Efficient coordinated control of regenerative braking with pneumatic anti-lock braking for hybrid electric vehicle

Urban bus has to start and stop frequently due to typical urban traffic conditions, which, however, can be put to good use by regenerative braking. Regenerative braking is a key technology which not only improves vehicle's fuel economy in mild braking, but also ensures vehicle safety in emergency braking conditions. Because of the inherent limitations of traditional braking system in recycling energy, it is necessary to change its structure to decouple the brake pressure and the brake pedal force. To solve this problem, a compromise design combining traditional pneumatic braking system with brake-by-wire (BBW) system is adopted in this paper on parallel hybrid electric bus. With the transformed braking system, an efficient coordinated control strategy is proposed to solve the problem caused by the different response speeds of pneumatic braking and regenerative braking. The proposed control strategy is carried out, where the road condition varies and different control methods are adopted. Results show that the adopted braking system and the proposed coordinated control strategy are suitable for different roads, and effective in recovering energy and ensuring vehicle safety. At the same time, shorter braking distance and better control of slip ratio verify the performance of MPC compared with a logical threshold-based control. Therefore, this study may offer a useful theoretical reference to the choice of braking system and braking control strategy design in hybrid electric vehicle (HEV).