P15001: Soft Ankle-Foot Orthotic
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Integrate & Assemble

Table of Contents

Phase Planning

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Engineering Requirements

Working Engineering Requirements
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Requirement Fruition Plans

Besides standard updates to the Engineering Requirements Fruition Plan (PDF) an additional plan was created to track the status and fruition of the customer requirements: Customer Requirements Status and Fruition Plan (PDF)

Video
Engineering Requirements and Customer Requirements Fruition Plan Video

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Budget Tracking

Our team has made several purchases thus far. Our budget tracking document displays these purchases in an organized manner as well as the total prototype cost thus far.

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Updated System Design

Lower System: Full Design

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Strap Control Diagram

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Lower Component Housing

The lower component housing assembly was 3D printed during this phase. The lower component housing, the PCB board cavity lid, and the IR sensor lid were all printed in the Construct at RIT. Also, fasteners, O-Rings, and threaded inserts were obtained for assembly. Going forward, the IR sensor will need to be reprinted in order to correctly assembly the design, and the assembly will be tested to determine if it meets our ingress protection metrics.

The 3 printed pieces are shown below:

Lower Component Housing (left), PCB Cavity Lid (Center) and IR Cavity Lid (Right)

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UCH housing preliminary prototype

A scaled prototype of the upper component housing box was constructed out of cardboard. The scaled model provides a practical way to check the arrangement of the internal UCH components before purchasing the Watertight Box

Scaled UCH model:

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Corrosion Test

Overview
During this phase, a corrosion test was completed to determine if our McKibbon muscle can withstand environmental conditions that our AFO could potentially see throughout a day’s use. Because our AFO needs to be used in a Rochester environment, we need to be sure our muscle will not corrode when exposed to the environment. It was decided that, instead of submerging the muscle into salt water or putting it in a freezer, we would instead expose the muscle to actual environmental conditions for the Rochester climate. A sample muscle was constructed and was then taken on a “walk” around the RIT campus, exposing the muscle to 2 snow piles, as well as 5 salt water puddles. These are potential environmental conditions that the AFO would see throughout a day. The muscle components and performance was compared before and after the test.


Procedure:

1. Construct sample McKibbon muscle to complete test, using identical materials used in our McKibbon muscle
2. Take pictures of muscle components before test
3. Test muscle performance before test
4. Expose muscle to environmental conditions around the RIT campus, including snow and salt water puddles
5. Allow muscle to completely dry for 2 days
6. Test performance of muscle after corrosion testing
7. Disassemble Muscle
8. Take pictures of components for comparison

Setup:

Conclusion:


Associated Documents
Corrosion Test Report

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Leak Test

Overview
When the muscle was placed into the hold state or constantly constricted, air would leak out and the muscle would fully relax within 30 seconds. The source of the leak had to be discovered and fixed.

Procedure
Components were systematically submerged in water to see if air bubbles could be observed due to a leak. The muscle and hosing proved to have no leaks. This left only the solenoid and the regulator as possible sources of the leak[s]. The regulator was a non critical component used to monitor pressure from the solenoid to the muscle. After a technical conversation with one of the members from the fish team it was discovered that the regulators are very leaky and should be removed. The regulator was removed and the solenoid was covered in silly putty so any leaks could be observed.

Setup

Video
Submersion Test Video

Results
After the regulator was removed the hold state was functioning properly and there were no apparent leaks from the solenoid.

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Weight Distribution

Overview
Two of the engineering requirements involved maximum weight of the AFO overall and on the leg. The purpose of this test is to ensure that the weight does not exceed these limits.

Procedure
Each individual component was weighed.

Results

Conclusion
The total weight of the AFO as well as the weight on the leg fall within the ideal values of the engineering requirements. The back pack and upper component housing still need to be weighed but we know we have 2.4 pounds to play with, which is easily achievable.

