Pre-processing nonlinear output regulation with non vanishing measurements

Abstract

The paper deals with the problem of output regulation for a class of nonlinear multivariable systems possessing a normal form. With respect to the most of the literature on the subject we deal with the design of the regulator in the cases in which, besides the regulation error, others measurements not necessarily zero in steady state are available. Motivated by a linear analysis that is overviewed in the initial part of the paper, we propose a control structure in which the extra measurements are filtered by a post-processor specifically designed to block their steady state value. The method proposed in the paper lends itself to address relevant cases of nonlinear systems that are nonminimum-phase between the control input and the regulation error and for which extra measurements are necessary, or simply desirable, to succeed in robust output feedback stabilisation.