| Electric vehicles(EV),as a type of new energy vehicles with excellent control performance and high integration,have been developed rapidly in recent years in China.However,electric vehicle industry in China still needs further exploration in the frontier technology of high-end electric vehicles to promote Chinese electric vehicle industry to lead the development of the global electric vehicle industry in the future.Among the new driving technologies for EV,dualmotor coupling drive and torque vectoring have received extensive investigation in recent years.Dual-motor coupling drive(DMCD)can significantly improve the efficiency of the drive system by optimizing its efficient range and thereby enhancing the energy economy of EV.Torque vectoring(TV)can directly control the driving torque of each driving wheels and thereby enhancing the stability,maneuverability,power,and energy economy performance of EV under different conditions.To fully improve the maneuverability and driving experience of EV while ensuring their excellent power performance and satisfactory energy economy,a novel dual-motor coupling TV drive system is proposed in this paper.The transmission of the drive system is composed of multiple planetary gear mechanisms,which can make the drive system working in single-motor drive mode,DMCD mode and TV mode respectively by controlling the working state of three clutches.Therefore,the drive system can not only effectively improve the driving performance of the EV through TV but also make EV achieve both satisfactory energy economy and high-power performance through DMCD.The energy economy improvement effect of the novel drive system on EV under full working conditions is studied and the electric vehicle equipped with the novel drive system on rear axle is taken as the research object in this paper.Firstly,basic structure,main function,power transmission route and the steady-state output characteristics under each drive mode of the novel drive system are detailly analyzed.The dynamic model of the drive system under TV mode is built based on bond graph theory and the TV effect of the drive system is simulated and verified.To provide a foundation of simulation platform for the research in this paper,a dynamic model of vehicle is built,which contains 3-degree-of-freedom dynamic model of vehicle body,wheel rotation dynamic model,tire model based on “magic formula”,longitudinal driver model based on PID controller and steering driver model based on single-point preview model.After that,to investigate the energy economy improvement effect by the application of DMCD in the novel drive system,a parameter matching and optimization method with the target of energy economy and the constraint of power performance demand and TV demand is proposed,which is calculated based on genetic algorithm.According to the instantaneous optimization results of full conditions,a drive mode switching control strategy is designed,which contains the optimal drive mode recognition strategy and the optimal power distribution strategy based on logical thresholds value.Finally,in order to investigate the energy economy improvement effect by the application of TV in the novel drive system,a TV strategy for steering energy saving is proposed,which contains the stability objective TV strategy based on the method of zeroing side slip angle of center of gravity(COG),the energy economy objective TV strategy based on the optimization of TV-related energy consumption,and the stability region division method based on the analysis of side slip angle of COG and side slip speed of COG phase plain.To verify the energy economy improvement effect of the novel drive system in EV under full conditions,a simulation platform based on MATLAB/Simulink is built in this paper,which contains the model of drive system,the model of vehicle and the control strategy of the drive system.Several simulations for EV equipped with the novel drive system on rear axle are completed under several cyclic conditions and several steering conditions.Simulation results under CLTC,NEDC and WLTC show that the application of DMCD in the novel drive system can effectively improve the drive efficiency of the drive system and thereby significantly improve the energy economy of EV.Simulation results under sinusoidal input steering wheel condition,double lane change condition,and U-turn condition show that the energy consumption during steering process can be effectively reduced by the application of TV in the novel drive system and thereby effectively improve the energy economy of EV in some specific conditions. |
