An integrated strategy for vehicle active suspension and anti-lock braking systems

In this paper, a decentralized integrated control structure is developed based on a quarter car vehicle model including longitudinal and vertical dynamics. In this structure, the antilock braking system (ABS) is designed to decrease the stopping distance by regulating the longitudinal slip for improved safety during hard braking while the active suspension system (ASS) decreases the sprung mass acceleration to improve the ride comfort on irregular roads. During hard braking, it is preferred for conventional ASS to control the variations of tire deflection to improve the braking performance. How ever, in a new strategy, it is shown that if the ABS controller follows the optimal longitudinal slip varied with the vehicle speed and tire normal force instead of a constant value, the dependency of ASS and ABS is decreased. In this way, the ABS performance has high quality performance even in the presence of passive suspension. Application of ASS causes more reduction in the body vibration to provide more ride comfort during braking. As a conclusion, when the ASS is integrated with the proposed strategy of ABS, the overall ride and safety performances are simultaneously improved during hard braking on a good road spectrum.