Experiments on Bending-Torsion Flutter in Presence of Piezoelectric Actuators

*† ‡ § In this study a medium-aspect-ratio aeroelastic wing model with a slender body attached to its tip has been designed and manufactured. The model was tested in the Technion subsonic wind tunnel and its response to flutter and a limit-cycle oscillation (LCO) has been measured and analyzed. The effects of geometric structural nonlinear behavior and aerodynamic stall on both flutter instability boundary, and on nonlinear response have been studied. A MSC/NASTRAN finite-element structural model was constructed for the wing model and calculations were performed for comparison with the experimental data. Structural equations of motion based on linear beam theory were combined with a ZAERO unsteady aerodynamic model. The flutter velocity and frequency obtained in the linear finite element analysis were practically identical with those observed in the experiment for an angle of attack, α = -0.7 deg. Also, the predicted behavior pattern was found to be very close to the shape of oscillations obtained in the experiments. The onset of LCO appeared to be dependent on a balance between stall aerodynamics and the structural nonlinear forces. Closed loop fuzzy logic based control tests of flutter/LCO suppressing were initiated and have indicated that improvements relative to the open loop case could be achieved.