system of the PUMA manipulator with an armexoskeletonrdquo in Proceedings of the IEEE Conference on RoboticsAutomation and Mechatronics pp 572ndash577 December 2004

[10] K Kiguchi T Tanaka K Watanabe and T Fukuda ldquoExoskele-ton for human upper-limb motion supportrdquo in Proceedings ofthe IEEE International Conference on Robotics and Automationpp 2206ndash2211 September 2003

[11] T H Massie and K J Salisbury ldquoPHANToM haptic interfacea device for probing virtual objectsrdquo in Proceedings of theInternational Mechanical Engineering Congress and Expositionpp 295ndash299 November 1994

[12] CCarignan andKCleary ldquoClosed-loop force control for hapticsimulation of virtual environmentsrdquo The Electronic Journal ofHaptics Research vol 2 no 2 pp 1ndash14 2000

[13] A Frisoli F Rocchi S Marcheschi A Dettori F Salsedo andM Bergamasco ldquoA new force-feedback arm exoskeleton forhaptic interaction in virtual environmentsrdquo in Proceedings ofthe First Joint Eurohaptics Conference and Symposium on HapticInterfaces for Virtual Environment and Teleoperator Systems pp195ndash201 2005

[14] D Lawrence ldquoImpedance control stability properties in com-mon implementationsrdquo in Proceedings of the IEEE InternationalConference on Robotics and Automation pp 1185ndash1190 1988

[15] A Nakai Y Kunii H Hashimoto and F Harashima ldquoArmtype haptic human interface sensor armrdquo in Proceedings of theInternational Conference on Artificial Reality and Tele-Existence(ICAT) pp 77ndash84 Tokyo Japan December 1997

International Journal of

AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

RoboticsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Active and Passive Electronic Components

Control Scienceand Engineering

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

RotatingMachinery

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

Journal ofEngineeringVolume 2014

Submit your manuscripts athttpwwwhindawicom

VLSI Design

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Shock and Vibration

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawi Publishing Corporation httpwwwhindawicom

Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

SensorsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Navigation and Observation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

DistributedSensor Networks

International Journal of

Journal of Robotics 9

Out In

sum

sum

MT2

100120583F

1 120583F

1 120583F

10120583F

CN5

CN6

1K 1K

1K1K

L298

REF7805

D1

D2

D3

D4

D5

D6 D7

D8

D9D10

D11 D12

R1 R2

R3R4

C1

C2

C3C4

(a)

Motor driver L298

H bridge driver

Power supply

(b)

Figure 17 (a) Schematic design of motor driver circuit (b) Developed motor driver circuit

Table 3 Segment mass and lengths of human arm [8]

Segment Segment masstotal body mass Centre of masssegment length Radius of gyrationsegment lengthProximal Distal CM Proximal Distal

Hand 0006 0506 0494 0297 0587 0577Forearm 0016 0430 0570 0303 0526 0647Upperarm 0028 0436 0564 0322 0542 0645Forearm and Hand 0022 0682 0318 0468 0827 0565Total arm 0050 0530 0470 0368 0645 0596

saturation voltage and over temperature protection In thecircuit diodes D1 to D8 are protection diodesThe state of themotor depends on the logic level of the pins 5 6 and 7 and10 11 and 12 and it is described in the table shown below thecircuit diagram

The diodes D1 to D4 and D5 to D8 provide a safer pathfor the back emf from the motor to dissipate and thus itprotects the corresponding bipolar transistors from damageThe input pins from motor driver are being connected tothe microcontroller port pins When the enable pins of thedriver pin are active then the input signal of the motor driveris amplified to 12 volt and sent to the motor According tothe configuration of port pins motor moves in clockwise oranticlockwise direction

In case of BLDCmotor controller every controller has itsparticular node for distinguishing one from the other It ispossible to control the speed of the motor either by varyingthe voltage supplied to it or by sending the serial command toit The speed of the motor is controlled by sending a string ofcommand to the BLDCmotor controller serially Also there isan encoder inside the BLDCmotor for getting the angle valuesimultaneously in a feedback loop

All the supply voltages are being bypassed through thosejunction circuits Actually all voltage sources are being sortedA 7812 IC voltage regulator is used to convert the 24Vinto 12V DC supply When the diode connected in junctioncircuit is in forward bias it sends the power supply to alldriver circuits but in the opposite case current from driver

10 Journal of Robotics

No

Serial communication configuration

Command comes from PC

GUI open

Serial port start

Serial port configuration

Commands send to the BLDC controller

Interrupt control

Select direction

Select BLDC motor

Send command to motor

Serial portclose

Select speed

DC motor controller

Motor moves

Formation of command package

Can be applied for all motors

SBUF Move motor 1 clockwise

SBUF Move motor 1 anticlockwise

SBUF Move motor 1 stop

Yes

Yes

Yes

No

No

CWCC

= A

= B

= X

Figure 18 Flow chart for PC based control

circuit cannot be sent to the controller circuit The flow chart(Figure 18) is showing the logic behind the algorithm

7 Graphical User Interface Model of Exorn v1

A proper Graphical User Interface (Figure 19) has beendeveloped for controlling all the motions serially through PCbased system It is being designed in Microsoft visual studioplatformThewholeGUImodel is divided into four divisionsFirst one is the configuration of serial communication whereuser has to select the particular COM port and baud rateIt has two buttons for opening and closing of COM portAfter opening of COM port any command can be sent to

the serial portThere are three divisions regarding themotionof human joint for proper treatment Here only one controlcan be selected out of three options Selection of one optionwill freeze the others The flow chart behind the GUI modelis shown in Figure 20

71 Orthopedic Lessons There are some movements whichare generally prescribed by different doctors for strokepatients for different problems All the motions are stored inmemory After selecting somemotion the patient presses thestart button and a command will be sent through serially fortaking proper action It will be updated with time accordingto orthopedic doctor advice

Journal of Robotics 11

Figure 19 GUI model

Serial communication and

configuration

Orthopaedic lessonsIsolateral exercises Angle oriented control

M1

Select BAUD

Select COM port

SpeedCW

CC

M2 Speed CW

CC

SpeedCW

CC

Arm movement

Elbow movement

Forearm movement

Wrist movement

Elevation and depression of shoulder griddle

Scapular abduction and adduction of shoulder griddle

Horizontal abduction and adduction of shoulder joint

Flexion and extension of wrist

M10

Figure 20 Flow chart of GUI model

72 Isolateral Exercises In isolateral exercises there are somepredefined exercises which are standard motions of all jointsof human arm Patients can follow those exercises so that theirmuscle rigidity becomes less After each selection a commandis being sent serially to master controller Master controlleralways takes care of proper actions

73 Angle Oriented Control In this configuration each jointis controlled in clockwise or anticlockwise manner withdifferent speedMore than one joint can be governed throughitWhen user selects jointmotions then a frame of commandbit serially sends with a start and stop bit to distinguish

between different commands User has to write the requiredspeed beside the box of direction of rotation In case twomotions are contradictory then the controller does not allowthat motion It is already preprogrammed in the controller

8 Predefined Control System

It is a predefined control (Figure 21) Already a vast scheduleof exercise modules is to be loaded in the memory Whensomeone wants to perform a task it is being sent to thecontroller through a manual switch or PC Master controllerwill generate a reference trajectory for that particular task

12 Journal of Robotics

PCandGUI

Master controller

Local controller

1H bridge

circuitDriver L298

Feedback

Exorn joint 1

Local controller

10H bridge circuit

Driver L298

Feedback

Exorn joint 10

Inverse kinematics

Forward kinematics

1205751205791

12057512057910

120575x

x

xd

120579

12057910

1205791

jminus1

Figure 21 Independent joint control system

0 20 40 60 80 100

0

2

4

6

8

10

Time (s)

Torque versus time

minus2

minus4

Com

pute

d to

rque

(N-m

)

Figure 22 Joint torque graph at shoulder due to flexion andextension

Then it is being sent to the local controller which takes careof that particular trajectory Always there is feedback loopconnected between the system and the master controllerWith the help of resolved motion rate control (Whitney 72)approach each joint can be controlled in an independent wayAccording to forward kinematics the kinematic model can beexpressed using the equation

120575119909 = 119869 (120579) 120575120579 (4)

Outside the singularities the inverse kinematics can beexpressed as

120575120579 = 119869minus1(120579) 120575119909 (5)

0 20 40 60 80 100 120

0

05

1

15

2

25

minus05

minus1

minus15

minus2

Time (s)

Torque versus time

Com

pute

d to

rque

(N-m

)

Figure 23 Joint torque graph at elbow due to elbow flexion andextension

There is a relation between task space and joint space Herethe current position at some angle 120579 can be expressed as

119909 = 119891 (120579) (6)

The desired location in 3D space is defined as 119909119889 So error

between current and desired position can be expressed as

120575119909 = 119909119889minus 119909

120575120579 = 119869minus1(120579) 120575119909

(7)

The next 120579 will be expressed as 1205791015840 = 120579 + 120575120579 In this way 120579value can be increased or decreased in an iterative way so that

Journal of Robotics 13

0 10 20 30 40 50 60 70 80 90005

01

015

02

025

03

035

04

045

Time (s)

Torque versus time

Com

pute

d to

rque

(N-m

)

Figure 24 Joint torque graph at wrist due to flexion and extension

0 10 20 30 40 50 60

0

1

2

3

4

5

6

minus1

minus2

minus3

times10minus3

Time (s)

Torque versus time

Com

pute

d to

rque

(N-m

)

Figure 25 Joint torque graph at elbow due to shoulder internal andexternal rotation

the desired location can be reached The error betweendesired location and current location can be compared usingforward kinematics in a feedback loop

