Characterization and Computation of Decentralized Fixed Modes of Multivariable Systems

In this paper, an algebraic characterization of "fixed modes" of a decentralized linear multivariable system is presented. It is shown that the fixed modes are related to the "blocking-zeros" of certain subsystems derived from the given decentralized system. A numerically stable algorithm is then presented which enables us to compute the fixed modes in a reliable and computationally efficient manner. Examples are provided to illustrate various results.