State Estimation And Energy-saving-based Optimal Torque Allocation Of Distributed Drive Electric Vehicle

With the worsening of environmental problems,such as energy shortage and exhaust emission,the demand for clean and renewable energy as a vehicle energy source has been gradually highlighted,pure electric vehicles become the development direction of alternative energy vehicle in china.The distributed drive electric vehicles(DDEVs),which is directly driven by four in-wheel motors,via its own technical advantages and development prospects,has attracted the support of the government and the wide attention of researchers in recent years.This paper proposed the method of longitudinal force estimation and the strategy of optimal energy-saving torque allocation for DDEVs.A DDEV was modified from a pure electric vehicle,the vehicle control system was constructed and the information transmission path was matched based on D2 P.A co-simulation platform of DDEV was built based on CarSim and Simulink,in which the Carsim vehicle model,the torque output model of in-wheel motors and the vehicle speed tracking model are established.Using the data of in-wheel motor characteristic test,the identification and verification of the in-wheel motor model parameters were carried out based on the subspace identification algorithm.The electric drive wheel model was put forward and applied to the estimation of vehicle longitudinal force,considering that the electric drive wheel model contains unknown input,the model reduction method was used to realize the decoupling of unknown input,an optimal method of longitudinal force estimation was presented based on Kalman filter and unknown input observer,the simulation and the road test of chassis dynamometer are carried out,the results demonstrated the superiority of the proposed method in estimating accuracy,real-time performance and anti-interference ability.The vehicle dynamics model with three degree of freedom and tire model were established,a cascaded estimation method of vehicle driving state was proposed based on strong tracking Kalman filter in which the output of longitudinal force observer is used as the known input.Simulation verification based on Carsim and Simulink joint simulation platform was carried out,the results show that the STF-based estimation method has better estimation accuracy and real-time performance compared to EKF.The motor efficiency map was fitted by the experimental data,and the mechanism of optimal torque distribution in DDEV was analyzed.A novel algorithm of optimal energy-saving torque allocation was proposed using the fuzzy function,In this algorithm,the motor torque is optimized in real time for vehicle energy saving.The simulation test of ECE urban road cycle and the vehicle road test were carried out,the results verified that the proposed algorithm can effectively improve the economic efficiency of vehicle.