P19305 System Level Design

Team Vision for System-Level Design Phase

Over the System Level Design Phase, Team 19305 will finalize the set of deliverables individual members and subsystems, maintain open communication and utilize consultation with our guides, and submit our initial design rendering to the Michelin Mobility Design Competition. After researching the subsystems, conducting a functional decomposition and assembling a morphological chart the selection of components will be considered via a weighted comparison chart. Updates to necessary documentation, criteria, etc. will be made as necessary and preparation for the preliminary detailed design will begin.

Functional Decomposition

Purpose

Define the total list of functions and Sub functions, based on the Customer and Engineering Requirements, that must be delivered by the final design. This will establish the need for specific concepts necessary to deliver the overall objectives of the project

Customer Requirements from Previously

Table 1: Customer Requirements Table

Functional Decomposition Chart

Benchmarking

Purpose

Avoid redundant work by identifying already available solutions and concept options

Pugh System Level Comparison

A pugh chart is used to examine comparable systems by using one system as a datum of reference to judge the achievements of the other systems against. The systems are scored in various categories pertinent to operation with a "+" if it's better than the datum, a "-" if it's worse than the data, or an "S" if it's the same as the datum. Plusses, minuses and Ss are summed at the bottom of the table to see which systems are the best alternatives to the datum. This process can be repeated multiple times for the same table with different systems used as the datum to get a relatively sensitivity.

Using the functions listed in the functional decomposition above, Our Board, the Boosted Board, and the Linky Board can be compared using a pugh chart. 

A More Specific Pugh Chart

While the general functions listed in the functional decomposition can be used to compare alternatives, it's also useful to compare the systems based on criteria that is both generally encouraged, and specifically encouraged. Functions may describe how the device needs to work, but important traits and features are key as well as they can give you more detail. The pugh chart below compares the same three systems with traits instead of functions. 

Weighted Objective System Level Comparison

An alternative to this approach is the use of a weighted objective table. In this table designs are given a score of 9, 3, 1 if they are very good, average, or poor at accomplishing the traits on the lefthand-most column. This comparison is done in an absolute sense where the numbers are in relation to the reach abilities of all other concepts. The multiplier column is used to properly weight the importance of the score each design receives for each given criteria. Finally, these products are summed for a final score. While this score may always tell you exactly which design best accomplishes all of the tasks, it won't tell you which one to pick as the multiplier system can be infinitely adjusted to increase the weight of categories that are deemed important and decrease the weight of less important categories. In the case below, we've used a weighted objective table to see how the strengths of our boards compare to that of it's closest competitors.

Concept Development

Purpose

Generate new concept options or combinations that can potentially exceed the benchmark concepts

Concept Advantages and Disadvantages Organized by Sub function

In the tables below various concepts are given a score of 9, 3, 1 if they are very good, average, or poor at accomplishing the traits on the lefthand-most column. This comparison is done in an absolute sense where the numbers are in relation to the reach abilities of all other concepts. In some overall trait cases (like with the "cost" criteria), concepts are compared against all other concepts across the tables.  A "-" is used if the criteria or trait is deemed to be non-applicable to the given concept. The multiplier column is used in the concept selection process and is not technically relevant in this section however it is being included so these tables can be referenced in the concept selection section later.

Feasibility: Prototyping, Analysis, Simulation

Purpose

The purpose of our feasibility analysis is to understand and prove that concepts are achievable.  We decided the main points to be analyzed at this time were cost, the stress our board can handle, the number of motors needed, the most feasible battery to use, and the effectiveness of the chosen folding mechanism. We were able to look over the engineering requirements and possible concepts in order to come up with logical phase-appropriate feasibility questions. 

Instructions

1. Will we be able to test and create a complete prototype with our current allowed budget of $500?
2. Is the folding mechanism we came up with able to be created and work like we planned for it work?
3. Will the unfolded board be able to withstand the desired stress load we want it to be able to withstand?
4. Does our team have enough time to complete all desired testing and prototyping necessary for the course? 
5. What type of battery will make our board the most reliable while still fitting all of the engineering requirements?
6. Can our ideal electronic long board specs be achieved with at most 2 electric hub motors?
7. Will all electronics be able to fit on the board in an organized and enclosed manor?

Inputs and Source

For feasibility purposes, our budget for the moment would not be able to suffice for the tasks we would like to complete. After research into costs for certain parts, we ideally would need a budget of at least $1000.

Through simulations in Solidworks, it seems as if the ideal design would be able to be sturdy, however more stress analysis needs to be done in order to get exact measurements.

The time constraint on our team will cause a lot of pressure however with mapping out very detailed schedules for each process, the team should be able to complete the necessary requirements for the course.

After research into the different battery options, the type that makes the most sense for our project is Li-ion batteries which would be an off the shelf product.

Through a few calculations, we were able to discover that the total power required will be roughly 3000 watts. With this, there are multiple different hub motors capable of achieving 1500 watts continuous, with a 3000 watt peak power consumption.

From designing our ideal board and folding mechanism, the dimensions of the board we discussed will be able to fit all the average sized electrical equipment that we will need.

Outputs and Destination

1. A list of Design Parameters, Quantified Targets, and acceptable tolerances
2. Sensitivity analysis
3. Concept Selection

Morphological Chart and Concept Selection

Reminder of Our Functional Decomposition

The Morphological Charts can be found in the concept development section. Below are the summations of scores given for general and specific criteria in those charts.

Systems Architecture

Top-level system view:

Acceleration control subsystem view:

Designs and Flowcharts

Purpose

Define a high-level view of the elements required to build and operate the entire system

Instructions

General Function Flowchart

Other mechanical elements including the collapsable deck, truck, and wheels are single function devices.

Risk Assessment

Table 7: Risk Assessment Table

Design Review Materials

• System Level Design Presentation

Plans for Next Phase

Individual Plans:

Matthew's three week plan

Deirdre Arcand's Three Week Plan