Team Vision for System-Level Design PhaseThis phase of our project design enabled our team to make informed decisions on the future design path for our project. We were able to deliberate multiple solutions of varying feasibility that satisfied the customer requirements and engineering requirements presented to our team. From there, we compared the theoretical solutions against one another to determine the ideal project path before purchasing the specific components for the upcoming Detailed Design Phase.
Our team goals for this phase were as follows:
- Determine the optimum means of communication between devices
- Determine the optimum means of powering the subsystems
- Determine the optimum display system and user interface layout
- Determine the optimum means of replicating a car's clutch pedal
- Determine the optimum means of replicating the shift assembly
- Determine the optimum means of affixing the devices to the automatic test vehicle
- Investigate potential design solutions and analyze their corresponding feasibility
- Agree upon a solution path for each subsystem
With our goals established, we accomplished the following during this phase:
- Updated Customer Requirements, Engineering Requirements, and Risk Assessment as necessary
- Conducted an FMEA to explore potential solutions to system failures
- Created a Functional Decomposition to simplify the tasks the O-Shift device needed to perform
- Created a Transformation Diagram to connect system inputs and outputs
- Used Benchmarking to compare various electrical solutions
- Developed Morphological Tables to explore solutions to individual system functions
- Used Pugh Charts to compare various solutions against a datum
- Conducted a Feasibility Analysis to better understand design limitations
- Developed a System Architecture to represent the O-Shift design
- Listed Standards our team referenced during this phase
- Presented a Gantt Chart of our upcoming project phase schedule
Updated Customer Requirements
A working document of the Customer Requirements can be found: https://docs.google.com/spreadsheets/d/1PiWiCmXyhGVuLG3a6Nnke63W18Wcn8_lX0GDFy26cww/edit#gid=0
Updated Engineering Requirements
A working document of the Engineering Requirements can be found: https://docs.google.com/spreadsheets/d/1PiWiCmXyhGVuLG3a6Nnke63W18Wcn8_lX0GDFy26cww/edit#gid=0
Updated Risk Assessment
A working document of the Engineering Requirements can be found: https://docs.google.com/spreadsheets/d/1uTs5DxRef5OmfrblO7XCYaX0OTRneTzGMSV83dLWO_A/edit?usp=sharing
- Demonstrates the breakdown of the overall project function into subfunctions
- Each subfunction shows how the higher level function is accomplished
- Shows the flow of inputs through the system to the outputs
Morphological Chart and Concept Selection
A Morphological Chart presents the challenges or functions required of our project and then proposes several reasonable solutions that our team is to analyze. These solutions have been pictorially displayed for clarity.
Pugh Chart and Concept Selection
With concept ideas for the overall system generated from the Morphological Chart, Pugh Charts were used to analyze the brainstormed solutions against one another and determine a score. This process was determined to be most effective when analyzing individual subsystems of our design rather than analyzing the entire system at once. A Pugh Chart works by comparing solutions of a (sub)system against various functional and aesthetic requirements of specified importance. A datum is selected and each solution is then determined to be better than (designated by a +) or worse than (designated with a -) the datum. Each solution option then tallies the total positive and negative scores as a form of grading each concept against the others. Some criteria are weighted higher than others based on perceived importance; this has been factored into the final scores for each solution. Using this information, the best option(s) for the design can then be identified.
Feasibility: Prototyping, Analysis, Simulation
Clutch Pedal Design
The clutch pedal module is believed to have the largest range of possible physical and mechanical structures. Basic concepts for the Pugh Chart clutch pedal designs were drawn for a better idea of what they may look like.
Three prototypes were then created for clutch pedal designs. The first was a simple linear spring (Top). The second was a clamp with a torsion spring (Middle). The third design was a more complicated one, with a small hydraulic piston and multiple brackets and joints (Bottom). This third setup was found in the surplus items of the senior design lab. It was a very viable design, so we included it in our prototyping.
For each of our three designs, the force needed to depress the pedal a given distance was found and a curve was generated. The exact numbers are not important, as they very could vary greatly depending on the exact size of each component and the strength of the spring or hydraulic. The shape of the curve is the important aspect of these graphs.
Some of the force curves we found in our research did not have the dip in force when the pedal was near full deppression, they simply leveled out. Either of those curves would be acceptable.
After testing the prototypes we compared them with the desired force per distance graph, as well aa a few other factors shown in the benchmarking table below. Our team found the third setup with the hydraulic piston to feel really smooth and natural, which we thought was a high-priority component of the clutch pedal design. With a few modifications to the structure of the rustic prototype, a clutch pedal using a hydraulic piston was determined to be a very viable solution.
Vehicle Dimensional Data
A feasibility analysis was conducted to determine if a clutch pedal system similar to that of a 2012 Chevy Cruze would fit in a 2010 Ford Fusion to fulfill the Customer Requirements. Data collection, as seen in the tables below, was performed prior to the analysis.
The available region of space comprising the floor of the Ford Fusion is 10.5cm by 27cm, providing an area of 283.5cm2 for the clutch pedal subsystem design to fit. The clutch pedal itself for our design will be roughly 6cm by 6cm, an area of 36cm2. It is constrained to be located 3-6cm from the brake pedal, which the 10.5cm width of space on the floor of the Fusion more than accommodates.
Communication and Data Rates
The above table captures various data points that may be present on the communications bus between each subsystem. This assumes a worst-case scenario to better understand the highest potential level of throughput required to maintain stable communications. This does not reflect the final implementation.
This is the initial mockup design for the display module. It indicates the RPM for the manual vehicle as well as the current gearing. There are two gear displays: one for which gear the user is in and the other for the "correct" gear. There are also indicators for initial teaching which will instruct the user approximately when to shift either up or down. There is also a feedback messages window which display the results of the shifting or any error messages needed.
StandardsThe following standards were referenced by our team for the O-Shift device.
Plans for next phase
- Design clutch pedal assembly
- Design shifter assembly
- Establish stress and failure analyses on clutch assembly
- Determine clutch pedal spring/hydraulic force
- Design shifter assembly
- Choose sensors for clutch and shifter
- Research/Decide on necessary chips (IMU, protocols, etc.) and begin design
- Design Power Regulation Test Circuitry
- Obtain Realistic Power Consumption (OBDII Power Feasibility)
- Determine mechanical-electrical interface for shifter/clutch
- Collect needed data of Manual Transmission Car
- Research on lock-out methods
- Initial Clutch/Shifter Electrical Sensor Design
- Initial Display Electrical Design
- Create OBD-II Data Gathering Device (Raspberry Pi)
- Decide on microcontroller
- Start laying groundwork for device drivers (CAN, UART, etc.)
- Research/decide on potential CAN transceivers, IMU ICs