Research On AFS/DYC Integrated Control Strategy Based On Disturbance Estimation Technology And Sliding Mode Theory

With the rapid development of electric vehicles,traffic crashes happen occasionally due to the complex driving environment.This makes more and more attention has been paid to the active safety of vehicles.In order to further improve the safety and stability of the vehicle.This paper taken the active front steering system and the integrated system of active front steering and direct yaw moment control as research objects.And designed related control strategies and algorithms.On the one hand,in order to reduce the adverse effects of internal uncertainty and external disturbance on the active front steering system under complex road conditions,two chattering-free discrete-time sliding mode controllers are proposed.In this study,a Lungerber observer is constructed to estimate the sideslip angle,and a parameter tuning scheme based on the two-degree-of-freedom model is proposed to reduce the computation.On this basis,a chattering free discrete sliding mode controller based on delay disturbance estimation is proposed.Then,the first-order disturbance difference is imposed on the control law to reduce the disturbance estimation error.Besides,in order to further improve the control accuracy,a generalized proportional integral observer is constructed and its stability is proved by the algebraic equations.Then,with the help of the observer,a composite chattering-free discrete-time sliding mode controller is constructed to further improve the control performance.Finally,through Car Sim and Matlab/Simulink,the feasibility and effectiveness of the proposed methods are verified.On the other hand,due to the limitation of the performance of active front steering system under extreme road conditions,an integrated control strategy of active front steering and direct yaw moment control based on disturbance observation technology and super-twisting sliding mode is proposed.In this study,a PID-like disturbance observer is proposed inspired by the nonlinear extended state observer to get a better tracking performance,thereby providing more appropriate feedforward information for the controller and reducing the disturbance rejection burden of the controller.Besides,the performances of PID-like disturbance observer and nonlinear extended state observer in the linear region are analyzed in frequency domain.On this basis,an integrated control strategy of active front steering and direct yaw moment control based on super-twisting sliding mode control is proposed,and its stability analysis is given.Furthermore,the ultimate lateral acceleration is converted into the ultimate front wheel angle with the help of the twodegree-of-freedom model,which realizes the direct correlation between the limit state of the vehicle and the output of the active front steering system.On this basis,an integrated control weight distribution scheme is designed.Finally,through the joint simulation of Car Sim and Matlab/Siumlink,it is verified that the proposed integrated control strategy of active front steering and direct yaw moment control can better ensure the safety and stability of the vehicles compared with the active front steering system under extreme road conditions.