P19014: Portable Upright Walker
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Preliminary Detailed Design

Table of Contents

Team Vision for Preliminary Detailed Design Phase

Summary: Our team spent much of our time this phase expanding off of the preliminary design phase. Concepts were further defined, drawn, and modeled, materials and dimensions were planned, ergonomics was studied, and professionals were consulted.

Feasibility: Prototyping, Analysis, Simulation

Purpose

  1. Confirm that the selected concepts can deliver functionality defined by the System Architecture.
  2. Define the optimal values of the most sensitive design parameters.
  3. Support the evaluation of your team's concepts with quantitative information.
  4. Make decisions about design drivers.

Modeling and Assumptions

Hand Calculations

FBD, Frictional, and Rotational Acceleration

FBD, Frictional, and Rotational Acceleration

As seen in our calculations, we have determined that on a fall the wheels will want to accelerate 1.716 m/sec^2 linearly and have and will have an angular acceleration of 22.52 rad/sec^2.

We have found that a frictional force of 461.87 newtons is applied on a fall to the walker brake bar.

FBD, Normal Force, and Shear Stress

FBD, Normal Force, and Shear Stress

As seen in our calculations, we have determined that our applied shear stress is significantly less than the elastic modulus of our selected 1060 aluminum.

Inputs and Source

  1. Engineering Requirements
  2. Concept Selection
  3. Results of preliminary prototyping, analysis, and simulation

Outputs and Destination

  1. A list of Design Parameters, Quantified Targets, and acceptable tolerances
  2. Sensitivity analysis
  3. Refined concept Selection
  4. Drawings, Schematics, Flow Charts, etc.

Drawings, Schematics, Flow Charts, Simulations

Purpose

In this section the team has developed visuals and additional elements that will help bring the design to reality.

Input and Source

  1. Selected Concepts
  2. Feasibility (Ergonomics) 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. Software design that specifies coding requirements
  4. Test plans, including expected performance vs. requirement and any applicable test standards (e.g., ASTM)

The detailed design included many sketches and dimmensions planning. The image below demonstrates the working ideas for the attachment device.

Sketch of attachment device

Sketch of attachment device

And bellow is a preliminary cad model of the device.

First CAD Model of the Prototype

First CAD Model of the Prototype

As part of the planning and preparation for the Bill of Materials, sketches and drawings of the components were completed. This gave a visual reference for determining the appropriate amounts and necessary components.

Sketch including Bill of Materials

Sketch including Bill of Materials

Additional time was spend studying ergonomics. This study was utilized when determining the angles for each component on the device. The image below indicates the maximum flexion positions the user should ever be in. These angular constraints are demonstrated in the schematic as well.

Visual to show ergonomic positioning (maximum angles)

Visual to show ergonomic positioning (maximum angles)

Ergonomics Study

How a walker should be utilized:
Reality of the positioning while people use the walker:
Ergonomics Summary Part 1

Ergonomics Summary Part 1

Ergonomics Summary Part 2

Ergonomics Summary Part 2

Updates on concept selection from Phase 2:

The original concept selection compared various aspects of the different concepts the team developed. Each aspect was weighted the same as the others. Moving into this phase, and with feedback during the phase 2 review, we realized a more accurate concept selection could be portrayed if we weighted certain aspects of an upright walker more heavily in the ranking than others. This update can be portrayed in the table below.

Weighted Concept Selection updated from Phase 2

Weighted Concept Selection updated from Phase 2

Bill of Material (BOM)

Bill Of Materials

Bill Of Materials

Budget

Explanation

This Bill Of Material is designed for the curent two design Plans

Ultimately a single design will be chosen and selected for production. This selection will be made upon mock ups and prototype testing. Due to the Budget supporting this project there will be time and money allocated in order to build two prototypes and test both.

Fabrication

Arm Rests: Constructed of Wooden board, Memory Foam, Cork Grips, Hand Brakes and Adjustment Bolts

Tube Bending: Tubes will be bent to the desired angle in the RIT Brinkman Lab

Brakes: Upon further research and Feasibility analysis Brakes will be evaluated for the final design

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 also be tested 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

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. Calculate braking deceleration

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

National and International Requirements

Design and Flowcharts

This phase we continued to expand off the ideas we had and solidify out our design. This can be seem in the above sections and respective images.

Risk Assessment

Design Review Materials

Include links to:

Plans for next phase

Team Level Goal

Our team level goal is to continue working efficiently in order to design the best walker attachment to improve stability, ergonomics and user safety. Take our current prototype design and confirm the designed details, parts lists and adjustability. All while further preparing the team for MSD 2.

Individual 3 week plans:


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