FEASIBILITY OF FEEDBACK CONTROL OF TRANSMITTED SOUND INTO A LAUNCH VEHICLE FAIRING USING STRUCTURAL SENSING AND PROOF MASS ACTUATORS

This work explores the feasibility of using proof mass actuators (PMA) to control launch vehicle noise transmission. Geometric and structural properties of a fairmg being designed for the Minotaur launch vehicle are used in a fully coupled structural/acoustic model to evaluate the feasibility of proof mass actuators and feedback control in reducing noise transmission. The use of the modal-interaction approach leads to a MIMO (multi-input-multi-output) radiation state-space model that relates the out-of-plane structural modal velocity inputs to the spatially varying pressure in the cavity. The modalinteraction approach also allows the decomposition of the acoustic response into radiation modes, which proved essential for the efftcient location of sensors and actuators. A fully coupled structural/acoustic state space model with integrated PMA’s as control actuators was derived that showed good agreement with the direct FEM solution of the fully coupled problem. The optimal control simulation showed that the noise reduction achieved using PMA’s in the launch vehicle problem was not significant enough to justify the added complexity of the active control system.