Anti-lock braking control of a hybrid brake-by-wire system

This paper presents a non-linear sliding mode type controller for slip regulation in a braking event for a hybrid electromagnetic-electrohydraulic brake-by-wire (BBW) system. The anti-lock braking system (ABS) controller modifies the brake torque command generated by a supervisory controller based on a driver request via the brake pedal sensor. The brake torque command is then generated by a closed-loop actuator control algorithm to control the eddy current brake (ECB) and electrohydraulic brake (EHB) systems. The proposed control algorithm shows very good slip regulation in a braking event on low friction coefficient surfaces when compared with non-ABS braking. It has been observed that the eddy current brake provided most of the torque while the electrohydraulic brake compensated for the difference between ABS torque command and estimated ECB torque. The result is a very smooth ABS stop minimizing the noise, vibration, and harshness (NVH) of current hydraulic ABS systems. It is also shown that the closed-loop system is stable in the sense of Lyapunov stability theory.