Phase Planning
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 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.
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 |
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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 |
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CAIR Capacity Test II
Related System: CAIR, Actuate muscleThe 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.
Conclusions:
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
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.
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Ingress Protection Code Testing
Related System: Use AFOThe 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.
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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.
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Results Conclusions:
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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
Wearibility Testing
Skin Temperature
Related System: Secure FootThe 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
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Procedure
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
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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.
Pressure to Leg
Related System: Secure footThe 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
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Procedure
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.
Nazareth 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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Results:
Number of Participants: 3
Number of Days of Collected Data per Participant: 3
Step Range between Participants: 122-3500
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"
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Strength Testing
Related System: Raise FootThe 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.
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Procedure
- Add weights to the muscle rig, note any deflection, failure, or other things worth note.
- Add as much weight as possible and then attempt to
drop the maximum weight to simulate impact forces.
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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.
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Conclusions
- Muscle and components supported the weight of 30lbs without failure or noticeable deflection. This corresponds to a factor of safety of about 3 for a max design lift of approximately 10lbs.
- Failure occurred between the inelastic ribbon and the
muscle base after a considerable amount of force was
applied at an unusual angle near the upper muscle
base.
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.
Results:
- Clean brace
- No noticeable tears, snags, or rips on brace
- Muscle attachment piece and straps remained fully
attached
- Brace was only slightly damp when taken out of
washer; therefore minimal air dry was necessary,
approximately 30 minutes.
Miscellaneous Videos
Several videos from this phase and the previous phase were combined into one video of miscellaneous items. Featured sub-videos include:- Phase 3 Tethered Walking
- Phase 4 Foot-Drop Footage
- Phase 4 Temperature Testing
- Phase 4 Untethered Walking
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)
Problem Tracking
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Risk Management Table
Imagine Deliverables
Working Poster
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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- Node updated 2015-05-11 16:04 by mde5019