Active damage detection method using support vector machine and amplitude modulation

A structural health monitoring (SHM) system for the purpose of maintenance cost reduction or performance guarantee of civil, mechanical and aerospace systems is proposed. The proposed system utilizes an active sensing diagnostic technique to predict the location of structure damage with a limited number of PZT elements and some vibrators if necessary. As PZT elements are inexpensive, small in size, and function as sensors and actuators, it is possible to integrate them into a structural component without reducing structural performance. In this study, an active sensing diagnostic technique using PZT elements is proposed to characterize damage in plates. Built-in PZTs working as Lamb wave emitters and receivers are used to predict damage by comparing differences of Lamb wave signals recorded before and after damage. Such differences are due to the change of the physical parameters relevant to damage in the structure. Amplitude modulation is used in this paper by actuating PZTs with different driving signals to effectively extract damage features. Modulated signals are processed to form feature vectors for support vector machines to estimate damage automatically.