In case of finding inverse kinematics there is a problem ofsingularity So we are imposing damped least square methodfor calculating the inverse kinematics The damped leastsquares solutions are intended to ensure a well-conditionedmatrix for the solution algorithmwhile limiting the size of thesolution vector 120575120579 This is done by adding a diagonal matrix120572119868 to the matrix 119869119869119879 The approximate solution of dampedleast squares method can be expressed as 120575120579 = 119869

+120575119909 where

119869+ can be expressed as the equation given below

119869+= 119869119879(119869119869119879+ 120572119868)minus1

120572 ge 0 (8)

0 20 40 60 80 100 120

0

2

4

6

minus2

minus4

minus6

times10minus3

Time (s)

Torque versus time

Com

pute

d to

rque

(N-m

)

Figure 26 Joint torque graph at wrist due to elbow pronation andsupination

When this equation is used then the solution satisfies

min120575120579

120575119909 minus 1198691205751205792+ 12057221205751205792 (9)

where sdot denotes the Euclidean norm For 120572 = 0 the dampedleast squares solution will become pseudoinverse solutionThen the Jacobian inversematrix will be 119869lowast where 119869lowast becomeexpressed as 119869119879(119869119869119879)minus1

In the damped least squares method the size of errorin the task space is weighed against the size of the resultingsolution For a given 120575119909 the size of the solution vector isdecreased by increasing 120572 However this is done at theexpense of using an approximate solution As 120572 increases sodoes the size of the error in the task space A large 120572 hasthe other benefit of ensuring a well-conditioned matrix forinversion It has been shown that the condition number 119870of the matrix 119875 equiv (119869119869

119879+ 120572119868) is 119870 = (120590

2

1+ 120572)(120590

2

119898+ 120572)

Here 1205901ge 1205902ge 1205903sdot sdot sdot ge 120590

119898ge 0 are the singular values of

the Jacobian matrix It can be seen in this equation that 119870is made arbitrarily close to 1 by increasing 120572 thus ensuringa well-conditioned matrix for inversion even in a singularconfiguration where 120590

119898= 0 Simply stated if one is willing

to give up the exactness of the solution then the size of thejoint rate can be reduced and a well-conditioned matrix forinversion can be ensured by increasing 120572

9 Simulation Results of Torque Level ofGeneral Human Arm

Maximum amount of torque is required to actuate humanjoints in vertical direction Here in Figure 25 the torqueneeded to twist the elbow with respect to shoulder joint isshown Figure 26 is showing the same kind ofmotion in wrist

14 Journal of Robotics

0 200 400 600 800 1000 12000500

1000

0500

1000

minus500

minus1000

minus500

minus1000

(a)

20

20

0

0

minus20

minus20

minus40

minus40

40

minus60

minus60

minus80 500

minus50

x

y z

Untitled fit 1x versus z y

(b)

Figure 27 (a) Outer region covered by Exorn (b) Workspace covered by Exorn

0

minus10

minus20

minus30

minus40

minus5040

3020

100minus10

minus20 0 1020 30

40 5060

70

Figure 28 Motion due to shoulder griddle

006

004

002

0

minus0020

001

002

003

004

005002

0 minus002 minus004minus006 minus008

minus01

Figure 29 Motion due to shoulder griddle glenohumerals andelbow joint movement

joint with respect to the elbow Figures 22 23 24 25 and26 will show torque variation in different joints in verticaldirection because of proper actuation signal From thosebelow graphs max and min torque for joint actuator can bedetermined because it is very much essential to select propermotor

006

004

002

0

minus0020

minus002minus004

minus006minus008

minus010

002

004

006

008

Figure 30 Motion due to shoulder joint and elbow joint movementin vertical direction

003

002

001

0

minus001

minus002

minus0030 minus002 minus004 minus006 minus008 minus01

0

001

002

003

Figure 31 Motion due to glenohumeral joint and elbow jointmovement in horizontal direction

10 Workspace Calculation and Motion due toForward Kinematics

For calculating the workspace of the robotic system aMATLAB code of nested for loop of all DOFs is being takenwith the joint range It will plot all the reachable points ofarm exoskeleton in 3D space Figure 27 is showing the outer

Journal of Robotics 15

region covered by human hand Figures 28 29 30 and 31 areshowing themotion of exoskeletonmodel due to several jointmovements

11 Conclusion

From the above discussion it may be concluded that thedeveloped system is useful for rehabilitation Comparisonsbetween human jointrsquos range and that of Exorn are alreadytabulated in Table 1 and the ranges are quite the same for boththe cases If the portable mechanical structure is attached tothe human arm it can be used as an assistive device for theparalyzed people The 3D model of exoskeleton is alreadybeing developed The model has been fabricated With thehelp of the GUI all the motions can be controlled throughserial communication The developed prototype is underworking condition We would like to build the real system sothat patient can be benefitted

References

[1] J W Krakauer ldquoArm function after stroke from physiology torecoveryrdquo Seminars in Neurology vol 25 no 4 pp 384ndash3952005

[2] T Nef and R Riener ldquoARMinmdashdesign of a novel arm reha-bilitation robotrdquo in Proceedings of the IEEE 9th InternationalConference on Rehabilitation Robotics (ICORR rsquo05) pp 57ndash60July 2005

[3] S J Ball I E Brown and S H Scott ldquoMEDARM a rehabilita-tion robot with 5DOF at the shoulder complexrdquo in Proceedingsof the IEEEASME International Conference on Advanced Intel-ligent Mechatronics (AIM rsquo07) September 2007

[4] M Mistry P Mohajerian and S Schaal ldquoArm movementexperiments with joint space force fields using an exoskeletonrobotrdquo in Proceedings of the IEEE 9th International Conferenceon Rehabilitation Robotics (ICORR rsquo05) pp 408ndash413 July 2005

[5] A Schiele and F C T van der Helm ldquoKinematic design toimprove ergonomics in human machine interactionrdquo IEEETransactions on Neural System and Rehabilitation vol 14 no4 pp 1534ndash4320 2006

[6] S J Ball I E Brown and S H Scott ldquoA planar 3DOF roboticexoskeleton for rehabilitation and assessmentrdquo in Proceedingsof the 29th Annual International Conference of IEEE-EMBSEngineering in Medicine and Biology Society (EMBC rsquo07) pp4024ndash4027 August 2007

[7] I Sardellitti E Cattin S Roccella et al ldquoDescription char-acterization and assessment of a bio-inspired shoulder joint-first link robot for neuro-robotic applicationsrdquo in Proceedings ofthe 1st IEEERAS-EMBS International Conference on BiomedicalRobotics andBiomechatronics (BioRob rsquo06) pp 112ndash117 February2006

[8] Source-winter Biomechanics and Motor Control of HumanMotion ISBN-978-0470398180 2010

[9] C-J Yang B Niu J-F Zhang and Y Chen ldquoDifferent structurebased control system of the PUMA manipulator with an armexoskeletonrdquo in Proceedings of the IEEE Conference on RoboticsAutomation and Mechatronics pp 572ndash577 December 2004

[10] K Kiguchi T Tanaka K Watanabe and T Fukuda ldquoExoskele-ton for human upper-limb motion supportrdquo in Proceedings ofthe IEEE International Conference on Robotics and Automationpp 2206ndash2211 September 2003

[11] T H Massie and K J Salisbury ldquoPHANToM haptic interfacea device for probing virtual objectsrdquo in Proceedings of theInternational Mechanical Engineering Congress and Expositionpp 295ndash299 November 1994

[12] CCarignan andKCleary ldquoClosed-loop force control for hapticsimulation of virtual environmentsrdquo The Electronic Journal ofHaptics Research vol 2 no 2 pp 1ndash14 2000

[13] A Frisoli F Rocchi S Marcheschi A Dettori F Salsedo andM Bergamasco ldquoA new force-feedback arm exoskeleton forhaptic interaction in virtual environmentsrdquo in Proceedings ofthe First Joint Eurohaptics Conference and Symposium on HapticInterfaces for Virtual Environment and Teleoperator Systems pp195ndash201 2005

[14] D Lawrence ldquoImpedance control stability properties in com-mon implementationsrdquo in Proceedings of the IEEE InternationalConference on Robotics and Automation pp 1185ndash1190 1988

[15] A Nakai Y Kunii H Hashimoto and F Harashima ldquoArmtype haptic human interface sensor armrdquo in Proceedings of theInternational Conference on Artificial Reality and Tele-Existence(ICAT) pp 77ndash84 Tokyo Japan December 1997

International Journal of

AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

RoboticsJournal of

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Active and Passive Electronic Components

Control Scienceand Engineering

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

RotatingMachinery

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

Journal ofEngineeringVolume 2014

Submit your manuscripts athttpwwwhindawicom

VLSI Design

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Shock and Vibration

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

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Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

SensorsJournal of

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Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014

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Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Navigation and Observation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

DistributedSensor Networks

International Journal of

10 Journal of Robotics

No

Serial communication configuration

Command comes from PC

GUI open

Serial port start

Serial port configuration

Commands send to the BLDC controller

Interrupt control

Select direction

Select BLDC motor

Send command to motor

Serial portclose

Select speed

DC motor controller

Motor moves

Formation of command package

Can be applied for all motors

SBUF Move motor 1 clockwise

SBUF Move motor 1 anticlockwise

SBUF Move motor 1 stop

Yes

Yes

Yes

No

No

CWCC

= A

= B

= X

Figure 18 Flow chart for PC based control

circuit cannot be sent to the controller circuit The flow chart(Figure 18) is showing the logic behind the algorithm

7 Graphical User Interface Model of Exorn v1

A proper Graphical User Interface (Figure 19) has beendeveloped for controlling all the motions serially through PCbased system It is being designed in Microsoft visual studioplatformThewholeGUImodel is divided into four divisionsFirst one is the configuration of serial communication whereuser has to select the particular COM port and baud rateIt has two buttons for opening and closing of COM portAfter opening of COM port any command can be sent to

the serial portThere are three divisions regarding themotionof human joint for proper treatment Here only one controlcan be selected out of three options Selection of one optionwill freeze the others The flow chart behind the GUI modelis shown in Figure 20

