Implications of using colocated strain-based transducers for output activestructural acoustic control

Piezoceramic transducers have become popular elements of smart structures t hat are used for active vibration control and active structural acoustic co ntrol. A spatial differentiation is performed by the piezoceramic transduce rs since they couple into the strain field of the piezostructure. This diff erentiation causes higher-frequency modes to be emphasized more heavily, ca using the effective compliance of the structure as seen by the piezoceramic transducer to increase with frequency. This nonuniform compliance has sign ificant impact on the performance that can be achieved through colocated di rect rate feedback control. It is shown that the rectangular piezoceramic t ransducer is a low-pass wave number filter with a cutoff frequency inversel y proportional to the aperture size. Thus DRFB performance can be greatly i mproved simply by making the size of the piezoceramic transducer large rela tive to the size of the structure. The resulting increase in coupling to th e lower-frequency modes, which are generally targeted by the control system , results in a much reduced control effort. In the event that a large apert ure is not practical, it is shown that dynamic compensation can be used to obtain good performance at the cost of much increased computational complex ity. Analytical open and closed loop results for an acoustically radiating simply supported plate piezostructure are presented. (C) 1999 Acoustical So ciety of America. [S0001-4966(99)01908-6].