Investigation on Anti-lock Braking Control System of a Passenger Car

• Main Authors: Ming-Cheng Wu, 吳銘欽
• Other Authors: Ming-Chang Shih
• Format: Others
• Language: zh-TW
• Online Access: http://ndltd.ncl.edu.tw/handle/y5ezuu

博士 === 國立成功大學 === 機械工程學系碩博士班 === 90 === The anti-lock braking system is a nonlinear system whose dynamic characteristics are very difficult to describe just using transfer functions or linearized equation sets. In order to take care of the dynamic motion as much as possible, this study tries to use original nonlinear equations without linearization to simulate the anti-lock braking system. Beside software simulation, a dynamic test stand is used to verify the software simulation results in parallel. For the controller design, this study adopts sliding-mode control theorem because of its well-known robustness. Two approaches are investigated to reduce the chattering problem caused by the sliding-mode controller. First, the controller is modified to have a boundary layer, whose control signal varies smoothly inside the boundary layer. The pulse width modulation method (PWM) is used to realize this quasi-continuous control using fast solenoid valves. With respect to the lifetime issue, we apply a hybrid sliding-mode control algorithm to minimize the on-off frequency and prolong the lifetime. The other way to bring the chattering down is trying to promote the sampling rate of the traditional on-off controller and achieve real time control. The performances of these two controllers are compared and evaluated in this article. To start the simulation and hardware testing, a closed-loop slip controller is designed to perform the anti-lock brake basing on the assumption that we know the real vehicle speed during the brake. Water sprays are used to simulate the brake on wet road surface or the brake on surface. Through special design, the four-wheel anti-lock brake controlled by the electric control unit (ECU) is also available on this test stand. The brake performance of the ECU is verified by the data gathered by the computer. Looking into the future, precise brake pressure control would be necessary in order to provide precise brake torque. Therefore hybrid sliding-mode PWM controller is used to get precise brake pressure. Both the software simulation and the hardware testing are used to verify the controller’s performance. Besides, an anti-lock brake controller with the brake pressure-tracking controller is designed basing on the tire acceleration signal feedback instead of slip feedback. Simulation and harware testing verify the brakes on dry and wet roads afterwards. The water-hammer phenomenon is also noticed and discussed together with the brake pressure control.