P15001: Soft Ankle-Foot Orthotic

System Validation

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)

Engineering Requirements and Customer Requirements Fruition Plan Video Phase 4

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Budget Tracking

Our team made several purchases this phase. Our major purchases included the fastenings and the air tank refills and repairs. 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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Circuit Board: Revision 2

The changes that could be made on the circuit board to improve usability were made. A list of these changes can be seen below.
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
Schematic (left), Top Layout(Center) and Bottom Layout(Right)

CAIR Capacity Test II

Related System: CAIR, Actuate muscle
The reason for this test is to find:
a.) Are the capacity test results better without the leaky BAD lab regulator?
b.) If the results are better, what are the new size limitations for a larger muscle?

Test Set up:
The original MSD II muscle was used for this second capacity test. The setup was very similar to the setup for the first capacity test which was performed in the subsystems phase of MSD I. The main differences were that this second test used a 6.125in muscle instead of a 7in muscle, the leaky BAD Lab regulator was removed, and the initial tank pressure on the second trial was 2,600 psig instead of 3,000psig.
Testing Procedure and Results:
The outer diameter of the inflated muscle was previously found to be 2/32in. The initial length of the muscle was measured to be 6.125 inches in a previous trial which also found the inflated muscle outer diameter to be 0.52 inches at 60psi. The muscle was automatically flexed and released 5 times after activating a switch and the number of switches was recorded. The tank's regulator was adjusted before testing began and the output was about 60 psig although there was initial variance of 65-60 psig. As in the previous test, a small leak could be heard from the tank regulator during set-up and testing. As a result of regulator adjustments and other possible causes the initial starting pressure of the tank was 2,600 psig. At approximately 625 flexes the pressure dropped below operating pressure. To adjust for the fact that the initial tank pressure was lower than normal, the number of steps was scaled to 3,000 psig by multiplying the number of steps at 2,600psi (625 steps) by the scale factor of 3,000/2,600. These results can be seen in the table below:

In the first capacity test the difference between estimated steps and actual steps was 26%. For this second test, the difference is smaller at 13%. This is reasonable since the BAD Lab regulator used in the first test was known to be leaky and its absence should intuitively lead to a smaller disparity between the model and the test results.
The table below depicts the feasibility to reach engineering design requirements based on the purchase of a larger tank noted as 'tank 2'. The grey and orange columns represent the estimated number of steps based on capacity tests I and II respectively. Since capacity test II did not use the leaky BAD Lab regulator it is taken as the more accurate projection. Since the current muscle is projected to exceed 2,000 single leg steps in one day, there is clearly room for muscle expansion.

In the table above, a simple proposed muscle expansion is highlighted in blue which is designed to have a longer initial length of 6.625 inches and an estimated deflection of 1.15 inches. The muscle expansion still leads to an estimated steps value that exceeds the ideal engineering requirement for untethered use so even further expansion may be pursued in order to achieve desired foot-lift.

a.) This second capacity test resulted in slightly more air capacity than the first test after scaling to account for initial tank pressure deficiency
b.) There is much room for muscle expansion in order to achieve better foot-lift results and proposed muscle designs can be modeled in the report spreadsheet

Next Steps
-Build new proposed muscle prototypes to increase foot-lift deflection and address strain problem

Report Spreadsheet

Lower Component Housing

Lower Component Housing Assembly

After the initial printing of the lower component housing assembly, he lid covering the Infared sensor cavity needed to be reprinted in order to fit inside the cavity and provide adequate waterproof protection. This lid was designed to be slightly smaller, keeping the same O-Ring groove and overall functionality, and then reprinted during the first week of Phase 4.

After lid was printed, all 3 parts were assembled, along with the O-Rings, sample ribbon wires, and appropriate socket head cap screws to be sure that all parts were printed correctly and there would be no need to reprint anything. All parts were assembled, and the dimensions and holes lined up correctly. This will be reassembled with all necessary electronics and components after testing is completed.

Ingress Protection Code 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 Lower Component Housing Assembly 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 Lower Component Housing was assembled to resemble the final prototype design to determine if the final design will meet our requirements. However, because the electronics are not being used, the "eyes" of the IR sensor will not be located to fill the holes in that lid. There, no water contacting that surface will be used to determine a test failure.

The LCH was assembled using the required O-Rings, socket head cap screws, and sample ribbon wires that will be used in the final design. The cavities of the LCH were filled with paper towels, so after the test, they can be analyzed to determine if any water entered the cavities where the electronics will be located.

Testing Procedure:
Running tap water was used to perform the splash test. The LCH 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 LCH. The LCH was continually rotated to test all surfaces and connections of the assembly, especially the mating surfaces where the O-Rings were located. Because our engineering requirements do not specify the LCH must be immune to running water, the LCH was not placed in the stream. After all surfaces were continually splashed, the LCH was dried and disassembled to analyze the wetness of the paper towels, as well as any water residue inside the cavities.

Results Conclusions:

a.) The paper towels were completely dry; therefore, no water is entering hte cavity.
b.) The cavities and cavity walls are dry as well, confirming the fact that the LCH is water tight.
c.) There was some water residue on the mating surface of the PCB lid and the main LCH; however, the water stopped at the O-Ring and did not travel beyond, showing the functionality of the O-Ring.

Overall, it has been determined that our LCH, and therefore our AFO, meeting our Ingress Protection Code requirements.

