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P13002: Ankle-Foot Orthotic Un-Tethered, Mechanical. Detailed Design Review. The Team. Team Members: Pattie Schiotis – Team Manager (ME) Shane Reardon – Lead Engineer (ME) Dana Kjolner (EE) Robert Ellsworth (EE) Sam Hosig (CE) John Williams (CE) Faculty Guide: Dr. DeBartolo. - PowerPoint PPT Presentation
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P13002: Ankle-Foot Orthotic Un-Tethered, Mechanical
Detailed Design Review
Team Members:◦Pattie Schiotis – Team Manager (ME)◦Shane Reardon – Lead Engineer (ME)◦Dana Kjolner (EE)◦Robert Ellsworth (EE)◦Sam Hosig (CE)◦John Williams (CE)
•Faculty Guide: Dr. DeBartolo
The Team
Introduction Project Background System Architecture Locking Mechanism Power Characterization Sensor Characterization Microcontroller/ Coding Progress Component Testing Bill of Materials Budget Breakdown Updated Risk Assessment
Agenda
Lasting side effect of a stroke: foot drop◦ Inability to dorsiflex the foot
Ankle Foot Orthotics (AFOs) currently used to aid dorsi-flexion.◦ Passive devices don’t allow for movement when
walking on ramps and stairs Foot is always pointed upwards
Project Background
User will have no ability to either plantar-flex or dorsi-flex their foot
Side to side stability of the foot will be ignored
Worst case will be analyzed:◦ 95 percentile male having heavy foot.◦ Fast walker – gait cycle less than 1 second.
Device may not use air muscles as an actuation source
Assumptions & Constraints
Key Customer NeedsPrimary Needs: Secondary Needs:
Safety Portable
◦ Lasts all day without charging/refueling
◦ Lightweight◦ Tolerable to wear all day
Reliable Accommodates Flat Terrain Accommodates Special
Terrain◦ Stairs◦ Ramps◦ Obstacles
Comfortable◦ Aesthetically Pleasing
Durable◦ Water Resistant◦ Corrosion Resistant
Salt & Environment Biocompatibility
Convenient◦ Easy to put on and take
off
Key Engineering Specifications
Engineering Specification
Number
Engineering Specification Description
Units of Measure
Preferred Direction
Nominal Value
Method of Validation
Stems From Customer Need
s1 torque on Foot N-m Up ≥±3.0 Test FT1,2,4,ST1,5
s2 system response time (sensing terrain to actuating device) ms down <400 Test ST3
s4 predicts step down yes/no - yes Test ST1,2,4s5 predict flat yes/no - yes Test FT1,ST5s7 predicts ramp down yes/no - yes Test ST1,2,4
s10 allowable range of motion between foot and shin degrees range 70 to 135 Test FT1,3,CF8,9,ST1
s12 untethered usage time hrs/steps up 8 hrs or 3000 steps P1,2,D1
s17 force to secure constraints N down < 80 Test C4s18 force to remove constraints N down < 80 Test C3s23 radius of edges/corners on AFO mm up 0.5 - S4,CF1,2s24 weight of entire device lb down ≤2.2 Test FT6
s28 Operates in environment temperature range °C range -17.8 to
37.8Component
Ratings D2
s31 Minimum life until failure steps up 5.5 million test D1
Characterizations used for calculations
Average # of steps per day: 10,000 # steps on stairs: 100 # steps on ramps: 100 Time for rotation: ~0.6 seconds
Walking Patterns
CAD modelSystem Architecture
Sensors
Piston/Cylinder
Mounting Bracket
Valve
Battery
Processor
Reservoir
CAD Model: DOF Analysis
1
2
34
Component #
Component Description
Connected to Joint Type # of
Constraints
1 Bottom of AFO Ground Fixed 6
2 Piston Bottom of AFO Pin 5
3 Cylinder Piston Slide 4
4 Top of AFO Cylinder Pin 5
4 Top of AFO Bottom of AFO Tamarack 4
4 Components 24 DOF Total: 24
Locking Mechanism:Selection Matrix
Concepts A B C D E E Hydraulic
LockingPiston/
Cylinder (Air)
Piston/ Cylinder
(Oil)
Socket Linear ratchet
