Zero dynamics and tracking performance limits in nonlinear feedback systems

Abstract

Among Alberto Isidori's many seminal contributions, his solution of the nonlinear tracking problem and the underlying concept of zero dynamics have had the widest and strongest impact. Here we use these results to investigate and quantify the limit to tracking performance posed by unstable zero dynamics. While some aspects of this limit are nonlinear analogs of Bode's T-integral formula, the dependence on the exosystem dynamics is an added complexity of nonlinear tracking. © 2008 Springer-Verlag.