Débruitage des signaux par approche EMD : Multi-EMDSG

Le but de ce travail est de mettre en œuvre la Décomposition Modale Empirique (EMD) [1] dans une problématique de débruitage des signaux via une nouvelle approche appelée Multi-EMDSG, combinant l'EMD et le filtre polynomial de Savitzky-Golay (SG) [2]. Pour cela, on exploite les caractéristiques des modes empiriques issus de l'EMD pour étudier une nouvelle approche de débruitage des signaux. On montre, sur la base de simulations intensives, que l'application itérative du même processus EMDSG proposé dans [3]: (EMD ⇒ débruitage par filtre de Savitzky-Golay (SG) ⇒ reconstruction du signal) permet d'améliorer sensiblement les résultats du débruitage. Ainsi, l'EMD associée à un filtrage et appliquée d'une manière itérative permet d'améliorer le Rapport Signal à Bruit (RSB) comparé à l'approche ondelettes. L'influence de certains paramètres sont étudiés (taille de la fenêtre de filtrage...) aussi bien pour l'approche EMDSG que pour son extension Multi-EMDSG. Enfin, l'approche Multi-EMDSG est comparée aux approches EMDSG et ondelettes

Damage localization by statistical evaluation of signal-processed mode shapes

Due to their inherent ability to provide structural information on a local level, mode shapes and their derivatives are utilized extensively for structural damage identification. Typically, more or less advanced mathematical methods are implemented to identify damage-induced discontinuities in the spatial mode shape signals, hereby potentially facilitating damage detection and/or localization. However, by being based on distinguishing damage-induced discontinuities from other signal irregularities, an intrinsic deficiency in these methods is the high sensitivity towards measurement noise. The present article introduces a damage localization method which, compared to the conventional mode shape-based methods, has greatly enhanced robustness towards measurement noise. The method is based on signal processing of spatial mode shapes by means of continuous wavelet transformation (CWT) and subsequent application of a generalized discrete Teager-Kaiser energy operator (GDTKEO) to identify damage-induced mode shape discontinuities. In order to evaluate whether the identified discontinuities are in fact damage-induced, outlier analysis of principal components of the signal-processed mode shapes is conducted on the basis of T2-statistics. The proposed method is demonstrated in the context of analytical work with a free-vibrating Euler-Bernoulli beam under noisy conditions