Stability Augmentation and Active Flutter Suppression of a Flexible Flying-Wing Drone

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Stability Augmentation and Active Flutter Suppression of a Flexible Flying-Wing Drone

Schmidt, David K.

Integrated control laws are developed for stability augmentation and active flutter suppression of a flexible flying-wing research drone. The vehicle is a 12 lb unmanned flying-wing research aircraft with a 10 ft wingspan. Active flutter suppression is flight critical, since the subject vehicle is designed to flutter within its flight envelope. The critical flutter condition involves aeroelastic interactions between the rigid body and elastic degrees of freedom; hence, the control laws must simultaneously address both rigid-body stability augmentation and flutter suppression. The conventional control-synthesis approach is motivated by the concept of identically located force and acceleration, which was successfully applied on some previous operational aircraft. Based on the flutter characteristics and on conventional stability-augmentation concepts, two simple loop closures are suggested. It is shown that this control architecture robustly stabilizes the body-freedom-flutter condition, increases the damping of the second aeroelastic mode (which becomes a second flutter mode at higher velocity), and provides a reasonably conventional vehicle pitch-attitude response. The critical factors limiting the performance of the feedback system are identified to be the bandwidth of the surface actuators and the pitch effectiveness of the control surfaces.