Hover Test of Mach-Scale Active Twist Rotor Using Piezo-Bending-Torsion Actuators

The active twist rotor investigated in this research is a derivative of the previously developed smart-activeblade-tip (SABT) rotor. On the SABT rotor, the blade tips are independently pitched, with respect to the main blade. A novel piezo-induced bending ‐torsion coupled actuator beam, located spanwise in the hollow midcell of the main rotor blade, is used to actuate the blade tip. When the blade tip is locked to the main blade, the actuator beam twists the entire blade. A Mach scale rotor with a 1.542 m diameter was hover tested, open loop, to evaluate the control authority for vibration reduction. A nonrotating tip-twist amplitude of 0.78 deg was achieved (below resonance, 150 V rms ). Analysis indicates that no signie cant twist actuation degradation is expected at full rotor speed. In 2000-rpm hover (tip Mach 0.47 ), at 8-deg collective, and for a single blade actuation of 150 V rms at 1, 2, and 3 per revolution, respectively, the measured oscillatory thrust coefe cients are 1 :4 £ 10 3 , 0:55 £ 10 3 , and 0:7 £ 10 3 . The corresponding e nite element model estimated blade twist amplitudes are 0.8, 1.0, and 1.9 deg. Good correlation of the predicted and measured rotor thrust was achieved up to 3 per revolution. The hover test demonstrates the potential of the active twist rotor system using an internal actuation beam and warrants further research for a dedicated next-generation model-scale design and full-scale feasibility study.

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