P18221: RIT Baja Driveshaft Efficiency Tester
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Systems Design

Table of Contents

Team Vision for System-Level Design Phase

At this stage, the team planned to come up with a system-level design for the Driveshaft Efficiency Tester, hoping to select major components and selecting design concepts to continue to pursue.

An initial step was taken to come up with a functional decomposition of the device, defining all of the functions it needed to fulfill. Once these functions were defined, a few solutions were brainstormed to complete each function. These various solutions to each function were then combined into complete concepts. Each concept was then compared by feasibility, cost, complexity, etc to each other. Now that the phase is complete, the team has selected a single concept to continue designing to.

The group will now be pursuing a concept utilizing a 3D Cartesian rail fixturing system with an AC Motor providing the drive torque. The load will be another DC motor tied to some switchable resistive loads, and the torque efficiency will be measured by two inline torque sensors on the inboard drive side and the outboard load side of the driveshaft. Data acquisition and user interface will be done using a built-in Raspberry Pi with a screen and the appropriate hardware needed for component interaction.

Review of Problem Statement

The RIT Baja team currently lacks a method of determining the capacity of the driveline to efficiently transmit torque to the wheels. The Baja drivetrain engineers require a metric to quantitatively measure the efficiency of several half-shaft designs, specifically CV and U-Joints, so that they can use verifiable test results to make a more informed engineering decision as to which half-shaft design to use.

The goals of this project are to design a test apparatus for the Baja team to use in their shop to measure the applied and transmitted torque through a variety of half-shaft designs, to do so through the entire range of the outboard hub travel, and to convey this information to the user to allow for the power loss comparison of different designs.

Functional Decomposition

Flowchart

Functional Decomposition

Functional Decomposition

Benchmarking Cases

Document containing products considered for benchmarking design

Parameter Baja Tester MT Series Torsion Tester MTS 813.42B AVL Sensor T12
Torque Capacity 200 ft-lb 417-4170 ft-lb 1475 ft-lb "High Torque Measurement Accuracy"
Speed 700 RPM 18 RPM 3000 RPM 0-6000Hz
Number of Torque Cells 1 1 2 N/A
Power Requirements 110-220V N/A 115V 20A N/A
Process Baja Tester MT Series Torsion Tester MTS 813.42B AVL Sensor T12
Adjustable Cell Torque Yes Linearly Yes N/A
Adjustable Torque Measurement Yes Yes Yes Yes
Efficiency Measurement Yes No Yes N/A

Concept Development

After the functional decomposition step, the group built an extremely rough morphological chart, containing options of various feasibility/viability on a whiteboard. This later led into refining this chart into the one seen further below, as well as driving our feasibility analysis.

Concept Development Whiteboard

Concept Development Whiteboard

Preliminary research and analysis of the concepts for each sub-function was then carried out in order to make more informed estimates and decisions during Feasibility Analysis and Concept Selection.

Sub-Function
Adjustable Outboard
Drive Spinning Shaft
Resistive Load
Measure Efficiency
User Interface
Shielding
Safety Interlocks
Chassis

Feasibility: Prototyping, Analysis, Simulation

A cost analysis was made to further prove the feasibility of each concept.
Cost Feasibility Analysis

Cost Feasibility Analysis

Morphological Chart and Concept Selection

The feasibility analysis led to a refinement of the original rough draft on the whiteboard. This is seen below.

Morphological Chart containing all concepts for system functions

Morphological Chart containing all concepts for system functions

Concept Selection

The concepts that were generated using the morphological chart were evaluated using Pugh Concept Selection. The selection criteria used for the analysis are listed below.

Selection Criteria

  1. Repeatability - How easy does the concept allow for identical setups to be recreated?
  2. Adjustability of Outboard - How many different settings for outboard positioning does the concept allow for within the range defined in the Customer Requirements?
  3. Manufacturability - Does the concept require any complex geometry parts to be machined or CNCed?
  4. Portability - Does the concept require components that exceed the weight and/or size constraints defined in the Engineering Requirements?
  5. Durability - Does the concept incorporate elements that could wear or break during normal use?
  6. Design Complexity - Does the team have the bandwidth and/or expertise to design, manufacture, and implement the concept design?
  7. Forward Compatibility - Does the concept allow for the easy adaptation to different half shaft, hub, and/or suspension designs?
  8. Aesthetics - Does the concept look professional?
  9. Cost - Does the concept require components that exceed the project's budget?
  10. Maintainability - Does the concept require regular maintenance?
  11. Accuracy - How accurately can the concept position the outboard?
  12. Power Consumption - Does the concept require power beyond what is feasible?
  13. User Friendliness - Does the concept allow for ease of use during the setup, testing, and retrieval of data? This can include tooling, time, and effort involved.

Pugh Charts

Using these selection criteria, the concepts were evaluated and iterated using a series of Pugh Charts.
Pugh Concept Selection Iteration 1

Pugh Concept Selection Iteration 1

Pugh Concept Selection Iteration 2

Pugh Concept Selection Iteration 2

Pugh Concept Selection Iteration 3

Pugh Concept Selection Iteration 3

Concept Sketch

Concept Sketch - CP#9

Concept Sketch - CP#9

Systems Architecture Designs and Flowcharts

System Architecture based on Customer Requirements

System Architecture based on Customer Requirements

System Power Architecture

System Power Architecture

System Data Architecture

System Data Architecture

Risk Assessment

Live Risk Management Document

Updated Risk Assesment

Updated Risk Assesment

Design Review Materials

All on this Edge page

Plans for next phase

Identify high and medium risk items with respect to timeline, finances, and technical challenges. Systematically address these and then reevaluate before Phase III review to close the loop.

Live Schedule for Phase III

P-DDR Schedule

P-DDR Schedule


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