Study On Performance Comparison Of Electric Vehicles Equipped With Fixed Ratio Gearbox And Multi-speed Gearbox

Parameters matching of transmission systems directly affect the dynamic and economy of electric vehicles(EVs).In order to further explore the impact of powertrain system on vehicle performance,the parameters of drive motors and automatic transmissions are calculated based upon the performance requirements of target vehicle in this paper.Transmission systems with one-speed gearbox and multi-speed gearbox are obtained respectively then.After the optimization of gearboxes ratios,the ratios are used to simulate over different driving cycles and the performance of the two transmission schemes are compared and analyzed.The main contents of this paper are as follows:(1)The research subject is provided by introducing the development background of EVs,which is to compare the dynamic and economy performance of EVs with one-speed gearbox and multi-speed gearbox.The introduction summarizes the current development in terms of the governments,the enterprises,etc.Besides,the work on EVs' powertrain systems by the researchers at home and abroad is also listed.(2)The basic parameters of motors and the gear ratios of automatic transmissions and reducer are calculated through the performance requirements of target vehicle.The powertrain systems with one-speed gearbox and 2-speed gearbox are determined and initially verified.(3)The simulation model to get the energy consumption over driving cycles is built in MATLAB/Simulink/Stateflow.The model contains the modules of a driving cycle,a driving motor,a transmission,the vehicle longitudinal dynamics and shift logic.(4)A review of existing gear ratios optimization is given and the evaluation indexes of dynamic and economy are selected.Comprehensive performance evaluation function,which contacts the acceleration time from 0 to 100 km/h and the energy consumption over an ECE+EUDC driving cycle,is structured through normalization method,and the gear ratios are chosen as the variables for the function.(5)The dynamic and the energy consumption over an ECE+EUDC driving cycle of the two programs are compared and analyzed.The results demonstrate that the dynamic are substantially the same;the energy consumption of 2-speed scheme is lower than that of one-speed gearbox,but EV with one-speed gearbox consumes less over the ECE driving cycle.What's more,the optimized ratios are used over other driving cycles and the simulation results show that there is difference between the two transmission systems in energy consumption over the other driving cycles.The 2-speed scheme has a better economy over the UDDS driving cycle,while the one-speed scheme has a little advantage of economy over the 1015 driving cycle.(6)Since the two schemes based on the ECE+EUDC driving cycle have different advantages over UDDS and 1015 driving cycles,energy consumption over the 3 driving cycles are all used to a new optimization method.The simulation results of the optimized two schemes demonstrate that the scheme with 2-speed gearbox is better than the single speed scheme in economy,while meeting the same dynamic requirements.