Research On Steering Stability Control Of Four-wheel Motor Driven Vehicle

In order to improve the active safety protection performance of four-wheel motor drive of electric vehicle and the vehicle steering stability.a layered controller was designed,a seven-degree-of-freedom vehicle motion model and a two-degree-of-freedom vehicle steering model were built.a steering stability controller and an optimal torque distribution controller were designed,and a simulation test model of the layered controller was built.The feasibility of the layered controller and its adaptability under different road adhesion coefficients are verified.The innovation of adaptive steering precision control method and torque optimal distribution strategy for vehicle driven by four-wheel hub motor is realized.The main work completed is as follows:(1)Based on the scientific assumptions such as four-wheel consistency,the dynamics modeling of the motor driven vehicle with four-wheel hub was carried out,and the sevendegree-of-freedom motion model and the two-degree-of-freedom vehicle steering model were built.The dynamic model of the wheel was built and the tire model was established.Based on CarSim and Matlab/Simulink software,parametric modeling of the vehicle body was carried out,and simulation models of the driveline,driver and road,motor control were built,which provided the simulation experiment basis for the subsequent steering stability controller and torque distribution controller.(2)Based on the neural network PID algorithm of genetic algorithm,the yaw moment controller is designed.By using the adaptive characteristics of neural network and the global optimization characteristics of genetic algorithm,the actual yaw velocity can closely follow the ideal value;Based on the fuzzy control theory,the slip rate controller is designed.The actual slip rate can follow the ideal value under different driving conditions by fuzzy control,and the slip rate is controlled within the ideal threshold.(3)Based on the optimal moment distribution strategy of the improved genetic algorithm,the objective function and constraint conditions of moment distribution are given.The optimal solution of torque distribution for vehicle steering is obtained.(4)Through CarSim and Matlab/Simulink co-simulation,the layered controller is simulated and verified under sine,double shift and snake.The results show that:Compared with the ordinary PID control,the maximum speed error will not exceed 0.8km/h.the actual yaw speed following error is reduced by more than 50%,the stability is increased by more than 24.4%,the centroid side deflection angle is reduced by more than 0.015rad,the slip rate control is improved by more than 25%,the torque distribution is optimized,and the steering stability of the vehicle is effectively improved.(5)Based on different pavement adhesion coefficients,CarSim and Matlab/Simulink co-simulation were used to conduct simulation experiments on the layered controller.The results show that the designed layered controller can realize stable steering when the road adhesion coefficient is not less than 0.5.