Fuzzy adaptive robust control of a class of nonlinear systems

A fuzzy adaptive robust tracking controller for a class of uncertain nonlinear dynamical systems is proposed and analyzed. The controller´s construction and its analysis involve sliding modes. The proposed controller consists of two components. A robust feedback component is employed to eliminate the effects of disturbances, while a fuzzy logic component equipped with an adaptation mechanism reduces modeling uncertainties by approximating the model´s nonlinearities on-line. A projection method is used to prevent the adaptation parameters from going unbounded in the presence of disturbances. It is shown that the closed-loop system driven by the proposed controller is stable and the adaptation parameters are bounded. A guaranteed transient performance and a guaranteed final tracking accuracy in the presence of parametric uncertainties and disturbances are achieved. Furthermore, if there are no disturbances and the unknown model´s nonlinearities are within the approximation range of the fuzzy logic system, asymptotic output tracking is also achieved