Trajectory learning and output feedback control of nonlinear discrete-time systems

Output tracking control of a general class of nonlinear discrete-time systems is considered. A block input-output realization of the plant is first introduced that transforms the system into one with equal number of inputs and states. This realization is subsequently used to formulate a novel output feedback controller for regulation or tracking. The proposed controller only requires measurement of the system´s outputs, and is applicable to both minimum and nonminimum phase plants of arbitrary relative degree. For applications involving a finite-duration or periodic desired outputs, a new recursive algorithm based on the Newton-Raphson method is proposed to learn the feedforward input. A simulation example of a nonlinear nonminimum phase system is presented to further illustrate and evaluate the performance of the proposed control scheme