Regulator problem with internal stability: A frequency domain solution

This paper considers the general regulator problem with internal stability where the measured outputs are not necessarily the same as the regulated outputs. Using polynomial matrix techniques, necessary and sufficient conditions are obtained in terms of skew-primeness of two polynomial matrices; one of these polynomial matrices represents the disturbance modes, whereas the other is the polynomial system matrix representing the system zeros. Various special cases considered in the literature are also analyzed in terms of these necessary and sufficient conditions.