71 Orthopedic Lessons There are some movements whichare generally prescribed by different doctors for strokepatients for different problems All the motions are stored inmemory After selecting somemotion the patient presses thestart button and a command will be sent through serially fortaking proper action It will be updated with time accordingto orthopedic doctor advice

Journal of Robotics 11

Figure 19 GUI model

Serial communication and

configuration

Orthopaedic lessonsIsolateral exercises Angle oriented control

M1

Select BAUD

Select COM port

SpeedCW

CC

M2 Speed CW

CC

SpeedCW

CC

Arm movement

Elbow movement

Forearm movement

Wrist movement

Elevation and depression of shoulder griddle

Scapular abduction and adduction of shoulder griddle

Horizontal abduction and adduction of shoulder joint

Flexion and extension of wrist

M10

Figure 20 Flow chart of GUI model

72 Isolateral Exercises In isolateral exercises there are somepredefined exercises which are standard motions of all jointsof human arm Patients can follow those exercises so that theirmuscle rigidity becomes less After each selection a commandis being sent serially to master controller Master controlleralways takes care of proper actions

73 Angle Oriented Control In this configuration each jointis controlled in clockwise or anticlockwise manner withdifferent speedMore than one joint can be governed throughitWhen user selects jointmotions then a frame of commandbit serially sends with a start and stop bit to distinguish

between different commands User has to write the requiredspeed beside the box of direction of rotation In case twomotions are contradictory then the controller does not allowthat motion It is already preprogrammed in the controller

8 Predefined Control System

It is a predefined control (Figure 21) Already a vast scheduleof exercise modules is to be loaded in the memory Whensomeone wants to perform a task it is being sent to thecontroller through a manual switch or PC Master controllerwill generate a reference trajectory for that particular task

12 Journal of Robotics

PCandGUI

Master controller

Local controller

1H bridge

circuitDriver L298

Feedback

Exorn joint 1

Local controller

10H bridge circuit

Driver L298

Feedback

Exorn joint 10

Inverse kinematics

Forward kinematics

1205751205791

12057512057910

120575x

x

xd

120579

12057910

1205791

jminus1

Figure 21 Independent joint control system

0 20 40 60 80 100

0

2

4

6

8

10

Time (s)

Torque versus time

minus2

minus4

Com

pute

d to

rque

(N-m

)

Figure 22 Joint torque graph at shoulder due to flexion andextension

Then it is being sent to the local controller which takes careof that particular trajectory Always there is feedback loopconnected between the system and the master controllerWith the help of resolved motion rate control (Whitney 72)approach each joint can be controlled in an independent wayAccording to forward kinematics the kinematic model can beexpressed using the equation

120575119909 = 119869 (120579) 120575120579 (4)

Outside the singularities the inverse kinematics can beexpressed as

120575120579 = 119869minus1(120579) 120575119909 (5)

0 20 40 60 80 100 120

0

05

1

15

2

25

minus05

minus1

minus15

minus2

Time (s)

Torque versus time

Com

pute

d to

rque

(N-m

)

Figure 23 Joint torque graph at elbow due to elbow flexion andextension

There is a relation between task space and joint space Herethe current position at some angle 120579 can be expressed as

119909 = 119891 (120579) (6)

The desired location in 3D space is defined as 119909119889 So error

between current and desired position can be expressed as

120575119909 = 119909119889minus 119909

120575120579 = 119869minus1(120579) 120575119909

(7)

The next 120579 will be expressed as 1205791015840 = 120579 + 120575120579 In this way 120579value can be increased or decreased in an iterative way so that

Journal of Robotics 13

0 10 20 30 40 50 60 70 80 90005

01

015

02

025

03

035

04

045

Time (s)

Torque versus time

Com

pute

d to

rque

(N-m

)

Figure 24 Joint torque graph at wrist due to flexion and extension

0 10 20 30 40 50 60

0

1

2

3

4

5

6

minus1

minus2

minus3

times10minus3

Time (s)

Torque versus time

Com

pute

d to

rque

(N-m

)

Figure 25 Joint torque graph at elbow due to shoulder internal andexternal rotation

the desired location can be reached The error betweendesired location and current location can be compared usingforward kinematics in a feedback loop

In case of finding inverse kinematics there is a problem ofsingularity So we are imposing damped least square methodfor calculating the inverse kinematics The damped leastsquares solutions are intended to ensure a well-conditionedmatrix for the solution algorithmwhile limiting the size of thesolution vector 120575120579 This is done by adding a diagonal matrix120572119868 to the matrix 119869119869119879 The approximate solution of dampedleast squares method can be expressed as 120575120579 = 119869

+120575119909 where

119869+ can be expressed as the equation given below

119869+= 119869119879(119869119869119879+ 120572119868)minus1

120572 ge 0 (8)

0 20 40 60 80 100 120

0

2

4

6

minus2

minus4

minus6

times10minus3

Time (s)

Torque versus time

Com

pute

d to

rque

(N-m

)

Figure 26 Joint torque graph at wrist due to elbow pronation andsupination

When this equation is used then the solution satisfies

min120575120579

120575119909 minus 1198691205751205792+ 12057221205751205792 (9)

where sdot denotes the Euclidean norm For 120572 = 0 the dampedleast squares solution will become pseudoinverse solutionThen the Jacobian inversematrix will be 119869lowast where 119869lowast becomeexpressed as 119869119879(119869119869119879)minus1

In the damped least squares method the size of errorin the task space is weighed against the size of the resultingsolution For a given 120575119909 the size of the solution vector isdecreased by increasing 120572 However this is done at theexpense of using an approximate solution As 120572 increases sodoes the size of the error in the task space A large 120572 hasthe other benefit of ensuring a well-conditioned matrix forinversion It has been shown that the condition number 119870of the matrix 119875 equiv (119869119869

119879+ 120572119868) is 119870 = (120590

2

1+ 120572)(120590

2

119898+ 120572)

Here 1205901ge 1205902ge 1205903sdot sdot sdot ge 120590

119898ge 0 are the singular values of

the Jacobian matrix It can be seen in this equation that 119870is made arbitrarily close to 1 by increasing 120572 thus ensuringa well-conditioned matrix for inversion even in a singularconfiguration where 120590

119898= 0 Simply stated if one is willing

to give up the exactness of the solution then the size of thejoint rate can be reduced and a well-conditioned matrix forinversion can be ensured by increasing 120572

9 Simulation Results of Torque Level ofGeneral Human Arm

Maximum amount of torque is required to actuate humanjoints in vertical direction Here in Figure 25 the torqueneeded to twist the elbow with respect to shoulder joint isshown Figure 26 is showing the same kind ofmotion in wrist

14 Journal of Robotics

0 200 400 600 800 1000 12000500

1000

0500

1000

minus500

minus1000

minus500

minus1000

(a)

20

20

0

0

minus20

minus20

minus40

minus40

40

minus60

minus60

minus80 500

minus50

x

y z

Untitled fit 1x versus z y

(b)

Figure 27 (a) Outer region covered by Exorn (b) Workspace covered by Exorn

0

minus10

minus20

minus30

minus40

minus5040

3020

100minus10

minus20 0 1020 30

40 5060

70

Figure 28 Motion due to shoulder griddle

006

004

002

0

minus0020

001

002

003

004

005002

0 minus002 minus004minus006 minus008

minus01

Figure 29 Motion due to shoulder griddle glenohumerals andelbow joint movement

joint with respect to the elbow Figures 22 23 24 25 and26 will show torque variation in different joints in verticaldirection because of proper actuation signal From thosebelow graphs max and min torque for joint actuator can bedetermined because it is very much essential to select propermotor

006

004

002

0

minus0020

minus002minus004

minus006minus008

minus010

002

004

006

008

Figure 30 Motion due to shoulder joint and elbow joint movementin vertical direction

003

002

001

0

minus001

minus002

minus0030 minus002 minus004 minus006 minus008 minus01

0

001

002

003

Figure 31 Motion due to glenohumeral joint and elbow jointmovement in horizontal direction

10 Workspace Calculation and Motion due toForward Kinematics

For calculating the workspace of the robotic system aMATLAB code of nested for loop of all DOFs is being takenwith the joint range It will plot all the reachable points ofarm exoskeleton in 3D space Figure 27 is showing the outer

Journal of Robotics 15

region covered by human hand Figures 28 29 30 and 31 areshowing themotion of exoskeletonmodel due to several jointmovements

11 Conclusion

From the above discussion it may be concluded that thedeveloped system is useful for rehabilitation Comparisonsbetween human jointrsquos range and that of Exorn are alreadytabulated in Table 1 and the ranges are quite the same for boththe cases If the portable mechanical structure is attached tothe human arm it can be used as an assistive device for theparalyzed people The 3D model of exoskeleton is alreadybeing developed The model has been fabricated With thehelp of the GUI all the motions can be controlled throughserial communication The developed prototype is underworking condition We would like to build the real system sothat patient can be benefitted

References

[1] J W Krakauer ldquoArm function after stroke from physiology torecoveryrdquo Seminars in Neurology vol 25 no 4 pp 384ndash3952005

[2] T Nef and R Riener ldquoARMinmdashdesign of a novel arm reha-bilitation robotrdquo in Proceedings of the IEEE 9th InternationalConference on Rehabilitation Robotics (ICORR rsquo05) pp 57ndash60July 2005

[3] S J Ball I E Brown and S H Scott ldquoMEDARM a rehabilita-tion robot with 5DOF at the shoulder complexrdquo in Proceedingsof the IEEEASME International Conference on Advanced Intel-ligent Mechatronics (AIM rsquo07) September 2007

