P19014: Portable Upright Walker
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Detailed Design

Table of Contents

Team Vision for Detailed Design Phase

Our vision of this phase was to flesh out our test plan, iron out the details of our design in reference to our customer requirements, and move the system to a state it is ready for prototyping next semester.

We achieved our goals of: enhancing our design, completing the test plan, completing the IRB board application, completing the BOM for MSD I, and finishing CAD models.

Prototyping, Engineering Analysis, Simulation

Iterative activities to demonstrate feasibility, including assumptions you made in your analyses or simulations. Have you completed sufficient analysis to ensure that your design will satisfy requirements? Have you included all usage scenarios in your modeling?

The theoretical calculations were input into matlab to allow for easier adjustment for design and concept changes. In the process some assumptions were reassessed, but more were held constant. The only change was the assumption of the force is applied on the upper arm rest is now assumed to be 15 degrees. This slightly changed some of the results.

New Baseline Values:

Matlab Code

Drawings, Schematics, Flow Charts, Simulations

Purpose

Define instructions that will enable fabrication of the elements required to build and operate the entire system. Present final design drawings and documentation.

To ensure more adjustability of the device two possible clamp methods were explored. Both used off the shelf biking clamps, but were oriented in different directions.

Clamp Straight Hole

Clamp Straight Hole

Clamp Rotated Hole

Clamp Rotated Hole

These would then be applied to the model such as bellow, letting the arm rest to slide up and down the support as needed.

Upper Attachment

Upper Attachment

The team also designed a lower braking system to construct and test next semester. The design will let the user brake with their hands in the upper position, as requested by the customer, while still allowing the system to be applied to any "Rollater" walker as per our customer requirements.

Prototype Braking Construct

Prototype Braking Construct

 Walker Assmebly

Walker Assmebly

All CAD files from this module can be found here

Fabrication and Assembly

Fabrication and assembly plans can be found here

Input and Source

  1. Selected Concepts
  2. Feasibility Models
  3. System design and interface definitions

Output and Destination

  1. Complete hierarchy of design files from system level down to components
  2. Parts list
  3. Test plans, including expected performance vs. requirement and any applicable test standards (e.g., ASTM).

Bill of Material (BOM)

Bill Of Material

Bill Of Materials

Bill Of Materials

Budget

Explanation

Fabrication

Test Plans

Purpose

The purpose of these test plans are to ensure a successful product. The stability, angles, adjustments, comfort, and usability will be put to the test in order to meet the engineering requirements. Customer requirements must be considered throughout the second phase of the test plan.

These test plans are currently in draft form and will be adjusted according to the IRB process at RIT.

Aspects to Test - Human
  1. Walking with the normal walker
  2. Setting up the add on component to the walker
  3. Standing positioning with the upright walker
  4. Walking in a straight line
  5. Taking turns
Aspects to Test - Physical
  1. Frictional coefficient between wheel and brakes
  2. Total force on attachment
  3. Braking stop time
Populations
Survey Components

Procedure - Human

Overview:

Step by step:

  1. Video recording (if permitted by participant)
  2. Practice walking and turning with generic walker (X min or until comfortable)
  3. Walk at leisurely pace from point A to point B (100 m) 3x
    • Record time taken to do task
  4. Walk at leisurely pace around defined course (Curves and tight turns)
    • Obstacles indicated by cones
    • Record time taken to do task
  5. Give instructions for device set up
    • Follow instructions to set device to desired position
  6. Have participant stand in place with the device
    • Measure angles:
      • Elbow
      • Shoulder
      • Wrist
      • Back
      • Neck
    • Record time taken to do task
  7. Ask participant to practice walking and turning with the full upright walker for (X min or until comfortable)
  8. When ready, walk at a leisurely pace from point A to point B (100 m) 3x
    • Record time taken to do task
  9. Walk at leisurely pace around defined course (Curves and tight turns)
    • Obstacles indicated by cones
    • Record time taken to do task

Procedure - Physical

Overview:

Step by Step Friction Coefficient:

  1. Set block in starting position on metal surface
  2. Pull until movement with spring gage
  3. Record force required to overcome static friction
  4. Repeat 10x
  5. Calculate mu for each trial

Final mu value will not have a baseline, but will be important when designing the upper brakes for the unit. As such, more trials will be completed as needed to confirm authenticity.

Step by Step Braking Time

  1. Set device up for human use
  2. record a shot parallel to trial location
  3. Walk device forward and apply brakes
  4. Record initial velocity and time to stop
  5. Repeat 10x
  6. Calculate braking deceleration

Target value for this is zero. One of the customer requirements is full control of the walker, and as such the user must be able to stop on demand.

Step by Step Total Force on the device

  1. Set up a pressure scale at the same angle as the device
  2. Lean human weight on the scale while the walker is stationary
  3. Record force value
  4. Remove breaks
  5. Push walker forward
  6. Record value

This is to confirm the factor of safety calculated for the device. This does not have a target value, beyond the fact that the target pressure must not exceed the limits of the selected material.

Step by Step Stability of the Device

  1. Attach six strain gauges to the walker
    • One on each leg of the base walker
    • One on each arm of the attachment
  2. User places pressure on the device
  3. Strain is recorded
  4. User walks five feet forward
  5. Strain is record
  6. Repeat three times

Each leg should be approximately equal in applied, and each attachment must also be approximately equal in applied strain. Applied strain when moving must stay in a range bellow the materials elastic modulus.

Human Subject Research Testing Updates:

Part of the test plan involves testing the device on human subjects. In order to start these trials, a submission must be presented to the Institutional Review Board (IRB) at RIT. Components for this submission include (but are not limited to):

Form A and supporting material for submission (full link supporting material here and Form A here):

Form A

Form A

Form A

Form A

Form A

Form A

Form A

Form A

Form A

Form A

Additional Documents
Consent Form

Consent Form

Protocol

Protocol

Inputs and Source

  1. Engineering Requirements.
  2. Test standards (e.g., ASTM). The RIT library maintains an infoguide with links to standards databases, many of which provide industry-standard test procedures for a variety of components and systems.
  3. Feasibility Models.

Outputs and Destination

  1. Report that summarized the degree to which Eng Reqs are satisfied.
  2. Assessment of accuracy of feasibility models.

Design and Flowcharts

Design Decision related to CR & ERs
Design justification

Design justification

A link to the live document can be found here:

Meeting CRs and ERs

Meeting CRs and ERs

Updates have been made to the morphological table surrounding the continuous adjustment row.

Morphological Table:

Updated from prior phases

Continuous adjustment (Morphological Table)

Continuous adjustment (Morphological Table)

Additional edits to the customer requirements and engineering requirements can be seen in section above (design and flowchart).

Risk Assessment

Updated Risk Table

Updated Risk Table

Design Review Materials

Include links to:

Plans for next phase

As a team, what do you need to accomplish between now and the end of the semester?
The GATE review is scheduled for Thursday at 11:30 AM. This is the last scheduled item the team will need to do for the end of the semester. In order to be ready for our GATE review we will populate that EDGE page as well as add any additional notes from the Detailed Design Review.
As a team, what do you need to do to prepare for MSD II?
As a team we need to discuss our progress and success in MSD I and adjust anything accordingly in order to be prepared for MSD II. We need to discuss the first prototype and work together effectively if we want to see success in this second half of the project. Overall the team is looking forward to the process of building and testing our device.

Individual 3 week plans:


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