Stochastic Nonlinear Control And Application In Vehicle Suspension

With the development of science and technology and the improvement of people's living standards,cars have become an indispensable means of transportation.Vehicle suspension system,as the key to improve ride comfort and driving safety,has been widely concerned by researchers.However,random disturbance has always been an important problem in automobile suspension system.Solving the problem of random disturbance can effectively improve the performance of the suspension system.Therefore,the research on stochastic control theory of vehicle active suspension has important theoretical and practical significance.The adaptive stochastic control design and the stability of the closed loop system for several classes of active suspension system are studied in this paper.Considering the quarter electromagnetic active suspension systems,the fuzzy adaptive controllers are designed based on the adaptive reverse control method.The details are as follows:(1)For a class of active suspension systems with stochastic disturbance,the stability problem of vehicle suspension with stochastic disturbance is solved.The stochastic perturbance is realized by the roughness of the road and the vehicle moves with constant velocity.Fuzzy logic systems(FLSs)are used to approximate unknown nonlinear functions.Meanwhile,the mean value theorem is employed to ensure the existence of the affine virtual control variables and control input.The backstepping technique is applied to construct the ideal controller.On the basis of Lyapunov stability theory,the proposed control method proves that the displacement and speed of the vehicle is reduced to a level ascertain by a true “desired” conceptual suspension reference model.Finally,a simulation study was carried out on the vehicle suspension system.Considering the influence of design parameters on the simulation results,different design parameters were selected for comparative simulation to further verify the feasibility and effectiveness of the control method when selecting appropriate design parameters.(2)The fuzzy adaptive fault-tolerant stochastic control design problem for a class of electromagnetic active suspension systems is investigates in this paper.The fuzzy adaptive fault-tolerant controller is designed to increase the vehicle stability in presence parameter uncertainties.Considering the nonlinear characteristics of springs and dampers in suspension space,FLSs are applied to identify unknown dynamics.The backstepping technique is applied to design the ideal controller.Furthermore,unknown time varying delay and dynamic abrupt fault are considered,which helps deal with emergencies and transmission delays.On the basis of Lyapunov stability theory,it is proved that all the signals of the closed-loop system are stable.Finally,a simulation study is carried out on the automobile suspension system with unknown delay and dynamic abrupt fault,and the effectiveness of the control method in the case of system failure is verified by comparing the simulation results with and without dynamic abrupt fault.(3)An observer-based adaptive fuzzy stochastic control method is proposed for a class of vehicle active suspension system with stochastic disturbance.Due to the unmeasurable state of the controlled system,in the control design process,the FLSs are used to approach the unknown nonlinear function,and a state observer is established to estimate the unmeasurable state.Based on adaptive backstepping control technology,an adaptive fuzzy controller is designed.Combined with the stability theory of Lyapunov,it is strictly proved that all the signals of the suspension system tend to be stable.Finally,by comparing the simulation results of two groups of different design parameters through simulation examples,it is verified that the control scheme can effectively guarantee the performance of the suspension when selecting appropriate design parameters,including the speed and displacement of sprung and unsprung can reach the ideal state.