[4] M Mistry P Mohajerian and S Schaal ldquoArm movementexperiments with joint space force fields using an exoskeletonrobotrdquo in Proceedings of the IEEE 9th International Conferenceon Rehabilitation Robotics (ICORR rsquo05) pp 408ndash413 July 2005

[5] A Schiele and F C T van der Helm ldquoKinematic design toimprove ergonomics in human machine interactionrdquo IEEETransactions on Neural System and Rehabilitation vol 14 no4 pp 1534ndash4320 2006

[6] S J Ball I E Brown and S H Scott ldquoA planar 3DOF roboticexoskeleton for rehabilitation and assessmentrdquo in Proceedingsof the 29th Annual International Conference of IEEE-EMBSEngineering in Medicine and Biology Society (EMBC rsquo07) pp4024ndash4027 August 2007

[7] I Sardellitti E Cattin S Roccella et al ldquoDescription char-acterization and assessment of a bio-inspired shoulder joint-first link robot for neuro-robotic applicationsrdquo in Proceedings ofthe 1st IEEERAS-EMBS International Conference on BiomedicalRobotics andBiomechatronics (BioRob rsquo06) pp 112ndash117 February2006

[8] Source-winter Biomechanics and Motor Control of HumanMotion ISBN-978-0470398180 2010

[9] C-J Yang B Niu J-F Zhang and Y Chen ldquoDifferent structurebased control system of the PUMA manipulator with an armexoskeletonrdquo in Proceedings of the IEEE Conference on RoboticsAutomation and Mechatronics pp 572ndash577 December 2004

[10] K Kiguchi T Tanaka K Watanabe and T Fukuda ldquoExoskele-ton for human upper-limb motion supportrdquo in Proceedings ofthe IEEE International Conference on Robotics and Automationpp 2206ndash2211 September 2003

[11] T H Massie and K J Salisbury ldquoPHANToM haptic interfacea device for probing virtual objectsrdquo in Proceedings of theInternational Mechanical Engineering Congress and Expositionpp 295ndash299 November 1994

[12] CCarignan andKCleary ldquoClosed-loop force control for hapticsimulation of virtual environmentsrdquo The Electronic Journal ofHaptics Research vol 2 no 2 pp 1ndash14 2000

[13] A Frisoli F Rocchi S Marcheschi A Dettori F Salsedo andM Bergamasco ldquoA new force-feedback arm exoskeleton forhaptic interaction in virtual environmentsrdquo in Proceedings ofthe First Joint Eurohaptics Conference and Symposium on HapticInterfaces for Virtual Environment and Teleoperator Systems pp195ndash201 2005

[14] D Lawrence ldquoImpedance control stability properties in com-mon implementationsrdquo in Proceedings of the IEEE InternationalConference on Robotics and Automation pp 1185ndash1190 1988

[15] A Nakai Y Kunii H Hashimoto and F Harashima ldquoArmtype haptic human interface sensor armrdquo in Proceedings of theInternational Conference on Artificial Reality and Tele-Existence(ICAT) pp 77ndash84 Tokyo Japan December 1997

International Journal of

AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

RoboticsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Active and Passive Electronic Components

Control Scienceand Engineering

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

RotatingMachinery

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

Journal ofEngineeringVolume 2014

Submit your manuscripts athttpwwwhindawicom

VLSI Design

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Shock and Vibration

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawi Publishing Corporation httpwwwhindawicom

Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

SensorsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Navigation and Observation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

DistributedSensor Networks

International Journal of

Journal of Robotics 11

Figure 19 GUI model

Serial communication and

configuration

Orthopaedic lessonsIsolateral exercises Angle oriented control

M1

Select BAUD

Select COM port

SpeedCW

CC

M2 Speed CW

CC

SpeedCW

CC

Arm movement

Elbow movement

Forearm movement

Wrist movement

Elevation and depression of shoulder griddle

Scapular abduction and adduction of shoulder griddle

Horizontal abduction and adduction of shoulder joint

Flexion and extension of wrist

M10

Figure 20 Flow chart of GUI model

72 Isolateral Exercises In isolateral exercises there are somepredefined exercises which are standard motions of all jointsof human arm Patients can follow those exercises so that theirmuscle rigidity becomes less After each selection a commandis being sent serially to master controller Master controlleralways takes care of proper actions

73 Angle Oriented Control In this configuration each jointis controlled in clockwise or anticlockwise manner withdifferent speedMore than one joint can be governed throughitWhen user selects jointmotions then a frame of commandbit serially sends with a start and stop bit to distinguish

between different commands User has to write the requiredspeed beside the box of direction of rotation In case twomotions are contradictory then the controller does not allowthat motion It is already preprogrammed in the controller

8 Predefined Control System

It is a predefined control (Figure 21) Already a vast scheduleof exercise modules is to be loaded in the memory Whensomeone wants to perform a task it is being sent to thecontroller through a manual switch or PC Master controllerwill generate a reference trajectory for that particular task

12 Journal of Robotics

PCandGUI

Master controller

Local controller

1H bridge

circuitDriver L298

Feedback

Exorn joint 1

Local controller

10H bridge circuit

Driver L298

Feedback

Exorn joint 10

Inverse kinematics

Forward kinematics

1205751205791

12057512057910

120575x

x

xd

120579

12057910

1205791

jminus1

Figure 21 Independent joint control system

0 20 40 60 80 100

0

2

4

6

8

10

Time (s)

Torque versus time

minus2

minus4

Com

pute

d to

rque

(N-m

)

Figure 22 Joint torque graph at shoulder due to flexion andextension

Then it is being sent to the local controller which takes careof that particular trajectory Always there is feedback loopconnected between the system and the master controllerWith the help of resolved motion rate control (Whitney 72)approach each joint can be controlled in an independent wayAccording to forward kinematics the kinematic model can beexpressed using the equation

120575119909 = 119869 (120579) 120575120579 (4)

Outside the singularities the inverse kinematics can beexpressed as

120575120579 = 119869minus1(120579) 120575119909 (5)

0 20 40 60 80 100 120

0

05

1

15

2

25

minus05

minus1

minus15

minus2

Time (s)

Torque versus time

Com

pute

d to

rque

(N-m

)

Figure 23 Joint torque graph at elbow due to elbow flexion andextension

There is a relation between task space and joint space Herethe current position at some angle 120579 can be expressed as

119909 = 119891 (120579) (6)

The desired location in 3D space is defined as 119909119889 So error

between current and desired position can be expressed as

120575119909 = 119909119889minus 119909

120575120579 = 119869minus1(120579) 120575119909

(7)

The next 120579 will be expressed as 1205791015840 = 120579 + 120575120579 In this way 120579value can be increased or decreased in an iterative way so that

Journal of Robotics 13

0 10 20 30 40 50 60 70 80 90005

01

015

02

025

03

035

04

045

Time (s)

Torque versus time

Com

pute

d to

rque

(N-m

)

Figure 24 Joint torque graph at wrist due to flexion and extension

0 10 20 30 40 50 60

0

1

2

3

4

5

6

minus1

minus2

minus3

times10minus3

Time (s)

Torque versus time

Com

pute

d to

rque

(N-m

)

Figure 25 Joint torque graph at elbow due to shoulder internal andexternal rotation

the desired location can be reached The error betweendesired location and current location can be compared usingforward kinematics in a feedback loop

In case of finding inverse kinematics there is a problem ofsingularity So we are imposing damped least square methodfor calculating the inverse kinematics The damped leastsquares solutions are intended to ensure a well-conditionedmatrix for the solution algorithmwhile limiting the size of thesolution vector 120575120579 This is done by adding a diagonal matrix120572119868 to the matrix 119869119869119879 The approximate solution of dampedleast squares method can be expressed as 120575120579 = 119869

+120575119909 where

119869+ can be expressed as the equation given below

119869+= 119869119879(119869119869119879+ 120572119868)minus1

120572 ge 0 (8)

0 20 40 60 80 100 120

0

2

4

6

minus2

minus4

minus6

times10minus3

Time (s)

Torque versus time

Com

pute

d to

rque

(N-m

)

Figure 26 Joint torque graph at wrist due to elbow pronation andsupination

When this equation is used then the solution satisfies

min120575120579

120575119909 minus 1198691205751205792+ 12057221205751205792 (9)

where sdot denotes the Euclidean norm For 120572 = 0 the dampedleast squares solution will become pseudoinverse solutionThen the Jacobian inversematrix will be 119869lowast where 119869lowast becomeexpressed as 119869119879(119869119869119879)minus1

In the damped least squares method the size of errorin the task space is weighed against the size of the resultingsolution For a given 120575119909 the size of the solution vector isdecreased by increasing 120572 However this is done at theexpense of using an approximate solution As 120572 increases sodoes the size of the error in the task space A large 120572 hasthe other benefit of ensuring a well-conditioned matrix forinversion It has been shown that the condition number 119870of the matrix 119875 equiv (119869119869

119879+ 120572119868) is 119870 = (120590

2

1+ 120572)(120590

2

119898+ 120572)

Here 1205901ge 1205902ge 1205903sdot sdot sdot ge 120590

119898ge 0 are the singular values of

the Jacobian matrix It can be seen in this equation that 119870is made arbitrarily close to 1 by increasing 120572 thus ensuringa well-conditioned matrix for inversion even in a singularconfiguration where 120590

119898= 0 Simply stated if one is willing

to give up the exactness of the solution then the size of thejoint rate can be reduced and a well-conditioned matrix forinversion can be ensured by increasing 120572

9 Simulation Results of Torque Level ofGeneral Human Arm

Maximum amount of torque is required to actuate humanjoints in vertical direction Here in Figure 25 the torqueneeded to twist the elbow with respect to shoulder joint isshown Figure 26 is showing the same kind ofmotion in wrist

