ANALYSIS AND REDESIGN OF AN ANTILOCK BRAKE SYSTEM CONTROLLER

Antilock braking (ABS) systems are a combination of hydromechanical br aking components with switching solenoids and relays which operate the brakes in response to wheel and vehicle speed information. The contro l law which calculates the braking is a complex set of logical rules d esigned to allow for variations in road conditions and the nonlinear n ature of tyre friction characteristics. The piecewise linear action of the actuator components (solenoids and relays) and the logical contro l rules make it difficult to analyse the dynamical behaviour of an ABS using conventional methods. The paper describes the analysis and subs equent redesign of an ABS using a new method for studying the dynamica l behaviour of piecewise linear systems. The method is applied to a co nventionally designed ABS controller. Undesirable performance features , not evident from conventional simulation and testing procedure, are found and the controller is redesigned to give a satisfactory dynamica l performance.