Study On Vehicle Active Suspension Based On Homogeneous Control Strategy

Although automobile has been developed and popularized for many years,the handling stability and ride comfort of the car is still the focus of vehicle design.The suspension system is a key factor in determining vehicle stability and ride comfort.To get good suspension performance,there are two problems need to be solved.The first is to study the active suspension system which can be able to automatic regulation based on driving conditions and different vehicle states.The second is to select a proper active suspension control method.To pursue the better performance of the suspension system,this paper employs the homogeneous control theory to study the vehicle active suspension system.(1)A two-degree-of-freedom(2-DOF)quarter-car active suspension model is constructed.According to the ride comfort and handling stability of the vehicle problem.From the perspective of dynamics,the suspension models are established for the 7-DOF vehicle suspension model,the 4-DOF half-car suspension model,the 2-DOF quarter suspension model respectively.The corresponding differential equations are established according to the Lagrange equation.The advantages and disadvantages of these three models are compared and analyzed.The 2-DOF suspension model contains most of the information about the force and load changes of the vehicle suspension system.Therefore,the 2-DOF suspension model is selected as the research object of this paper.(2)The active suspension homogeneous control law is designed based on the homogeneous control theory.Firstly,the state equation of the 2-DOF active suspension is given.Secondly,the homogeneous state controller is designed based on the state equation.Then,the homogeneous observer and the output feedback controller are designed based on the state controller.Finally,the global stability analysis of closed-loop system is demonstrated.What’s more,the input of the homogeneous control law just requires the vertical displacement of the suspension spring-mass.Meanwhile,an active suspension system is designed based on sliding mode control method.This method introduces a damping low-pass filter and a spring-stiffness high-pass filter.The switching vector of sliding mode control is designed employs virtual eigenvalue method,then the output feedback controller of sliding mode control is design based on Kalman filter.The results show that homogeneous control has strong stability and convergence.(3)MATLAB/Simulink simulation analysis.The homogeneous control active suspension model,the sliding mode control active suspension model and the passive suspension model are constructed respectively based on the designed homogeneous controller and sliding mode controller.Different road surfaces are used as input signals,and the vertical displacement of the suspension spring mass,the vertical displacement of the unsprung mass,tire dynamic load,and the output force of the controller are used as the evaluation indexes of the suspension performance.The results show that homogeneous control is better than the sliding mode control and passive suspension.(4)Co-simulation of carsim and simulink.Further,the effect of the designed control algorithm was verified in a practical environment.Select the D-Type Sedan model in carsim as the simulation object and run on the sine input road,convergence sine input road and step input road at speeds of 40km/h,80km/h,120km/h respectively.Effects of a comprehensive of the designed control method are verified utilizing vehicle body centurion acceleration,suspension stroke,and magnitude of the controller output force.The simulation results show that the designed homogeneous control method can improve the handling stability and ride comfort of vehicle compare with the slip mode control method.What’s more,the proposed controller has better performance in convergence.