14 Journal of Robotics

0 200 400 600 800 1000 12000500

1000

0500

1000

minus500

minus1000

minus500

minus1000

(a)

20

20

0

0

minus20

minus20

minus40

minus40

40

minus60

minus60

minus80 500

minus50

x

y z

Untitled fit 1x versus z y

(b)

Figure 27 (a) Outer region covered by Exorn (b) Workspace covered by Exorn

0

minus10

minus20

minus30

minus40

minus5040

3020

100minus10

minus20 0 1020 30

40 5060

70

Figure 28 Motion due to shoulder griddle

006

004

002

0

minus0020

001

002

003

004

005002

0 minus002 minus004minus006 minus008

minus01

Figure 29 Motion due to shoulder griddle glenohumerals andelbow joint movement

joint with respect to the elbow Figures 22 23 24 25 and26 will show torque variation in different joints in verticaldirection because of proper actuation signal From thosebelow graphs max and min torque for joint actuator can bedetermined because it is very much essential to select propermotor

006

004

002

0

minus0020

minus002minus004

minus006minus008

minus010

002

004

006

008

Figure 30 Motion due to shoulder joint and elbow joint movementin vertical direction

003

002

001

0

minus001

minus002

minus0030 minus002 minus004 minus006 minus008 minus01

0

001

002

003

Figure 31 Motion due to glenohumeral joint and elbow jointmovement in horizontal direction

10 Workspace Calculation and Motion due toForward Kinematics

For calculating the workspace of the robotic system aMATLAB code of nested for loop of all DOFs is being takenwith the joint range It will plot all the reachable points ofarm exoskeleton in 3D space Figure 27 is showing the outer

Journal of Robotics 15

region covered by human hand Figures 28 29 30 and 31 areshowing themotion of exoskeletonmodel due to several jointmovements

11 Conclusion

From the above discussion it may be concluded that thedeveloped system is useful for rehabilitation Comparisonsbetween human jointrsquos range and that of Exorn are alreadytabulated in Table 1 and the ranges are quite the same for boththe cases If the portable mechanical structure is attached tothe human arm it can be used as an assistive device for theparalyzed people The 3D model of exoskeleton is alreadybeing developed The model has been fabricated With thehelp of the GUI all the motions can be controlled throughserial communication The developed prototype is underworking condition We would like to build the real system sothat patient can be benefitted

References

[1] J W Krakauer ldquoArm function after stroke from physiology torecoveryrdquo Seminars in Neurology vol 25 no 4 pp 384ndash3952005

[2] T Nef and R Riener ldquoARMinmdashdesign of a novel arm reha-bilitation robotrdquo in Proceedings of the IEEE 9th InternationalConference on Rehabilitation Robotics (ICORR rsquo05) pp 57ndash60July 2005

[3] S J Ball I E Brown and S H Scott ldquoMEDARM a rehabilita-tion robot with 5DOF at the shoulder complexrdquo in Proceedingsof the IEEEASME International Conference on Advanced Intel-ligent Mechatronics (AIM rsquo07) September 2007

[4] M Mistry P Mohajerian and S Schaal ldquoArm movementexperiments with joint space force fields using an exoskeletonrobotrdquo in Proceedings of the IEEE 9th International Conferenceon Rehabilitation Robotics (ICORR rsquo05) pp 408ndash413 July 2005

[5] A Schiele and F C T van der Helm ldquoKinematic design toimprove ergonomics in human machine interactionrdquo IEEETransactions on Neural System and Rehabilitation vol 14 no4 pp 1534ndash4320 2006

[6] S J Ball I E Brown and S H Scott ldquoA planar 3DOF roboticexoskeleton for rehabilitation and assessmentrdquo in Proceedingsof the 29th Annual International Conference of IEEE-EMBSEngineering in Medicine and Biology Society (EMBC rsquo07) pp4024ndash4027 August 2007

[7] I Sardellitti E Cattin S Roccella et al ldquoDescription char-acterization and assessment of a bio-inspired shoulder joint-first link robot for neuro-robotic applicationsrdquo in Proceedings ofthe 1st IEEERAS-EMBS International Conference on BiomedicalRobotics andBiomechatronics (BioRob rsquo06) pp 112ndash117 February2006

[8] Source-winter Biomechanics and Motor Control of HumanMotion ISBN-978-0470398180 2010

[9] C-J Yang B Niu J-F Zhang and Y Chen ldquoDifferent structurebased control system of the PUMA manipulator with an armexoskeletonrdquo in Proceedings of the IEEE Conference on RoboticsAutomation and Mechatronics pp 572ndash577 December 2004

[10] K Kiguchi T Tanaka K Watanabe and T Fukuda ldquoExoskele-ton for human upper-limb motion supportrdquo in Proceedings ofthe IEEE International Conference on Robotics and Automationpp 2206ndash2211 September 2003

[11] T H Massie and K J Salisbury ldquoPHANToM haptic interfacea device for probing virtual objectsrdquo in Proceedings of theInternational Mechanical Engineering Congress and Expositionpp 295ndash299 November 1994

[12] CCarignan andKCleary ldquoClosed-loop force control for hapticsimulation of virtual environmentsrdquo The Electronic Journal ofHaptics Research vol 2 no 2 pp 1ndash14 2000

[13] A Frisoli F Rocchi S Marcheschi A Dettori F Salsedo andM Bergamasco ldquoA new force-feedback arm exoskeleton forhaptic interaction in virtual environmentsrdquo in Proceedings ofthe First Joint Eurohaptics Conference and Symposium on HapticInterfaces for Virtual Environment and Teleoperator Systems pp195ndash201 2005

[14] D Lawrence ldquoImpedance control stability properties in com-mon implementationsrdquo in Proceedings of the IEEE InternationalConference on Robotics and Automation pp 1185ndash1190 1988

[15] A Nakai Y Kunii H Hashimoto and F Harashima ldquoArmtype haptic human interface sensor armrdquo in Proceedings of theInternational Conference on Artificial Reality and Tele-Existence(ICAT) pp 77ndash84 Tokyo Japan December 1997

International Journal of

AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

RoboticsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Active and Passive Electronic Components

Control Scienceand Engineering

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

RotatingMachinery

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

Journal ofEngineeringVolume 2014

Submit your manuscripts athttpwwwhindawicom

VLSI Design

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Shock and Vibration

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawi Publishing Corporation httpwwwhindawicom

Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

SensorsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Navigation and Observation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

DistributedSensor Networks

International Journal of

12 Journal of Robotics

PCandGUI

Master controller

Local controller

1H bridge

circuitDriver L298

Feedback

Exorn joint 1

Local controller

10H bridge circuit

Driver L298

Feedback

Exorn joint 10

Inverse kinematics

Forward kinematics

1205751205791

12057512057910

120575x

x

xd

120579

12057910

1205791

jminus1

Figure 21 Independent joint control system

0 20 40 60 80 100

0

2

4

6

8

10

Time (s)

Torque versus time

minus2

minus4

Com

pute

d to

rque

(N-m

)

Figure 22 Joint torque graph at shoulder due to flexion andextension

Then it is being sent to the local controller which takes careof that particular trajectory Always there is feedback loopconnected between the system and the master controllerWith the help of resolved motion rate control (Whitney 72)approach each joint can be controlled in an independent wayAccording to forward kinematics the kinematic model can beexpressed using the equation

120575119909 = 119869 (120579) 120575120579 (4)

Outside the singularities the inverse kinematics can beexpressed as

120575120579 = 119869minus1(120579) 120575119909 (5)

0 20 40 60 80 100 120

0

05

1

15

2

25

minus05

minus1

minus15

minus2

Time (s)

Torque versus time

Com

pute

d to

rque

(N-m

)

Figure 23 Joint torque graph at elbow due to elbow flexion andextension

There is a relation between task space and joint space Herethe current position at some angle 120579 can be expressed as

119909 = 119891 (120579) (6)

The desired location in 3D space is defined as 119909119889 So error

between current and desired position can be expressed as

120575119909 = 119909119889minus 119909

120575120579 = 119869minus1(120579) 120575119909

(7)

The next 120579 will be expressed as 1205791015840 = 120579 + 120575120579 In this way 120579value can be increased or decreased in an iterative way so that

Journal of Robotics 13

0 10 20 30 40 50 60 70 80 90005

01

015

02

025

03

035

04

045

Time (s)

Torque versus time

Com

pute

d to

rque

(N-m

)

Figure 24 Joint torque graph at wrist due to flexion and extension

0 10 20 30 40 50 60

0

1

2

3

4

5

6

minus1

minus2

minus3

times10minus3

Time (s)

Torque versus time

Com

pute

d to

rque

(N-m

)

Figure 25 Joint torque graph at elbow due to shoulder internal andexternal rotation

the desired location can be reached The error betweendesired location and current location can be compared usingforward kinematics in a feedback loop

In case of finding inverse kinematics there is a problem ofsingularity So we are imposing damped least square methodfor calculating the inverse kinematics The damped leastsquares solutions are intended to ensure a well-conditionedmatrix for the solution algorithmwhile limiting the size of thesolution vector 120575120579 This is done by adding a diagonal matrix120572119868 to the matrix 119869119869119879 The approximate solution of dampedleast squares method can be expressed as 120575120579 = 119869

+120575119909 where

119869+ can be expressed as the equation given below

119869+= 119869119879(119869119869119879+ 120572119868)minus1

120572 ge 0 (8)

0 20 40 60 80 100 120

0

2

4

6

minus2

minus4

minus6

times10minus3

Time (s)

Torque versus time

Com

pute

d to

rque

(N-m

)

