P15001: Soft Ankle-Foot Orthotic
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System Verification

Table of Contents

Phase Planning

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Engineering Requirements

Working Engineering Requirements
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Requirement Fruition Plans

Updates were made to the Engineering Requirements Fruition Plan (PDF) and the Customer Requirements Fruition Plan (PDF)

Video
Engineering Requirements and Customer Requirements Fruition Plan Video Phase 5

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Budget Tracking

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

Budget Tracking
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Electrical System Response Time Testing

Related Engineering Requirement: ER11

Test Set up:
This test was done to see the response time between when the user's foot first hits the grounds and when the muscle starts to articulate. This tests the response time of multiple systems: The heelstrike sensors, the communication system, the analog to digital converters, and the internal software polling.

An important note is that when the muscle articulates is a function of the threshold level that is set in code. If the threshold is too high, there might be false triggers. If the threshold is too low, the system would seem to response slowly.

To test the system, the AAFO was used during normal walking and the output data was examined. The time frame that was measured was from the first drop in the heelstrike sensor to the beginning of the muscle ramping.

Results Conclusions:


The heelstrike was examined for 10 differnt cases of changing speeds. The average was found to be 133ms, well within our engineering requirements. The max time that was found was 237ms, which is outside of our engineering requirements, but was the only case were a single values was outside of our marginal engineering requirements. Return To Top

IR Sensor

In the last week of Sensor design the IR sensor broke. After talking with our guide, it was decided that the data which we already had showed the validity of the sensor placements and that when it was properly working, the sensor detected the distance to the ground correctly.



Replacement recommendations

If the IR sensor needs to be replaced, then it should be reordered with a smaller profile. Some recommendations for the new sensor can be seen below.

This sensor is very similar to the one that is used now but has a smaller profile, it would be a one-for-one replacement and can be found here.

This sensor is similar to the one that is used now but has a smaller much profile, there would have to be larger design changes to fit this in the LCH and can be found here.

This sensor has the largest risk because it is a homemade sensor. However because we are not going for precision and it has the smallest profile by far, it might be the best choice and can be found here.


In addition, if a replacement IR sensor would be ordered, the lower component housing would need to be modified. Because the LCH was designed to hold the IR sensor as is, taking into consideration line of site as well as ingress protection, it would be need to be slightly modified and reprinted if a different sensor is ordered. There are some general critical design criteria that must be followed, which take into account line of sight, overall functionality, and ingress protection. These design criteria are shown below in an annotated drawing;

If the IR sensor profile ever has a height of less than 0.25", then the surface the sensor sits on would actually be raised when compared to the surface the lid sits on; i.e., the depth of the cavity would be 0.25" on the corners, and shallower in the middle where the sensor sits.

A document with a summary of these changes for each case is provided below for future reference:
Future LCH modifications documentation

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New Muscle Testing

Foot-Lift Testing

The test is being completed to determine the angle range at which the foot is lifted by the actuation of the new, longer McKibben Muscle. This test is being conducted to address the issue of low dorsiflexion mobility seen in the previous phases of MSDII. Our goal is to obtain a value of at least 30 degrees, in order to meet our engineering requirement.

Procedure(s)
Test:

1. Have volunteer sit on a chair 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. Have user point their foot down, as much as possible, and then return to a resting position
7. Actuate the muscle using the Solenoid
8. Repeat Steps 6 & 7 until desired number of foot lifts is achieved
9. Stop the video recording
10. 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


Conclusions


Final Test Report


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Projected Capacity Testing

Objective: To project the capacity of the new black muscle.

Test Set up:
The new black MSD II muscle was used for this capacity testing. The set up followed standard muscle capacity testing with the black muscle supporting just over ten pounds of suspended weights.

Testing Procedure and Results:
The initial length of the muscle was measured to be 6.75 inches. The muscle was subjected the three cycles of testing to measure inflated length and diameter at approximately 60 psig. The results were averaged and the values were inserted in the calculation model refined in System Validation. The resulting averages and calculations can be seen in the table below:

It is clear that the new black muscle is projected to exceed the engineering requirements by a comfortable margin using the proposed tank. The orange muscle projections are also provided, however the orange muscle was only tested once in the previous phase and the test was not re-iterated in this phase.

Conclusions:
The new black MSD II muscle is projected to exceed the engineering requirements for untethered use using the proposed tank.

Spreadsheet


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Upper Component Housing

Assembly

The upper component housing was assembled as according to our initial designs and layouts for the cavity. A watertight box was purchased during last phase to ensure that the electronics would be protected from water. Even though water is not anticipated to get through the backpack, if it did, this watertight box provides additional protection for the electronics.

