Fuzzy Logic Continuous and Quantizing Control of an ABS Braking System

The paper discusses means to adapt the braking pressure to changing road conditions by analyzing the relation between brake torque and slip ratio in real time. No additional sensory inputs are used. The fuzzy logic controller and a decision logic network identify the current road condition, based on current and past readings of the slip ratio and brake pressure. The controller detects wheel blockage immediately and avoids excessive slipping. The fuzzy logic controller output signal represents the brake torque applied to the vehicle. The ABS system performance is examined on a quarter vehicle model with nonlinear elastic suspension. The parallelity of the fuzzy logic evaluation process ensures rapid computation of the controller output signal, requiring both less time and fewer computation steps than controllers with adaptive identification. Two actuator types are investigated, one with a customary quantizing characteristic, and the other capable of generating continuous braking pressure variations. The paper describes design criteria, the decision and rule structure of the control system, and presents simulation results on various road types, and under rapidly changing road conditions.