The Active Skid Steering Dynamics And Stability Coordinate Control Of Distributed Drive Electric Vehicles

Distributed drive electric vehicle can independently control the torque and speed of four wheels.It is easy to achieve active differential steering by changing the speed of the left and right wheels of the vehicle.Due to different steering principles,there are great differences in the tire mechanical characteristics and vehicle dynamic characteristics and steering performance in steering process.At present,there is little research on this aspect and no perfect theoretical system has yet been formed.There are also many problems in the application of real vehicles.For this reason,this paper takes the distributed drive electric vehicle as the research object,makes a thorough study of the tire mechanics characteristics in the process of differential steering,and designs the coordinated control strategy of vehicle handling and stability with active differential steering.The active research work is as follows:The relationship between kinematics and dynamics of each parameter of distributed drive electric vehicle is analyzed.The 7-DOF non-linear vehicle dynamics model,tire model and motor model are established.Simulink and Carsim are used to establish the simulation model of distributed drive electric vehicle,which is used as the simulation experimental platform.The mechanical characteristics of differential steering tire were studied.Based on the two-dimensional distribution of vertical loads,a simplified tire model for pure sideslip conditions under different load distributions is established.The relationship between tire force,tire tow distance,steering radius and vehicle structural parameters is analyzed.The differential equation of differential steering kinematics is derived.On this basis,the influence of vehicle parameters on differential steering performance is studied.The comparative simulation analysis of differential steering vehicle and traditional front-wheel steering vehicle is carried out,which provides a theoretical basis for dynamic coordinated control of subsequent differential steering vehicle.A hierarchical control system for coordinated control of active differential steering and torque distribution of distributed drive electric vehicles is designed.The upper layer is the vehicle state tracking controller,and the speed PID controller and the yaw rate sliding mode variable structure controller are designed to track the ideal model with the speed and steering wheel angle of the driver as the input of the system.The lower layer is based on the total driving force and yaw moment calculated by the upper layer to improve the stability of the vehicle.The constrained nonlinear global quadratic sequence is adopted.Train planning method is used to optimize the torque distribution of four wheels.On this basis,active differential steering is introduced to compensate the sideslip angle of the center of mass,so as to improve the control performance of vehicle dynamic handling and stability.The simulation results of double line shifting and steering wheel step verify the effectiveness of the designed coordinated controller.