Hierarchical intelligent control of automobile anti-lock braking system

A new method using difference of the peak values of wheel velocity to calculate reference vehicle velocity and reference slip ratio is proposed, which is based on the analyses of the mechanics characteristics between the tire and the road when the vehicle is being braked. To solve complex control problem of automobile anti-lock braking system (ABS) in different conditions, a hierarchical intelligent control (HIC) system is investigated. It includes running control level, parameters adjusting level and organization coordination level. According to the instantaneous performance index of reference slip ratio, a human-simulation intelligent controller (HSIC) aiming at controlling reference slip ratio is designed in running control level. The characteristic model, control modes set and reasoning rules set are built. In parameter adjusting level, to decrease the deficiency of reference slip ratio control, a method is pointed that modifies the calculation values of HSIC pursuant to wheel angle deceleration. In coordination level, a fuzzy intelligent controller with the inputs of wheel deceleration and reference slip ratio is designed to implement road automatic identification. Then four wheels braking coordination control rules are also given. The simulation on HIC system of ABS is developed with Matlab. An automotive ABS test and control system is constructed and the road tests under different conditions are completed according to the international standards. Compared to traditional logic gate control, test results show that the HIC is an effective new ABS control method with better braking stability, adaptiviness and control accuracy.