A Study On Electronic Differential Control For In-wheel Motor Rear Driven EV

In-wheel electric vehicle is the focus of research in the field of new energy vehicles.Multi-wheel independent drive has obvious advantages,on the one hand,it simplifies the complex transmission system of traditional car,on the other hand,it has evident advantage in the driving force distribution and traction control field.Therefore,many car companies and research units invest in the important resources for research.This paper does studies on the control system of in-wheel electric vehicle.Firstly,The author designs Double Motor Control System Based on Rear wheel driving,builds a vehicle longitudinal driving model and completes the motor parameters to determine for the vehicle design goals.By analyzing and comparing several control algorithms,PWM with PI control method is identified as the motor control strategy.In the end of this part,the vehicle model and the motor model are established by Matlab/Simulink,and the simulation results show that control theories are correct.Then,the design of road recognition system based on fuzzy control theory is designed.The actual use of the current pavement and the slip rate are used as the input of fuzzy control,through the fuzzy processing of the input variables,the fuzzy operation and the output variables are clarified,the weight coefficients of the six different standard pavements are obtained,and the maximum adhesion coefficient and the optimal slip rate of the current road surface can be obtained.With joint simulation of the fuzzy toolbox in Matlab and Simulink,setting three kinds of the road adhesion coefficient(The high,medium and low)under the three kinds of slipping rate of large,the corresponding six kinds of road weight coefficients and the optimal slip rate,the maximum road adhesion coefficient can be achieved,and then compared with the fuzzy rule table to observe whether the simulation results are consistent with the theoretical analysis.Lastly,an electronic differential control algorithm based on target slip rate control is proposed.First,the 4-DOF dynamic model of the vehicle is constructed,The optimum slip ratio of the one side drive wheel is estimated in real time by the road surface recognition system,and the optimum slip ratio of the other side wheel is estimated by the rate of change of the tire side angle.According to the optimum sliding rate of each drive wheel,the torque output of each driving wheel is controlled by the sliding mode variable structure control theory so that the slip rate of the wheel is always kept near the target slip rate.Final,the simulation models are constructed in Matlab/Simulink,the simulation results show that the designed control strategy can control the wheel slip rate near the optimal slip rate and ensure the driving of vehicle along preset direction on curved road,making the vehicle have good steering performance.