Development of an active rotor blade for vibration and noise reduction

A research program dedicated to the development of an active, variable twist rotor blade has recently been completed at the German Aerospace Center (DLR). The main program goal was to develop a rotor blade for Higher Harmonic Control (HHC) and Individual Blade Control (IBC) applications. The structural concept incorporates a blade skin build from non-isotropic fiber material, and an integrated, tip-mounted, piezoelectric actuation device. The actuator's linear expansion is directly transformed into a rotational motion through the coupling of elongation and torsion deflections within the non-isotropic blade skin. This allows to directly control the blade twist angle in the region of highest aerodynamic efficiency without the need for additional trailing edge flaps. Wind tunnel tests (non-rotating) and rotor tests were carried out to assess the twist performance under aerodynamic and centrifugal loads.