Study On Shifting Schedule For Automated Mechanical Transmission Of Parallel Hybrid Electric Vehicle

Hybrid electric vehicle(HEV),a product in the transition from conventional vehicle to electric vehicle,is playing a more and more important role in today’s automotive market.HEV has two or more power sources and the study of the control issues of hybrid electric system at present is mainly about the study of the energy distribution problem in the steady-state process or dynamic process and the study of the dynamic coordinated control problem in dynamic process,such as the coordinated control problem during shifting process and mode switching control problem and so on.In this dissertation, research of the shift schedule in different modes of HEV based on a hybrid electric bus which is equipped with an automated mechanical transmission(AMT) was conducted systematically to improve the vehicle fuel economy combined with Major Natural Science Research Project of Universities and Colleges of Jiangsu Province “ Power Switching and Dynamic Coordinated Controlling of Hybrid Electric Vehicle”.The main contents are as follows:First of all,the structural characteristic of the hybrid electric bus was introduced.The bench test datas of the engine and the motor were obtained by the hybrid bench test system and the efficiency models of these two components were built.The component modules and the full vehicle simulation model were established in Cruise.Secondly,the classical logic threshold energy management strategy that is used in the hybrid electric bus currently was introduced. On the basis of the analysis of different working mode, the torque distribution rules were developed.Due to the defects of the torque distribution rules of the logic threshold energy management strategy, a multi-objective optimization algorithm was designed choosing the power source efficiency and the vehicle emissions as the optimization objectives to increase the vehicle fuel economy and reduce the vehicle emissions. The simulation results show that the optimized control strategy can increase the power source efficiency and at the same time reduce the vehicle emissions.Then, the concept of the efficiency of the hybrid system including battery pack efficiency,motor efficiency, engine efficiency and power train efficiency based on the optimized energy management strategy was proposed. The shift schedule was obtained by choosing the hybrid system efficiency as optimum objective and by selecting the engine torque 、vehicle speed and the motor torque as shift control parameters under different working modes of the hybrid electric bus.Fuzzy control method was used in the realization of the shift schedule and the shift fuzzy controller was designed. The simulation results based on the co-simulation of Matlab/Simulink and Cruise under urban driving cycles show that the shift schedule designed in this paper can improve the vehicle fuel economy.Finally, according to the existing test conditions the revolving drum test of the hybrid electric bus was designed.Three tests including prototype bus, bus using the optimized energy management strategy and bus using the shift schedule designed in this paper were conducted under typical Chinese City Bus Cycle(CCBC).The emissions curve, the electric power consumption and the engine fuel consumption of the battery were obtained during the experiments.The combined vehicle fuel consumption was obtained by converting electric power consumption of the battery into equivalent fuel consumption according to the national standard.The results of the experiments show that the optimized energy management strategy can improve vehicle fuel economy to some extent and reduce the vehicle emissions and the shift schedule designed in this paper can improve vehicle fuel economy.