Design of Drive-By-Wire Throttle Control System

Photo of Kevin Gentry, Tyson McKinney, Bret Schneider Students: Kevin Gentry, Tyson McKinney, Bret Schneider

Sponsor: The University of Texas at Austin

Date: Fall 2009

Requirements:
The most important requirement of this project was to control the valve to within 1° of resolution and ±0.5° accuracy. The valve's position must be indicated on the user interface and is scaled between 0 and 100 (fully closed to fully open). The idle setpoint is scaled between 0 and 30. Additional requirements involve the valve's response to a step input: a maximum settling time of 200 ms, less than 10% overshoot, and no more than a 100 ms rise time. Control housing dimensions were constrained to 3" x 4" x 6" and the system was required to use a 13.8V power source. The project's budget was $1000.

Problem:
The focus of this project was to develop and implement a control system for an electronic throttle body for use on an engine/dynamometer test setup in the Automotive Lab at The University of Texas at Austin. The system provides accurate and precise positioning of a butterfly valve in the throttle body. Knobs on the user interface control the valve position and idle setpoint from an adjacent control room. The accuracy and stability of the valve were the most important aspects of the problem.

Solution:
The team solved this problem two ways: analytically and experimentally. These paths were taken simultaneously throughout the design process. The analytical model included developing a bond graph and transfer function of the system. The team then identified system parameters and generated P, I, and D values using LabVIEW's System Identification Toolkit. The experimental method involved setting up a PI control system in LabVIEW and tuning the P and I values using the Ziegler-Nichols method. Overall, the experimental method of developing a control system resulted in much better control of the throttle valve position. After implementing the system in LabVIEW, the control algorithm was reprogrammed in C to deploy the control system to a PIC18F2620 microcontroller. For final testing, the system response to various step inputs and sine waves was evaluated. The system performed within the requirements and constraints of the project. The team installed the electronic throttle control system in the Automotive Lab at The University of Texas at Austin. Electronic throttle control will increase the response and stability of experiments conducted in the Automotive Lab.

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