Research on fuzzy road surface identification and logic control for anti-lock braking system

Quarter vehicle braking model with four-degrees of freedom (including vertical and longitudinal motions of body as well as vertical and spin motions of wheel) subject to irregular excitation from a road surface is presented. This model along with tire and brake actuation system models can be used not only to examine ABS (Anti-lock Braking System) controller performance and investigate its robustness but also to provide input and output testing data of fuzzy model of road surface identification. According to fuzzy logic capable of dealing with dynamic systems having complexity, uncertainty and nonlinear characteristics, Takagi-surgeno fuzzy identification model of road conditions is introduced to detect the current road condition and generate corresponding optimal slip. In addition, the parallelity of fuzzy logic evaluation process ensures rapid computation of the controller output signal, requiring less time and fewer computation steps than some controllers based on controlled-object mathematical model. ABS fuzzy control algorithm is proposed to offer appropriate command braking pressure signal, based on current slip ratio and road condition as well as brake pressure, to detects wheel blockage immediately and avoids excessive slipping, and finally to minimize the stopping distance under emergency braking conditions. Fuzzy controller simulation results on various road types and under rapidly changing road conditions are provided so that proves the feasibility and validity of fuzzy road identification and fuzzy control logic.