Study On Control Strategy Of Dual-motor Coupling System For Pure Electric Vehicles

Dynamic coupling technology is one of the future powertrain development directions and has broad application prospects for dynamic transmission system. It can combine multiple power sources through coupler and achieve a series of function such as power combination or decomposition, regenerative braking, work mode-switching and other auxiliary function. Recently, dynamic coupling technology applied to Hybrid Electric Vehicle(HEV) has been very matured but applied to the Electric Vehicle(EV) is rarely. According to the research of dynamic coupling technology on HEV, such as Toyota PRIUS and GM VOLT, the objective of this paper is to apply dynamic coupling technology on EV, which uses coupler to combine with multiple small_power motors to instead of the original high-power motor. So that not only reduced the volume and weight of the entire dynamic system but also reduced cost of production, and let the pure EV dynamic system towards a more efficient integration of direction. Reference on the HEV dynamic coupling system, the pure EV used multiple drive motor as power source, to achieve the combination of multiple motors through reasonably control the work status of drive motor and coupler, so that supply a series of function such as power coupling, energy recovery, reasonably mode-switching to avoid energy waste for pure EV.This paper used dual-motor coupling power system as the research objective of pure EV dynamic coupling technology, according to the structure and function of this dynamic coupling system and the performance requirements of pure EV, matching the reasonable relationship parameters for dual-motor coupling power system, also according this parameters to formulate the control strategy of each work mode and mode-switching between different modes, finally, build the simulation model to evaluate the relevant control strategy.The several aspects of research content as following:(1) Dual-motor coupling power transmission system matching parameters. According to the performance requirements of pure EV, matching the suitable parameters includes two motors, coupler and final drive.(2) Research on the dynamic model for dual-motor coupling power system. Improving and modifying the existing dual-motor coupling power system model, the point to research is analyze the characteristic of torque and speed for a planetary gear mechanism.(3) Developing a series of control strategy for different work mode. Analyzing the work mode for dynamic coupling transmission system, develop the reference control strategy of work mode includes motor 1 alone drive, motor 2 alone drive and dual-motor joint drive.(4) Analyzing the relation of different work mode for dynamic coupling system, and research on the point of mode-switching for a driver have different control intention.(5) Developing a series of control strategy based on the driver’s different control intention. Put the driver’s control intention simply define as the dynamic performance and economic performance, and develop the the control algorithm of the optimal dynamic and economic performance.Use the optimization method of genetic algorithm to optimize control algorithm, and formulate the control strategy of the optimal dynamic and economic performance based on a driver have different control intention.(6) SimulinkMatlab is used to build the EV simulation model. This model includes motor model, the planetary gear mechanism model, vehicle model, working mode control model and the driver model, and finally, the reference control strategy was evaluated by the simulation model.