Asymptotic tracking of constant references in the face of periodic disturbances

Asymptotic tracking of constant reference inputs in the presence of arbritrary periodic disturbances is considered. Robust servomechanism theory calls for an infinite dimensional servocompensator to mitigate such periodic disturbances. In this paper a formulation leading to a very simple-precompensator is given as an alternative. It is shown that a certain delay type operator will accomplish the type of disturbance rejection considered.