Using adaptive structures to attenuate rotary wing aeroelastic response

This article investigates the feasibility of employing adaptive material to build both sensors and actuators to attenuate the higher harmonic loads developed at the helicopter rotor blades using the individual blade control (IBC) concept. Both the first elastic flatwise bending (second for hingeless rotors) and the first elastic torsion modes of a single blade deserve special attention in the vibration control. Theoretical investigations, supported by wind-tunnel and flight tests, confirmed that these modes are responsible for the larger amplitude loads at 3/rev in four-blade hingeless rotors. This is a situation for which IBC, based on a collocated actuator-sensor arrangement along the blade, and tailored to act specifically on the bending and the torsion modes, is expected to bring further improvements to the reduction of the overall dynamic response of rotary wings. The results indicate that there are already real situations for which the adaptive material has enough power to accomplish the task without saturation of the applied electrical field.

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