Use of frozen-time H-infinity controllers in time-varying applications

This paper considers the use of frozen-time H-infinity optimal controllers for time-varying applications. It is shown that, under suitable requirement s on the plant. this method will result in an internally stable time-varyin g plant. This is done by first showing that the algebraic Riccati equations associated with the H-infinity control problem are analytic with respect t o the plant data. Classical results of Desoer on the stability of frozen-ti me systems are then invoked.