Electro-Hydraulic Composite Braking Control Optimization for Front-Wheel-Driven Electric Vehicles Equipped with Integrated Electro-Hydraulic Braking System

With the development of brake-by-wire technology, electro-hydraulic composite braking technology came into being. This technology distributes the total braking force demand into motor regenerative braking force and hydraulic braking force, and can achieve a high energy recovery rate. The existing composite braking control belongs to single-channel control, i.e., the four wheel braking pressures are always the same, so the hydraulic braking force distribution relationship of the front and rear wheels does not change. For single-axle-driven electric vehicles, the additional regenerative braking force on the driven wheels will destroy the original braking force distribution relationship, resulting in reduced braking efficiency of the driven wheels, which are much easier to lock under poor road adhesion conditions. The integrated Electro-Hydraulic Braking system (iEHB) is the current advanced brake-by-wire system, which can build brake hydraulic pressure by its motor, and independently adjusts the four wheel braking pressures through the solenoid valves. Based on the characteristics of the iEHB, a composite braking control strategy for front-wheel-driven electric vehicles is proposed, which adjusts the braking force distribution relationship dynamically. Firstly, the structure of the iEHB system and the wheel braking pressure control principle are analyzed. Secondly, a composite braking control strategy that adjusts the braking force distribution relationship based on current regenerative braking force and wheel braking pressures is designed. Finally, simulations are carried out with the proposed control strategy and the single-channel composite braking control strategy. The simulation results show that the proposed composite braking control strategy can improve the braking efficiency of the driven wheels and improve the energy recovery rate.