Adaptive Control For Vehicle Active Suspension Systems And Its Dynamic Performance Analysis

With the development of the living standard,people put forward more requirements for the riding comfortable,handling stability and driving safety.The key of achieving these targets is suspension systems.In particular,the active suspension systems receive widely attention because the stiffness and damping are adaptive adjusted.How to utilize the intelligent method to solve the control problem is a hot research topic in this field.This thesis main studies the following three aspects.(1)For the quarter-car vehicle active suspension systems(ASSs),the adaptive control problem of the time-varying speed and displacement constraints is studied in this thesis.The controller and adaptive law are designed by backstepping technique.The constraint bounds of vertical displacement and speed of the car-body are not violated by constructing time-varying Barrier Lyapunov function(TVBLF).The unknown continuous function in the systems can be approximated by the radial basis function neural network(RBFNN).The stability of the systems is discussed based on Lyapunov stability theorem.The simulation results are used to verify the effectiveness of the proposed constraints approach by comparing without constraints approach.For the half-car ASSs,the adaptive control problem of the constant constraints is studied.The ASSs with constraints can be transformed into without constraints systems by nonlinear mapping.Similarly,the controller and adaptive law can be designed base on Backstepping technique,and the stability of the systems can be discussed by Lyapunov theorem.The effectiveness of the presented method can be verified by the simulation study in the last.(2)For the quarter-car ASSs with the hydraulic actuator,the adaptive dynamic surface control(DSC)problem of the systems is studied in this thesis.The dynamic equation is built according to force analysis and the dynamic performance of the hydraulic actuator,then the state-space expression is built by coordinating transformation.The controller and adaptive law can be designed based on Backstepping technique and DSC algorithm.The proposed method can guarantee all signals in ASSs are bounded by Lyapunov stability theorem,and the tracking error can be limited in a small neighborhood of zero.The simulation results show that the proposed control algorithm can ensure the requirements of ASSs including the suspension space limits and road holding.Finally,the control target is achieved.(3)For the quarter-car ASSs with the actuator failure,the adaptive control problem of the systems is studied in this thesis.In order to guarantee the transient performance when the actuator failure occur,the prescribed performance function(PPF)is discussed in the controller design.The controller and adaptive law are designed based on Backstepping technique.The stability of the systems is discussed by the Lyapunov stability theorem.The simulation study compares PPF approach with basic approach(without PPF).The results show that different from the basic approach,the proposed adaptive control algorithm based on PPF can guarantee the vertical displacement limited in the PPF bounds effectively when the actuator failure in ASSs.Meanwhile,the transient response of the tracking error can be effectively guaranteed at the moment of the actuator failure.Finally,the control target is achieved and the effectiveness of the presented method is verified.