Uncertain Nonlinear System Stability And Tracking Control Study

Nonlinear system control is an important topic in control theory.A lot of studies are designed and analysed for nonlinear control systems with uncertain parameters and structures. And it is always a hot problem that how to achieve robust stabilization or tracking of a nonlinear system via feedback control.In this paper,we mainly discussed robust control of tow classes of uncertain nonlinear systems.Both output-feedback adaptive control of uncertain nonlinear systems and robust output tracking control of uncertain systems are considered in this paper.This paper mainly consists of 5 chapters,In chapter 1,the research background and significance are introduced,and the phylogeny of this whole field and the main results in existence are summarized respectively.The preparative knowledge is also presented roundly.Chapter 2 considers robust tracking design of a class of nonlinear systems with parameter uncertainty and bounded disturbance.Using Back-stepping method,we recursively designed a robust tracking controller based on the nominal systems and the bounds of uncertainties.This controller can guarantee that the closed-loop output signals asymptotically track the desired signals.In chapter 3,for a class of nonlinear systems with dynamic uncertainties,output-feedback adaptive control problem is considered.The adaptive stable controller designed in this chapter are mainly based on assumptions as follows:The modeled dynamics satisfy the multivariable nonlinear monotony increasing condition,and the unmodeled dynamics can be dominated by a known function multiplying an unknown constant.Firstly,a state observer is introduced,then the estimation of all state controller is proposed.Based on this state observer,using Lyapunov stable theory and Back-stepping method,output-feedback adaptive controller is proposed recursively. Finally,it is proved that the controller keeps the equilibrium at origin,and all the signals are uniformly bounded or asymptotical convergent.A simulation example further demonstrates the efficiency of the control scheme.Chapter 4 considers output-feedback tracking control problem for a class of nonlinear systems,which systems are special types of systems of last chapter.Namely,when the uncertainties of the system are zero,the problem of the output-feedback asymptotical tracking control is designed.The controller designed based on the observer ensures that all the signals of the closed system are uniformly bounded and the output of the system asymptotically tracks the desired output.A simulation example further demonstrates the efficiency of the control scheme.Chapter 5 summarizes the main results of this paper and a prospect of the future research work.