Integrated Optimal Control Strategy of Electro-Mechanical Hybrid Braking System for Four-Wheel Independent Drive/Brake Electric Vehicles

X-by-wire skateboard chassis is one of the most attractive and prospective chassis architectures for future intelligent electric vehicles. Since the characteristics of the four-wheel regenerative brake torque and electromechanical friction brake torque of the four-wheel independent drive/brake electric vehicle are all independently controllable, the coordinated distribution of the over-actuated four-wheel electric and mechanical hybrid braking torque have the considerable potential to supply systematically improvement on recovery of braking energy than conventional vehicles. To further explore the potential of energy recovery and achieve better cross-system control, a framework of integrated optimal control strategy (IOTD) is proposed for four-wheel independent drive/brake electric vehicles with electro-mechanical hybrid braking systems. Wherein, orientation estrangement among inter-axis, inter-wheel and inter-system torque distribution under multiple conditions is eliminated. Instead, the torque distribution process is highly integrated. Co-simulation verification results show clear improvement in terms of stability and economy. HDiL test results further show that the IOTD reaches up to about 3.32% more energy recovery rate with a reasonable computing load under combined braking conditions.