P15001: Soft Ankle-Foot Orthotic
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Build & Test

Table of Contents

Phase Planning

Build & Test Shared Vision

Our vision for week five is to finalize the design and begin building to have an initial prototype completed and demonstrated for our end-of-phase review.

Functional Demonstration:
Electrical- The electrical team will demonstrate the following during our phase 2 design review:

Mechanical- The mechanical team will demonstrate the following during our phase 2 design review:

Additionally, our team plans to complete the following tests by the time of our end-of-phase review

Tests to be performed:
Electrical:

Mechanical:

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Engineering Requirements

Working Engineering Requirements
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Engineering Fruition Plan

Engineering Fruition Plan
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Completed Tests

Dorsiflexion Mobility: Lift Test

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:


Results:

Angle Results


Deflection Results
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Video:
Foot Lift Test Tracker Video


Conclusion:


Next Steps:

Foot Lift Test Report

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Extended Use Test Stage 1

Overview
This test is an extension of the lift foot integrated test. The extended use test was designed to subject the integrated mechanical components of the AFO to extended use testing to determine performance and reliability over time.

Procedure(s):
Test
The procedure for stage one of the extended use test is essentially the same as that of the lift foot test with the additional step of actuating the McKibben air muscle a total of 100 times and noting lift measurements and changes over time, if any.

Post Test
In addition to the extended use test an experimental post test was performed to mimic a worst case scenario. In the post test, the user stretched their toe downward as far as they could while the muscle was flexed. Following this worst case situation, the basic foot lift test was performed again in order to quantify the impact that the worst case slippage had on AFO performance. Tracker was again used to mine data from the post test.

Results:

Extended Use Test and Post Test Results

Summary of Extended Use S1 Results
Video:
Extended Use Test S1 Video
Conclusion:
Test: Plots indicate no adverse effects from extended use with the current brace. Post test: Permanent deflection is possible with the current brace resulting in adverse effects on AFO performance.



Next Steps:

Extended Use Test Stage 1 Report

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Comfort and Application

During this phase, 2 additional team members wore the AFO. Each member was asked to apply the device onto their right foot. Once the device was secure, the McKibben muscle was actuated several times. At the end of the test, both individuals were asked to complete a survey. Their completed surveys are shown below.

Survey
1.) Please rate the comfort of this device by circling one of the numbers (1-10) on the scale below.


2.) Are there specific parts/areas of the device that make it uncomfortable to wear? Please be specific and feel free to offer suggestions for improvement.

Results
Average Comfort Rating: 1

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Problem Tracking

Working Problem Tracking
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Failure Modes

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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.


Budget Tracking Spreadsheet
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Mechanical Build

Component Housing Redesign

Motivation

After the MSD II, week 2 progress review and more discussion amongst the team, it was determined that the lower component housing, along with the associated parts, needed redesigned to provide better functionality to our design. The old design was not easy to integrate with the PCB board, nor did it provide appropriate ingress protection for our electrical components. The lid for the PCB board cavity was redesigned, and a second lid for the IR sensor cavity was designed. Pictures of the current assembly design are as follows:
Lower Component Housing Assembly

The individual part redesigns and details are as follows:

Lower Component Housing


Lower Component Housing

In View 1, showing the PCB board cavity:

In View 2, showing the PCB board cavity:


PCB Board Cavity Lid


Lower Component Housing

In View 1, showing the top of the lid:

In View 2, showing the mating side of the lid


IR Sensor Cavity Lid


Lower Component Housing

In View 1, showing the top of the lid:

In View 2, showing the bottom side of the lid


Associated Documents

PCB Lid O-Ring Report
IR Lid O-Ring Report

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Slow Motion Deflection

Motivation

The reason for this test is to find the approximate amount of deflection required by an air muscle based on data taken from a slow motion video.

Procedure

A camera was placed near a treadmill and video footage (hehe:) was taken while walking slow on a treadmill with the foot rig. The rig is designed to keep tension on the knot in order to take up the slack during the gait cycle to find the deflection required of the air muscle.

