DISTRIBUTED SENSORS AS SPATIAL FILTERS IN ACTIVE STRUCTURAL CONTROL

The response of a spatially continuous distributed sensor mounted on a vibrating structure is examined in this paper. The response of the distributed sensor to structural deformations is interpreted as a filtered version of the response of a point sensor to the same deformations, where the wavenumber filtering characteristics are determined by the spatial weighting pattern of the distributed sensor. When the distributed sensor is well removed from structural boundaries, discontinuities or forcing locations, the sensor dynamics are given by the Fourier transform of the sensor’s spatial weighting. This relationship can be utilized to design distributed sensors having specified sensor dynamics. In this paper, the design process is illustrated by means of the design of a distributed sensor such that its sensor dynamics feature high order gain roll-off without phase lag. The spatial filtering of the resulting sinc function sensor is verified computationally and, through the use of piezoelectric polymer film, experimentally. The situation in which the distributed sensor is not well removed from a forcing location is also considered. The sensor dynamics are then determined by the coherent sum of several transforms of the sensor’s spatial weighting. It is shown that the response of the sinc function sensor to point actuation collapses, at high frequencies, to an attenuated version of the “backbone” of the point sensor’s response, i.e., the high frequency structural resonances are not observable through this distributed sensor. © 1994 Academic Press Limited.