In the real world, since many physical systems, for instance, the ball and beam system and the cart-pendulum system, can be transformed to feedforward nonlinear systems, which are also called upper-triangular systems, the regulation or stabiliza-tion problems of feedforward nonlinear systems have attracted much attention from the nonlinear control community. This dissertation is concerned with the problem of output feedback regulation for several classes of uncertain nonlinear systems whose structure is more general form than feedforward nonlinear systems. The main con-tents of the dissertation are as follows:1. Adaptive output feedback regulation for a class of uncertain nonlinear sys-temsThe problem of global state regulation by output feedback is investigated for a class of uncertain nonlinear systems satisfying some relaxed upper-triangular-type condition. The uncertainties of the considered systems are bounded by unmeasured states with growth function of input multiplying an unknown constant. Based on a linear-like observer with two dynamic gains, the linear-like output feedback con-troller is explicitly constructed. It is proved that the proposed adaptive controller guarantees that all the states of the closed-loop system are globally bounded and the states of the original systems converge to zero. It is worth pointing out that, By re-defining an unknown constant and a known function, the continuous function of the dynamic equation of the gain can be appropriately chosen such that the amplitude values of the states of the closed-loop system are acceptable.2. Disturbance attenuation via output feedback for nonlinear systems with out-put and input depending growth functionThe problem of output feedback disturbance attenuation is addressed for a class of uncertain nonlinear systems. The uncertainties of the considered systems are bounded by unmeasured states with growth function of output and input multiplying an unknown constant. The uncertainties associated with the disturbance are bounded by an unknown constant multiplying growth function of output and input. Based on a dynamic gain observer, an adaptive output feedback controller is proposed such that the states of the closed-loop system are globally bounded, and the disturbance attenuation is achieved in the L2-gain sense. Furthermore, if the disturbance is uni-formly bounded and square integrable on the infinite interval, then the states of the original systems converge to zero. Compared with the previous works, the stability analysis of the closed-loop system is more complicated due to the presence of the disturbance and a growth function depending on the input and output.3. Global output feedback regulation of uncertain nonlinear time-delay systemsThe problem of global output feedback regulation is studied for two classes of nonlinear systems with unknown time delay. Firstly, for a class of nonlinear time-delay systems, the adaptive output feedback controller is explicitly construct-ed. Strictly speaking, the uncertain delay is not included in the inputs of the consid-ered time-delay systems. By using the dynamic gain scaling technique and choosing an appropriate Lyapunov-Krasovskii functional, it is proved that the proposed con-troller can make all the states of the considered time-delay systems converge to zero while maintaining global boundedness of the closed-loop system. Then, by using the appropriate state transformation, the output feedback regulation problem is also solved by the preceding controller for a class of more general uncertain nonlinear systems with delay in the input.4. Adaptive output feedback regulation for large-scale uncertain nonlinear sys-tems with time delaysThe problem of adaptive output feedback regulation is considered for large-scale uncertain nonlinear systems with time delays in the states and inputs. The systems are assumed to be bounded by a class of feedforward systems satisfying a linear growth condition in the unmeasurable states multiplying by unknown growth rates and continuous functions of the inputs or delayed inputs. Under two dif- ferent assumptions, the delay-dependent output feedback controller and the delay-independent output feedback controller design approaches are proposed. Firstly, by using a series of coordinate transformation and choosing the appropriate Lyapunov-Krasovskii functionals, the delay-dependent adaptive controller is explicitly con-structed such that all the states of the closed-loop system are globally bounded and the states of large-scale uncertain systems converge to zero. Then, under a strict as-sumption, it is proved that the adaptive output feedback problem of the considered time-delay systems can be solved by a delay-independent adaptive controller.To sum up, the output feedback regulation problem is solved by using the dy-namic gain scaling technique for several classes of uncertain nonlinear systems in this dissertation, which promote the development of theoretical research of feedfor-ward nonlinear systems. |