| This dissertation addresses various control problems for nonlinearly parameterized systems. Unlike most of the existing results, the uncertain parameters considered here are not assumed to be in a known compact set nor satisfy a certain type of nonlinearity, e.g. convex/concave or polynomial conditions.; The first part of this dissertation addresses global regulation problems for uncertain systems by using a time-varying approach. First, two new time-varying control designs are introduced and used to solve the problem of global regulation for both lower-triangular and upper-triangular systems with nonlinear parameterization. The time-varying approach presents a unified framework to deal with both lower-triangular and upper-triangular systems. Then, time-varying output feedback is explicitly constructed to solve the problem of global regulation for a class of uncertain nonlinear systems dominated by a linear growth triangular system. Using this approach, a so-called universal output, feedback controller in which one controller can globally regulate a whole family of systems, can be developed.; In the second part, we consider the problem of practical output tracking for nontriangular systems with nonlinear parameterization. This class of the systems represents high-order nonlinear systems with uncontrollable unstable linearization which, in general, asymptotic output tracking is not possible. Using a universal, adaptive controller, we show that the practical output tracking problem is solvable without requiring knowledge of the bound of uncertain parameters. |
