Electronic Shifter Lee Redstone V00662175 Lewis Weston V00766616 Jason Deglint V00730963 Group #5 Supervisor Ashoka K. S. Bhat Due Oct. 16, 2012 Dept. Electrical and Computer Engineering University of Victoria All rights reserved. This report may not be reproduced in whole or in part, by photocopy or other means, without the permission of the author.
Electronic Shifter 1 Table of Contents Background... 2 Motivation... 2 Proposed Project... 2 Possible Solutions... 3 Linear Actuator... 3 Steering Wheel connection... 3 Microcontroller... 3 Work Plan... 4 Milestones... 5 Deliverables... 6 Force Measurements... 6 Acquisition and testing of a linear actuator... 6 Website... 6
Electronic Shifter 2 Background The UVic FSAE team competes annually in the Formula SAE competition series hosted by the Society of Automotive Engineers. The nature of the competition involves designing, fabrication, and running a new open wheeled race car each year. The majority of the components on the vehicle are built by the team for the specific purpose of the competition. The driver controls are a major design consideration each year, and the team is hoping to increase their competitiveness by making the vehicle easier to drive. It is vital that reliability is not sacrificed for this project, weight reductions can be made through iterative designs, but the device is required to operate at 100% in a very extreme environment. Motivation The Formula SAE car is built to compete in high speed autocross course specifically designed for the small cars built by the teams. Speeds easily reach 80-90km/hr and the driver must constantly move between 1st, 2nd, and 3rd gears while on the course. The current mechanical design requires the driver to remove their left hand from the steering wheel to engage the shifting lever. The time required to shift gears is on the order of magnitude of seconds. With the incorporation of an electronically actuated shifting mechanism the switching functionality can be moved onto the steering wheel through the use of paddles or push-buttons. This will allow the driver to keep both hands on the wheel, and has the potential to lower the shifting time to the order of 10 s of milliseconds. Proposed Project The following report outlines the proposed project for Group 5, of the Fall 2012 class of ELEC 399. The group intends to design and construct a fully electric shifting mechanism specifically designed for the UVic Formula SAE team. The team is investigating the feasibility of replacing the current mechanical shifting mechanism with an electric actuator. The device must be capable of shifting gears on the transmission of a 2003 Honda CBR F4i engine. To limit the scope of this project the clutch actuation will be reserved for a separate project. The design considerations for this project are: 1. Reliability- Shifting gears is a critical operation while the vehicle is being driven. The device must be capable of shifting thousands of times before weakening. 2. Weight- The implemented system must be as light as possible. The entire car is constrained to be as light as possible, and the mechanical system is currently very light weight. 3. Cost- The system must have a reasonable base price. There exists store bought solutions with very high price points. The team currently cannot afford these products.
Electronic Shifter 3 Possible Solutions In order to design and construct a fully electric shifting mechanism specifically designed for the UVic Formula SAE team different aspects of the project must be considered. 1. Linear Actuator 2. Steering Wheel Connection 3. Microcontroller Linear Actuator There are two different types of electric linear actuators which can be used to shift the transmission: 1. Electric Motor 2. Solenoid A comparison of the major advantages and disadvantages are discussed in the following chart: DC Motor Solenoid Advantages Much cheaper than solenoid. Minimal moving parts. Disadvantages Requires additional moving parts such as gears which can cause additional losses. Very expensive relative to a DC motor. Both options plan to be researched and tested to see which better suits the projects needs. Steering Wheel connection In addition, during driver egress, the steering wheel will be removed quickly and potentially thrown. For this reason, all electric connections from the buttons on the steering wheel to the main control system will need to be very robust. The initial idea to solve this problem is the use a TRS (Tip, Ring, Sleeve) connector which will allow the steering wheel to rotate freely while driving as well as have the capability of being removed. Either a 35 mm or ¼ Jack could be used for this. Microcontroller Currently we are planning to use the F28069 Piccolo controlstick from Texas Instruments. It uses a microcontroller mounted on a USB-accessible breakout board. Some reasons for choosing this platform include: Ease of programming through USB Dedicated PWM outputs (if required for motor control) Pre-written code for motor/solenoid control. These features will save time and complexity, allowing us to focus on developing a more effective solution on the electromechanical side of the project.
Electronic Shifter 4 Work Plan The Work Plan can be summarized by the following steps: 1. Determine specifications and requirements for the project - What kind of mechanism is best suited for the actuator solenoid or motor? - What are the torque/force requirements to shift the transmission? - What are the speed/timing requirements to shift the transmission? - Will the actuator require its own power source? - Where and how will the shift buttons be mounted? - What gauge of wire is required and how will it be connected? If the buttons are on the steering wheel, how can we ensure that the wheel is still removable? - Do the shift buttons need debouncing? If so, how? - How can we determine what gear the transmission is in, and how can we easily shift into neutral? 2. Design a solution based around answering the above questions 3. Physical implementation of the design 4. Testing the implementation by comparing it to the design specifications 5. Adjust the specifications and design/implementation as dictated by test results Below is a rough timeline for each stage of the project, mid-september: 1. Determining specifications and requirements - Two weeks, specifications first draft complete by first week of October 2. Designing a solution - Four weeks, ready for production by first week of November 3. Implementation - Two weeks, ready for testing by mid-november 4. Testing and adjustments - Two weeks, project is at a stage where it can undergo real-world use Obviously, each stage of the project will overlap considerably with others, as design, implementation, and testing may be done simultaneously, and specification and respecification will occur constantly throughout the project. However, the timeline above serves as a guide to keep the team on schedule, and to remind them of the short period of time available to complete the project. At the same time as this, there is an informational aspect of this project which involves keeping logbooks to track organize our ideas, preparing reports for describe our progress, and developing a website to showcase our results. Due to its nature, the informational portion of this project will be ongoing throughout the semester.
Electronic Shifter 5 Milestones The project can be divided into three major sections, which have their own milestones 1. Electromechanical systems connected to the transmission - Determine what kind of mechanism is best suited for the actuator - Find the torque/force requirements to shift the transmission - Find the speed/timing requirements to shift the transmission - Determine if actuator will require its own power source 2. Electronic and software systems for controlling the electromechanical system - Find how best to mount the three shift buttons (up, down, neutral) - Determine the best method for connecting the steering wheel wiring to the microcontroller - Ensure that the shift buttons are debounced in the microcontroller or in hardware - Figure out how the microcontroller will know which gear the transmission is in 3. Informational showcasing - Develop, publish, and maintain a website
Electronic Shifter 6 Deliverables The Deliverables so far in this project are as follows: 1. Force Measurements 2. Acquisition and testing of a linear actuator 3. Website Force Measurements The Force needed to move the shifter out the transmission was measured. Both Shifting Up and Shifting Forces were measured. From To Shifting Down Force (kilos) 6 5 11 5 4 11 4 3 10 3 2 11 2 1 11 From To Shifting Up Force (kilos) 1 2 10 2 3 11 3 4 10 4 5 10 5 6 10 As seen, the maximum force measured was 11 kilos. Since we need a force that will always guarantee to shift the transmission 150% of 11 kilos will be used. Therefore, 16.5 kilos will be used when deciding on a linear actuator. Acquisition and testing of a linear actuator Based on the force measurements above, an automotive power lock actuator was purchased and tested. It was capable of applying 4-5 kgf. This indicates that it is a third to a quarter of the required force for the project. Possible solutions involve using a force-multiplying lever or gearset, a more powerful motor in the actuator, or using several actuators in parallel. Website The website has been created in order to share any news updates and documentation with the public. The URL of the website is http://electronicshifter.wordpress.com/.