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

This paper considers the use of frozentime X, optimal controllers for time-varying applications. It is shown that, under suitable requirements on the plant, this method will result in an internally stable time-varying plant. This is done by first showing that the algebraic Riccati equations associated with the ʹH, control problem are analytic with respect to the plant data. Classical results of Desoer on the stability of frozen-time systems are then invoked.