The Study On The Regenerative Braking Control Strategy 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.At present,there are two problems exists in regenerative braking system of hybrid bus.One is the slow response of pneumatic braking system,and the other is the effect of braking energy recovery on battery life.Based on the above problems,a parallel hybrid electric bus is used as the research object,then make a research on the regenerative braking system and its control strategy.Research background and the research status at home and abroad are studied.The existing problems of regenerative braking system are analyzed and concluded,which demonstrates the meaning of this study.Firstly,according to the configuration characteristic of a parallel hybrid bus,the motor model,pneumatic brake model,tire model and battery model are established in MATLAB.The vehicle dynamics model is established and the vehicle's parameters are set in the TruckSim.According to different braking condition,tire-road friction coefficient and the desired slip ratio are estimated by the appropriate methods.Secondly,the coordinated control of regenerative braking and ABS is analyzed,and the mutual compensation control strategy is put forward,which is used to solve the problem of pneumatic brake slow response problem.The effect of battery current,battery temperature and battery SOC on the battery life is analyzed,and a new brake control strategy considering the battery life is proposed.Finally,the braking control strategies put forward are verified by the simulation.The mutual compensation control strategy is verified through the co-simulation of MATLAB with TruckSim.The difference in the braking distance,energy recovery and the slip rate are analyzed Through the comparison of mutual compensation control strategy and logic threshold control strategy,which is used to solve the slow response of pneumatic braking system.The braking control strategy considering the battery life is verified through hardware in loop test.The difference between braking control strategy considering the battery life and general braking control strategy are analyzed,which is used to find a balance between recycled energy and its effects on battery life.