Study On Shift Strategy Of Pure Electric Logistics Vehicle Based On Variable Load Under Urban Condition

At present,pure electric vehicle technology is in the process of continuous development.In order to improve the performance of pure electric vehicles,driving multiple gears has become a trend.Because the traditional shift strategy does not take into account the impact of vehicle mass and road slope change on the optimal shift point,it will affect the performance of some truck models.In this paper,the pure electric logistics vehicle is taken as the research object.Firstly,motor parameters and transmission ratio range of the transmission are determined by the vehicle design performance index,and finally a four-speed automatic transmission(AMT)is selected.Then the battery parameters are determined according to the vehicle design mileage target.Due to the logistics vehicle in the distribution process,the vehicle mass changes significantly with the loading and unloading of goods.In addition,the road slope is also changing,which has a significant impact on dynamic performance and economic performance.Therefore,according to the strong tracking extended Kalman filter(STEKF)algorithm which has the advantages of shorter convergence time and smaller estimation error of mass and slope,this paper designed parameters estimation of vehicle mass and road slope based on STEKF,and compared the estimation results with the results of forgetting factor recursive least squares(FFRLS)combined with extended Kalman filter(EKF)estimated the parameters,which verified the effectiveness of the estimation method used in this paper.The changes of mass and slope are taken into account in the method of formulating the optimal power shift strategy,and the effects of only mass change,only slope change,and simultaneous changes of mass and slope on the optimal power shift are analyzed.By analyzing the vehicle braking energy recovery and safety,the optimal economic shift strategy based on mass and slope is formulated.In order to verify the effectiveness of the proposed shift strategy,the vehicle simulation model is built by MATLAB/Simulink.Under different typical working conditions,the effectiveness of the proposed shift strategy to improve vehicle performance is verified by comparing with the traditional shift strategy.By comparing the acceleration time and braking distance of the two dynamic shift strategies under the conditions of only mass changed,only slope changed and the simultaneous changed of mass and slope,it is verified that the shift strategy proposed in this paper has better acceleration ability and braking ability.Through the simulation of vehicle power consumption under typical urban conditions UDDS,it is found that using an economical shift strategy that considers mass and slope saved 0.022 comparing to the battery SOC that using a traditional economical shift strategy,the effectiveness of the optimal economic shift strategy used to improve the vehicle economy is verified.