Spatio-temporal filter for structural health monitoring

This paper considers the use of combined spatial and temporal filtering to improve the quality of a structural health monitoring (SHM) damage estimate. Many SHM systems produce two-dimensional (2-D) array data that contains structure damage estimate, which is distorted by noise from sensor sources, changing environmental conditions, and other inspection factors. We describe a filtering architecture for processing a sequence of damage estimates generated by a SHM system. We show that the approach can reduce the noise variability and enhance the damage estimate. The filter is designed as an infinite impulse response (IIR) filter in time and space and is predicated on an understanding of the point spread function for the ultrasonic interrogation. We discuss the basis for using a spatially invariant blurring operator to represent this interrogation process as well as the design of the filter. The filtering is performed in space by rejecting component of the input signal outside of the spatial frequency pass band. The filtering is also performed in time by rejecting the components of the signal outside of the dynamical pass band