How to represent a repetitive control system in the state space

Repetitive control is a specialized control scheme to track and/or attenuate a periodic reference trajectories and/or disturbances. Most research results about repetitive control have been performed in the frequency domain. In this paper, we present a method to represent repetitive control systems in the state space. The problem to describe a repetitive control system in the state space is equivalent to representing a q filter in the repetitive controller, which is a typical time-delayed system, as a state equation. The obtained results will be used to apply a lot of control theories in the state space to design of repetitive control systems.