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Electrical Build

Schematic (left), Top Layout(Center) and Bottom Layout(Right)
Tested Systems

Unsoldered Systems

Board Changes

Mistake Made How it effects the system Actions Taken
Ordered 0402 not 0805 for the 100nF part (C5,C6,C7) These are decoupling capacitors. They will help long term stability but the system should be fine without them in the short term Found the right 0805 part in the Makers Space. Corrected the BOM for future use.
Incorrectly routed D5 (tied it to 5V) D5 was an additional digital pin that was being sent to the lower housing for debug. We lose no functionality by losing this pin. The pin will stay connected for the time being. The trace can be cut later if needed. The schematic should be updated to see this change.
Connected wrong LEDs One of the low batteries alerts is green and the power LED is yellow. None. Will take action when design is finalized. Not worth the risk of fixing it now.
Inconsistent Switch Labeling Wrong name on jumper. No real effect. The schematic should be updated to see this change.
Number of 12V connections It would be nice if there was one more connection to 12V. No real effect. The schematic should be updated to see this change.
Programming header A header to program the microcontroller on the board would be nice. No real effect. The schematic should be updated to see this change.
Indicator on 12V Added LED to 12V would be nice. No real effect. The schematic should be updated to see this change.
Better Labels on LEDs Added labled to LEDs. No real effect The schematic should be updated to see this change
Use brighter LEDs Make the LEDs easier to see. No real effect Update the BOM with these changes.
Thicken 12V trace 12V trace burnt when shorted. Thicker trace may have prevented that. The schematic should be updated to see this change
Redo the Traces on the SD Card Didn’t cause issues but they could be done better The schematic should be updated to see this change
Add LED for working SD Card Would be nice to have The schematic should be updated to see this change
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Power Source Testing

Procedure The power source was tested to help determine how long it could run for on a typical days use as well as measuring current drop. This device was tested in two modes: active and idle. For both modes, voltage drop was measured across a 1 ohm, high power resistor to help detect current drop. Using previously obtained statistics for how long long a client could use this system in each mode as well as a typical gait cycle, calculations were used to help determine how long this system could be used on a daily basis. These calculations, as well as the power rating that the battery was rated were used to calculate how long the battery could last on a daily basis.

Results

Current draw from power source for both modes
Table of calculations
Conclusions The test verified that the power source can last for a period greater than expected marginal value as well as not going above maximum current.

Full Report

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Noise Test

Procedure
1. A sound meter app on a smart phone was used to monitor the solenoid noise level.
2. the phone was placed directly next to the exhaust port without the muffler. the muscle was contracted and released 15 times. the average noise of the quite room, contraction and release was recorded.
3. The same procedure in step two was done with the muffler.
4. The same procedure was repeated with the solenoid in a leater case to simulate the bag, the sound meter was still placed directly next to the leather case.
5. Step four was repeated with the sound meter at ear height relative to the solenoid.
Setup
Noise Test
Results

It was very interesting to note that the noise level was not reduced with the muffler even though it seemed much quieter, in iterated testing the pitch will be recorded. Also our Engineering requirement is only met when the sound meter was placed at head level. Next Steps
the test will be iterated with an actual sound meter and with the solenoid placed in the UCH and backpack. In addition the pitch will be recorded.
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Solenoid Ramping

Reason: It was found that the motion of the muscle was two jarring. Therefore, the code was changed to articulate the muscle in five stages. This was done for both contracting the muscle and releasing it.

Video: Solenoid Ramping Video

Issue Encountered: When the data was examined from after the change, it was clear that there was to data that was being recorded during the ramping cycle. This data is seen below.


The code was fixed and the updated data is seen below.


Next Steps: Next steps for this would be to continue to test the AAFO for comfort.

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Walking with System

Full system video

Dorsiflexion Mobility: Lift Test Stage 2

Overview
During this phase, a lift test was completed to determine the angle range at which the foot is lifted by the actuation of the McKibben Muscle as well as determine the amount of deflection experienced by the upper muscle attachment piece during muscle actuation.

