Global regulation for systems with output dependent nonlinearities and unknown linear exosystems

Abstract

The class of nonlinear observable systems with known output dependent nonlinearities and with disturbances and/or references generated by an unknown exosystem is considered; non-minimum phase systems are also allowed. When the exosystem is unknown and the resulting reference input consists of a biased sum of sinusoids we address the problem of adaptively generating the reference input on line. A global solution to this problem is provided when only an upper bound on the number of harmonics contained in the reference input is known. The designed controller requires the availability of both the output reference signal and the system output. The regulation design is tested by simulation on an unstable non-minimum phase nonlinear system perturbed by an uncertain number of noisy sinusoidal disturbances.