Global Output Feedback Stabilisation For A Class Of Uncertain High-order Nonlinear Systems

Feedback stabilization of nonlinear systems is one of the hotspots in automatic control theory,which widely exists in many branches of national defense and industry,for eample,variable structure attitude of flexible satellite,robot motion,rail pressure of vehicle GDI engine,high-performance anti-swing positioning of underactuated cranes.In the study of practical systems,compared with the linear systems,the nonlinear systems become more accurate and reliable,but also study is more complicated.However,actual systems are always affected by uncertainties such as model errors,external disturbances,random noises and measurement errors.Hence,it is of great significance to investigate the output feedback stabilization for uncertain nonlinear systems from the point of theory and practical application.The dissertation study global stabilization by a output feedback for a class of uncertain high-order nonlinear systems by combining Lyapunov stability theory,the backstepping method and adding a power integrator technique with inequality processing technology.The main work of this dissertation can be summarized as follows:(1)Output feedback of a class of uncertain high-order nonlinear homogeneous systems is addressed.Based on the backstepping method and adding a power integrator technique,a state feedback control law is constructed.And then a high-gain observer is designed to estimate the unmeasurable states of the systems.The gains of the observer design can be assigned in an iterative manner.Further,a output feedback controller of the systems is designed such that the nonlinear systems is globally asymptotic stable.Finally,a simulation example is provided to demonstrate the effectiveness of the proposed method.(2)Output feedback of a class of uncertain high-order nonlinear non-homogeneous systems is considered.Under the nonlinear terms satisfying the high-order growth condition and the system output function satisfying a certain condition,a state feedback controller is constructed based on the backstepping method and adding a power integrator technique,and then the unmeasurable states of nonlinear systems are estimated via a nonlinear observer.Based on this foundation,the gains of the observer are obtained in an iterative manner and the output feedback controller is designed to solve the global stabilization problem of the nonlinear systems.The effectiveness of the proposed method is illustrated by simulation examples.