Disturbance Rejection of a Class of Nonlinear Mimo Systems Using Adaptive Internal Models

This paper deals with disturbance rejection with global stabilization of a class of nonlinear multi-input-multi-output (MIMO) systems using output feedback. The class of nonlinear MIMO systems are assumed to be transformed into an upperblock-triangular structure with each block in the output feedback form with respect to its own state variables, and the interactions among the outputs are allowed as long as they do not violate the upper-block-triangular structure. The disturbances are unknown and they are generated from an unknown exosystem. A new control design is proposed for the disturbance rejection of the class of MIMO systems using adaptive internal models. The proposed control design starts from the lowest block, based on a recent control design method proposed by the author, with possible adaptive backstepping design inside the block, and then moves forward to the subsequent block above until the control design of the block at the top is completed. The proposed control design ensures the complete disturbance rejection of unknown disturbances and the global stability of the closed-loop system. The disturbance frequencies are also estimated via the convergence of the adaptive parameters.