Fluid Brake (benchmark)
Selection Criteria Rating Rating Rating Rating Rating Rating
weight 0 1 1 -1 -1 -1ease of design (electrical) 1 1 1 0 0 -1ease of design (mechanical) 0 1 1 -1 -1 -1response time (electrical) 1 1 1 -1 -1 0response time (mechanical) 1 -1 1 0 0 0locking force 1 -1 1 0 0 1attachment to orthotic 0 0 0 0 0 0safety -1 1 -1 0 0 0reliability 1 1 1 0 0 0Range of Motion 1 0 0 0 0 1Energy consumption 0 0 0 -1 -1 0
Total Score 5.00 4.00 6.00 -4.00 -4.00 -1.00Rank 2 3 1 4 4 4
Cylinder Selection
In order to swing foot, joint must apply ~2.75Nm
If locking device is 1.5” (3.81cm) away from joint,
Round up to 9/16” to be safe
lbfNm
NmFl 1718.72
0381.0
75.2
4,
2DA
A
FP
"416.0
)125(
)17(44min
psi
lbf
P
FD
Cylinder Benchmarks
BIMBA HL Original Line Bimba "500" Series MAXIM Hyd CylinderBore 9/16" 1+1/16" 1+1/2"
Stroke 3" 3" 4"Weight 0.09 lbs 0.5 lbs 7 lbs
PSI Rating 250 500 3000Cost $21.80 $61.90 $104.75
Material 304 Stainless Steel 304 Stainless Steel Iron/Steel
Picture
Valve Selection Criteria Capable of 125 Psi #10-32 or 1/8” NPT threads Allows max flow rate of 0.6213 in3/s
◦ Cv > 0.013◦ Assuming laminar, incompressible flow
min1618.06213.06.0
"5.1
2
"169 3
2
GALs
in
st
lA
t
VQrequired
0145.0125
11618.0
P
SGQCv
Valve Selection
•Cv=0.035•Solenoid Powered•Normally Closed (solenoid opens valve)•12 or 24 VDC•1/8” NPT threaded•~3 ms response time
Locking Mechanism: Stress Calculations
1
NOV 1 201213:29:30
ELEMENTS
1
X
Y
Z
NOV 1 201213:05:35
VOLUMES
TYPE NUM
UROTF
HD Polyethylene•E=125,000 Psi•Yield Strength=4,600
Locking Mechanism: Stress Calculations
1
MX
.024902
581.9071163.79
1745.672327.55
2909.433491.32
4073.24655.08
5236.96
NOV 1 201213:35:57
NODAL SOLUTION
STEP=1SUB =1TIME=1SEQV (AVG)DMX =.485218SMN =.024902SMX =5236.96
1
.024902
581.9071163.79
1745.672327.55
2909.433491.32
4073.24655.08
5236.96
NOV 1 201213:35:07
NODAL SOLUTION
STEP=1SUB =1TIME=1SEQV (AVG)DMX =.485218SMN =.024902SMX =5236.96
Stress at Joint:5000 Psi
Stress at Bolt Locations:
2000 Psi
Locking Mechanism: Stress Calculations
1
X
Y
Z
NOV 1 201217:17:34
ELEMENTS1.67”
F
M
F=17 lbfM=22.695 in-lb
Locking Mechanism: Stress Calculations
Stress at Joint:1500 Psi
Stress at Piston Connection:
1250 Psi
1
MX
X
Y
Z
.136886
179.46358.783
538.106717.428
896.7511076.07
1255.41434.72
1614.04
NOV 1 201217:11:41
NODAL SOLUTION
STEP=1SUB =1TIME=1SEQV (AVG)DMX =.066138SMN =.136886SMX =1614.04
What we plan on buying:◦ Piston/Cylinder◦ Valve◦ Fluid Reservoir, 0.72 in3
◦ Pivot bracket to mount cylinder to top of AFO What we need to make
◦ Bracket to mount piston to bottom of AFO
Locking Mechanism:Component Breakdown
Power Calculations
Total Power Consumption
Steps TakenActuation (mWhr)
Sensing System (mWhr)
Total Power (mWhr)
200 1311 590 1902
Sensing System Power Consumption
SystemTime Hours
Duty Cycle Seconds Current Voltage mWhr QTY
Total Power (mWhr)
Sensor 8 0.2 5760 0.03 5 240 2 480Micro Controller 8 1 28800 3.00E-04 5 12 1 12 80% Efficiency 590
Chemistry Cost Weight Temp ( °C) Cycle Life Volts per cell
Lead Acid $13.50 4 lb -65 to 80 300 2.0
Nickel Cadmium $37.95 1.6 lb -20 to 65 500+ 1.2
Nickel Metal Hydride $49.95 1.36 lb -10 to 65 500 1.2
Lithium Ion $64.95 0.65 lb -20 to 60 500 3.7
Lithium Polymer $61.95 0.825 lb -20 to 60 500 3.7
Battery Selection
Circuit Design
Charger ConnectorD 1
D 1 N 4 0 0 2
Micro Controller and SensorsM 1
I R F 5 3 0
V 11 2 V
V B S D 1 -S I P
6
24
V O U TVIN
GN
D
U 31 2
D 2
D 1 N 4 0 0 2
C 1
1 0 0 u F
R 2
1 0 k
C 2
1 0 0 u F
Solenoid
Sensor Characterization Measure the output when compared to a
known distance. Yardstick or tape measure required.
