Simultaneous robust tracking and disturbance rejection with stable plants

The robust asymptotic tracking and disturbance rejection problem is studied with a two-output plant and a two-input compensator, with disturbances entering directly into the plant and in the two junctions between plant and compensator. Two situations are considered with respect to that part of the plant which is connected to the compensator´s output, namely, when one of its block matrices is fixed while the other is perturbed arbitrarily and when the two block matrices are related by another (fixed) block matrix. Necessary and sufficient conditions are obtained for the compensators which solve the problems. Conditions for the solvability of the general problems are obtained as well