Adaptive Output Feedback Analysis And Design For Several Classes Of Uncertain Nonlinear Systems

Adaptive output-feedback control of uncertain nonlinear systems is an important part of modern control theory,which has been widely used in industrial control,national defense and other aspects.On the one hand,nonlinearities and uncertainties are unavoidable in the mathematical models established,which pose major challenges to control theories and methods.On the other hand,with the continuous improvement of control system performance requirements in modern industry,it is necessary to strengthen the research of system adaptive output-feedback control.Therefore,the study of adaptive output-feedback control for uncertain nonlinear systems has important theoretical significance and application value.By using observer theory and adaptive technique,we study the adaptive output-feedback control of several classes of uncertain nonlinear systems by constructing a new dynamic gain to deal with the serious unknows and nonlinearities of the system,and designing a suitable observer to reconstruct the unmeasured states of the system or simultaneously estimate the input matching uncertainty of the system.The research content includes the following three aspects:(Ⅰ)We investigate the adaptive output-feedback global practical tracking problem for a class of uncertain nonlinear systems.Unlike the existing work,the system growth rate is the system input-output polynomial function multiplied by an unknown constant.The observer is constructed by introducing two new dynamic gains,and based on which the adaptive outputfeedback controller is designed.The two new dynamic gain updating laws introduced in this paper can effectively solve the serious uncertainties from the system growth rate and reference signal.The controller can make all the states of the closed-loop system globally bounded,and the tracking error will be arbitrarily small after a finite time.(Ⅱ)We address the global adaptive output-feedback stabilization problem for a class of uncertain nonlinear systems with generalized control coefficients.Such nonlinearities from function control coefficients and unknowns from unknown growth rate bring great technical difficulties to controller design.A novel dynamic gain is introduced to deal with the extra system nonlinearities from function control coefficients and unknowns from the growth rate.On this basis,the extended state observer is designed to reconstruct the unmeasured states of the system and estimate the input matching uncertainty.By integrating the dynamic gain and extended state observer,an adaptive output-feedback controller is designed,which ensures that the states of the system globally converge to zero,and the estimation of the input matching uncertainty converges to its actual value.(Ⅲ)We investigate a class of more general adaptive output-feedback global stabilization problems for nonlinear systems.It is worth emphasizing that the system studied not only has the function control coefficients and input matching uncertainty,but also has a more general growth rate,which is the product of an unknown constant and the polynomial-of-output,which brings technical difficulties to the controller design.Remarkably,only one dynamic gain is introduced to overcome the function control coefficients and the serious uncertainty in the system growth rate.The designed controller finally achieves the stabilization goal.In view of the above three parts of the research,the corresponding simulation examples are given respectively to verify the effectiveness of the proposed control design method.