| With the growing shortage of oil resources and continuous improvement of livingenvironmental requirment, energy-saving, environmental and efficient electric vehicleis becoming the new research direction of the governments and auto companiesaround the world. Powertrain system is the heart of electric vehicle, its parametermatching and dynamic characteristics directly impact the vehicle’s power, economyand driveability performance.In this paper, firstly, the selection and parameter matching of powertraincomponents are implemented according to the design goals of LF620pure electricvehicle. Then an analysis invloves in the influence of different transmission matchingon vehicle power and economy performance is made. Combined with research project,two transmission matching programs, that is, two-speed mechanical automatictransmission and continuous variable transmission, are proposed. Besides, in order tomeet the needs of electric motor, structural improvements of CVT are made.Secondly, based on the research of two different vehicle modeling methodcharacteristics, forward-simulation method and backward-simulation method, anelectric vehicle forward-simulation model of LF620is developed in Matlab/Simulinkwith the method of theoretical modeling and experimental modeling, including thedriver module, battery module, motor module, transmission module, vehicle dynamicmodule and regenerative braking module. Then a comparison is made betweenexperimental data and simulation data to validate the rationality of the establishedvehicle model.Thirdly, according to the principle of maximizing powertrain efficiency andvehicle acceleration, an optimization procedure is carried out to optimize the besteconomic shift schedual and power shift schedual of two-speed automatictransmission as well as the motor and CVT’s optimal control law of electric vehiclesequipped with CVT in driving and braking condition. Taking advantage of theoptimization results, a comparative analysis on power and economy performancebetween two tranmission program is implemented.Finally, after analyzing the mechanical transfer characteristics of electric vehiclepowertrain system, a model which reflects the driveline dynamic characteristics isestablished. On the basis of the model, the transient response characteristics of the motor and the dynamic characteristics of powertrain system under a tip-in condition isprelimilarily simulated. Then a discussion is made on the effect of differenttransmission ratio and driveshaft stiffness on the dynamic performance of vehicle.The simulation results provide reference and groundwork for further research on thedesign and dynamic characteristics of electric vehicle’s powertrain system. |
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