P15001: Soft Ankle-Foot Orthotic
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Gate Review

Table of Contents

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:

Technical questions to address:

In addition, our team plans to address items discussed in detail design review as well as review and finalize all documentation including:


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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


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System Architecture



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Bill of Materials

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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


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Electrical System Concept

Schematic

Schematic (left), Top Layout(Center) and Bottom Layout(Right)

Critical Systems

Optional Systems



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Three Sensor Layout

Schematic (Left) and PCB board layout (right) for attaching the sensors for heelstrike, toestrike, and distance sensing


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Software Documentation

Top Level Pseudocode



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Functional Description

Documentation for the Functions that were used.

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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.

Conclusions - First and foremost, it is clear that this method of adapting to different terrains. Also, as mentioned above, it is also clear that there are different ways of adapting to terrain. It might be more stable to use a different algorithm.
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.


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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

3D model of the Component housing: Collapsed (left), Exploded (Center) and Drawing (Right)

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

3D model of the Muscle Attachment: Assembly (Left), Integrated Plug (Center) and Base (Right)

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

1) Machine prototype parts
2) Complete initial prototype testing to ensure muscle function
3) Investigate if contour will be needed and if thickness can be reduced
4) Investigate if Ansys stress analysis will need to be done on Lower Plug
5) Attach to brace for integrated AFO testing

Associated Documents
Stress Analysis
Integrated Plug Drawing
Base Drawing
Lower Plug Drawing



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Muscle Optimization Stage III

Motivation
The 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

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.
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.


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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.

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Risk Assessment



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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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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