Ingress Protection Testing Report

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Wearibility Testing

Skin Temperature

Related System: Secure Foot
The reason for this test is to determine the following:
Does the average change in skin temperature when using the AFO meet the engineering requirement?

Test Set up
This test requires two thermocouples (one on each leg) to be used for measuring skin temperature. Each thermocouple is connected to a data logger which can store data. To use these data loggers, each of them must be set up using the USB-500 series software before each trial. Once the data loggers are set up, they can be connected to the thermocouples and the ends with the wire are then taped to the front of the lower legs. The left leg has a compression sleeve placed over the wire on the bare skin, while the right leg has the AFO placed over the pants. The whole set-up for each leg is shown below

The only thing to do for the procedure is to start walking or do normal activities, while making sure the wire does not come out of the pants and that the thermocouples stay connected to the data loggers. When finished using the system, the data can then be uploaded from the data loggers onto the same software.

Results and Conclusions

Originally, the whole system was worn while walking a mile in thick jeans. This caused the change in temperature to be outside the engineering requirements. However, this was performed beyond a worst case scenerio and what may have caused this rapid change was access moisture inside the AFO. Since the compression sleeve is made of spandex, this absorbed a lot of the moisture. Several more trials were performed doing normal routines. There were times when the wire inside the AFO came loose which caused the change in temperature to actually drop. As a result of this, the wire was taped to the skin, which really improved the measurements. In addition, convertible pants worked best for this experiment since it allowed a place for the wire to stick out. Upon these improvements in the experiment, the change in temperature fell within our engineering requirements.

Temperature Test Report

Pressure to Leg

Related System: Secure foot
The reason for this test is to determine the following:
Does the added pressure of attaching the AFO to the leg fall within the engineering requirement?

Test Set up
A blood pressure instrument is used to measure added pressure to the leg. One leg has the blood pressure instrument attached, while the other leg has the AFO attached. The set-up is shown below

To work the blood pressure instrument, compressing the bulb will inflate it, while releasing the air valve will deflate it. Air is let into the instrument till the pressure feels greater than the AFO. Air is then slowly released till pressure matches the AFO pressure. Then pressure on the gage is recorded.

Results and Conclusions
Several trials produced an average pressure of 18 mm Hg which is below the ideal value of 20 mm Hg for the engineering requirements. As a result, the pressure added to leg from the AFO fell within our engineering requirements.

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Nazareth Pedometer Program

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.

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


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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Number of Participants: 3
Number of Days of Collected Data per Participant: 3
Step Range between Participants: 122-3500

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Distance Sensing

Based on discussions with our customer and observations from clients with foot drop, it has been decided that we will monitor the distance sensing form the IR sensors and that the clients will manually control terrain navigation through the use of the passive mode with manual articulation. A picture of the data that is recorded from this system is recorded below.

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Upper Component Housing

Since it is necessary to house the upper components in a more structured and water resistant box, research was performed on current watertight boxes and measurements were taken from the current temporary cardboard box. The current inner dimensions were measured to be: 9-1/2"x6-1/8"x1-3/4"
Most watertight boxes currently available on the market are slightly smaller that the desired size, however the Small MTM Survivor Dry Box with O-Ring Seal has very close dimensions with some room to spare 9.75" x 7.75" x 2.8"
The box is available in orange or forest green and can be purchased through Amazon prime with two day shipping. (Photo courtesy of Amazon.com)

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Strength Testing

Related System: Raise Foot
The test is designed to test the strength of the air muscle and related components to determine the durability of the prototype.

Test Set up
A secondary muscle was made with similar materials and arrangements as that of the first muscle. The muscle base was sewn to the red inelastic ribbon to mimic the actual brace and test the strength of the thread as well. The red inelastic strap was taped to the top of the table via packing tape as shown below.


Results Conclusions
The muscle successfully supported 30 lbs of vertical force with no apparent signs of deflection or failure.
When impact testing was ready to be performed, the red inelastic ribbon actually slipped off the table and pulled away from the packing tape. A group member elected to simply hold the weights by the ribbon with their own hand but in the process the red ribbon was pulled with at an unusual angle and as a result, tore away from the muscle base.


Strength Test Report

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Switch Holder

A part was designed to hold the 2 switches and indicator that will be present in our final design. This part was designed for convenience for the user, so the 2 switches and LED indicator could be easily held in one spot next to the user's hip. This part helps contribute to our easy to interface system, which is a engineering requirement. This part was 3D printed in the Construct in a similar process to that of our Lower Component Housing.

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Machine Wash Test

During this phase, our team machine washed the device. To do this, the muscle was removed and the device was turned inside out, to prevent the plastic attachment piece from scratching the inside of the washer. The washer was set on a delicate cycle and cold water and Tide detergent was used to clean the device. After the wash cycle, the device was taken out of the washing machine and placed on the back of a chair to air dry.


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Miscellaneous Videos

Several videos from this phase and the previous phase were combined into one video of miscellaneous items. Featured sub-videos include:

The music to this video is based on the Johnny Cash song "I Walk the Line" with Modified Lyrics

Miscellaneous Videos (I'm Walking Fine)

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Problem Tracking

Working Problem Tracking
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Risk Management Table

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Imagine Deliverables


Working Poster

Imagine Flyer

Technical Paper

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Week 5 Demo

Within the Week 11 Project Progress Review Agenda is an agenda for the week 11 meeting. An updated list of Phase 3 Action Items is also provided.

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