Research On Steering Stability Of Distributed Drive Electric Vehicle Based On Hierarchical Control

With the increasing energy crisis and environmental pollution problems,the development of electric vehicles has become the mainstream of current automobile development.The distributed drive electric vehicle directly supplies power to each wheel through the motor,which has the advantages of high transmission efficiency and specific power,and can realize independent control of each wheel drive or braking torque.Therefore,how to avoid the conflict and interference of the driving or braking torque of each wheel for the structural characteristics of the distributed electric vehicle,and coordinate the driving or braking torque of each wheel while controlling the steering stability of the vehicle The optimal distribution of torque in each wheel is an urgent problem to be solved in distributed electric vehicles.In order to improve the control stability of distributed electric vehicles,the main research contents are as follows(1)Modeling of vehicle dynamics in distributed drive electric vehicles.Aiming at the structural characteristics of distributed drive electric vehicles,a nonlinear vehicle dynamics model is established: including vehicle longitudinal motion,lateral motion,yaw motion and wheel dynamics model,hub motor model and nonlinear Dugoff tire model.The simulation accuracy of the model is verified by the Carsim simulation software under the conditions of steering wheel step steering and sinusoidal steering.It lays the foundation for the estimation of the vehicle running state parameters and the design of the steering stability controller.(2)Vehicle state parameter estimator based on unscented Kalman filter algorithm.The driving state parameter of the vehicle is an important reference variable in the controller design.For the problem that some state parameters are difficult to obtain during vehicle operation,a vehicle critical state parameter estimator based on the unscented Kalman filter algorithm is designed.The real-time online estimation of the centroid side yaw angle,the yaw rate and the lateral force of each wheel during the running of the vehicle is performed.The vehicle simulates the design of the estimator under continuous steering conditions.(3)Research on hierarchical controllers for distributed drive electric vehicle handling stability.The vehicle's steering stability control is divided into two layers.The upper layer uses the ideal and actual values of centroid side yaw angle and yaw rate as control inputs,and designs a generalized target yaw moment controller based on model predictive control.The lower layer is optimized with the torque adjustment amount,road surface adhesion utilization rate and control error.The multi-objective coordinated torque distribution controller is designed to realize the optimal distribution control of each wheel torque under the constraint conditions.The simulation results show that the steering stability of the vehicle is effectively improved under the action of the layered controller.