Compressive Sensing and Sparse Signal Representation of Ultrasonic Signals for Structural Health Monitoring Applications
Alessandro Perelli, University of Bologna, Italy

Seminar • 12 March 2014 • BM 4.233

Abstract
Passive source localization in dispersive systems with sparse sensors array represent a fundamental issue in applications such as seismic, radar, underwater acoustics, wireless transmission. In this presentation a new in-situ Structural Health Monitoring (SHM) system based on wave propagation approach able to assess damages and to identify the location of acoustic emission (AE) sources due to impacts is shown. When we deal with such channels, it is necessary to compensate the frequency dependent propagation and then the localization is achieved from time-difference-of-arrival (TDOA) between sensor outputs. In this presentation a novel impact localization algorithm based on the frequency warping unitary operator applied to wavelet multiresolution analysis will be displayed. Unitary frequency warped representation is important to analyze class of signal covariant to group delay shift as those propagating through frequency-dependent channels. Finally a compressive acquisition scheme of Lamb wave signal for damage detection will be presented. Compressive Sensing has emerged as a potentially viable technique for the efficient acquisition that exploits the sparse representation of dispersive ultrasonic guided waves in the frequency warped basis. The framework is applied to lower the sampling frequency and to enhance defect localization performances of Lamb wave inspection systems. The approach is based on the inverse Warped Frequency Transform as the sparsifying basis for the Compressive Sensing acquisition and to compensate the dispersive behaviour of Lamb waves.