Active flutter suppression and gust load alleviation of wings incorporating floating wingtips

In this paper, a two degree of freedom mathematical model was used to analyse active flutter suppression on wings featuring flared folding wingtips, via an additional control surface on the wingtip. The active control system took the wingtip fold angle as the input parameter. Using a proportional controller gain, the flutter onset speed could be increased by 25%, and a proportional controller can also be used to recreate the effect of a flare angle. Using a derivative controller, it was found that flutter could be prevented across all reasonable airspeeds. Both benefits could be realised without a significant change in the gust load alleviation provided by the flared folding wingtip. However, the control surface angular rates required to achieve flutter suppression were very high under certain conditions. If these control surface velocities are limited to realistic values, then the controller can no longer suppress the growth of instabilities for larger gust amplitudes.