Procedure(s):
Test

1. Have volunteer sit on table top with their right foot hanging freely
2. Place the AFO brace on volunteer’s foot
3. Attach the McKibben muscle to the brace
4. Place yellow indicators near user’s heel, arch, and on brace near upper strap
5. Set up and start the video recording
6. Actuate the muscle using the Solenoid- complete this step 5 times
7. Stop the video recording
8. Remove the device from the volunteer’s leg

Data Analysis

1. Import the recorded video in Tracker (video tracking software)
2. Create tracking points using the yellow indicators on the brace
3. Use the protractor measure function to find the ankle angle (foot relative to leg)
4. Copy ankle angle data from Tracking Software and put into Excel document


Setup:

Test #1 Test #2 Test #3
Test #4 Test #5 Heel Tracking

Test 1

Conditions:
Buckle sewn in front of brace with tension strap under the lower brace and over pant leg.
Results:


Test 2

Conditions:
Same conditions as test 1 but with inelastic material added to the back of the upper brace from the leg strap to the bottom of the muscle base. The buckle was also more tightly secured plus the general upper brace strap sewing was redone.
Results:

Test 3

Conditions:
a) Same conditions as test 2
b) Same conditions as test 2 but with tracker heel measurement located at a lower position on the foot.
Results:

Test 4

Conditions:
Same conditions as test 3a. but with the tension strap placed over the lower brace.
Results:

Test 5

Conditions:
a) Same conditions as test 3a.
b) Same conditions as test 3a but with the user pointing the toe and relaxing the foot before air muscle flexion.
Results:

Summary


Conclusion:


Video
Videos for phase 3 tests


Next Steps:

Foot Lift Test Report
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Upper Brace Strap Modifications

As mentioned in the previous phase, it was necessary to make changes to the upper brace strap design since slippage was clearly observed.
Upper Brace Strap (left), Buckle Sewing Close-up (Right)



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Force Test

Motivation:
In order to test the new brace design and fulfill Engineering Requirement 4, a force test was conducted in Phase 3.
Procedure:
The force test followed standard procedure as performed in MSD I although a new force scale was used in this test. The scale did not appear to read accurately so calibration of the scale was necessary. The calibration was performed by suspending masses of known weight from the scale, recording the readings, plotting the results, and curve fitting. A picture of the scale curve fit is shown below:
Results:
With an approximate leaver arm of 4.5 inches from heel to the lift area, the resulting peak torque observed from this test is 3.42 ft-lbs as shown below:
Conclusions:

Force Test pdf



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Nazareth Clinic

Pedometer Program

Overview
Our team is working closely with the Physical Therapy Clinic at Nazareth College, also located in Rochester, NY. We are currently setting up a pedometer program in which we will have several Foot Drop clients keep track of the number of steps that they take per day for a total of 3 days. The data collected in this program will be used in a model to calculate the amount of hours that our device will last before needing to refill the air tank.

Instructions
Listed below are the instructions that each client will follow to collect data.

Questionnaire


The following document will be given to each participant: Nazareth Pedometer Program Handout. They will be required to fill it out and return it when complete.
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Application, Aesthetics, and Comfort Testing

Application, Aesthetics, and Comfort Testing was completed at Nazareth College on Wednesday, March 18, 2015. Several clients at Nazareth Clinic tried on our prototype, lower brace part only, and completed a series of questions.

Application Test
For this test, users were asked to put on the device after given verbal instructions on how to do so. Each user was timed which applying the device and were asked to answer the following questions when finished.


Aesthetics Test
Test 1: Aesthetics - Users were asked to analyze the device and answer the following questions:
1.) Compared to current commercially-available ankle-foot orthotics, would you consider this device aesthetically pleasing? (better, same, worse)


2.) Are there any specific features that make our device not aesthetically pleasing?

Comfort Testing
While wearing the device, users were asked to answer the following questions.




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Problem Tracking

Working Problem Tracking
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Risk Table


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Home Planning & Execution Problem Definition Systems Design Subsystems Design Detailed Design Gate Review
MSD I
Build Preparation Build & Test Integrate & Assemble System Validation System Verification Final Review
MSD II