Optimization Of Power Train System Of Electric Vehicle

Unlike traditional fuel vehicles,the pure electric vehicles use power batteries as their energy source to achieve "zero emissions" during driving and high energy utilization rate.They have already become the major development direction of automobiles all over the world.However,due to the limitation of current battery technology,the driving range of pure electric vehicles is relatively short and the cost of the whole vehicle is high.Therefore,it is necessary to reasonably match the parameters of the power systems of the pure electric vehicle in order to achieve better driving range.Relying on the project "The key technology research and industrialization of a certain type of electric commercial vehicle ",this paper has made modifications on the power system structure according to the test results of the prototype vehicle.Based on the structure of its transmission system,a main decelerator with single fixed speed ratio,the paper proposes a method with two-speed transmission being installed in the transmission system,and it matches the power system parameters of the purely electric commercial vehicle after structural modification.According to the knowledge of the automobile theory,theoretical calculations and analysis are performed to carry out parameter matching and model selection of the driving motor,the power battery and driveline transmission ratios.The AVL Cruise software is used to establish a whole vehicle model,establish simulation tasks,then implement the simulation of dynamic and economic.The simulation results meet the design goals of performance and demonstrate that the dynamic system parameters are compatible.In order to improve the driving range and acceleration performance of the pure electric commercial vehicle,an optimized plan of the power transmission system is proposed.Take the transmission ratio of the transmission system as the optimized variable,the acceleration time of 0-50km/h,the driving range of the NEDC operating conditions and the 40km/h constant speed operating conditions as the optimization objectives,and the maximum speed and the maximum climbing grade as the constraints.The paper selects the multi-island GA to optimize the transmission ratio of the transmission system through the joint simulation conducted by Isight and Cruise The results show that the continuous driving range of the vehicle increases after optimizing the transmission ratio,and the acceleration time from 0 to 50 km/h is reduced.The paper has formulated the dual-parameter shift control law based on the opening degrees of the accelerator pedal and the vehicle speed,and the dynamic shift schedule based on the relation curve of vehicle drive torque and the speed for two gear positions at different accelerator pedal opening degrees;according to the relation curve of drive motor efficiency and speed for two gear positions at different accelerator pedal opening degrees,the economic shift law is formulated and the comprehensive shift law is determined by combining the dynamic shift law and the economic shift law.Finally,the verification and comparison simulations of the three different shift laws are conducted.