Active structural-acoustic control of a rocket fairing using proof-mass actuators

The feasibility of using proof-mass actuators to control noise transmission actively into a small rocket fairing, given practical constraints on actuator power and mass, is explored. The modal-interaction approach was used to develop a fully coupled structural-acoustic state-space model that relates the out-of-plane structural modal velocities to the spatially varying pressure response in the cavity, The dynamics of the proof-mass actuators were included in the structural-acoustic model. The modal-interaction approach also allowed the decomposition of the acoustic response into radiation modes, which proved essential for determining the optimal locations for sensors and actuators, Numerical simulations using linear quadratic Gaussian controllers with collocated proof-mass actuators and displacement sensors demonstrated approximately 4.2 dB of attenuation over the 300-Hz bandwidth for the given actuator constraints. However, this was only slightly more than the attenuation provided by the passive effects of the proof-mass actuators, which was approximately 3.5 dB.