Research On Extended Range Four-wheel Drive Energy Management System Based On Longitudinal Torque Distribution

With the many problems caused by pure electric vehicles,on the one hand,because the energy density of the power battery of the pure electric vehicle cannot be greatly improved in a short time,it seriously affects the cruising range of the pure electric vehicle;on the other hand,the energy density of the power battery is too large,Security issues will also increase.In order to solve these problems,a large amount of research has been carried out at home and abroad on range-extended vehicles and mass production has been successful.Range-extended electric vehicles can pass reasonable energy management strategies.It also has the low emissions of electric vehicles and the high endurance of traditional fuel vehicles.It can also extend battery life and optimize safety performance.However,the research on improving the efficiency of the energy management system of the extended-range four-wheel drive vehicle by rationally distributing the longitudinal torque of the front and rear motors is insufficient.Therefore,this paper takes the extended-range four-wheel drive vehicle as the research object and focuses on optimizing the distribution of the longitudinal torque of the front and rear motors through key research to reduce the vehicle Energy loss.Based on the mass-produced models of an automobile OEM,this paper studies the energy management system of the extended-range four-wheel drive vehicle based on the rational distribution of longitudinal torque.The main research work and results of this paper are as follows:(1)Establish a recursive least squares vehicle weight identification system with multiple forgetting factors,and build a Simulink simulation model.Assuming that the wheel is a rigid body traveling along a straight line,under the condition of a fixed slope,a comparative simulation of different initial vehicle weights is performed to verify that the identification quality error is within 5%,which meets the actual calculation requirements,and provides data for subsequent calculation of the longitudinal moment basis.(2)Using the vehicle weight and vehicle longitudinal acceleration output by the identification system,combined with the calculation formula of longitudinal torque,a model of an energy management system based on longitudinal torque distribution is built.According to the working mode of the extended-range four-wheel drive vehicle,a driver demand analysis model,working state transition model,and motor model are built.A range extender model based on speed control and a battery model based on the ampere-hour integration method are also established to provide input and output interfaces for forming a closed-loop data distribution longitudinal torque model.(3)Combine the CRUISE forward simulation of the vehicle module,use the DLL module and the energy management system model based on longitudinal torque distribution to integrate the vehicle,and conduct joint simulation verification with the CRUISE software.The results show that,compared with the average longitudinal torque distribution method,it is verified that the optimized longitudinal torque distribution method can improve the economic performance of the whole vehicle,and provide a reference for later real vehicle verification.