Analysis and redesign of an antilock brake system controller

Antilock braking (ABS) systems are a combination of hydromechanical braking components with switching solenoids and relays which operate the brakes in response to wheel and vehicle speed information. The control law which calculates the braking is a complex set of logical rules designed to allow for variations in road conditions and the nonlinear nature of tyre friction characteristics. The piecewise linear action of the actuator components (solenoids and relays) and the logical control rules make it difficult to analyse the dynamical behaviour of an ABS using conventional methods. The paper describes the analysis and subsequent redesign of an ABS using a new method for studying the dynamical behaviour of piecewise linear systems. The method is applied to a conventionally 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 dynamical performance