Design and multifunction tests of a frequency domain-based active flutter suppression system

Abstract

This article describes the process of analysis, design, digital implementation, and subsonic testing of an active controls flutter suppression system for a full-span, free-to-roll, wind-tunnel model of an advanced fighter concept. A frequency domain representation of the plant was employed, and a robust multiinput/multioutput controller was generated by using optimization techniques to maximize singular value robustness criteria and insensitivity to uncertainty in the flutter frequency. During testing in a fixed-in-roll configuration, simultaneous suppression of both symmetric and antisymmetric flutter was successfully demonstrated. For a free-to-roll configuration, symmetric flutter was suppressed to the limit of the tunnel test envelope. During aggressive rolling maneuvers above the open-loop flutter boundary, simultaneous flutter suppression and maneuver load control were demonstrated. Finally, the flutter suppression controller was reoptimized during the test using combined experimental and analytical frequency domain data, resulting in improved stability robustness. The reoptimization, accomplished overnight, shows the potential, with a much faster computer, to apply the design procedure to a tuningtype adaptive active flutter suppression controller.