2 holes were drilled in the box to allow for the cords to leave the box and then leave the backpack, including the wires and air tubing to connect to the lower component assembly of the AFO. Also included in the upper component housing include the batteries, solenoid, PCB board, and other associated electronics. Pictures of the assembly are shown below:


Testing

Related System: Use AFO
The reason for this test is to find:
a.) Does our AFO meet the Ingress Protection Code as specified by our engineering requirements?
b.) More specifically, is the Upper Component Assembly of our AFO waterproof to the environment?

Test Set up:
Our ingress protection code is "54". There are 2 components of the IP code; the first number is the solid object protection code, while the second number is the water protection code. This test was to verify our water component of the IP code. A 4 in the IP code indicated that the AFO must be protected against the “splashing of water”, by testing for water splashing against the enclosure from any direction having no harmful effect.

For the test, the Upper Component Assembly of our AFO was assembled to resemble the final prototype design to determine if the final design will meet our requirements. The upper component contains both the backpack, as well as the watertight box contained within the backpack. However, the waterproof tight box that was purchased was not inserted into the backpack because it was already assembled with electronics. If the backpack itself failed the test, the test would be repeated with the watertight box present.

The backpack was emptied and zipped up as according to the user manual, which mimics the final assembly of the prototype. The test was performed similar to the LCH test, with the backpack being subjected to the ingress protection code.


Testing Procedure:
Running tap water was used to perform the splash test. The Upper Component was held near, BUT NOT IN, the running stream of water, and a hand was used to splash the water onto the surface of the backpack. The backpack was continually rotated to test all surfaces and connections of the assembly, especially where the zippers were present. Because our engineering requirements do not specify the AFO must be immune to running water, the backpack was not placed in the stream. After all surfaces were continually splashed, the backpack was dried and disassembled to analyze the wetness of the inside of the backpack, as well as any water residue.


Results Conclusions:

a.) The inside of the backpack was completely dry.
b.) There was no water residue on the inside of the backpack.

Overall, it has been determined that our Upper Component Assembly, and therefore our AFO, meeting our Ingress Protection Code requirements. Because the backpack passed the ingress protection test, the test did not need to be iterated with the waterproof box that contains our electronics.

Ingress Protection Testing Report

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Switch Holder Assembly

The switch holder that was designed to hold the 2 switches and the low battery LED was assembled. The switch holder is designed to keep all the switches and indicators in one central location. After a slight design modification to fit a different switch than originally designed for, the switch holder was reprinted and the switches were inserted into the holder. The holder was designed to hold all 3 components by a press fit. The holder was then attached to the actual AFO itself, specifically the wires that connect the upper and lower assemblies so the holder was located near the users hip. A picture of the holder is shown below:

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Wearablity Testing: Weight

Overview With additional components added to the system, these components were weighed to determine how much weight has added as well as the total weight of the system. With the additional weight added, the total weight falls within the marginal value of the engineering requirement of 13 pounds.

Results and Conclusion

From the previous trial, the only additional weight added was the weight of the backpack and the weight of the switch case. The additional weight added brings the total weight of the system to 8.65 pounds which is less than the marginal value in the engineering requirements of 13.65 pounds.

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RIT Subject Testing

Subject testing was conducted on Monday, May 4th at RIT. A table displaying the device and project information was set up in the main lobby of Building 09. We selected individuals who expressed interest, in the study, at the booth. Due to the small nature of the device, ideal participants was those with a women shoe size of approximately US8-10 and men shoe size of approximately US6-US8. However, everyone, over the age of 18, who expressed interest in the study was able to participate.

Procedure
Participants will be asked to test the new device by wearing it and walking across a room on flat ground. Following this activity, the device will be removed, and participants will be asked to complete a brief survey. This study will take approximately 10 minutes to complete.

Application Testing
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 Testing
Users will be asked to complete the following questions:


Compared to current commercially-available ankle-foot orthotics, would you consider this device aesthetically pleasing? (better, same, worse)

Comfort Testing
Users will be asked to complete the following questions:





Consent Form
All participants will be asked to sign a consent form prior to putting on the device. Click here for Consent Form

Results


Conclusions

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Moving Data Capture

Data was taken for the SD card and synced with video of a team member walking. this video was used during imagine and was a good demonstration of our product.

Video of the device walking

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Risk Management Table


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Problem Tracking

Working Problem Tracking
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Imagine Deliverables

P15001_MSDII_Problem_Tracking

Working Poster

P15001_MSDII_Problem_Tracking
Imagine Flyer

Technical Paper

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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