DESIGN AND MULTIFUNCTION TESTS OF A FREQUENCY DOMAIN-BASED ACTIVE FLUTTER SUPPRESSION SYSTEM

This article describes the process of analysis, design, digital implem entation, and subsonic testing of an active controls nutter suppressio n system for a full-span, free-to-roll, wind-tunnel model of an advanc ed fighter concept. A frequency domain representation of the plant was employed, and a robust multiinput/multioutput controller was generate d by using optimization techniques to maximize singular value robustne ss criteria and insensitivity to uncertainty in the nutter frequency. During testing in a fixed-in-roll configuration, simultaneous suppress ion of both symmetric and antisymmetric nutter was successfully demons trated. For a free-to-roll configuration, symmetric nutter was suppres sed to the limit of the tunnel test envelope. During aggressive rollin g maneuvers above the open-loop nutter boundary, simultaneous nutter s uppression and maneuver load control were demonstrated. Finally, the n utter suppression controller was reoptimized during the test using com bined experimental and analytical frequency domain data, resulting in improved stability robustness. The reoptimization, accomplished overni ght, shows the potential, with a much faster computer, to apply the de sign procedure to a tuning-type adaptive active nutter suppression con troller.