Phase Planning
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:
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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 BoxScaled UCH model:
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Corrosion Test
OverviewDuring 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:
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1. Construct sample McKibbon muscle to complete test,
using identical materials used in our McKibbon
muscle
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2. Take pictures of muscle components before test
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3. Test muscle performance before test
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4. Expose muscle to environmental conditions around the
RIT campus, including snow and salt water puddles
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5. Allow muscle to completely dry for 2 days
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6. Test performance of muscle after corrosion
testing
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7. Disassemble Muscle
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8. Take pictures of components for comparison
Setup:
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Conclusion:
- There was no drop in performance of the sample McKibbon muscle after the corrosion test; the before and after performance testing yielded identical results
- There was no noticeable defects from the corrosion test on the muscle 2 days later besides a small amount of dried salt on the metal components; the metal components did not rust, nor did the silicon tubing corrode from being exposed to the environment. (See report for before and after comparison pictures)
Associated Documents
Corrosion Test Report
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Leak Test
OverviewWhen 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
OverviewTwo 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
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- Power Input: Power connection and 5V regulator
- Power LED
- System Clock: 16 MHz microcontroller clock
- TO_AFO Connection
- TO_SOLENOID: Two drive circuits for the Solenoid control as well as a ground connection
- Hardware Low-battery system
- Audio System
- SD Card: Level shifter and MicroSD card shield as well as the 3.3V regulator
Unsoldered Systems
- TO_FLOW_SENSOR: Power and ground connections as well as an ADC input to read the flow control as needed.
Board Changes
| Mistake Made | How it effects the system | Actions Taken |
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| 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 |
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
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Noise Test
Procedure1. 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 videoDorsiflexion Mobility: Lift Test Stage 2
OverviewDuring 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
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1. Have volunteer sit on table top with their right
foot hanging freely
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2. Place the AFO brace on volunteer’s foot
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3. Attach the McKibben muscle to the brace
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4. Place yellow indicators near user’s heel,
arch, and on brace near upper strap
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5. Set up and start the video recording
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6. Actuate the muscle using the Solenoid- complete this
step 5 times
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7. Stop the video recording
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8. Remove the device from the volunteer’s leg
Data Analysis
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1. Import the recorded video in Tracker (video tracking
software)
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2. Create tracking points using the yellow indicators
on the brace
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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
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Test #2
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Test #3
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Test #4
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Test #5
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Heel Tracking
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Test 1
Conditions:Buckle sewn in front of brace with tension strap under the lower brace and over pant leg.
Results:
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- The foot lift angle range is between -20.89 and -34.45 degrees
- The foot lift angle range during a natural gait cycle is between -8.2 and -38.6 degrees
- Difference natural Gait: 30.4 degrees
- Difference device: 11.10 degrees
- Vertical Displacement: 0.37 inches
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:
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- The foot lift angle range is between -37.47 and -47.03 degrees
- The foot lift angle range during a natural gait cycle is between -8.2 and -38.6 degrees
- Difference natural Gait: 30.4 degrees
- Difference device: 9.56 degrees
- Vertical Displacement: 0.42 inches
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:
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- The foot lift angle range for a.) is between -34.15 and -42.31 degrees
- The foot lift angle range for b.) is between -15.83 and -23.37 degrees
- The foot lift angle range during a natural gait cycle is between -8.2 and -38.6 degrees
- Difference natural Gait: 30.4 degrees
- Difference device a.): 8.16 degrees
- Difference device b.): 7.54 degrees
- Vertical Displacement: 0.18 inches
Test 4
Conditions:Same conditions as test 3a. but with the tension strap placed over the lower brace.
Results:
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- The foot lift angle range is between -25.35 and -37.79 degrees
- The foot lift angle range during a natural gait cycle is between -8.2 and -38.6 degrees
- Difference natural Gait: 30.4 degrees
- Difference device: 12.44 degrees
- Vertical Displacement: 0.16 inches
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:
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- The foot lift angle range is between -29.78 and -56.34 degrees
- The foot lift angle range during a natural gait cycle is between -8.2 and -38.6 degrees
- Difference natural Gait: 30.4 degrees
- Difference device a.): 10.63 degrees
- Difference device b.): 26.56 degrees
- Vertical Displacement: 0.34 inches
Summary
Conclusion:
- The difference between Delta_natural Gait and Delta_device decreased since the phase 2 test from 13.6° to 10.63° (it should be noted that the difference may actually be largely accounted for when tolerance on tracker data is considered)
- Average vertical displacement experienced by the Upper Muscle Attachment piece decreased since the phase 2 test from 0.35” to 0.18”, 0.16”, and 0.34” after the addition of the inelastic material. (note: the last data point is affected by an outlier and is closer to 0.28”)
- Using tracker based on a lower heel location resulted in a slightly lower angle; ankle angle of 7.54° vs. 8.16°
- When no shoe is necessary, more ankle lift [12.44° vs. 8.16° and 10.63°] can be achieved if the tension strap is worn over the lower brace.
- The total ankle angle range increased to 26.56° when the user pointed the down and then relaxed foot prior to air muscle articulation
Video
Videos
for phase 3 tests
Next Steps:
- Discuss ways to minimize the upper muscle attachment deflection during muscle actuation and increase the difference between Delta_natural gait and Delta_device.
- Implement chosen solution and repeat test.
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.- The first attempt at redesigning the strap attachment was performed February 27-28 and the first phase three foot-lift test was performed on March 3. This first sewing job followed the design modifications indicated phase 3 but it did not perform as well as expected since the bracket had a tendency to slip to one side or another and cause mild discomfort when applied to larger subjects. As a result, a second sewing job seemed appropriate.
- The second upper brace strap sewing adjustment was performed March 6-8 which resolved the issue of buckle slippage by securing the lower portion of the buckle tightly to the brace.
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- Since the results of the first foot-lift test were
not as desirable as hoped, a third upper brace sewing
modification was performed March 10-11 and the second
foot-lift test was performed March 12 (note: performed on
bare skin). This third sewing modification involved
raising the location of the muscle base by approximately
1/2" and adding inelastic material to the back of the
brace extending from the upper brace strap to the bottom
of the muscle base.
- The third, fourth, and fifth foot lift tests were performed March 17 but this time brace was applied over jeans and various arrangements were tested.
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:
- The resulting forces fit within the previously tested operating range of the air muscle and the peak torque of 3.42 ft-lbs is between the ideal and marginal engineering requirement values.
- The calibrated scale can be used for force test on other subjects if necessary.
Nazareth Clinic
Pedometer Program
OverviewOur 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.
- At the beginning of the day, put on the pedometer. Note: Please refer to the attached document for instructions on how to properly wear the pedometer.
- Wear pedometer for the duration of the day
- Right before bed, remove the pedometer and complete the questionnaire below for the appropriate day of program (i.e. day 1, 2 or 3)
Questionnaire
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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.
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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)
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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
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Risk Table
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- Viewing the latest revision
- Node updated 2015-05-11 16:04 by mde5019