A comprehensive approach for the optimal control of tiltrotor cabin noise through actively-driven piezoelectric actuators

This paper deals with the abatement of the tonal noise generated by the propulsive system inside the fuselage of a mid-range tiltrotor aircraft. The problem is basically multidisciplinary, involving interactions among exterior noise field, elastic fuselage dynamics, interior acoustics and control system. A stiffened fuselage, with piezoelectric patches embedded into the structure, is supposed to be impinged by the aeroacoustic field generated by propellers and forced by the wing/pylon/proprotor vibratory loads at the wing-fuselage attachment. An optimal LQR cyclic control formulation, coupled with a genetic optimization algorithm (GA), is applied to synthesize the control law driving the smart actuators so as to alleviate cabin noise. The aeroacoustoelastic model considered in the control problem is obtained by combining a modal approach for the description of the acoustic field within the cabin, the elastic displacements of the smart shell and the wing/pylon/proprotor system, with a Boundary Element Method (BEM) for the prediction of exterior pressure disturbances. Numerical results examine the effectiveness and robustness of the proposed active control strategy when synthesized through the proposed LQR/GA algorithms.