A Model Predictive Control Allocation Approach to Hybrid Braking of Electric Vehicles

With the recent emergence of electric drivetrains, a faster and energy efficient braking actuator the electric motor has become available to complement the operation of the traditional friction brakes. The decision on how to split the braking torque among the friction brake and the electric motor is one of the main issues of such hybrid braking systems. With this challenge in mind, a new model predictive control allocation (MPCA) approach for hybrid braking is proposed. In comparison to state of the art torque blending solutions (daisy chain and dynamic control allocation) the MPCA offers faster transient response, without compromising the energy recuperation efficiency of the actuators. In addition, we also develop a linear wheel slip controller to regulate the braking force during emergency braking maneuvers. The tuning of this wheel slip controller is carried out using robust pole placement techniques, which ensures good operation in spite of uncertainties in the tire-road friction coefficient and the vertical load. Simulation results demonstrate the effectiveness of the proposed method.