Figure 26 Joint torque graph at wrist due to elbow pronation andsupination

When this equation is used then the solution satisfies

min120575120579

120575119909 minus 1198691205751205792+ 12057221205751205792 (9)

where sdot denotes the Euclidean norm For 120572 = 0 the dampedleast squares solution will become pseudoinverse solutionThen the Jacobian inversematrix will be 119869lowast where 119869lowast becomeexpressed as 119869119879(119869119869119879)minus1

In the damped least squares method the size of errorin the task space is weighed against the size of the resultingsolution For a given 120575119909 the size of the solution vector isdecreased by increasing 120572 However this is done at theexpense of using an approximate solution As 120572 increases sodoes the size of the error in the task space A large 120572 hasthe other benefit of ensuring a well-conditioned matrix forinversion It has been shown that the condition number 119870of the matrix 119875 equiv (119869119869

119879+ 120572119868) is 119870 = (120590

2

1+ 120572)(120590

2

119898+ 120572)

Here 1205901ge 1205902ge 1205903sdot sdot sdot ge 120590

119898ge 0 are the singular values of

the Jacobian matrix It can be seen in this equation that 119870is made arbitrarily close to 1 by increasing 120572 thus ensuringa well-conditioned matrix for inversion even in a singularconfiguration where 120590

119898= 0 Simply stated if one is willing

to give up the exactness of the solution then the size of thejoint rate can be reduced and a well-conditioned matrix forinversion can be ensured by increasing 120572

9 Simulation Results of Torque Level ofGeneral Human Arm

Maximum amount of torque is required to actuate humanjoints in vertical direction Here in Figure 25 the torqueneeded to twist the elbow with respect to shoulder joint isshown Figure 26 is showing the same kind ofmotion in wrist

14 Journal of Robotics

0 200 400 600 800 1000 12000500

1000

0500

1000

minus500

minus1000

minus500

minus1000

(a)

20

20

0

0

minus20

minus20

minus40

minus40

40

minus60

minus60

minus80 500

minus50

x

y z

Untitled fit 1x versus z y

(b)

Figure 27 (a) Outer region covered by Exorn (b) Workspace covered by Exorn

0

minus10

minus20

minus30

minus40

minus5040

3020

100minus10

minus20 0 1020 30

40 5060

70

Figure 28 Motion due to shoulder griddle

006

004

002

0

minus0020

001

002

003

004

005002

0 minus002 minus004minus006 minus008

minus01

Figure 29 Motion due to shoulder griddle glenohumerals andelbow joint movement

joint with respect to the elbow Figures 22 23 24 25 and26 will show torque variation in different joints in verticaldirection because of proper actuation signal From thosebelow graphs max and min torque for joint actuator can bedetermined because it is very much essential to select propermotor

006

004

002

0

minus0020

minus002minus004

minus006minus008

minus010

002

004

006

008

Figure 30 Motion due to shoulder joint and elbow joint movementin vertical direction

003

002

001

0

minus001

minus002

minus0030 minus002 minus004 minus006 minus008 minus01

0

001

002

003

Figure 31 Motion due to glenohumeral joint and elbow jointmovement in horizontal direction

10 Workspace Calculation and Motion due toForward Kinematics

For calculating the workspace of the robotic system aMATLAB code of nested for loop of all DOFs is being takenwith the joint range It will plot all the reachable points ofarm exoskeleton in 3D space Figure 27 is showing the outer

Journal of Robotics 15

region covered by human hand Figures 28 29 30 and 31 areshowing themotion of exoskeletonmodel due to several jointmovements

11 Conclusion

From the above discussion it may be concluded that thedeveloped system is useful for rehabilitation Comparisonsbetween human jointrsquos range and that of Exorn are alreadytabulated in Table 1 and the ranges are quite the same for boththe cases If the portable mechanical structure is attached tothe human arm it can be used as an assistive device for theparalyzed people The 3D model of exoskeleton is alreadybeing developed The model has been fabricated With thehelp of the GUI all the motions can be controlled throughserial communication The developed prototype is underworking condition We would like to build the real system sothat patient can be benefitted

References

[1] J W Krakauer ldquoArm function after stroke from physiology torecoveryrdquo Seminars in Neurology vol 25 no 4 pp 384ndash3952005

[2] T Nef and R Riener ldquoARMinmdashdesign of a novel arm reha-bilitation robotrdquo in Proceedings of the IEEE 9th InternationalConference on Rehabilitation Robotics (ICORR rsquo05) pp 57ndash60July 2005

[3] S J Ball I E Brown and S H Scott ldquoMEDARM a rehabilita-tion robot with 5DOF at the shoulder complexrdquo in Proceedingsof the IEEEASME International Conference on Advanced Intel-ligent Mechatronics (AIM rsquo07) September 2007

[4] M Mistry P Mohajerian and S Schaal ldquoArm movementexperiments with joint space force fields using an exoskeletonrobotrdquo in Proceedings of the IEEE 9th International Conferenceon Rehabilitation Robotics (ICORR rsquo05) pp 408ndash413 July 2005

[5] A Schiele and F C T van der Helm ldquoKinematic design toimprove ergonomics in human machine interactionrdquo IEEETransactions on Neural System and Rehabilitation vol 14 no4 pp 1534ndash4320 2006

[6] S J Ball I E Brown and S H Scott ldquoA planar 3DOF roboticexoskeleton for rehabilitation and assessmentrdquo in Proceedingsof the 29th Annual International Conference of IEEE-EMBSEngineering in Medicine and Biology Society (EMBC rsquo07) pp4024ndash4027 August 2007

[7] I Sardellitti E Cattin S Roccella et al ldquoDescription char-acterization and assessment of a bio-inspired shoulder joint-first link robot for neuro-robotic applicationsrdquo in Proceedings ofthe 1st IEEERAS-EMBS International Conference on BiomedicalRobotics andBiomechatronics (BioRob rsquo06) pp 112ndash117 February2006

[8] Source-winter Biomechanics and Motor Control of HumanMotion ISBN-978-0470398180 2010

[9] C-J Yang B Niu J-F Zhang and Y Chen ldquoDifferent structurebased control system of the PUMA manipulator with an armexoskeletonrdquo in Proceedings of the IEEE Conference on RoboticsAutomation and Mechatronics pp 572ndash577 December 2004

[10] K Kiguchi T Tanaka K Watanabe and T Fukuda ldquoExoskele-ton for human upper-limb motion supportrdquo in Proceedings ofthe IEEE International Conference on Robotics and Automationpp 2206ndash2211 September 2003

[11] T H Massie and K J Salisbury ldquoPHANToM haptic interfacea device for probing virtual objectsrdquo in Proceedings of theInternational Mechanical Engineering Congress and Expositionpp 295ndash299 November 1994

[12] CCarignan andKCleary ldquoClosed-loop force control for hapticsimulation of virtual environmentsrdquo The Electronic Journal ofHaptics Research vol 2 no 2 pp 1ndash14 2000

[13] A Frisoli F Rocchi S Marcheschi A Dettori F Salsedo andM Bergamasco ldquoA new force-feedback arm exoskeleton forhaptic interaction in virtual environmentsrdquo in Proceedings ofthe First Joint Eurohaptics Conference and Symposium on HapticInterfaces for Virtual Environment and Teleoperator Systems pp195ndash201 2005

[14] D Lawrence ldquoImpedance control stability properties in com-mon implementationsrdquo in Proceedings of the IEEE InternationalConference on Robotics and Automation pp 1185ndash1190 1988

[15] A Nakai Y Kunii H Hashimoto and F Harashima ldquoArmtype haptic human interface sensor armrdquo in Proceedings of theInternational Conference on Artificial Reality and Tele-Existence(ICAT) pp 77ndash84 Tokyo Japan December 1997

International Journal of

AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

RoboticsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Active and Passive Electronic Components

Control Scienceand Engineering

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

RotatingMachinery

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

Journal ofEngineeringVolume 2014

Submit your manuscripts athttpwwwhindawicom

VLSI Design

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Shock and Vibration

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawi Publishing Corporation httpwwwhindawicom

Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

SensorsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Navigation and Observation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

DistributedSensor Networks

International Journal of

Journal of Robotics 13

0 10 20 30 40 50 60 70 80 90005

01

015

02

025

03

035

04

045

Time (s)

Torque versus time

Com

pute

d to

rque

(N-m

)

Figure 24 Joint torque graph at wrist due to flexion and extension

0 10 20 30 40 50 60

0

1

2

3

4

5

6

minus1

minus2

minus3

times10minus3

Time (s)

Torque versus time

Com

pute

d to

rque

(N-m

)

Figure 25 Joint torque graph at elbow due to shoulder internal andexternal rotation

the desired location can be reached The error betweendesired location and current location can be compared usingforward kinematics in a feedback loop

In case of finding inverse kinematics there is a problem ofsingularity So we are imposing damped least square methodfor calculating the inverse kinematics The damped leastsquares solutions are intended to ensure a well-conditionedmatrix for the solution algorithmwhile limiting the size of thesolution vector 120575120579 This is done by adding a diagonal matrix120572119868 to the matrix 119869119869119879 The approximate solution of dampedleast squares method can be expressed as 120575120579 = 119869

+120575119909 where

119869+ can be expressed as the equation given below

119869+= 119869119879(119869119869119879+ 120572119868)minus1

120572 ge 0 (8)

0 20 40 60 80 100 120

0

2

4

6

minus2

minus4

minus6

times10minus3

Time (s)

Torque versus time

Com

pute

d to

rque

(N-m

)

Figure 26 Joint torque graph at wrist due to elbow pronation andsupination

When this equation is used then the solution satisfies

min120575120579

120575119909 minus 1198691205751205792+ 12057221205751205792 (9)

where sdot denotes the Euclidean norm For 120572 = 0 the dampedleast squares solution will become pseudoinverse solutionThen the Jacobian inversematrix will be 119869lowast where 119869lowast becomeexpressed as 119869119879(119869119869119879)minus1

