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Beamforming is widely used in structural health monitoring (SHM) systems for impact or damage localization. Beamforming directionality is achieved by the constructive interference of sensor wavefronts, which results in a significant amplification of the measured signal in a particular direction. For beamforming applications, the cost per sensor is typically significant, because of the sensor itself, and the associated electronics. Therefore, in order to minimize the cost of SHM in practice, it is highly desirable to reduce the number of sensors. Beamforming with an array of sensors requires an advanced signal processing technique to detect the direction-of-arrival (DOA). In addition, by deploying more sensors, better detection accuracy can be achieved. In this paper, the non-equidistant linear sensor array is proposed, to obtain lower costs while guaranteeing reasonable detection accuracy. In addition, the proposed sensor deployment scheme is able to reduce the effects of "spatial aliasing," which phenomenon is typically encountered in the equidistant linear sensor array layout. To validate the performance of the proposed non-equidistant linear array technique in SHM applications, several finite element models (FEM) simulation and experimental investigations are carried out. Different sensor array layouts are also compared to optimize the performance of the non-equidistant linear array. [ABSTRACT FROM AUTHOR]

This study proposes a new sensor cluster configuration for localizing an acoustic source in a plate using uniform linear array beamforming and T-shaped sensor clusters. This technique requires neither the properties of the plate material nor a dense array of sensors to find the direction of arrival of the acoustic source. It functions by placing four sensors in a cluster in the shape of the letter "'T" over a small region of the plate. Uniform linear array beamforming-based source localization is carried out by the constructive interference of different sensor signals. However, this approach has the disadvantage of a very low resolution when the direction of arrival approaches certain values. The L-shaped sensor clusters use the information from the time difference of arrival between the sensors to estimate the direction of arrival, which has a high resolution in all directions except for the direction that is very close to vertical to the cluster. In this study, we numerically and experimentally demonstrate that the proposed T-shaped sensor cluster can accurately localize the acoustic source with no blind area. We also detail its superior performance compared to both uniform linear array beamforming and L-shaped clusters. In the experimental investigation, the maximum deviation of impact source localization was reduced significantly, from 54° to 4° for an aluminum plate, and from 42° to 3° for a composite plate. Furthermore, this novel combined sensor array layout requires only a few sensors, which can significantly reduce the cost of structural health monitoring practice. [ABSTRACT FROM AUTHOR]