Trajectory tracking and disturbance rejection for linear time-varying systems: Input/output representation

This paper considers the problem of asymptotic trajectory tracking and/or disturbance rejection for linear time-varying systems via input/output representation. Inspired by the structure of repetitive control, a novel feedback mechanism is proposed based on which the necessary and sufficient condition for the problem is derived. This condition is a generalization to the time-varying case of the result in time-invariant setting. Based on the complete knowledge of the plant model, a design is provided and it is applicable to repetitive control for time-varying plants. An important feature of the proposed approach is that a systematic way of constructing time-varying internal model unit is provided.