Preliminary Detailed Design
Table of Contents
Team Vision for Preliminary Detailed Design Phase
The Detailed Design Phase lays the groundwork for the ultimate project deliverable. Through detailed drawings, calculations, simulations, and flow charts, other engineers should be able to reconstruct our project. In order to form these detailed documents, the O-Shift team separated into smaller units to tackle tasks that suited our disciplinary strengths.
- Created CAD Model for Clutch Pedal Design
- Created CAD Drawings for Clutch Pedal Design
- Developed Mechanical BOM for Clutch Pedal Design
- Ran Solidworks Analysis on Clutch Pedal Design
- Created OBDII CAN Logging Device (Raspberry Pi)
- Validated OBDII logger
- Decided on STM32F446RE and STM32F091RC microcontrollers
- Created software project with STM32CubeMX
- Drafted preliminary software architecture
- Decided on BNO055 IMU
- Researched major electrical components needed for each subsystem
- Assembled rough BOM for funding and component list
- Decided on BNO055 IMU
- Began Work on Subsystem Schematics
- Work on Shifter Lockout
- Collected Data & Analyzed
- Select sensors for the shifter and clutch
- Choose MCU IO Pinouts
- Display Board Schematic
- Drew initial shifter designs
- Built shifter prototypes
- Refined shifter design with lockout plates
Prototyping, Engineering Analysis, Simulation
We used the prototype clutch pedals from our Systems Design Phase to aid in our solution path for this phase. The prototype clutch pedal that was determined most reliable has been displayed again for convenience.
From there, a CAD model was constructed in Solidworks so that a static analysis could be conducted and a working drawing could be created. The lengths of the beams in the model could be resized and retested in the software.
There were many ideas for the mechanical design of the shifter module. Three designs were chosen for their simplicity and size. The three designs are shown below.
Prototypes were built for each of these designs from available scrap wood and hardware. Their pictures are below.
Friction between the wooden components caused a large issue in the slider prototype. This was mitigated by soaking the wooden pieces in water and freezing them. If this design were to be more practically built, lower friction materials and ball bearings would likely be used.The prototypes were compared to each other as well as to the motion and feel of a real manual shifter to generate the benchmarking table below.
The ball and socket design was ultimately selected. Its feel of movement closely resembled that of a real manual shifter.
After the shifter prototypes were built, there was a discussion about a lockout mechanism. A brainstorming session resulted in the idea for 2 sliding lockout plates driven by solenoids. The plates and their function are demonstrated below.
When the clutch is depressed, the lockout plates will be pulled aside by the solenoids, allowing the shifter to be put into a gear
When the clutch pedal is released, the plate will apply pressure to the shifter to hold it in place. The shifter can still be pulled out of gear if necessary
Below is a rough idea of what the cabling routing inside the shifter is going to be.
OBD-II Data LoggingA PiCAN shield was used to interface a Raspberry Pi 2 with the vehicle (Chevy Cruze) CAN bus, and an open-source Python script was used to log vehicle speed, RPM, and throttle position.
The following shows a 1st gear acceleration run extracted from the logs with a 2nd order polynomial fit curve.
Below presented the RPMs achieved by the the first three gears during the test.
This represents our 1st attempt at proper data collection, but there is still work to be done on the script used to communicate over OBD-II to achieve higher sample rates for each of the parameters, as well as adding BNO055 IMU data to the logging procedure as well. Below is the data collection scenarios we are going to be recording, this list is a work in progress:
- Hill Data (Starting Up, Slowing Down)
- Clutch Riding
- Slow Paced Up Shift and Down Shift
- Fast Paced Up Shift and Down Shift
- Releasing Clutch Late & Early
- Rolling Stops
- Stalling Scenarios
- RPM to Velocity Ratio for Each Gear
Drawings, Schematics, Flow Charts, Simulations
From the SolidWorks model of the clutch pedal, rudimentary drawings were created of the assembly and all the individual components. Please note that these drawings do not currently incorporate tolerancing and exist largely for display purposes. Drawings may be subject to change and will be updated in the final Detailed Design Phase. Engineering drawings were not created for COTS items.
Our team is further considering acquiring stainless steel and machining the parts, particularly the beams, brackets, and pedal mounting unit, ourselves. The Bill of Materials, presented later on this page, outlines the components and materials needed to create the clutch pedal unit.
The display board MCU is an STM32f446RET which has control over the data communication lines between the different systems. There are two CAN busses for ODB-II and system communications, SDIO for data logging to an SD card, I2C for IMU communication, and QSPI for communicating with the display controller.
This software architecture is an adaptation of the architecture used at RIT Electric Vehicle Team. It is comprised of several layers, starting with the hardware itself and becoming more abstract as you work your way up. Layer-agnostic functionality such as the Task Manager and Error Handler aid in program flow and fault detection.
Bill of Material (BOM)The following is a very rough Bill of Materials created to achieve a basic understanding of the components we will need as well as a basic idea of pricing. Our team has a definite need to search for more money.
A working document of Test Plans for the Upcoming Phase can be seen below.
During this new phase, there has not been any change to the risk assessment.
Plans for next phase
- Finalize Solidworks Model for Clutch Pedal Design
- Focus on integration of Clutch Pedal into car mat
- Determine BOM for Clutch Pedal design
- Create CAD Model and Drawings for Shifter unit
- Improve ease of use for OBDII logger script
- Add IMU capability to Raspberry Pi for data logging
- Develop device drivers for CAN, I2C, etc.
- Create software main application flow chart
- Collect and analyze OBDII data
- Finish Subsystem Schematics in Progress
- Complete New Schematics
- Create True BOM for each section of design
- Keep Collecting Data & Analysing
- Finalize Shifter Sensors
- Work on the Clutch Sensor
- Finalize Display Board Schematic
- Begin Display Board PCB Layout
- Begin Board Interface Design
- Determine Shifter housing design
- Finalize Shifter BOM
- Work with team to integrate sensors with mechanics