Research On Differential Steering Control Of Distributed Drive Electric Vehicles

The Distributed Drive Electric Vehicle(DDEV)has the advantages of independent and controllable four-wheel torque,fast torque response and high precision,easy to realize chassis modularization,etc.It is very helpful to improve the whole vehicle dynamic stability control.Because the change of the road surface condition will affect the handling stability and safety of the vehicle.Therefore,in order to improve the self-adaptive ability of the DDEV under the complicated road conditions and ensure the stability of the vehicle.The research object of this paper is distributed electric vehicle.The identification method of road adhesion coefficient and vehicle torque optimal allocation strategy are studied.The main research contents are as follows:A vehicle model was established to realize distributed drive electric vehicle dynamic.Compared to a conventional car,Car Sim was used to build the system model of car body,brake,transmission system,etc.Finally,a complete DDEV model was constructed,and the validity of the model is verified by a single-laneshifting test.It provides a reliable simulation model for the follow-up research.In view of the importance of vehicle state parameter information for Vehicle dynamics control,the road surface adhesion coefficient was estimated.In order to overcome the influence of the uncertain measurement noise on the state estimation accuracy while the vehicle is running,the adaptive filtering method is used to estimate the state of the vehicle.Based on the non-linear Vehicle dynamics model and the square root Kalman filter model,the adaptive filter was used to estimate the state of the vehicle,forgetting factor was introduced to realize the real-time estimation of system noise.Finally,the simulation results of single pavement,docking pavement and open pavement show that the proposed estimation method improves the estimation accuracy and convergence speed.In order to solve the problem that the vehicle Thermodynamic versus kinetic reaction control can’t realize the dynamic adaptive control under different road conditions,the coordinated control weighting coefficient is introduced,and the additional yaw moment controller is established based on the sliding mode variable structure control theory.In order to improve the adaptive ability of vehicles in complex conditions,the influence factors of tire and road surface are considered.The quadratic programming is applied to optimize each wheel torque with the goal of minimum tire load rate.Finally,the simulation results under three road conditions show that the control strategy can effectively track the reference model and improve the vehicle handling and stability.