Active Twist Rotor Controller Identification for Blade-Vortex Interaction Noise Alleviation

Several sources of acoustic annoyance may be detected in a rotorcraft in operating conditions. The current research pays particular attention to the noise generated aerodynamically by the main rotor because of blade-vortex interactions (BVIs). This paper deals with the reduction of helicopter BVI noise by application of the active twist rotor concept (ATR), that exploits smart materials for twisting rotor blades through higher harmonic torque loads. An optimal, multi-cyclic, control approach is applied to identify the control law driving the ATR actuation during the occurrence of strongest BVI events. Numerical predictions are obtained through a computational tool that is able to predict the aeroelastic response of the rotor blades, as well as to evaluate the emitted noise in arbitrary steady flight conditions. The approach for the control law identification is described, and numerical results concerning the alleviation of the noise field emitted by the controlled rotor are presented.

[1]  James D. Baeder,et al.  Blade-vortex interaction noise reduction with active twist smart rotor technology , 2001 .

[2]  Johannes Riemenschneider,et al.  Development of active twist rotors at the German Aerospace Center (DLR) , 2011 .

[3]  Yung H. Yu,et al.  Reduction of helicopter blade-vortex interaction noise by active rotor control technology , 1997 .

[4]  Inderjit Chopra,et al.  Review of State of Art of Smart Structures and Integrated Systems , 2002 .

[5]  Inderjit Chopra,et al.  Status of Application of Smart Structures Technology to Rotorcraft Systems , 2000 .

[6]  Jianhua Zhang,et al.  Active-Passive Hybrid Optimization of Rotor Blades With Trailing Edge Flaps , 2000 .

[7]  Massimo Gennaretti,et al.  A Unified Boundary Integral Methodology for Aerodynamics and Aeroacoustics of Rotors , 1997 .

[8]  Earl H. Dowell,et al.  Nonlinear equations of motion for the elastic bending and torsion of twisted nonuniform rotor blades , 1974 .

[9]  Giovanni Bernardini,et al.  Aeroelastic response of helicopter rotors using a 3D unsteady aerodynamic solver , 2006, The Aeronautical Journal (1968).

[10]  Giovanni Bernardini,et al.  Novel Boundary Integral Formulation for Blade-Vortex Interaction Aerodynamics of Helicopter Rotors , 2007 .

[11]  Johannes Riemenschneider,et al.  OVERVIEW OF THE COMMON DLR/ONERA PROJECT "ACTIVE TWIST BLADE" (ATB) , 2004 .

[12]  D. L. Hawkings,et al.  Sound generation by turbulence and surfaces in arbitrary motion , 1969, Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences.

[13]  Yung H. Yu,et al.  Rotor blade–vortex interaction noise , 2000 .

[14]  J Mayo Greenberg,et al.  Airfoil in sinusoidal motion in a pulsating stream , 1947 .

[15]  Giovanni Bernardini,et al.  Prediction of Tiltrotor Vibratory Loads with Inclusion of Wing­-Proprotor Aerodynamic Interaction , 2010 .

[16]  Peretz P. Friedmann,et al.  Simultaneous Vibration and Noise Reduction in Rotorcraft Using Aeroelastic Simulation , 2004 .

[17]  Giovanni Bernardini,et al.  Analysis of helicopter vibratory hub loads alleviation by cyclic trailing-edge blade flap actuation , 2009, The Aeronautical Journal (1968).