Advanced sensing strategies for the active control of vibration and structural radiation

The active control of sound and vibration of extended systems and structures requires a thorough understanding of the physical mechanisms involved in the generation and propagation of the disturbance. For the active control system to be physically compact and efficient in globally reducing the disturbance, the secondary sources and error sensors usually need to be located dose to the primary source (possibly integrated on the structure in the case of active structural acoustic control), On the other hand, minimizing the acoustic near-field or structural response does not guarantee that the far-field, propagating disturbance is minimized accordingly. This then poses the problem of the active control strategy, definition of the cost function and type of error sensors to be used in the control system. In this review paper, advanced sensing strategies that address this generic problem are presented in the case of several vibration/acoustic systems, and associated advantages and limitations are discussed. These include structural intensity sensing in the active control of beam vibration, near-field acoustic intensity sensing in the active control of free space radiation from extended sources, and structural volume velocity and discrete strain sensing in the active structural acoustic control. (C) 2001 Institute of Noise Control Engineering.