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

This paper considers the use of frozen-time H_∞ 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 H_∞ control problem are analytic with respect to the plant data. Classical results of Desoer (1970) on the stability of frozen-time systems are then invoked