Hierarchical braking accurate control of electrohydraulic composite braking system for electric vehicles

For the electrohydraulic composite braking system, the general total braking force calculation strategy frequently ignores the resist forces, thereby cannot track the braking intention of driver perfectly. Moreover, the torque allocation process reduces the control reliability and energy recovery effect. In this research, a novel hierarchical braking accurate control (HBAC) algorithm is designed to achieve both the control accuracy and the ideal energy recovery efficiency. It includes target calculation, parameter adjustment, and organization coordination levels. In the target calculation level, the resist forces such as air, tire roll resistances are considered to calculate the demanded-braking force accurately. In the parameter adjustment level, the ideal demand-braking force is constrained by the estimated road adhesion coefficient and the vertical load transfer. At the organization coordination level, the torque allocation process is omitted by applying a compensation control of the hydraulic braking torque. The simulation results indicated outstanding braking distances by the proposed HBAC are 111.5 m, 40.8 m, and 63.2 m under the varying adhesion, dry asphalt, and wet asphalt roads, respectively. Moreover, compared with the comparative control strategy, the energy recovery efficiency of HBAC is increased by 11.74 %, 6.67 %, and 8.4 % under these road conditions. Experimental implementation corroborates the effectiveness of proposed strategy.