Coordination Control Of Active Rear Wheel Steering And Torque Distribution For Distributed Drive Electric Vehicle

Distributed driving electric vehicles can achieve real-time independent precision control of four-wheel torque,which provides a new strategies and methods for vehicle stability control.In order to make full use of the advantage of four-wheel steering technology in improving vehicle handling stability,the distributed driving electric vehicles was taken as the research object,dynamic characteristics and control of active rear wheel steering tires were studied,the active rear wheel steering and steering moment distribution coordination control strategy was designed.The main research work is as follows:A non-linear dynamic model of a four-wheel-steering vehicle was established.A 7-degree-offreedom vehicle dynamic model,a tire model,a motor model,and a driver model were established by MATLAB/Simulink,the numerical calculation of non-linear dynamic vehicle model was realized,and the validity of the model was verified by open-closed-loop control simulation test and vehicle model test results in Carsim,it provides a simulation test platform with high precision for the research.The relationship between optimal control parameters of active rear wheel steering and the pros and cons of the control performance is analyzed,and the influence of changes in vehicle operating conditions is considered.By analyzing the influence conditions of vehicle stability and determining the control parameters,a fuzzy adaptive parameter adjustment of active rear wheels was proposed steering optimal controller,and through open and closed-loop control simulation verification and manipulation stability evaluation index analysis,it is concluded that the proposed active rear wheel steering controller has better adaptability on roads with different adhesion coefficients,and improves vehicle trajectory tracking performance and driving safety.In order to overcome the limitation of single steering control under special conditions,a coordinated control strategy of active rear wheel steering and torque distribution is proposed based on phase plane method(side slip angle)judgment principle,and the effectiveness of the proposed control strategy is verified by continuous sine gain open-loop simulation test.In order to increase the stability range of the vehicle in the stable area to cope with sudden conditions,the layered control with the lowest tire utilization as the objective function.The upper layer is the vehicle motion tracking and control layer.Using external input and vehicle speed as system inputs,the vehicle speed PID controller and yaw stability sliding mode controller are designed respectively.The linear vehicle model is introduced to eliminate the centroid side deflection angle,yaw angle speed and additional coupling relationship between yaw moment,combined with active rear wheel steering controller and reference model to calculate generalized longitudinal force and additional yaw moment required.The lower layer adopts a nonlinear global quadratic programming method with constraints to solve the generalized control force globally and input the assigned value to each wheel to improve the stability of the vehicle.Finally,the open-loop and closed loop simulation results show that the designed coordinated control strategy can improve the active safety of the vehicle at high speed.