In the damped least squares method the size of errorin the task space is weighed against the size of the resultingsolution For a given 120575119909 the size of the solution vector isdecreased by increasing 120572 However this is done at theexpense of using an approximate solution As 120572 increases sodoes the size of the error in the task space A large 120572 hasthe other benefit of ensuring a well-conditioned matrix forinversion It has been shown that the condition number 119870of the matrix 119875 equiv (119869119869

119879+ 120572119868) is 119870 = (120590

2

1+ 120572)(120590

2

119898+ 120572)

Here 1205901ge 1205902ge 1205903sdot sdot sdot ge 120590

119898ge 0 are the singular values of

the Jacobian matrix It can be seen in this equation that 119870is made arbitrarily close to 1 by increasing 120572 thus ensuringa well-conditioned matrix for inversion even in a singularconfiguration where 120590

119898= 0 Simply stated if one is willing

to give up the exactness of the solution then the size of thejoint rate can be reduced and a well-conditioned matrix forinversion can be ensured by increasing 120572

9 Simulation Results of Torque Level ofGeneral Human Arm

Maximum amount of torque is required to actuate humanjoints in vertical direction Here in Figure 25 the torqueneeded to twist the elbow with respect to shoulder joint isshown Figure 26 is showing the same kind ofmotion in wrist

14 Journal of Robotics

0 200 400 600 800 1000 12000500

1000

0500

1000

minus500

minus1000

minus500

minus1000

(a)

20

20

0

0

minus20

minus20

minus40

minus40

40

minus60

minus60

minus80 500

minus50

x

y z

Untitled fit 1x versus z y

(b)

Figure 27 (a) Outer region covered by Exorn (b) Workspace covered by Exorn

0

minus10

minus20

minus30

minus40

minus5040

3020

100minus10

minus20 0 1020 30

40 5060

70

Figure 28 Motion due to shoulder griddle

006

004

002

0

minus0020

001

002

003

004

005002

0 minus002 minus004minus006 minus008

minus01

Figure 29 Motion due to shoulder griddle glenohumerals andelbow joint movement

joint with respect to the elbow Figures 22 23 24 25 and26 will show torque variation in different joints in verticaldirection because of proper actuation signal From thosebelow graphs max and min torque for joint actuator can bedetermined because it is very much essential to select propermotor

006

004

002

0

minus0020

minus002minus004

minus006minus008

minus010

002

004

006

008

Figure 30 Motion due to shoulder joint and elbow joint movementin vertical direction

003

002

001

0

minus001

minus002

minus0030 minus002 minus004 minus006 minus008 minus01

0

001

002

003

Figure 31 Motion due to glenohumeral joint and elbow jointmovement in horizontal direction

10 Workspace Calculation and Motion due toForward Kinematics

For calculating the workspace of the robotic system aMATLAB code of nested for loop of all DOFs is being takenwith the joint range It will plot all the reachable points ofarm exoskeleton in 3D space Figure 27 is showing the outer

Journal of Robotics 15

region covered by human hand Figures 28 29 30 and 31 areshowing themotion of exoskeletonmodel due to several jointmovements

11 Conclusion

From the above discussion it may be concluded that thedeveloped system is useful for rehabilitation Comparisonsbetween human jointrsquos range and that of Exorn are alreadytabulated in Table 1 and the ranges are quite the same for boththe cases If the portable mechanical structure is attached tothe human arm it can be used as an assistive device for theparalyzed people The 3D model of exoskeleton is alreadybeing developed The model has been fabricated With thehelp of the GUI all the motions can be controlled throughserial communication The developed prototype is underworking condition We would like to build the real system sothat patient can be benefitted

References

[1] J W Krakauer ldquoArm function after stroke from physiology torecoveryrdquo Seminars in Neurology vol 25 no 4 pp 384ndash3952005

[2] T Nef and R Riener ldquoARMinmdashdesign of a novel arm reha-bilitation robotrdquo in Proceedings of the IEEE 9th InternationalConference on Rehabilitation Robotics (ICORR rsquo05) pp 57ndash60July 2005

[3] S J Ball I E Brown and S H Scott ldquoMEDARM a rehabilita-tion robot with 5DOF at the shoulder complexrdquo in Proceedingsof the IEEEASME International Conference on Advanced Intel-ligent Mechatronics (AIM rsquo07) September 2007

[4] M Mistry P Mohajerian and S Schaal ldquoArm movementexperiments with joint space force fields using an exoskeletonrobotrdquo in Proceedings of the IEEE 9th International Conferenceon Rehabilitation Robotics (ICORR rsquo05) pp 408ndash413 July 2005

[5] A Schiele and F C T van der Helm ldquoKinematic design toimprove ergonomics in human machine interactionrdquo IEEETransactions on Neural System and Rehabilitation vol 14 no4 pp 1534ndash4320 2006

[6] S J Ball I E Brown and S H Scott ldquoA planar 3DOF roboticexoskeleton for rehabilitation and assessmentrdquo in Proceedingsof the 29th Annual International Conference of IEEE-EMBSEngineering in Medicine and Biology Society (EMBC rsquo07) pp4024ndash4027 August 2007

[7] I Sardellitti E Cattin S Roccella et al ldquoDescription char-acterization and assessment of a bio-inspired shoulder joint-first link robot for neuro-robotic applicationsrdquo in Proceedings ofthe 1st IEEERAS-EMBS International Conference on BiomedicalRobotics andBiomechatronics (BioRob rsquo06) pp 112ndash117 February2006

[8] Source-winter Biomechanics and Motor Control of HumanMotion ISBN-978-0470398180 2010

[9] C-J Yang B Niu J-F Zhang and Y Chen ldquoDifferent structurebased control system of the PUMA manipulator with an armexoskeletonrdquo in Proceedings of the IEEE Conference on RoboticsAutomation and Mechatronics pp 572ndash577 December 2004

[10] K Kiguchi T Tanaka K Watanabe and T Fukuda ldquoExoskele-ton for human upper-limb motion supportrdquo in Proceedings ofthe IEEE International Conference on Robotics and Automationpp 2206ndash2211 September 2003

[11] T H Massie and K J Salisbury ldquoPHANToM haptic interfacea device for probing virtual objectsrdquo in Proceedings of theInternational Mechanical Engineering Congress and Expositionpp 295ndash299 November 1994

[12] CCarignan andKCleary ldquoClosed-loop force control for hapticsimulation of virtual environmentsrdquo The Electronic Journal ofHaptics Research vol 2 no 2 pp 1ndash14 2000

[13] A Frisoli F Rocchi S Marcheschi A Dettori F Salsedo andM Bergamasco ldquoA new force-feedback arm exoskeleton forhaptic interaction in virtual environmentsrdquo in Proceedings ofthe First Joint Eurohaptics Conference and Symposium on HapticInterfaces for Virtual Environment and Teleoperator Systems pp195ndash201 2005

[14] D Lawrence ldquoImpedance control stability properties in com-mon implementationsrdquo in Proceedings of the IEEE InternationalConference on Robotics and Automation pp 1185ndash1190 1988

[15] A Nakai Y Kunii H Hashimoto and F Harashima ldquoArmtype haptic human interface sensor armrdquo in Proceedings of theInternational Conference on Artificial Reality and Tele-Existence(ICAT) pp 77ndash84 Tokyo Japan December 1997

International Journal of

AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

RoboticsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Active and Passive Electronic Components

Control Scienceand Engineering

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

RotatingMachinery

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

Journal ofEngineeringVolume 2014

Submit your manuscripts athttpwwwhindawicom

VLSI Design

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Shock and Vibration

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawi Publishing Corporation httpwwwhindawicom

Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

SensorsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Navigation and Observation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

DistributedSensor Networks

International Journal of

14 Journal of Robotics

0 200 400 600 800 1000 12000500

1000

0500

1000

minus500

minus1000

minus500

minus1000

(a)

20

20

0

0

minus20

minus20

minus40

minus40

40

minus60

minus60

minus80 500

minus50

x

y z

Untitled fit 1x versus z y

(b)

Figure 27 (a) Outer region covered by Exorn (b) Workspace covered by Exorn

0

minus10

minus20

minus30

minus40

minus5040

3020

100minus10

minus20 0 1020 30

40 5060

70

Figure 28 Motion due to shoulder griddle

006

004

002

0

minus0020

001

002

003

004

005002

0 minus002 minus004minus006 minus008

minus01

Figure 29 Motion due to shoulder griddle glenohumerals andelbow joint movement

joint with respect to the elbow Figures 22 23 24 25 and26 will show torque variation in different joints in verticaldirection because of proper actuation signal From thosebelow graphs max and min torque for joint actuator can bedetermined because it is very much essential to select propermotor

006

004

002

0

minus0020

minus002minus004

minus006minus008

minus010

002

004

006

008

Figure 30 Motion due to shoulder joint and elbow joint movementin vertical direction

003

002

001

0

minus001

minus002

minus0030 minus002 minus004 minus006 minus008 minus01

0

001

002

003

Figure 31 Motion due to glenohumeral joint and elbow jointmovement in horizontal direction

10 Workspace Calculation and Motion due toForward Kinematics

For calculating the workspace of the robotic system aMATLAB code of nested for loop of all DOFs is being takenwith the joint range It will plot all the reachable points ofarm exoskeleton in 3D space Figure 27 is showing the outer

Journal of Robotics 15

region covered by human hand Figures 28 29 30 and 31 areshowing themotion of exoskeletonmodel due to several jointmovements

