Research On Coordinated Control Of Regenerative Braking And ABS For HEV

The basic functions of the vehicle include driving, steering and braking, and the braking performance is directly related to traffic safety. Compared with traditional vehicles, the braking system of Hybrid Electric Vehicles (HEV) is composed by regenerative braking and friction braking. Regenerative braking can improve energy utilization rate by recovering and storing part of braking energy to energy storage system, which is of great significance to extending driving range and saving energy for the vehicle.However, regenerative braking also makes the braking system of HEV more complex and has a negative impact on the control of Anti-lock Braking System (ABS). Therefore, to achieve the dual goals of safety braking and efficient energy recovery, a sound braking force distribution strategy and regenerative braking control strategy is needed, which can distribute regenerative braking force and front and rear wheel friction braking force reasonably, and realize the coordinate control of regenerative braking system with ABS.Taking into account the characteristics of urban conditions and regenerative braking, series Hybrid Electric Bus (HEB) is selected for the study in this paper. The restriction of front and rear wheel braking force is determined based on the analysis of vehicle braking process. At the same time, the maximum regenerative braking torque acting on the drive wheels is determined considering main affecting factors of regenerative braking. As the shifting of Automated Mechanical Transmission (AMT) will disconnect the motor and drive system, it is unable to use regenerative braking any more. To improve the ride comfort and maintain the continuity of the energy recovery, shifting rules of AMT is optimized and the breaking force is adjusted in advance.At present, several typical braking force distribution strategies can only be used on the front-wheel-driven vehicles but not on HEB driven by rear wheel, so their applicability are improved in this paper. The anti-lock control of the pneumatic brake system is realized based on logic threshold algorithm, then the adverse impact of regenerative braking on ABS is analyzed. However, closing regenerative braking system directly will also affect the control effect of ABS, which could be improved by decreasing the regenerative braking torque smoothly and quickly. In order to achieve the target of the coordinated control of regenerative braking and ABS, this paper build up a braking force fuzzy controller based on brake pedal travel, which can adjust the regenerative braking torque reasonably under different braking conditions. The controller aims at taking full use of regenerative braking during conventional braking to recovery as much energy as possible, but restricting the regenerative braking torque during emergency braking to ensure the braking safety.The HEV model is built up in Cruise and the braking control strategy model is built up in MATLAB/simulink, then the co-simulation is achieved by them. The simulation results show that braking force fuzzy controller can increase the energy recovery rate under city cycle-run conditions compared with typical braking force distribution strategies, which can extend driving range effectively. On the other hand, braking force fuzzy controller can reduce the adverse effects on ABS under emergency braking conditions, which ensure the braking safety and stability. In summary, the fuzzy strategy in this paper realizes the coordinate control of regenerative braking system and ABS.