Research On Integrated Control Strategy Of Active Front Steering And Direct Yaw Control Based On The Kalman Filter

Steering system is an important part of the vehicle,and it influences the handling stability and safety of vehicles.AFS can improve the handling stability and improve the safety of vehicles on slippery and opposite roads by applying an front wheel angle that is independent of the driver.The vehicles are more likely to be unstable on the slippery road,but the control ability of AFS is limited on the this road.DYC produces an additional yaw moment by braking the wheels,the DYC has good control ability on the slippery road,but it has great negative influence on the longitudinal velocity.So it is necessary to integrate AFS and DYC to give full play to the advantages of AFS and DYC.Firstly,the 4-DOF of vehicle and nonlinear tire model are built in the Matlab/Simulink software,the Carsim software is used to test the vehicle model.Secondly,considering the tire-road friction coefficient has a great influence on the control of chassis and is difficult to measure directly,the theory of Kalman filter is introduced,and the UKF and Runge Kutta discretization method are introduced in detail.The low tire-road coefficient is estimated by using unscented Kalman filter,and the Carsim software is used to verify the results.The simulation results show that the accuracy of this method can be used in the following chassis control system.Then,the principle of sliding mode variable structure control is introduced,and the 2-DOF of ideal model is established that consider the influence of tire-road friction coefficient on the ideal yaw rate.Then,the AFS controller is established by using the sliding mode controller,and the effectiveness of the controller is verified on the slippery road.The DYC controller is also established by using the sliding mode controller,the DYC controller is divided into two layers,the upper controller gets the total additional yaw moment required by the vehicle,and the lower controller distributes the tire braking force that the effect of tire attachment ellipse is considered.Finally,This paper introduces the mutual influence of AFS and DYC control,analyzes the necessity of integrated control of AFS and DYC,and sums up the control scheme of AFS and DYC integrated control of many scholars,At last,this paper adopts AFS and DYC coordinated control by using the additional yaw moment limit which can be provided by AFS and DYC under different lateral acceleration and different tire-road friction coefficient.When the AFS can provide the required additional yaw moment,AFS control alone,when the AFS can not provide the required additional yaw moment,the lack of part provided by the DYC.When AFS intervene the longitudinal velocity changes smoothly,and the DYC has good control ability in tire nonlinear region,This control scheme makes full use of the advantage of AFS and DYC,and the safety of the vehicle is greatly improved without affecting the driving comfort obviously.