PHASE MARGINS FOR MULTIVARIABLE CONTROL-SYSTEMS

This paper presents a new definition for the phase margin of multi variable systems. The properties of the phase margin are such that a stable closed-loop multi-input multi-output system will remain stable for all unitary perturbations in the feedback path whose phases are less than the phase margin of the system. It is also shown that the definition of phase margin is invariant under unitary transformations of the system. © 1990 Taylor and Francis Group, LLC.