Patent ID: 8521444

Claim:
A method of detecting damage in a structure, comprising: for a structural health monitoring system having sensing elements coupled to the structure, collecting data from the sensing elements, the data corresponding to stress waves in the structure detected by the sensing elements; determining an estimate for a density function at least partially according to the data collected from the sensing elements; determining an estimate for an expectation maximization parameter (E) from the estimate for the density function; revising the estimate for the density function at least partially according to E; repeating, in order, the determining an estimate for a density function, the determining an estimate for an expectation maximization parameter, and the revising so as to determine a converged estimate for the density function; receiving previous data corresponding to previous stress waves propagated through the structure; determining Mahalanobis distances from the converged estimate for the density function and the previous data; determining Euclidian distances from the converged estimate for the density function and the previous data; determining a maximum value of the Euclidian distances; determining a damage index (DI) based on the Euclidian distances and the maximum value of the Euclidian distances; and determining the presence of damage in the structure at least partially according to DI and the Mahalanobis distances; wherein determining the presence of damage in the structure is based on whether DI exceeds a first predetermined threshold value, and whether a change in a Mahalanobis distance from one or more previously determined Mahalanobis distances exceeds a second predetermined threshold value.