Adaptive control of a class of time-varying and nonlinear plants

A reduced-order adaptive feedback controller with regular or variable structure is developed for a class of time-varying and nonlinear plants. Neither smallness of parameter variations nor parametrizableness of nonlinearity is required for the plant. Global stability and small tracking error in the mean are guaranteed for the closed-loop plant in which the parameter variations may not be small and the nonlinearity only satisfies a relative boundedness condition. The idea of using bounding signals in feedback control schemes is shown to be feasible