Peaks Over Threshold–based detector design for structural health monitoring: Application to aerospace structuresReport as inadecuate

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1 PIMM - Procédés et Ingénierie en Mécanique et Matériaux Paris 2 LM2S - Laboratoire Modélisation et Sûreté des Systèmes

Abstract : Structural health monitoring offers new approaches to interrogate the integrity of complex structures. The structuralhealth monitoring process classically relies on four sequential steps: damage detection, localization, classification, andquantification. The most critical step of such process is the damage detection step since it is the first one and becauseperformances of the following steps depend on it. A common method to design such a detector consists of relying on astatistical characterization of the damage indexes available in the healthy behavior of the structure. On the basis of thisinformation, a decision threshold can then be computed in order to achieve a desired probability of false alarm. To determinethe decision threshold corresponding to such desired probability of false alarm, the approach considered here isbased on a model of the tail of the damage indexes distribution built using the Peaks Over Threshold method extractedfrom the extreme value theory. This approach of tail distribution estimation is interesting since it is not necessary toknow the whole distribution of the damage indexes to develop a detector, but only its tail. This methodology is appliedhere in the context of a composite aircraft nacelle where desired probability of false alarm is typically between 1024and 1029 for different configurations of learning sample size and probability of false alarm and is compared to a moreclassical one which consists of modeling the entire damage indexes distribution by means of Parzen windows. Resultsshow that given a set of data in the healthy state, the effective probability of false alarm obtained using the Peaks OverThreshold method is closer to the desired probability of false alarm than the one obtained using the Parzen-windowmethod, which appears to be more conservative.

Keywords : Damage detection extreme value theory Peaks Over Threshold generalized Pareto distribution Lamb waves composite structures

Author: Marc Rebillat - Ouadie Hmad - Farid Kadri - Nazih Mechbal -



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