Design of an All-Digital Impact Monitoring System for Large-Scale Composite Structures

In order to ensure the safety of large-scale composite structures of aircraft as well as to reduce the cost and time of maintenance, the impact monitoring on-line is urgently needed. A piezoelectric transducer (PZT)-based wireless digital monitor is developed to record the history and impact area of impact events on-line. Although the digital monitor is compactness and high efficiency for impact monitoring, the output caused by environmental noises from PZTs will lead to the failure of impact area localization and the weight, power consumption and data transmission of the digital monitor have to be optimized. In this paper, an impact area localization method combined with a digital sequences based de-noising method is studied. In the impact area localization method, a characteristic digital sequence identification method is proposed to eliminate digital rising edge caused by the noises in the digital sequences and estimate the impact area by identifying the first three digital rising edges in the de-noised digital sequences. Based on this method, a small size, low power consumption, and online all-digital impact monitoring system (ADIMS) is designed. Three experiments on noise simulation, impact monitoring function and continuous impact monitoring are performed, respectively, to validate the ADIMS. The validating results show that the accuracy rate of the impact area localization method is approximately 86% in the situation of simulated strong noises and the ADIMS can record continuous impact event when the interval time of two adjacent impacts is equal or longer than 2.0 × 10^-3 s .