Research On Control Stability And Control Strategy Of Four-wheel Drive Electric Vehicle

As an important means of transportation for the development of human society,the automobile has brought tremendous contributions to the progress of human society.With the technological innovation,traditional fuel vehicles are transforming to new energy vehicles.The internal structure of electric vehicles is also significantly different from traditional vehicles.Four-wheel independent drive electric vehicles that omit traditional mechanical transmission components have emerged at the historic moment.Under the circumstances,the stability of handling has attracted wide attention.At present,four-wheel-drive technology is still not very mature.How to make use of the advantages of flexible motion of four-wheel-drive electric vehicles and improve the stability and safety of driving under driving conditions is the focus of research at home and abroad.The main research contents of this article include:(1)Model the vehicle’s plane motion and build a seven-degree-of-freedom model of the vehicle’s motion.Given that there is no model of a four-wheel-drive electric vehicle in CarSim software,external model building is performed on the basis of CarSim traditional fuel vehicles,including magic formulas Tire model,external characteristic model of permanent magnet synchronous motor,driver model(including PID vehicle speed following control and arbitrary path tracking control based on single-point preview algorithm),four-wheel wheel speed coordination model based on electronic differential control,etc.The established model’s ability to drive in a straight line and to steer is verified to ensure the accuracy of the model,which lays the foundation for further decision-making of the upper-layer torque and lower-layer torque distribution control.(2)Analyze the factors that affect the stability of the vehicle’s driving control,establish a phase plane instability judgment criterion based on the centroid side-sway angle,and take into account the effects of road adhesion and tire side-stiffness to construct a reasonable ideal twodegree-of-freedom model for vehicles The ideal value of the vehicle state parameter is output.Control in a layered architecture.The upper layer uses the deviation of the center of mass and yaw rate from the ideal value as input,sets the weight coefficient function to adjust,improves the sliding mode joint control algorithm,and outputs the yaw moment to adjust the vehicle’s driving state,and at low adhesion The simulation analysis is carried out under the condition of double shifting of road surface.The fuzzy PID algorithm is used to drive and accelerate the vehicle on the low-adhesion road.The slip rate is controlled near the ideal value to keep the vehicle running smoothly.(3)The lower torque distribution layer uses average distribution,dynamic load distribution,and generalized inverse method based on the minimum tire utilization as the objective function to optimize the distribution.The driving torque of the vehicle and the yaw moment determined by the upper layer of the controller are reasonable.The ground is allocated to four driving wheels.CarSim and Simulink are used to build a four-wheel-drive electric vehicle joint simulation platform.Four typical operating conditions,such as anti-rollover and angular step,are designed.The simulation verification of the key stability indicators shows that the optimal allocation algorithm has the best control effect,and has a significant effect on improving the vehicle’s handling stability.