Nonlinear control method for automotive anti-lock braking system

A controller is designed for anti-lock braking system (ABS) with discontinuous characteristics of on/off valves. Firstly, the dynamic characteristics under Increase, Hold and Decrease modes are discussed, and a math description is given for ABS with on/off valves, including wheel slip continuous dynamics and actuator discontinuous dynamics. Considering the requirement on applicability and robustness, an approach for nonlinear controller design is proposed which uses system state as switching law to guarantee the stability. The idea is to develop two switching surfaces using Lyapunov method in the sense of Filippov, and the state space partition is regarded as the switching law, with the stability ensured via switching surfaces selection. Further, to avoid frequent switches, the control objective is modified to the convergence of an equilibrium set, and the influence of the size about the equilibrium set on the closed-loop system performance is discussed. Simulation and experiment tests illustrate that both high braking efficiency and ride quality are obtained with few control parameters.