  A delayed feedback control framework for stabilizing unstable periodic orbits
of linear periodic time-varying systems is proposed. In this framework,
act-and-wait approach is utilized for switching a delayed feedback controller
on and off alternately at every integer multiples of the period of the system.
By analyzing the monodromy matrix of the closed-loop system, we obtain
conditions under which the closed-loop system's state converges towards a
periodic solution under our proposed control law. We discuss the application of
our results in stabilization of unstable periodic orbits of nonlinear systems
and present numerical examples to illustrate the efficacy of our approach.
