Research On Cooperative Control Of Vehicle Semi-active Suspension And Steering System

Semi-active Suspension System(SAS)and Electronic Power Steering System(EPS)are two important subsystems in the chassis of a car,which affect the smoothness and handling stability of the automobile respectively.However,there is a coupling relationship between SAS and EPS,and independent control for the two systems is difficult to eliminate the coupling effect between them,resulting in a decrease in ride comfort and handling stability.Therefore,this paper takes SAS and EPS as the research object and designs a coordinated controller of SAS and EPS to eliminate the coupling effect between them,so as to improve the ride comfort and handling stability of the vehicle.The specific work is as follows:Aiming at the problem that vehicle ride comfort is affected by the damping force of the CDC(Continuous Damping Control)damper in SAS,this paper proposes a damping force optimization method based on improved fuzzy control.Firstly,considering that there is an inverse relationship between the opening of the adjustable throttle valve and the damping force of the CDC damper,an improved fuzzy controller based on a genetic algorithm(GA)is designed to control the opening of the CDC valve to adjust the damping force.Then,an improved fuzzy controller based on linear quadratic gaussian(LQG)is designed to obtain the optimal damping force.Finally,the co-simulation is realized by establishing the AMESim model of the CDC shock absorber and the Simulink model of SAS.The results show that the method can effectively improve vehicle ride comfort.Aiming at the problem that the vehicle loses stability due to the roll risk during steering,this paper proposes a coordinated control strategy of SAS and EPS based on the adaptive fuzzy controller.Firstly,a 7-DOF vehicle model of SAS and EPS is established.Secondly,according to the vehicle ride comfort and handling stability index,the LQG optimal controller is designed,and the four SAS damping forces and EPS steering torque are calculated.Then,SAS and EPS adaptive fuzzy controllers are designed respectively.Among them,SAS adaptive fuzzy controller takes the deviation and deviation change rate between ideal and actual roll angle speed as input,adaptively adjusts SAS damping force,and outputs SAS damping force weight.The EPS adaptive fuzzy controller takes the ideal and actual lateral velocity deviation and its deviation change rate as input adaptively adjusts the EPS steering torque,and outputs the EPS steering torque weight.Furthermore,the weight output by the adaptive fuzzy controller is combined with the SAS damping force and EPS steering torque output by the LQG controller and fed back to the 7-DOF vehicle model,so as to realize the cooperative control of SAS and EPS.Finally,the proposed control strategy is simulated,and the results show that the method can effectively improve vehicle ride comfort and handling stability.Aiming at the problem that the vehicle is susceptible to external disturbances such as road surface and lateral wind during driving,this paper proposes a coordinated control strategy of SAS and EPS based on H∞ robust controller.Firstly,a 7-DOF vehicle model of SAS and EPS under lateral wind disturbance is established.Secondly,an H∞ robust controller is designed to suppress the disturbance of road surface and lateral wind.Then,an adaptive fuzzy controller is designed according to the different control efforts of different drivers,and the distribution ratio of EPS steering torque and SAS damping force is adjusted adaptively,so as to realize the coordinated control of vehicle ride comfort and handling stability under road and crosswind interference.Finally,the simulation results show that the proposed control method can effectively suppress the interference of road surface and lateral wind,and improve the ride comfort and stability of the vehicle.