Output Constrained/uncertain Nonlinear System Control Design And Application

The control design and stability analysis on nonlinear systems have always been the focal and difficult problems in the field of control theory that are widely used in practical industrial systems,such as power systems,aerospace systems,robotic systems and biochemical systems.Maglev system,as a typical nonlinear one,has been widely used in generator,satellite attitude control and other fields on account of its good performance.The stability and security during the system operation are the most important factors to be considered.Moreover,the finite-time stability has better robustness and antiinterference performance than the asymptotic stability.In addition,due to the limitations of external conditions and the structure of the system itself,the maglev system should be kept within a certain range during operation,otherwise it will destroy the stability of the system or even damage the system.Thus,it is of theoretical significance and practical value to consider the finite time control problem of the maglev system when the output is constrained.Uncertainties can be seen almost everywhere in practical industrial systems.Many interesting results have been obtained about the output feedback control problem of uncertain nonlinear systems.However,there exists unknown measurement sensitivity error originating from inaccurate detection of the sensor in the output function of the system.Therefore,the output feedback stabilization problem of nonlinear systems with unmeasurable sensitivity errors has been studied in recent years.This paper focuses on two types of nonlinear systems aforementioned and proceeds from two aspects.In the second part of the thesis,we consider the problem of finite-time stabilization for the maglev system with an output constraint whose range depends on the experimental platform.A tan-type barrier Lyapunov function is introduced to guarantee that the output of the maglev system is restricted in the prescribed region and the state converges to zero in a finite time.The novelty lies in the fact that the design and the analysis for constrained and unconstrained output are unified without changing the structure of the controller.Finally,simulations are given to validate the effectiveness of theoretical results.Global stabilization by output feedback is investigated for a class of uncertain nonlinear systems with unknown time-varying measurement sensitivity and nonlinear growth rate in chapter 3.An output feedback controller is successfully constructed to control nonlinear growth rate by introducing a high-gain state observer and using a new domination control method.The global boundedness of the closed-loop system and asymptotic convergence of original system's state are guaranteed.In the end,the effectiveness of the designed controller in dealing with unknown measurement sensitivity and nonlinear growth rate is verified by simulation results.