Abstract:
Antilock Braking System (ABS) is an electronically controlled system that prevents the wheels from locking by limiting the pressure delivered to each slave cylinder of the vehicle. By preventing lock up, ABS gives the driver the opportunity to maintain the steering control of the vehicle during emergency braking. The main control objective of ABS is to increase the tractive forces between wheels and road surface by keeping the wheel slip at the peak value of road adhesion coe cient vs wheel slip curve. Conventionally, it is assumed that optimal wheel slip is some constant. In this thesis, a grey sliding mode controller is proposed to regulate optimal wheel slip depending on the vehicle forward velocity. The selection of the sliding mode control algorithm is based on the fact that ABS exhibits strongly nonlinear and uncertain characteristics, and to overcome these di culties, robust control methods should be employed. The concept of grey system theory, which has a certain prediction capability, o ers an alternative approach to conventional control methods. The proposed controller anticipates the upcoming values of wheel slip and optimal wheel slip, and takes the necessary action to keep wheel slip at the corresponding optimum value. The control algorithm is applied to a quarter vehicle model, and it is veri ed through simulations indicating fast convergence and good performance of the designed controller. Simulated results are validated on real time applications using a laboratory experimental setup.
