Output-input stability implies feedback stabilization

We study the recently introduced notion of output–input stability, which is a robust variant of the minimum-phase property for general smooth nonlinear control systems. This paper develops the theory of output–input stability in the multi-input, multi-output setting. We show that output–input stability is a combination of two system properties, one related to detectability and the other to left-invertibility. For systems a4ne in controls, we derive a necessary and su4cient condition for output –input stability, which relies on a global version of the nonlinear structure algorithm. This condition leads naturally to a globally asymptotically stabilizing state feedback strategy for a4ne output–input stable systems. c © 2004 Elsevier B.V. All rights reserved.