Research On Vehicle AFS/DYC Control System Based On Delay Compensation And Constraint Control

With the continuous development of automobile technology,people have higher requirements for vehicle handling stability and driving safety,which promotes the improvement and perfection of vehicle active safety technology.Active Front Steering(AFS)can improve the operating stability and steering accuracy of the vehicle by applying an additional steering Angle to the front wheel independent of the steering wheel.Direct Yaw Moment Control(DYC)improves the lateral stability of the vehicle by adjusting the braking force of different wheels to obtain the desired additional yaw moment calculated by the upper controller.The control objects of the AFS and DYC systems,the sideslip angle and yaw rate,all have a constrained range.However,due to the time delay of the vehicle system and the influence of parameter changes,the sideslip angle and the yaw rate will oscillate in the process of tracking the ideal value,violating the constraint boundary,and even causing lateral instability of the vehicle,which seriously affects the lateral stability of the vehicle.Therefore,for vehicle systems with time delay,parameter variation,and constraint characteristics,based on LyapunovKrakovskii functions,(LKF),The AFS/DYC controllers are designed by combining Radial Basis Function Neural Network(RBFNN)with Barrier Lyapunov Function(BLF).When considering the impact of vehicle time delay and parameter changes,the sideslip angle and yaw rate can track their respective ideal values,and the state variables can be constrained in their own stable range during the whole control process,so as to improve the lateral stability of the vehicle.The main work of this paper is as follows:(1)A two-degree-of-freedom dynamic model of vehicle with time delay was established to solve the problem of non-time-varying constraint control of the sideslip angle and yaw rate under the influence of vehicle time delay.The AFS and DYC controllers are designed based on the non-time-varying BLF function,and LKF and RBF are introduced into the construction of BLF to deal with the delay problem of the system.Through Simulink simulation of the input conditions of different front wheel steering angles,it is verified that the proposed control scheme can ensure that the sideslip angle and the yaw rate can rapidly converge to their respective optimal values under the impact of time delay on the vehicle system,and in the whole control process are constrained in the preset stability range.It effectively improves the active safety and lateral stability of the vehicle.(2)Aiming at the time-varying constrained control problem of the sideslip angle and yaw rate under the influence of time delay and vehicle parameter variation,the time-varying stability boundary of the sideslip angle is obtained by the phase plane method.Based on the time-varying BLF function,the AFS and DYC controllers are designed respectively.LKF and RBF are introduced into the design of BLF to solve the time delay problem of the system.Meanwhile,the uncertainty of the system caused by parameter changes is dealt with by RBF.To solve the Unknown control direction problem caused by parameter changes,a reasonable adaptive rate is designed.In order to verify the effectiveness of the control algorithm,Simulink simulates the input conditions of different front wheel steering angles.The results show that considering the impact of the vehicle system time delay and parameter uncertainty at the same time,the sideslip angle and yaw rate can be kept in their own stable range in the simulation process,and quickly track the respective optimal value.Fundamentally improve the vehicle steering stability.(3)For AFS/DYC system,Car Sim software is used to build a vehicle model with time delay,and the control algorithm in this paper is simulated and verified on the Car Sim/Smulink based co-simulation platform.The co-simulation results show that the proposed AFS/DYC joint control scheme can keep the sideslip angle and yaw rate from crossing the stable boundary and track their respective ideal values at the same time,even though the vehicle system has time delay effects and parameter changes.