11 Conclusion

From the above discussion it may be concluded that thedeveloped system is useful for rehabilitation Comparisonsbetween human jointrsquos range and that of Exorn are alreadytabulated in Table 1 and the ranges are quite the same for boththe cases If the portable mechanical structure is attached tothe human arm it can be used as an assistive device for theparalyzed people The 3D model of exoskeleton is alreadybeing developed The model has been fabricated With thehelp of the GUI all the motions can be controlled throughserial communication The developed prototype is underworking condition We would like to build the real system sothat patient can be benefitted

References

[1] J W Krakauer ldquoArm function after stroke from physiology torecoveryrdquo Seminars in Neurology vol 25 no 4 pp 384ndash3952005

[2] T Nef and R Riener ldquoARMinmdashdesign of a novel arm reha-bilitation robotrdquo in Proceedings of the IEEE 9th InternationalConference on Rehabilitation Robotics (ICORR rsquo05) pp 57ndash60July 2005

[3] S J Ball I E Brown and S H Scott ldquoMEDARM a rehabilita-tion robot with 5DOF at the shoulder complexrdquo in Proceedingsof the IEEEASME International Conference on Advanced Intel-ligent Mechatronics (AIM rsquo07) September 2007

[4] M Mistry P Mohajerian and S Schaal ldquoArm movementexperiments with joint space force fields using an exoskeletonrobotrdquo in Proceedings of the IEEE 9th International Conferenceon Rehabilitation Robotics (ICORR rsquo05) pp 408ndash413 July 2005

[5] A Schiele and F C T van der Helm ldquoKinematic design toimprove ergonomics in human machine interactionrdquo IEEETransactions on Neural System and Rehabilitation vol 14 no4 pp 1534ndash4320 2006

[6] S J Ball I E Brown and S H Scott ldquoA planar 3DOF roboticexoskeleton for rehabilitation and assessmentrdquo in Proceedingsof the 29th Annual International Conference of IEEE-EMBSEngineering in Medicine and Biology Society (EMBC rsquo07) pp4024ndash4027 August 2007

[7] I Sardellitti E Cattin S Roccella et al ldquoDescription char-acterization and assessment of a bio-inspired shoulder joint-first link robot for neuro-robotic applicationsrdquo in Proceedings ofthe 1st IEEERAS-EMBS International Conference on BiomedicalRobotics andBiomechatronics (BioRob rsquo06) pp 112ndash117 February2006

[8] Source-winter Biomechanics and Motor Control of HumanMotion ISBN-978-0470398180 2010

[9] C-J Yang B Niu J-F Zhang and Y Chen ldquoDifferent structurebased control system of the PUMA manipulator with an armexoskeletonrdquo in Proceedings of the IEEE Conference on RoboticsAutomation and Mechatronics pp 572ndash577 December 2004

[10] K Kiguchi T Tanaka K Watanabe and T Fukuda ldquoExoskele-ton for human upper-limb motion supportrdquo in Proceedings ofthe IEEE International Conference on Robotics and Automationpp 2206ndash2211 September 2003

[11] T H Massie and K J Salisbury ldquoPHANToM haptic interfacea device for probing virtual objectsrdquo in Proceedings of theInternational Mechanical Engineering Congress and Expositionpp 295ndash299 November 1994

[12] CCarignan andKCleary ldquoClosed-loop force control for hapticsimulation of virtual environmentsrdquo The Electronic Journal ofHaptics Research vol 2 no 2 pp 1ndash14 2000

[13] A Frisoli F Rocchi S Marcheschi A Dettori F Salsedo andM Bergamasco ldquoA new force-feedback arm exoskeleton forhaptic interaction in virtual environmentsrdquo in Proceedings ofthe First Joint Eurohaptics Conference and Symposium on HapticInterfaces for Virtual Environment and Teleoperator Systems pp195ndash201 2005

[14] D Lawrence ldquoImpedance control stability properties in com-mon implementationsrdquo in Proceedings of the IEEE InternationalConference on Robotics and Automation pp 1185ndash1190 1988

[15] A Nakai Y Kunii H Hashimoto and F Harashima ldquoArmtype haptic human interface sensor armrdquo in Proceedings of theInternational Conference on Artificial Reality and Tele-Existence(ICAT) pp 77ndash84 Tokyo Japan December 1997

International Journal of

AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

RoboticsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Active and Passive Electronic Components

Control Scienceand Engineering

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

RotatingMachinery

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

Journal ofEngineeringVolume 2014

Submit your manuscripts athttpwwwhindawicom

VLSI Design

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Shock and Vibration

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawi Publishing Corporation httpwwwhindawicom

Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

SensorsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Navigation and Observation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

DistributedSensor Networks

International Journal of

Journal of Robotics 15

region covered by human hand Figures 28 29 30 and 31 areshowing themotion of exoskeletonmodel due to several jointmovements

11 Conclusion

From the above discussion it may be concluded that thedeveloped system is useful for rehabilitation Comparisonsbetween human jointrsquos range and that of Exorn are alreadytabulated in Table 1 and the ranges are quite the same for boththe cases If the portable mechanical structure is attached tothe human arm it can be used as an assistive device for theparalyzed people The 3D model of exoskeleton is alreadybeing developed The model has been fabricated With thehelp of the GUI all the motions can be controlled throughserial communication The developed prototype is underworking condition We would like to build the real system sothat patient can be benefitted

References

[1] J W Krakauer ldquoArm function after stroke from physiology torecoveryrdquo Seminars in Neurology vol 25 no 4 pp 384ndash3952005

[2] T Nef and R Riener ldquoARMinmdashdesign of a novel arm reha-bilitation robotrdquo in Proceedings of the IEEE 9th InternationalConference on Rehabilitation Robotics (ICORR rsquo05) pp 57ndash60July 2005

[3] S J Ball I E Brown and S H Scott ldquoMEDARM a rehabilita-tion robot with 5DOF at the shoulder complexrdquo in Proceedingsof the IEEEASME International Conference on Advanced Intel-ligent Mechatronics (AIM rsquo07) September 2007

[4] M Mistry P Mohajerian and S Schaal ldquoArm movementexperiments with joint space force fields using an exoskeletonrobotrdquo in Proceedings of the IEEE 9th International Conferenceon Rehabilitation Robotics (ICORR rsquo05) pp 408ndash413 July 2005

[5] A Schiele and F C T van der Helm ldquoKinematic design toimprove ergonomics in human machine interactionrdquo IEEETransactions on Neural System and Rehabilitation vol 14 no4 pp 1534ndash4320 2006

[6] S J Ball I E Brown and S H Scott ldquoA planar 3DOF roboticexoskeleton for rehabilitation and assessmentrdquo in Proceedingsof the 29th Annual International Conference of IEEE-EMBSEngineering in Medicine and Biology Society (EMBC rsquo07) pp4024ndash4027 August 2007

[7] I Sardellitti E Cattin S Roccella et al ldquoDescription char-acterization and assessment of a bio-inspired shoulder joint-first link robot for neuro-robotic applicationsrdquo in Proceedings ofthe 1st IEEERAS-EMBS International Conference on BiomedicalRobotics andBiomechatronics (BioRob rsquo06) pp 112ndash117 February2006

[8] Source-winter Biomechanics and Motor Control of HumanMotion ISBN-978-0470398180 2010

[9] C-J Yang B Niu J-F Zhang and Y Chen ldquoDifferent structurebased control system of the PUMA manipulator with an armexoskeletonrdquo in Proceedings of the IEEE Conference on RoboticsAutomation and Mechatronics pp 572ndash577 December 2004

[10] K Kiguchi T Tanaka K Watanabe and T Fukuda ldquoExoskele-ton for human upper-limb motion supportrdquo in Proceedings ofthe IEEE International Conference on Robotics and Automationpp 2206ndash2211 September 2003

[11] T H Massie and K J Salisbury ldquoPHANToM haptic interfacea device for probing virtual objectsrdquo in Proceedings of theInternational Mechanical Engineering Congress and Expositionpp 295ndash299 November 1994

[12] CCarignan andKCleary ldquoClosed-loop force control for hapticsimulation of virtual environmentsrdquo The Electronic Journal ofHaptics Research vol 2 no 2 pp 1ndash14 2000

[13] A Frisoli F Rocchi S Marcheschi A Dettori F Salsedo andM Bergamasco ldquoA new force-feedback arm exoskeleton forhaptic interaction in virtual environmentsrdquo in Proceedings ofthe First Joint Eurohaptics Conference and Symposium on HapticInterfaces for Virtual Environment and Teleoperator Systems pp195ndash201 2005

[14] D Lawrence ldquoImpedance control stability properties in com-mon implementationsrdquo in Proceedings of the IEEE InternationalConference on Robotics and Automation pp 1185ndash1190 1988

[15] A Nakai Y Kunii H Hashimoto and F Harashima ldquoArmtype haptic human interface sensor armrdquo in Proceedings of theInternational Conference on Artificial Reality and Tele-Existence(ICAT) pp 77ndash84 Tokyo Japan December 1997

International Journal of

AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

RoboticsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Active and Passive Electronic Components

Control Scienceand Engineering

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

RotatingMachinery

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

Journal ofEngineeringVolume 2014

Submit your manuscripts athttpwwwhindawicom

VLSI Design

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Shock and Vibration

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawi Publishing Corporation httpwwwhindawicom

Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

SensorsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Navigation and Observation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

DistributedSensor Networks

International Journal of

International Journal of

AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

RoboticsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Active and Passive Electronic Components

Control Scienceand Engineering

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

RotatingMachinery

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

Journal ofEngineeringVolume 2014

Submit your manuscripts athttpwwwhindawicom

VLSI Design

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Shock and Vibration

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Civil EngineeringAdvances in

Acoustics and VibrationAdvances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Electrical and Computer Engineering

Journal of

Advances inOptoElectronics

Hindawi Publishing Corporation httpwwwhindawicom

Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

SensorsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chemical EngineeringInternational Journal of Antennas and

Propagation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Navigation and Observation

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

DistributedSensor Networks

International Journal of