Active Flutter Suppression Of Flexible Wings

With the development of aeronautical materials and enhancement of the aircraft flight performa-nce requirements, the reduction of structural weight is an inevitable trend, which means that the wingstructure tends to be more flexible. The increment of the wing flexibility can directly affect theaircraft’s aerodynamic performance, so an important part of the aeroelastic problems about thisflexible wing will be discussed in this paper—flutter analysis and the active control.In this paper, the modal analysis for the finite element model of the flexible wing is carried outfirstly, then the distribution of the unsteady aerodynamics of lift surface is calculated by Matlabprogramming according to a doublet lattice method and we compare this result with one calculated bycommon software. The aeroelastic state-space equation of the system in time-domain is created, whilethe aerodynamic data in the frequency-domain is transformed into the time-domain by the minimumstate approximation. The flutter characteristics calculated by the root locus method through theequation mentioned before is compared with one calculated by the frequency-domain method. Thenthree kinds of flutter suppression control laws are designed for this model, which are classicalfeedback control law, LQG control law and LQG self-turning controller. The control effects are alsoanalyzed. Finally, the spanwise specific energy ratio of the lift surface according to aerodynamicenergy is calculated and control surface spanwise placement in active flutter suppression system isanalyzed. The flutter suppression control law is designed based on energy concept and we find thatthis law can effectively raise the critical flutter speed by about20%.