Table of Contents
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Phase Planning
Shared Phase Vision
Our vision for this phase is to integrate our subsystems into an initial prototype. The subsystems addressed in this phase are:- Distance, heel strike and toe sensor
- Secure foot – Upper (air muscle attachment)
- Lower and Upper base attachment
- McKibben muscle
- Upstairs/Downstairs Adaptation
- Component housing and integration
Technical questions to address:
- How should the new toe strike sensor integrate to measure and adapt to gait?
- What design and which materials should be used for upper/lower muscle attachment?
- Is the adjustable strap design a feasible solution?
- Does the single weave sleeve have potential as a muscle design material?
- What regulators should be used on the system?
- What power source should we use?
- How can we insure ingress protection on the lower component housing?
- How should the components in the backpack be
encased?
In addition, our team plans to address items discussed in detail design review as well as review and finalize all documentation including:
- CAD/GAD
- System BOM
- Schematics
- Software Code (70% complete)
- Build/Assembly/Debug Plan
- Test Plan
- Risk List
- Project Plan
- State of the System
Prioritized Tasks
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Week 15 Plan
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MSDII Test Plan
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System Design
GAD Drawing
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Design of Backpack Component Housing
System Architecture
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Bill of Materials
>Build, Assembly, and Debug Plan
The Build, Assembly, and Debug Plan was restructured and embellished in this phase. This document is designed to express our prototype construction process and debug plan for the early phases of MSD II. This document is also useful for explaining the system level integration of each component using sketches like the ones below.Build, Assembly, and Debug Plan
Electrical System Concept
Schematic
Critical Systems
- Power Input: Power connection and 5V regulator
- System Clock: 16 MHz microcontroller clock
- TO_AFO: FlexiForce (heelstrike) input, IR Sensor (distance sensor), 5V and ground connections
- TO_SOLENOID: Two drive circuits for the Solenoid control as well as a ground connection
- TO_SWITCH: This connects the manual switch on the board to a digital input on the microcontroller.
Optional Systems
- SD Card: Level shifter and MicroSD card shield as well as the 3.3V regulator
- TO_FLOW_SENSOR: Power and ground connections as well as an ADC input to read the flow control as needed.
- SERIAL_I2C: Debug connections to the I2C communication as well as the Serial line.
Three Sensor Layout
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Software Documentation
Top Level Pseudocode
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Functional Description
Documentation for the Functions that were used.Return To Top
Top Level Timing
Level Ground
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Terrain Adaptation
Motivation - The motivation of this test
was to use the new toe strike sensor in such a way to
adapt to different terrain.
Procedure - The nice part about this
testing was that in the previous testing, the toe strike
sensor was used. What was added in this testing was the
code that would identify if there was a toe strike
without a heelstrike. The microcontroller would then look
and see if the distance sensor has identified upstairs or
downstairs. Also, for ease of understanding at the
output, the state of the muscle was also recorded.
Results - It is clear that the
heelstike, toestrike and distance sensors are working
together and that the AFO now works for upstairs and
down. It is also clear that this can be done different
ways.
The output was also monitored and is seen below.
Next Steps - The next steps would be it iterate the test for stability and to try different methods of adaptation.
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Solenoid Plug
The plug seen below was selected to pug the exhaust port allowing the the valve to be opened in case of system malfunction.Return To Top
Mechanical System Concept
Component Housing
Motivation- The purpose of the component housing is to hold and protect the PCB board that is used for all three sensors. In addition, this sensor allows for easy attachment of the distance Sensor.Design
This model has been modified slightly during this phase to use as minimal material as possible to reduce the cost of 3D printing It also has been redesigned to make it as water proof as possible so that all the electric connections don't get messed up due to outside debris.
Additional parts that are part of this model include 2 socket head 5-44 screws, 4 socket head 3-56 screws, 4 flat head 3-56 screws, and a .125 inch thick o-ring.
Prototype
Next Steps
1) Iterate design for O-ring functionality
2) Order additional parts
3) Assemble the system
4) Perform the water proof test
5) Reiterate the casing if it does not perform well
6) Attach to the brace for AFO testing
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Muscle Attachment Design
Purpose - An assembly to attach the muscle to the brace needed to be designed that fit the following criteria established during the detailed design phase:a) The assembly must be small and lightweight
b) The assembly must be safe without dangerous abrasive protrusions
c) The assembly must allow the muscle to be easily attached and removed so the AFO can be washed
d) The assembly must be feasible to design during MSD and not overly complex
Design
Our design was changed slightly during this phase. After
our preliminary detailed design review feedback and more
consideration of the size of the piece, the design was
iterated to become easier for the user to attach and
detach the muscle. Our design continues to have 2 pieces:
the integrated plug, which combines the air inlet plug on
the McKibbon muscle with an attachment piece, and the
attachment base, which is designed to easily mate to the
integrated plug and attach to the brace.
