Semiglobal Stabilization Via Output-feedback For Several Classes Of Nonlinear Systems

In virtue of the method of backstepping method, output-feedback domina-tion approach, saturated state estimate, adding a power integrator, and other techniques, the dissertation mainly focuses on the investigation of the semiglobal stabilization via output-feedback for several types of uncertain nonlinear system-s, which contain more serious uncertainties and nonlinearities. For details, the following four parts composed of the main content:(I) Semiglobal stabilization via output-feedback for a class of un-certain nonlinear systems with unknown control coefficientsThis part addressed the semiglobal stabilizationvia output-feedback for a class of uncertain nonlinear systems with unknown coefficients and is Chapter 3 of the dissertation. Different from the existing results, the systems under investigation possess more serious nonlinearities and unknown control coefficients which sub-stantially increase the difficulty of output-feedback controller design. Combining the backstepping method and output-feedback domination approach, a semiglobal stabilizing controller is explicitly given, which can guarantee that the closed-loop system achieves the semiglobal asymptotic stability under the appropriate choice of design parameter.(II) Semiglobal stabilization via output-feedback for a class of un-certain nonlinear systems with general unknown control coefficientsThis part is Chapter 4 of the dissertation and devoted to the semiglobal sta-bilization via output-feedback for a class of uncertain nonlinear systems. Remark that the systems in question contain an unknown control coefficient which in-herently depends on the system output, and allow larger-than-two order growing unmeasurable states which is the obstruction of global stabilization via output-feedback. By introducing a recursive reduced-order observer and combining with saturated state estimate, a desired output-feedback controller is explicitly con-structed for the systems. Under the appropriate choice of design parameters, the controller can make the closed-loop system semiglobally attractive and locally exponentially stable at the origin.(III) Semiglobal stabilization via output-feedback for a class of feed-forward nonlinear systemsThis part consists of Chapters 5 of the dissertation, and considered the semiglobal stabilization via output-feedback for a class of feedforward nonlinear systems. Notably, the systems under investigation possess unmeasurable states dependent growth including linear and higher-order parts, which incorporate and extend those in the existing many literature. Based on a linear lower-gain observer, a linear output-feedback controller is constructed by output-feedback domination approach, which is structurally simple and easy to implement. By appropriate-ly choosing the design parameter, it can be guaranteed that the zero solution of resulting closed-loop system is locally exponentially stable, and by starting from the given compact set containing the origin, all the solutions of the closed-loop system converge to the origin.(IV) Semiglobal finite-time stabilization via output-feedback for a class of higher-order planar nonlinear systemThis part consists of Chapters 6 of the dissertation, and devoted to the semiglobal finite-time stabilization via output-feedback for a class of high-order planar nonlinear system. This problem can hardly be solved by the existing schemes, mainly since the systems under investigation contain unknown control co-efficients which are functions of system unmeasured states, In this paper, with the assumption that all the system states are available for feedback, a state-feedback controller is first constructed by adding a power integrator, which ensures that the closed-loop system is globally finite-time stable. Then, by certainty equivalence principle and saturation technique, an output-feedback controller is successfully constructed, which makes the closed-loop system semiglobal attractive and local finite-time stable.The corresponding simulation examples are presented for the above parts, and illustrate the effectiveness and feasibility of the semiglobal stabilization controller via output-feedback.