A New Torque Distribution Strategy for Blended Anti-Lock Braking Systems of Electric Vehicles Based on Road Conditions and Driver's Intentions

This paper proposes a new braking torque distribution strategy for electric vehicles equipped with a hybrid hydraulic braking and regenerative braking system. The braking torque distribution strategy is proposed based on the required braking torque and the regenerative braking system's status. To get the required braking torque, a new strategy is designed based on the road conditions and driver's braking intentions. Through the estimated road surface, a robust wheel slip controller is designed to calculate the overall maximum braking torque required for the anti-lock braking system (ABS) under this road condition. Driver's braking intentions are classified as the emergency braking and the normal braking. In the case of emergency braking, the required braking torque is to be equal to the overall maximum braking torque. In the case of normal braking, the command braking torque is proportional to the pedal stroke. Then the required braking torque is chosen as the smaller one between the overall maximum braking torque and the command braking torque. To acquire both high regenerative efficiency and good braking performance when the required braking torque is smaller than the maximum braking torque of the regenerative braking system, the whole braking torque can be provided by the regenerative braking system; when the required braking torque is bigger than the maximum braking torque of the regenerative braking system, the whole braking torque can be provided by both the hydraulic braking system and the regenerative braking system, while the maximum braking torque of the regenerative braking system is obtained based on the battery state of charge (SOC) and vehicle speed in real-time. Both fuzzy rule-based scheduling and robust control approaches will be applied to achieve the above proposed distribution strategy. The effectiveness of the proposed control system is validated by numerical simulations under various road conditions, vehicle speeds, driver's braking intentions, and the battery SOCs.