Research On Fuzzy Backstepping Control Of Semi-active Air Suspension System

Advances in science and technology have led to a substantial improvement in the quality of people's life.Meanwhile,they have also had a huge impact on people's lifestyle.Cars have gradually become one of the most important transportation for people's daily travel.However,because the automobile industry in our country starts relatively later,many key and even core automobile control technologies lag behind other developed countries and have to be imported from abroad.Therefore,it is of great practical significance to study how to control the automobile from the perspective of theory and method,improve the core technology level of our country's auto industry and the capacity of independent innovation,and promote the sustainable development of China's automobile industry.In this thesis,considering the uncertain parameters of the system,the vertical vibration of the semi-active air suspension with two degrees of freedom is studied.Several variables that affect the stiffness of the air spring and the relationship between them are studied.A simplified model of semi-active air suspension and a stochastic road excitation model are established.Aiming at the uncertain and immeasurable parameter problems in the quarter suspension for semi-active air suspension system,a variable universe fuzzy controller is designed.The method adjusts the fuzzy control rule by increasing the expansion factor and adjusts the stiffness of the air spring to reduce the vertical acceleration of the sprung mass and improve the performance of the suspension.In view of the external disturbances existing in the system,the sliding mode backstepping controller is designed to reduce the vertical acceleration of the sprung mass,the dynamic stroke of the suspension,and the dynamic load of the tire,improving the ride comfort,ride comfort and handling stability of the suspension system and reducing the impact of random road disturbances on the suspension system.Considering the nonlinear uncertain problem of damper damping coefficient existing in the suspension system,an indirect fuzzy sliding mode backstepping method is used to design the controller.The method uses a fuzzy logic system to approximate the uncertain function.By constructing the Lyapunov function,the stability of the suspension system is guaranteed and the damping performance of the suspension system is improved.