Smart panel with an array of decentralised control systems for active structural acoustic control

Bianchi, Emanuele (2003) Smart panel with an array of decentralised control systems for active structural acoustic control. University of Southampton, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

This thesis presents the results of a theoretical and experimental study of active sound transmission through a smart panel. The system studied consists of a thin aluminium panel with an embedded 4x4 array of square piezoceramic actuators. The sensing system consists of a 4x4 array of accelerometers positioned above the centres of the sixteen piezoceramic patches on the other side of the panel. Each of the sixteen sensor-actuator pairs is arranged to implement local (decentralised) velocity feedback control. The smart panel is mounted on the top of a rectangular cavity with rigid walls in order to measure the sound radiation from the panel when excited by either a primary acoustic source (a loudspeaker) within the cavity or a primary structural source (a shaker) acting directly on the panel.

This thesis can be divided into three parts. The first part contains a theoretical and numerical study of the smart panel with sixteen decentralised control units. A fully coupled model of the smart panel mounted on the cavity has been formulated, from which the total kinetic energy and sound radiation can be derived as a function of the feedback gain implemented in the sixteen decentralised control units. The stiffness and mass effects of the piezoelectric actuators, and the mass effects and local dynamics of the accelerometers have been taken into account in the model.

The second part describes the detailed design and implementation of the sixteen decentralised control units. The behaviour of the sensor-actuator pairs has been studied and their open loop frequency response functions are analysed, with particular regard to the effects of the sensor-actuator local dynamics and of the piezo patch dimensions. The implementation of velocity feedback on a single control unit is first described and its stability discussed. The implementation of the complete system with sixteen individual control loops has then been discussed and the stability of the multi-channel system has been analysed. In the third part, the control effectiveness of the smart panel has been assessed experimentally. The reduction of the panel's total sound power radiation has been measured in an anechoic chamber when excited either by the acoustic field produced by a loudspeaker placed in the Perspex box or directly by a point force generated with a shaker. The variation of the vibratory field over the panel surface has also been measured with a laser vibrometer to describe the action of the smart panel and compare it with the predictions of the theoretical model.

Text

895417.pdf - Version of Record

Available under License University of Southampton Thesis Licence.

Download (14MB)