Decentralized complex envelope controller for ASAC by virtual mechanical impedances

The problem of Active Structural Acoustic Control (ASAC) is to attenuate the radiated sound power by energy injection using structural actuators to modify deflection shapes. Collocated and dual actuator-sensor pairs allow the feedback problem to be formulated as the implementation of virtual mechanical impedances. The approach is based on a two-step process: (1) the virtual impedance is derived from measurements of the primary sound and transfer functions; (2) the centralized or decentralized complex envelope controller is designed to ensure stable feedback loops. Experiments are performed on a curved composite aircraft panel comprising a window. The proposed approach leads to the implementation of active virtual impedances and unstable compensators. An increased kinetic energy of the panel is observed, thus demonstrating that the control inputs needs to provide vibrational energy to achieve sound power reduction (2.7dB).