The major design change is the way the pieces mate to
each other. Our preliminary design had 2 very small pins
that absorbed most of the loading; our current design now
eliminate those small pins, and the base lip on the
bottom of the base that mates to the muscle now absorbs
the stresses in the connection. The integrated plug now
slides into a cavity on the base for easy attachment. A
larger hole was drilled for a safety pin to attach the 2
to be sure the muscle does not come detached during
function. The base is now thicker as well, which allows
room for a contour to be added if needed
Lower Attachment
Another plug was needed to be design for the opposite end
of the muscle, the side that will be moving when the
muscle is actuated. Our plug is integrated with a hook
that easily attaches to the ladder-lock buckle that is
being used in our design. This ladder-lock buckle,
similar to what is used to adjust backpack straps, is
attached to the strap that is being used as the tether to
raise the foot when the muscle is actuated. This plug was
designed to easily be detached from the tether while
providing enough securement to ensure the AFO functions
correctly.
A 3D model of our design is shown below. Associated
drawings are found in the Associated Documents section
below.
Next Steps
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1) Machine prototype parts
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2) Complete initial prototype testing to ensure muscle
function
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3) Investigate if contour will be needed and if
thickness can be reduced
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4) Investigate if Ansys stress analysis will need to be
done on Lower Plug
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5) Attach to brace for integrated AFO testing
Associated Documents
Stress Analysis
Integrated Plug Drawing
Base Drawing
Lower Plug Drawing
Muscle Optimization Stage III
MotivationThe purpose of this test was to design and construct an optimized muscle for the integrated system. This test will decide our final muscle selection for our design and help drive our integrated testing going forward. The two muscles we had pinned as our best potential options were tested, each 3 times, and compared to each other.
Procedure and Results
These tests were conducted following the same general procedure and data processing methods as in Muscle Optimization Stage I and II. A series of 12 formal, distinct, tests were conducted during this phase consisting of 2 muscles- one with the orange sleeve, and one with the pink, "single weave" sleeve. The muscles were tested 3 times each in 2 different configurations. The muscles had identical lengths for easy comparison. The tables below describes the average deflection and estimated steps for each muscle:
Conclusions - After comparing the two
muscles, it was determined that the orange sleeving
outperformed the pink, "single-weave" sleeving, and will
be used for our integrated testing going forward. This
muscle provided the desired strain at much lower
pressures than the pink muscle did, which operated well
at very high pressures. This allows us to use much less
air per actuation of the muscle. By factoring in the air
used, the deflection of them muscle, and the associated
force, it was determined that the orange sleeving is our
best option.
Next Steps
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1) Purchase smaller silicon tubing to reduce the
initial displacement of the pink, "single-weave"
sleeving and test during stage 1 of MSD II to determine
performance.
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2) Construct final 6” muscle with orange sleeving
and designed plugs for integrated testing of the
prototype going forward.
A CAD model of our Final Muscle Design is shown below,
along with the exploded view:
A full CAD drawing directory of our associated McKibbon muscle assembly parts:
Muscle Assembly Drawing
Integrated Plug Drawing
Lower Plug Drawing
Silicon Tubing Drawing
Orange Sleeving Drawing
Full Report with additional information:
P15001_Muscle_Optimization_Stage_III
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Customer Meeting
The team held a customer meeting on 11/25/14 to discuss our deflection concern as outlined in the meeting Agenda.Expectations were clarified and the following Notes and Action Items were taken.
Strap Analysis
During this phase, our team decided to not complete an analysis on the strap that will be used in our prototype. We originally planned to complete this during this phase and noted so in our prioritized tasks table; however, after re-analyzing the tasks, we felt that it was a more appropriate task to be completed in MSDII since adding the thinner strap is an enhancement. Therefore, this analysis will be completed by phase 1 of MSDI.Return To Top
Risk Assessment
Gate Review
The Previous Action Items taken during the last review have been updated as well as the items taken from the customer meeting.
The agenda was used during our week 15 Detail Design Review.
The following
Phase 5 Action Items were taken as a result of
our week 15 Review.
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