7th ECCOMAS Thematic Conference on Smart Structures and Materials SMART 2015 A.L. Araújo, C.A. Mota Soares, et al. (Editors) © IDMEC 2015 Damage detection in structures using robust baseline models Jhonatan Camacho-Navarro *† , Magda Ruiz * , Rodolfo Villamizar † , Luis Mujica * , Fernando Martínez †† * Department of Applied Mathematics III, Escola Universitària d’Enginyeria Tècnica Industrial deBarcelona (EUETIB), Universitat Politécnica de Catalunya (UPC) BARCELONATECH, Comte d’Urgell 187, E-08036, Barcelona, Spain jhonatan.camacho@estudiant.upc.edu, magda.ruiz@upc.edu, luis.eduardo.mujica@upc.edu, † Escuela de Ingenierías Eléctrica, Electrónica y de Telecomunicaciones (E3T), Universidad Industrial de Santander (UIS). Grupo de Control Electrónica Modelado y Simulación (CEMOS). Santander, Colombia. rovillam@uis.edu.co †† Department of sensors, Ikerlan Research Center, Spains fmartinez@ikerlan.es Key words: Piezo-diagnostics, principal component analysis, time feature extraction, pipe leak damage detection, crack detection in a laboratory tower. Summary: This work deals with a previously proposed piezo-diagnostic methodology based on principal component analysis for structural damage detection. Previous works have demonstrated the effectiveness of baseline models to distinguish between structural damage and undamaged conditions, however, its robustness and reproducibility depends on a proper estimation of the principal components from undamaged data matrix measurements. Principal components are highly sensitive to the algorithm parameters used to compute the singular value decomposition, on the number of experiments collected for building the baseline model and on atypical measurements. In this work, the above conditions are studied by including a pre-processing state using time feature extraction in order to solve the ill-conditioned statistical problem due to the low ratio between undamaged cases and time piezo-electrical samples used for building the baseline model. In addition, a comparison between two methods (Proper Orthogonal Decomposition Vs NIPALS) used to estimate the principal components is done. Average of several experiments is computed to deal with atypical data cases and experimental results are obtained from two structures: i.) a carbon steel pipe section and ii.) a laboratory tower that mimics a wind turbine. Finally, damages are conditioned in order to produce leaks in the pipe section and a crack in one element of the laboratory tower. 1 INTRODUCTION The high sensitivity of the guided-wave ultrasonic technique has been an advantage for structural health monitoring applications [1]. Guided waves have been extensively studied for damage detection and characterization in a wide range of industrial applications, including transportation and civil engineering [2]. In this sense, it has been demonstrated that guided waves can be easily generated by using Lead Zirconate Titanate piezoelectric devices (PZT).