Generalized Nyquist Stability Criterion for Linear Time Periodic Systems

A generalized Nyquist stability criterion for linear time periodic systems is presented. This stability criterion is similar in many respects to the generalized Nyquist stability criterion for linear time invariant multi-input multi-output systems. The criterion is graphical and is based on the eigenloci of the transfer function operator that describes the input/output behavior of the system. The criterion has the advantage that it can determine the stability of a feedback system for a range of gains, whereas Floquet theory determines stability for only a specific gain.