Automated WheelchairAutomated WheelchairDone By

HARIHARAN LKARTHIKEYAN S P

NARESH SLAKSHMI V

Guided ByMr. RATHINAM ASenior lecturer

SRM Engg. College

IntroductionMechanical designSelection of motorsCircuit designSoftwareConclusionFuture scope

Battery 2

Battery 1

MG

wheel

chair

supply processor

plank

Control circuit

M

40 cm

80 c

m

Proper Weight balance

Dead weight = 50 kg

Plank size: 80 x 40 cm

gear

Gears

Back wheel setup

Front wheel setup

Formulae Used/

Calculation

Braking

Spur Gear

Bevel Gear

Worm Gear

V = 3.14xDxNw/60 Pw =2x3.14xNwxTw/60 Tw = 9.81xWxRwhere

V => Linear Velocity Pw => Power of MotorTw => Torque of the

Wheel ShaftD => Diameter of

wheel Nw => Speed of wheel

Radius of the wheel Shaft Rw = 9mm

Maximum Weight that it can withstand Wmax

= 17.18/(0.9x10-2x9.81) = 194.59 kg (approx 200 kg)

Speed of wheel (Nw) = 50rpm

Diameter of wheel (D) = 32cm

Linear Velocity (V) = 3.14 x 32 x 10-2 x 50 / 60 = 0.837m/s (3Kmph)

Power of Motor (Pw) = 120W

Speed of the motor shaft =3000rpm

Diameter of Motor Shaft(d) = 9mm

Maximum Torque in Motor shaft = 0.382Nm

Assuming 75% efficiency for the worm wheel gear, a gear ratio of 1:60,

Torque of the Wheel Shaft Tw = 60 x 0.382 x 0.75 = 17.18Nm

Worm Gear -Serves Dual Purpose

Property:Torque improvement

Irreversibility

Instantaneous braking

Reasons for selecting PMDC Reasons for selecting Servo Motor

Motor Ratings Vehicle Testing

Reasons for selecting PMDC

Efficiency of PMDC > Efficiency of DC Motor

Smaller size of PMDC than DC for same Power

Less voltage => Less noise

Less Radio or TV interference

Lower manufacturing cost

Reasons for selecting Servo Motor

Low inertia due to the fact that armature mass is less

Fast torque response

Step change in armature voltage or current produces quick change in position or speed of the rotor

PMDC

Voltage: 24V

Current: 7A

Power Rating: 120W

Speed: 3000rpm

SERVO MOTOR

Voltage: 24V

Current: 1.25A

Torque: 1.5KgCm

 

Loading ConditionVoltage Applied

(V)

Current Drawn

(A)

Wheel Speed(RPM)

 

No Load Reading

During Straight

run

 

24 

4.5 

60

During Turning

 

24 

5.5 

50

 

Load Reading

 

During Straight

run

 

24 

7 

50

During Turning

 

24 

9 

40

H-Bridge Control of Motor

Control Box

Block Diagram

8085 Based Relay Control Circuit

Forward Direction

Supply (positive)

relay3 – motor – relay4

Supply (negative)

Reverse Direction

Supply (positive)

relay1 – motor – relay2

Supply (negative)

Start/Stop

Forward

Reverse

Left Right

HornHead lamp

Control box

Port C8085

Microprocessor

Port A & B

Control circuit

8255interfaced

withprocessor

Control Logic

Algorithm

Flow Chart

Port C (Input port) Operation

C7 C6 C5 C4 C3 C2 C1 C0

HEX

CODE

Stop 1 (01) H

Forward 1 (02) H

Reverse 1 (04) H

Left 1 (08) H

Right 1 (10) H

Step1:Configure Peripheral Programmable Interface (PPI-8255) as the following:

Port A => Output PortPort B => Output PortPort C => Input Port

Step2: Initialize Stack PointerStep3: Begin scanning the commands issued by the user.Step4: Check for the position of the start/stop switch

If in Start position Begin scanning other inputsElse Go to Step1

Step5: Check whether Forward Key is pressed.If pressed Go to Forward subroutineElse Go to next step

Step6: Check whether Reverse Key is pressed.If pressed Go to Reverse subroutineElse Go to next step

Step7: Check whether Left Key is pressed. If pressed Go to Left subroutineElse Go to next step

Step8: Check whether Right Key is pressedIf pressed Go to Right subroutineElse Go to next step

Step9: Go to Step3 for scanning inputs again

Start

Initialize stackpointer

Is forwardkey pressed?

Is reversekey pressed?

Is left keypressed?

Is right keypressed?

Is mainswitch off?

Stop

Switch ‘OFF’ fwd.relays and switch ‘ON’reverse relays

Switch ‘OFF’ reverserelays and switch‘ON’ fwd. relays

Check keydebounce

Check keydebounce

‘ON’ leftrelaysmomenta-rily

‘ON’ rightrelaysmomentarily

Y

Y

Y

Y

Y

N

N

N

N

N

Note:

Main Switch

=>ON

Other Operations carried out

Some salient features about our vehicle are

User friendly.Proper direction control (automatic steering system).Additional manual steering.Designed to withstand a weight of a normal human being.Designed to run at an average speed of 3kmph.Compact design (hind wheel set up is fitted underneath the plank).A horn facility (as in any normal vehicle).

Some of the additional features that can be implemented are

Replace Microprocessor by Microcontroller.Remote control to operate from anywhere.Predefined motion to facilitate parking etc.A light dependent headlight (for easy propagation in the dark as well) and Obstacle detector.Replace batteries by a Solar Panel.