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