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
Introduction
Project Background
System Architecture
Locking Mechanism
Power Characterization
Sensor Characterization
Microcontroller/ Coding Progress
Component Testing
Bill of Materials
Budget Breakdown
Updated Risk Assessment
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
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
Primary 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
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 ST1,2,4
s5 predict flat yes/no - yes Test FT1,ST5
s7 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 C4
s18 force to remove constraints N down < 80 Test C3
s23 radius of edges/corners on AFO mm up 0.5 - S4,CF1,2
s24 weight of entire device lb down ≤2.2 Test FT6
s28 Operates in environment
temperature range °C range
-17.8 to
37.8
Component
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
CAD model
Sensors
Piston/Cylinder
Mounting Bracket
Valve
Battery
Processor
Reservoir
1
2
3 4
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
Concepts
A B C D E E
Hydraulic
Locking
Piston/
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 -1
ease of design (electrical) 1 1 1 0 0 -1
ease of design (mechanical) 0 1 1 -1 -1 -1
response time (electrical) 1 1 1 -1 -1 0
response time (mechanical) 1 -1 1 0 0 0
locking force 1 -1 1 0 0 1
attachment to orthotic 0 0 0 0 0 0
safety -1 1 -1 0 0 0
reliability 1 1 1 0 0 0
Range of Motion 1 0 0 0 0 1
Energy consumption 0 0 0 -1 -1 0 Total Score 5.00 4.00 6.00 -4.00 -4.00 -1.00
Rank 2 3 1 4 4 4
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
BIMBA HL Original Line Bimba "500" Series MAXIM Hyd Cylinder Bore 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 3000 Cost $21.80 $61.90 $104.75
Material 304 Stainless Steel 304 Stainless Steel Iron/Steel
Picture
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
min1618.06213.0
6.0
"5.1
2
"16
9 32
GALs
in
st
lA
t
VQrequired
0145.0125
11618.0
P
SGQCv
•Cv=0.035 •Solenoid Powered •Normally Closed (solenoid opens valve) •12 or 24 VDC •1/8” NPT threaded •~3 ms response time
1
NOV 1 2012
13:29:30
ELEMENTS
1
X
Y
Z
NOV 1 2012
13:05:35
VOLUMES
TYPE NUM
U
ROT
F
HD Polyethylene •E=125,000 Psi •Yield Strength=4,600
1
MX
.024902
581.9071163.79
1745.672327.55
2909.433491.32
4073.24655.08
5236.96
NOV 1 2012
13:35:57
NODAL SOLUTION
STEP=1
SUB =1
TIME=1
SEQV (AVG)
DMX =.485218
SMN =.024902
SMX =5236.96
1
.024902
581.9071163.79
1745.672327.55
2909.433491.32
4073.24655.08
5236.96
NOV 1 2012
13:35:07
NODAL SOLUTION
STEP=1
SUB =1
TIME=1
SEQV (AVG)
DMX =.485218
SMN =.024902
SMX =5236.96
Stress at Joint: 5000 Psi
Stress at Bolt Locations: 2000 Psi
1
X
Y
Z
NOV 1 2012
17:17:34
ELEMENTS1.67” F
M
F=17 lbf
M=22.695 in-lb
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 2012
17:11:41
NODAL SOLUTION
STEP=1
SUB =1
TIME=1
SEQV (AVG)
DMX =.066138
SMN =.136886
SMX =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
Total Power Consumption
Steps Taken Actuation (mWhr)
Sensing System (mWhr)
Total Power (mWhr)
200 1311 590 1902
Sensing System Power Consumption
System Time Hours
Duty Cycle Seconds Current Voltage mWhr QTY
Total Power (mWhr)
Sensor 8 0.2 5760 0.03 5 240 2 480 Micro 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
Charger Connector
D1
D1N4002
Micro Controller
and SensorsM1
IRF530
V1
12V
VBSD1-SIP
6
24
VOUTVIN
GN
D
U31 2
D2
D1N4002
C1
100uF
R2
10k
C2
100uF
Solenoid
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
Long range IR sensor: 20-150 cm
Lower Sensor
Heel Strike: ~15 cm
Lift-Off: >~15
Tolerance: +/- 2 cm
Angle of Lower Sensor: ~20° from vertical
15 c
m
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
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
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
Subsystem/ Function/ Feature Name: Locking Mechanism- Reservoir
Owner: Shane/Pattie
Subsystem/ Function/ Feature Name: Locking Mechanism- Cylinder
Owner: Shane/Pattie
Subsystem/ Function/ Feature Name: Locking Mechanism- Valve
Owner: Shane/Pattie
Engr.
Spec. # Specification (description)
Unit of
Measure
Marginal
Value
Recorded
Value Comments/Status
ES10
Allowable 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
Measure
Marginal
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
Measure
Marginal
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
Subsystem/ Function/ Feature Name: Sensors
Owner: John/Dana
Subsystem/ Function/ Feature Name: Microcontroller
Owner: Sam/John
Engr.
Spec. # Specification (description)
Unit of
Measure
Marginal
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
ES28
Operates 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
Measure
Marginal
Value
Recorded
Value Comments/Status
ES24 Weight of entire device kg 1 Will weigh when arrived
ES8 Predicts speed of person m/s ±0.1
ES22 Error status - Yes
ES28
Operates in environment temperature
range ºC
-17.8 to
37.8 Verify component specs
Memory KB 16/256
Subsystem/ Function/ Feature Name: Battery/ Electrical components
Owner: Rob/Dana
Subsystem/ Function/ Feature Name: Orthotic
Owner: Shane/Pattie
Engr.
Spec. # Specification (description)
Unit of
Measure
Marginal
Value
Recorded
Value Comments/Status
ES24 Weight of entire device Kg 1 Will weigh when arrived
ES13 Charging time for full discharge Hours 8
ES28
Operates in environment temperature
range ºC
-17.8 to
37.8 Verify component specs
Output voltage V 24
Test in circuit - Yes
Engr.
Spec. # Specification (description)
Unit of
Measure
Marginal
Value
Recorded
Value Comments/Status
ES24 Weight of entire device kg 1
ES10
Allowable 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
Projected budget usage: $235.49
Total estimated weight: 0.51 kg
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