Abstract: Active flutter suppression (AFS) of a multi-input/multi-output (MIMO) airplane configuration is studied on an imitational F/A-18A model. The controllers are designed by linear quadratic Gaussian (LQG) method truncated by a balanced truncation method. First, by merely using the wing flaps, the AFS of the wing and the airplane are performed. Then, all-moving horizontal empennage are involved into flutter control. Finally, a pair of fuselage flaps is combined with the wing flaps for AFS. It is found that the AFS of the wing is effective with the flutter speed increasing by 28%. However, the increment is only 4.6% for the airplane because of the fuselage modes coupling into flutter. The addition of all-moving horizontal empennage can improve low-frequency flutter, but it can also cause low-speed high-frequency instability. Combining the fuselage flaps with the wing flaps can increase the flutter speed by 14.9%. Finally, the trailing-edge in-board flaps and the fuselage flaps are selected to achieve a 14.5% flutter speed increment, which is a satisfactory AFS design.

Key words: aeroelasticity, active flutter suppression, optimal control, model reduction, balanced truncation