Preliminary Detailed Design
Table of Contents
Team Vision for Preliminary Detailed Design Phase
Our team planned to design the most critical/high risk subsystems during this phase. We also planned to have a full Bill of Materials created as well as an updated budget. An essential part of our plan for this phase was creating test plans to validate that all of our engineering requirements are being met.
In this phase, we were able to create a CAD model of our cart and do feasibility analysis to ensure the sizing of it was adequate to hold all components and be easily transported to the dynamometer room. We also researched the best way for us to use the dynamometer and determined it would be best to run it in manual mode for system testing and data collection. The team was able to create test plans for ensuring engineering requirements have been met. GUI models were made and sensor interfacing was planned. A Bill of Materials was created and the team's budget was updated.
Prototyping and Feasibility
Server Implementation - TCP vs UDP
- Implement a basic UDP server when the RPi arrives
- Create a database with dummy data to interface with Flask microframework
- Create a model that updates an HTML with changing random values
Cart DesignRevision A: 3D Model Initial cart components and spacing were designed based on team conversations about items which needed to fit on cart. An initial footprint was decided on based on preliminary benchmarking of previous years carts and other similar industry tools.
The figures below show different views of the 1st draft of the cart that was created.
Feasibility testing : Part 1 The first stage in testing the feasibility of the cart size and layout was creating a footprint which we could move throughout the areas we will be working in to test the size and mobility of the cart.
Below is a list of the major locations that we completed our testing:
1. Test fit through team room doorway which has the most limited mobility
Test: Push cart out of Hot Wheelz team room and into hallway in direction that would allow the cart to move towards the elevator.
Results: A cart with 4 casters (with locking abilities) of size 3' by 6' is easily able to fit out of the Hot Wheelz team room 1 1/2 door and into the main senior design hallway.
2.Test ability to fit and maneuver into shop elevator
Test: Fit cart model into elevator and be able to easily push out into shop hallway.
Results: Cart fit into elevator with enough room to have at least 4 team members around it. Upon exiting, the carts caster wheels successfully allowed for easy change of direction.
3. Dyno integration
Test: Bring the cart directly next to the permanently mounted table so that the long side of the cart would be next to the table.
Results: Cart model was brought into the dyno room and maneuvered around tables and items in the room. When we attempted to rotate the model to place it with its long side next to the table we found there was not enough room for it to fit. *Please stand on head to view the below picture.
Revision B: 3D model -After completing round 1 feasibility analysis we learned that if we were to have the ability to integrate the dyno into our plans we would need to shrink the size of the cart.-We modified the overall length of our model to be 64" x 38" . With this modification the cart was able to be placed next to the dyno table. We then were able to modify the CAD models size.
Test Bench Assembly Walkthrough
To test the ability of the user to change out components on the cart, the CAD model and a mental walk through was completed. A team member who did not create the CAD drawing walked through the process of adjusting shelves and attaching components to the test bench.
This walkthrough resulted in several important pieces of feedback.
1) It might be difficult to hold up horizontal shelves while putting vertical shelves in place.
2) The team members using the bench will have to build the shelf from one side to the other. It would be somewhat difficult to go back and change the position of one shelf without adjusting the position of at least one other shelf or removing it and putting it back on.
3) It would be very helpful for us to label where the best location of each component is so the team can easily see the shelf that the motor, engine, or other component should go.
4) Pegboard for horizontal shelves should be included in the model.
This feedback will be important moving forward to make sure the test bench & shelf design is feasible and user-friendly.
FEA testing Plans:
|Test Bench item to be tested||How FEA will be completed||Reasons for FEA|
|Motor Shelf||Apply engine mass at center of plate and have mounting at from and rear side as if held by hand or table on one side and cart on other||The engine is the heaviest component which will need to move. Most of the weight will be supported by the dyno table but FEA will test for the transition|
|Main Base Pegboard||Apply a distributed load of the max estimated weight of components with fixtures at edges||The base is the main weight holder of the entire cart|
|Main supporting walls||Take weight of heaviest component (or max weight on the shelf) and have the weight applied at a slot with fixtures along the edge of the dividing wall and at base||Supporting walls will hold the main weight of each of the shelves|
How to Use the DynamometerDetailed document attached here
Preliminary manufacturing details
-Machines being used
- Mill, lathe, Waterjet
-Tools being used
- Standard machine tooling
To be completed for Detailed Design Review
-Conduct FEA on noted components
-Evaluate and make modifications as needed
-Add final components to CAD model (mostly electronic items)
-Talk to Hot Wheelz team about properties of basic cart items and modify as needed
Test Bench Data OutputsThe Test Bech will Collect the Following Data:
- Voltage of GLV battery supply
- Current of GLV battery
- Voltage of High Voltage Battery Pack
- Current of High Voltage Battery Pack
- Temperature of 3 user-defined locations
- CAN messages from CAN-enables devices
Data will be displayed on a web-based GUI on a team laptop. The bench sensor values will always be displayed and the user can choose to display up to 150 CAN messages.
All data can be collected "simultaneously". Data will be poled by the micro-controller every 0.5s and updated on the display at that time.
The data will be used to validate and optimize electrical designs. For example, a team member designs the GLV circuit to consume an average of 10A. After viewing the data from the test bench they discover it is actually consuming 8A. Their designs for power ratings are then validated. Since the current rating was lower than expected,a lower wire gauge can now be used on the final design.
Full document attached here
Plans for wire usage
The permanent shutdown circuitry on the car will have wiring that does not change from year to year. Therefore, care will be taken to secure wire out of the way of other components, or the wire will be adequately protected.
All temporary wiring will be done on a year to year basis. However, any wiring of components that are likely to be re-used will stay on the cart after testing is completed. This saves on the amount of wire that will need to be purchased each year, while negating the need for numerous connectors and wire lengths.
All current sensors will be mounted on the bench via the pegboard design so it is secure, but may be moved. Voltage circuitry will need lead wires that can be connected to any appropriate point. Temperature sensors (in the form of thermistors) can be taped to the desired location with kapton tape.
Basic GUI Models
Sensor InterfacingThere will be a total of 7 on-bench sensors that will deliver data to the wireless system to be displayed on the GUI. Preliminary Schematics for data acquisition from these devices can be seen below:
Full schematic attached here
Updated System Architecture
Full document attached here
Note: The 12V power supply shown on the bench goes to many devices including sensors, the raspberry pi, and other low voltage components.
- Complete basic skeleton models for each of the other pages that will be used
- Connect models to server and map links between the pages
- Create a full electrical schematic of all permanent bench components (shutdown, micro-controller, sensors)
- Perform power analysis on the entire electrical circuit to determine how much power the system consumes.
Bill of Material (BOM)
This Bill of Materials includes all of the components that have been selected for each subsystem as well as projected costs for items that have not been sourced yet. Additionally, the ordering status of each component is noted in the leftmost column.
Test plans have been created for each engineering requirement. The full test plan document is located here
Full updated risk assessment located here
Plans for next phase
At the end of the next phase, our team plans to have all of the subsystems fully designed. We plan to have our Bill of Materials finalized and major components with long lead times purchased. We plan to have all our subsystems designed and test plans finalized. FEA will be completed on the cart. A full system schematic will be completed, and more detailed GUI models will be made.