Initial comparisons indicate strong correlation between expected and measured characterization curves.
Short range IR sensor: 10-80 cm (4-31 in) Long range IR sensor: 20-150 cm (8-59 in)
Calibration with Paper
Calibration with Paper
Multiple Surface Testing
Multiple Surface Testing
Placement of the Sensors: Top
10.25 in31.63 in
30 in
Lower SensorHeel Strike:
~15 cm (5.9 in)
Lift-Off: >~15 cm (5.9
in)
Tolerance: +/- 2 cm (.79 in)
Angle of Lower Sensor: ~20° from vertical
Placement of the Sensors: Bottom
15
cm
Functions written for determining upcoming terrain based on sensor readings
Function written to read sensor values Working on what needs to be written for SD
card Working on function calculation for gait
cycle time
Coding Progress
System UML
Price: $5 for each model◦ TI-MSP430G2553◦ Stellaris
Memory capability◦ MSP430 16KB flash memory◦ Stellaris 256KB flash memory
Speed◦ MSP430 16 MHz◦ Stellaris 80 MHz
No need to create separate PCB Ability to connect SD card for writing out data
Microcontroller Selection
Currently using 2 MSP430
For final assembly: will be using 1 Stellaris*If not enough memory, will add 1 MSP430
NOTE: Stellaris due to come in mid-December
Component Testing
Subsystem/ Function/ Feature Name: Locking Mechanism- ReservoirOwner: Shane/Pattie
Subsystem/ Function/ Feature Name: Locking Mechanism- CylinderOwner: Shane/Pattie
Subsystem/ Function/ Feature Name: Locking Mechanism- ValveOwner: Shane/Pattie
Engr. Spec. #
Specification (description)Unit of
MeasureMarginal
Value
Recorded Value Comments/Status
ES10Allowable range of motion between foot and shit º
94.5 to 137.7
ES24 Weight of entire device Kg 1 Will weigh when arrived
Force to move piston (fluid, valve closed) Lbf 17 Force to move piston (no fluid, valve open) lbf minimize Leak rate of cylinder In3/s minimize Stroke In 3
Engr. Spec. #
Specification (description)Unit of
MeasureMarginal
Value
Recorded Value Comments/Status
ES24 Weight of entire device Kg 1 Will weigh when arrived Volume In3 >=0.7456
Engr. Spec. #
Specification (description)Unit of
MeasureMarginal
Value
Recorded Value Comments/Status
ES24 Weight of entire device kg 1 Will weigh when arrived
Opens/closed in prototype circuit - Must open
Flow rate through open valve In3/s maximize
Component TestingSubsystem/ Function/ Feature Name: SensorsOwner: John/Dana
Subsystem/ Function/ Feature Name: MicrocontrollerOwner: Sam/John
Engr. Spec. #
Specification (description)Unit of
MeasureMarginal
Value
Recorded Value Comments/Status
ES24 Weight of entire device kg 1 Will weigh when arrived ES3 Predicts step up - ES4 Predicts step down - ES5 Predicts flat -ES6 Predicts ramp up -ES7 Predicts ramp down -ES8 Predicts speed of person m/s ±0.1
ES28Operates in environment temperature range ºC
-17.8 to 37.8 Verify component specs
Verify distances with calibration curve cm
Engr. Spec. #
Specification (description)Unit of
MeasureMarginal
Value
Recorded Value Comments/Status
ES24 Weight of entire device kg 1 Will weigh when arrived ES8 Predicts speed of person m/s ±0.1ES22 Error status - Yes
ES28Operates in environment temperature range ºC
-17.8 to 37.8 Verify component specs
Memory KB 16/256
Component TestingSubsystem/ Function/ Feature Name: Battery/ Electrical componentsOwner: Rob/Dana
Subsystem/ Function/ Feature Name: OrthoticOwner: Shane/Pattie
Engr. Spec. #
Specification (description)Unit of
MeasureMarginal
Value
Recorded Value Comments/Status
ES24 Weight of entire device Kg 1 Will weigh when arrivedES13 Charging time for full discharge Hours 8
ES28Operates in environment temperature range ºC
-17.8 to 37.8 Verify component specs
Output voltage V 24Test in circuit - Yes
Engr. Spec. #
Specification (description)Unit of
MeasureMarginal
Value
Recorded Value Comments/Status
ES24 Weight of entire device kg 1
ES10Allowable range of motion between foot and shit Degrees
94.5 to 137.7
ES32 Allowable toe extension/flexion degrees 0-50 ES26 Noise level (at ears of user) dB 60
Bill of Materials/Budget Breakdown
Projected budget usage: $235.49 Total estimated weight: 0.51 kg
Updated Risk Assessment
Updated Risk Assessment
Updated Risk Assessment
What’s Next
Questions?