Novel Strategy for Suppressing the Flutter Oscillations of Aircraft Wings

A new strategy, based on the nonlinear phenomenon of saturation, is proposed for controlling the flutter of a wing. The concept is illustrated by means of an example with a rather flexible, high-aspect wing of the type found on such vehicles as high-altitude long-endurance aircraft and sailplanes. The wing is modeled structurally as an Euler-Bernoulli beam with coupled bending and twisting motions. A general unsteady nonlinear vortex-lattice technique is used to model the flow around the wing and provide the aerodynamic loads. The structure, the flowing air, and the controller are considered the elements of a single dynamic system, and all of the coupled equations of motion are simultaneously and interactively integrated numerically in the time domain. The results indicate that the aerodynamic nonlinearities alone can be responsible for limit-cycle oscillations and that the saturation controller can effectively suppress the flutter oscillations of the wing when the controller frequency is actively tuned.