Output Feedback Control Of Uncertain Nonlinear Systems With Time Delay Is Studied

Nonlinear time delay systems have existed in actual production and life widely，whichdestroy good performance for nonlinear system seriously. So, how to deal with stability anddesign control law for nonlinear time delay systems, has been important research area for controltheory and control engineering. At the same time, with the development of deeply researchingfor nonlinear systems including uncertainty, it gets good research achievements on robust controland adaptive control for nonlinear system. In addition， the technology on time delay problemalso become more perfect with gradually researching by researchers， including bothLyapunov-Krasovskii and Lyapunov-Razumikhin method. Therefore, together with the waysand theory, it has widely space to research nonlinear uncertainty time-delay system.The text mainly researches output feedback control problem of two kinds of nonlinear timedelay systems. The two kinds of systems include wide uncertainties, for example, uncertainparameter, uncertain control coefficient, unmodeled inverse dynamics, uncertain nonlinear timedelay, unknown time-variant time delay, uncertain output dynamics and so on. For the systems,together with backstepping method,changing supply function method, Nussbaum functionmethod and online estimating method, it can get proper controller, which makes the closedsystem stability in a certain sense.Specifically speaking，the text mainly researches two kinds ofproblems：1. Robust adaptive control problem for a class of nonlinear time delay systemIn chapter3，the research problem is on robust adaptive control problem of nonlinear timedelay system including unmodeled dynamics, uncertain parameter，uncertain nonlinear timedelay.The research key of the problem is how to structure a observer on output variable anduncertain parameter. The designing of control law and adaptive law is used backsteppingmethod. And designing adaptive law is made use of tuning function idea. With changing supplyfunction idea, it can deal with the effect of unmodeled dynamics efficiently, and using theLyapunov function of system, it can prove the designed control law is stable in the semi-globalmeaning for the closed loop system.2. Robust control problem for nonlinear time delay system with unknown control coefficientIn chapter4， research object contains not only unknown control coefficient but alsounmodeled inverse dynamics and uncertain output dynamics. With a proper observer andbackstepping designing method, it can formulate the control law of system. For unknown controlcoefficient, the technology of Nussbaum function is vital for the control law of designing. Forthe unmodeled dynamics, it is the same as the first part with changing supply function idea to deal with. In the system, obvious feature is unmodeled output dynamics in the output variable. Itbrings some difficulty for Lyapunov function structure, which needs to increase a term forLyapunov function. Using it, it can prove the designed control law makes all the signals boundedand output variable y(t) intend to zero gradually for the closed loop system.