ON DISCRETE-TIME H-INFINITY PROBLEM WITH A STRICTLY PROPER CONTROLLER

In this paper the standard discrete-time H-infinity control problem is considered under the constraint imposed upon the controller to be str ictly proper. The necessary and sufficient conditions for the existenc e of a gamma-suboptimal controller are derived and the set of all line ar time-invariant controllers, which solve the problem, is parametrize d. In contrast with the unconstrained case, the state-space solution o btained is very transparent and actually is not more complex than the solution of the continuous-time H-infinity problem.