Cooperative control of regenerative braking and friction braking in the transient process of anti-lock braking activation in electric vehicles

Regenerative braking significantly improves the energy efficiency in electric vehicles. Cooperative control between regenerative braking and friction braking during anti-lock braking control is a critical issue in brake system coupling. For safety concerns, regenerative braking is often terminated at the beginning of anti-lock braking control. Oscillations between activation of an anti-lock braking system and exit from anti-lock braking system control may occur under poorly matched control parameters. To solve these problems, we propose an index that indicates the possibility of activation of an anti-lock braking system. It is derived by a fuzzy logic algorithm which is based on the estimated regenerative braking torque, the estimated friction braking torque and other vehicle state variables. Regenerative braking can be adjusted on the basis of the index to ensure that such braking is of a low level when an anti-lock braking system is activated. Simulations and experiments are carried out to evaluate the effectiveness of the index. The results show that regenerative braking decreases as the index increases, thereby improving the braking safety and the driving comfort during the transient process of activation of an anti-lock braking system.