(i) A pure small gain approach is proposed to handle a disturbance attenuation problem for a class of feedforward systems subject to both dynamic uncertainty and disturbance. Two versions of small gain theorem with restrictions are employed to establish the global attractiveness and local stability of the closed-loop system at the origin, respectively. Unlike Lyapunov's linearization method and asymptotic small gain theorem combined approach, the proposed approach does not require the stabilizability assumption of the Jacobian linearization of the system at the origin. / (i) We first identify structural properties of the plant so that an internal model candidate exists. Then, by looking for a suitable internal model and performing appropriate transformations on the augmented system, we succeed in converting the global robust output regulation problem for a class of feedforward systems into a global robust stabilization problem for a class of feedforward systems subject to both time-varying static and dynamic uncertainties. As a result, the global robust stabilization result obtained in the first part of this thesis is used to solve the global robust output regulation problem for a class of feedforward systems. / (ii) A small gain based bottom-up recursive design is developed to solve a global robust stabilization problem for a class of feedforward systems subject to both time-varying static and dynamic uncertainties. Unlike most existing results, our design does not require the bottom dynamics at each recursion be locally exponentially stable. / (ii) We apply the result of the global robust output regulation problem to solve two trajectory tracking problems for a chain of integrators with uncertain parameters and the Vertical Take-Off and Landing (VTOL) aircraft, respectively. In contrast with the existing designs, for the chain of integrators, our design is low gain and does not need to know the reference trajectory exactly, and for the VTOL aircraft, our design is a complete low gain design and thus is more cost effective. / (iii) The small gain based bottom-up recursive design is further extended to deal with a global robust stabilization problem for a class of feedforward systems which are approximated at the origin by a nonlinear chain of integrators and perturbed by some type of input unmodeled dynamics. Even in the special case where the input unmodeled dynamics is not present, our result is new in the sense that our approach can handle some cases that cannot be handled by any existing approaches. / (iii) We propose a Lyapunov approach to a special case of the output regulation problem, the input disturbance suppression problem for a class of feedforward systems. When the exosystem is known, we solve the problem via dynamic output feedback control. When the exosystem is unknown, we solve the problem via adaptive dynamic state feedback control and we also give the conditions under which an estimated parameter vector can converge to the true parameter vector. / It is now well known from the general framework for tackling the output regulation problem that the robust output regulation problem can be approached in two steps. In the first step, the problem is converted into a robust stabilization problem of a so-called augmented system which consists of the original plant and a suitably defined dynamic system called an internal model candidate, and in the second step, the robust stabilization problem of the augmented system is further pursued. The success of the first step depends on whether or not an internal model candidate exists. Even though the first step succeeds, the success of the second step is by no means guaranteed due to at least two obstacles. First, the stabilizability of the augmented system is dictated not only by the given plant but also by the particular internal model candidate employed. Second, the stabilization problem of the augmented system is much more challenging than that of the original plant with the exogenous signal set to 0, because the structure of the augmented system may be much more complex than that of the original plant. Perhaps, it is because of these difficulties, so far almost all papers on semi-global or global robust output regulation problem are focused on the lower triangular systems, feedback linearizable systems and output feedback systems. The second part of this thesis aims to study the global robust output regulation problem of feedforward systems. The major results are summarized as follows. / The stabilization problem of feedforward systems has absorbed a lot of attention during the past fifteen years. More recently, the stabilization problem of feedforward systems subject to input unmodeled dynamics is studied. Nevertheless, the more realistic case where the system is subject to both time-varying static and dynamic uncertainties has not been adequately investigated. The first part of this thesis focuses on the global robust stabilization problem for various classes of feedforward systems containing both time-varying static and dynamic uncertainties. The major results are summarized as follows. / This thesis contains two parts. The first part studies the global robust stabilization problem of feedforward systems and the second part further addresses the global robust output regulation problem of the same class of nonlinear systems. / Chen, Tianshi. / Adviser: Jie Huang. / Source: Dissertation Abstracts International, Volume: 70-09, Section: B, page: . / Thesis submitted in: December 2008. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references (leaves 136-143). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.
| Identifer | oai:union.ndltd.org:cuhk.edu.hk/oai:cuhk-dr:cuhk_344421 |
| Date | January 2009 |
| Contributors | Chen, Tianshi., Chinese University of Hong Kong Graduate School. Division of Automation and Computer-Aided Engineering. |
| Source Sets | The Chinese University of Hong Kong |
| Language | English, Chinese |
| Detected Language | English |
| Type | Text, theses |
| Format | electronic resource, microform, microfiche, 1 online resource (ix, 145 leaves : ill.) |
| Rights | Use of this resource is governed by the terms and conditions of the Creative Commons “Attribution-NonCommercial-NoDerivatives 4.0 International” License (http://creativecommons.org/licenses/by-nc-nd/4.0/) |
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