Braking force decoupling control without pressure sensor for a novel series regenerative brake system

Abstract

Regenerative braking can save energy consumption greatly for electric vehicles. For a series regenerative brake system, it is foundational to make the hydraulic braking torque and braking force decoupled and to provide the same pedal feeling as conventional braking system. In this paper, a high-performance and low-cost solution of series regenerative brake system is designed, which consists of a conventional anti-lock brake system and a motor-driven electromechanical booster (E-booster). Based on the series regenerative brake, a braking force decoupling control scheme without pressure sensor is proposed. First, a dynamic model of vacuum booster is established to calculate the desired brake pedal feeling in real time. Then, a sliding mode observer is used to estimate the load torque of the E-booster so that the expensive pressure sensors are eliminated. Finally, a sliding mode controller is developed to work with a robust threshold–controlled anti-lock brake system hydraulic control unit adjusting the pedal feeling and the wheel cylinder pressure simultaneously. Simulations and experiments were conducted in MATLAB/SIMULINK and on a test bench, respectively. The results show that the tracking ability of wheel cylinder pressure and quality of braking pedal feeling in different conditions are both good, providing a practical method to realize fully series regenerative brake.