Research On Economical Shift Strategy Of Pure Electrical Vehicle Based On Dynamic Programming

Pure electric vehicles usually only match single-stage reducer to reduce the quality of transmission system and manufacturing costs,but in order to meet the power requirements of the vehicle,there are higher requirements for motor performance,and the driving motor is often in a low-efficiency working area when the vehicle is driving under different conditions.Matching multi-gear transmission can greatly improve the torque of the vehicle at low speed and widen the maximum speed range.By optimizing the shift strategy or transmission ratio,the driving motor can work more in the high efficiency area and increase the vehicle’s endurance.Aiming at reducing the energy consumption of pure electric vehicles in actual driving,this paper optimizes the shift schedule of two-gear automatic transmission.The contents are as follows:Firstly,taking the driving cycles of passenger cars in Taiyuan City as the research object,the collection scheme of driving conditions data is planned,and the collected data are processed.The kinematic segments are processed by principal component analysis and cluster analysis.According to the correlation coefficient and time proportion,the typical driving cycles of Taiyuan city,such as urban congestion road cycles,urban unblocked road cycles,suburban roadcycles and comprehensive cycles,are constructed by dividing the working condition segments and defining the relevant characteristic parameters to describe the kinematics characteristics.The typical driving cycless of Taiyuan city are analyzed.According to the characteristics of the driving cycless of passenger cars in Taiyuan city,the power requirements of different levels of the target vehicle are put forward,and the driving motor,transmission ratio and battery of the vehicle are matched.The vehicle simulation model is built in MATLAB/Simulink,and the traditional economic shift schedule is formulated based on motor efficiency.In order to reduce energy consumption and increase the vehicle’s endurance in city driving cycless,the dynamic programming algorithm is used to solve the optimal working points of the first and second gears of the transmission under various driving cycless,and the calculation results are summarized to extract the two-parameter shift schedule that can be used in real vehicles.The results show that in terms of energy consumption of 100 km,The energy consumption of EV using shift schedule based on dynamic programming method is 3.55% less than that based on traditional economic shift schedule in urban congestion road cycles,4.00% less in urban unblocked road cycles,1.58% less in suburban road cycles and 3.10% less in comprehensive cycles.Therefore,the shift schedule after dynamic programming can improve the range of EV more effectively.