Tracker software is available as a free download and was used to mine data from the video footage. Key points were selected on the rig, namely:

These points were tracked manually and visually frame by frame during a gait cycle.

Video

Slow Motion Deflection Video

Results

The data from the video required some analysis in order to find useful results. The length and angle between the bottom of the protractor and the knot as well as the length and angle from the top of the protractor and the knot were measured in tracker. After trigonometric manipulation both sets of lengths and angles were resolved into the relative vertical distance between the bottom of the protractor and the knot. The results can be seen in Figure 2. Due to poor resolution in the video, the latter portion of the gait cycle was unreliable.

Conclusions

The strain requirement of 1.0 inche seems to be appropriate for our AFO. This test was based on a level slow terrain and required strain may still possibly be greater on stairs or other terrain. The ankle angle data from our tests is also not dissimilar from scientific data.

More details including the ankle angel data analysis and comparison to Posture data can be found in the Slow Motion Deflection Report

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Working Model

Motivation

As part of the solution for the problem tracking item "Muscle strain will not provide required displacement" developing a Working Model 2D simulation became a priority for this phase. The potential benefits are twofold: modeling a real gait cycle with accurate foot dimensions could help us determine the amount of deflection required by the muscle and such a model could also be helpful in visualizing the project as a whole. This method involved simulating a virtual kinematic procedure using Working Model. This software can model kinematic processes and measure deflection and rotation.

Procedure

Using an adjustable switch, the amount of force provided by the muscle was varied in such a way as to mimic data from a Gait & Posture article [Bovi G., Rabuffetti M., Mazzoleni P., Ferrarin M, 2010, “A multiple-task gait analysis approach: Kinematic, kinetic and EMG reference data for healthy young and adult subjects”, Gait & Posture].
With the data mimicked by the switch, it is possible to measure the deflection required by the muscle without using hardware. In order to get accurate measurements, proper foot and leg dimensions must be used. This particular simulation did not use exact measurements, but was successful in visualizing how much flexion occurs during a slow gait cycle.

Video

The actual footage of the working model simulation from which the data above was taken is captured in the video below.
Working Model Video

Conclusions

The working model software has a steep learning curve. It has the potential to help determine the amount of deflection required by the muscle but this would require a significant amount of time. Since the integrated prototype is ready for testing and since the slow motion deflection test has already demonstrated low strain requirements, continuing Working Model simulation seems largely inefficient.

Recommendations

If this simulation was pursued further, the following recommendations would apply:

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Lower Attachment Strap

Control Diagram


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Upper Brace Design Modifications

Motivation

After assembling our phase 2 prototype for our AFO, it became evident that the upper brace would need to be modified to reduce the additional strain that was being absorbed by the brace. During MSD I testing, the upper brace was tested and it was determined that the brace would not become detached from the leg when the muscle was articulated, but it was not clear until the prototype was assembled that the muscle stretched the brace. Because the brace is elastic, the material stretched when the muscle was articulated. Also, because the strap was not sewn on to the front of the brace, but rather the back, and the top of the brace was slipping downward when the muscle was articulated.

Design Modification Proposal


Upper Brace Redesign

Design Modifications:


Conclusions


Associated Documents

Upper Brace Modification Plan

Integrated Prototype

Foot Lift Tests

Motivation

One of the main goals of this phase was to achieve mechanical integration and foot lift using the actual muscle to lift the foot.

Video

Preliminary Foot Lift Tests Video

Conclusions

Although formal measurements are yet to be taken, the preliminary foot-lift tests on 2/17/15 achieved comfortable foot-lift despite some apparent slippage in the upper brace. Upper brace design modifications may be necessary to address the apparent slippage.

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Electrical Build

Schematics

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

Tested Systems

Soldered 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.
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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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Risk List

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References


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Week 5 Demo

Within the Week 5 Project Progress Demonstration Agenda is an outline for the meeting, an updated list of action items, and additional phase specific documentation.

The Phase 2 Review Action Items PDF contains notes and action items taken from the week 5 project progress demo.


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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