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An impact source locating system using fiber Bragg grating rosette array

Some structures are vulnerable to localized internal damages incurred by impact of small objects. Previous work showed that the whereabouts of an impact event on a 0.8m×0.8m square aluminum plate can be located by analyzing the differential time-of-flight among signals picked up by a four-FBG (fiber Bragg grating) array. However, good location accuracy was obtained only when the impact position was well within the envelop of the sensor arrays. In the current work, it will be demonstrated when an impact occurs within ±60o on either sides of the FBG axis, the signal is strong and the time-of-flight can be measured accurately so that an impact can be located accurately to better than 1 cm. Beyond that range, the signal became heavily attenuated and masked by noises and the location errors could be larger than 20 cm. To investigate the possible directions for improvement on the system accuracy, FBG rosettes with two mutually perpendicular FBGs are used to replace single FBGs to alleviate the angular sensitivity problem. It was shown that with the rosette array, good location accuracy can virtually be extended to all over the plate.