On the parameterization of two-degree-of-freedom controller with tracking/disturbance rejection constraints

Considers the parameterization of two-degree-of-freedom controller for a MIMO four-block linear system with tracking/disturbance rejection constraints. The external signals considered are unstable and strictly proper deterministic signals. A stronger set of assumptions is introduced so as to ensure the existence of the solution to the servomechanism problem. A sufficient condition is presented to ensure that the Kronecker product is not involved. The solutions of the servomechanism problem are parameterized by free, stable, rational and proper matrices under the general case.