Fixed modes and local feedbacks in interconnected systems †

Abstract

A system L consisting of two interconnected subsystems is considered, and local state vector feedbacks are applied to it. It is then proven that if the global system, and the local ones are controllable, E has no fixed modes. That these conditions cannot be relaxed, as well that this property cannot be generalized to more than two subsystems, is shown with some appropriate examples. †The results reported here were obtained while the authors were with the Fachgruppe fiir Automatik, ETH, Zurich