Output Feedback Control Design For Several Classes Of Uncertain Nonlinear Systems

The present paper focuses on the investigation of output feedback control de-sign for uncertain nonlinear systems. For various classes of nonlinear systems with nonlinearities depending on unmeasured states, the problems of stabilizing con-trol, practical tracking and disturbance attenuation are solved by output feedback. The main contents of this paper are composed of the following three parts:(â… ) Output feedback stabilizing control of nonlinear systemsThis part contains Chapters 2-5, and investigates output feedback stabiliz-ing control for several classes of nonlinear systems. Specifically, in Chapter 2, the global asymptotic stabilization problem by output feedback is investigated for a class of nonlinear systems with unmeasured states dependent growth and hidden zero-dynamics. By linear state transformation, the new system is obtained which is convenient for controller design. Then, a simple design procedure is given for the output feedback control, and the global asymptotic stability of the closed-loop system can be guaranteed by the positive definiteness of the derived matrix. In Chapter 3, the results of Chapter 2 are extended to more general nonlinear systems, a state observer is constructed based on high-gain K-filters, and output feedback stable controller is designed using backstepping technique. Based on Chapter 3, Chapter 4 relaxes the assumption on system nonlinearities, and inves-tigates the problem of adaptive output feedback stabilizing control for a class of uncertain nonlinear systems. In Chapter 5, a first attempt is made to solve the adaptive output feedback stabilizing control for a class of planar nonlinear systems with unknown upper bound of the control coefficient.(â…¡) Output feedback practical tracking control of uncertain non-linear systemsThis part contains Chapter 6, and mainly investigates the adaptive practical tracking control by output feedback for nonlinear systems. For a class of nonlinear systems with nonlinearities restricted to be upper bounded by a constant plus a polynomial function of the output multiplied by unmeasured states, an observer with a dynamic high-gain is introduced, and then an adaptive output feedback tracking controller is successfully designed. It is shown that all the states of the closed-loop system are bounded, and the tracking error can be made arbitrarily small by an appropriate choice of the design parameters after some large enough time. Furthermore, the above results are generalized to nonlinear systems with uncertain control coefficient. By introducing dynamic high-gain K-filters, a state observer is constructed. Then, an adaptive output feedback tracking controller is successfully designed using the backstepping technique, and the objective of output feedback practical tracking control is realized.(â…¢) Output feedback disturbance attenuation of uncertain nonlin-ear systemsThis part contains Chapter 7, and mainly investigates the problem of dis-turbance attenuation by output feedback for a class of nonlinear systems with uncertain control coefficient. For a class of nonlinear systems with uncertain con-trol coefficient and unmeasured states dependent growth, the problem of output feedback disturbance attenuation is solved in the sense of (?)2-gain. As the main contribution of this chapter, high-gain K-filters are first introduced and an appro-priate state observer is constructed based on the K-filters. Then, a linear output feedback controller is designed using the backstepping technique. By choosing appropriate design parameters, disturbance attenuation is achieved in the sense of (?)2-gain. Besides, the results are extended to a more general class of nonlinear systems.For output feedback stabilizing control and practical tracking control, corre-sponding simulation examples are provided respectively, to illustrate the effective-ness and feasibility of the proposed results.