Chapter 1 Modal Analysis on a Wind Turbine Blade Based on Wind Tunnel Experiments L. G. Trujillo-Franco, H. F. Abundis-Fong, R. Campos-Amezcua, and R. Gomez-Martinez Abstract This paper describes the evaluation of a time domain algebraic modal parameters identification methodology. This methodology is applied on a wind turbine blade. The natural frequencies and modal damping factors associated to the blade are estimated from measurements of velocities. A comparison with usual modal identification techniques is performed in order to evaluate and establish the main contributions of the proposed approach. The modal parameter identification algorithms are implemented to run (but not limited to) on a Matlab platform running in a PC using measurements obtained from a laser vibrometer and the corresponding data acquisition system. The results show the performance and parametric estimation of the proposed algebraic identification approach. Keywords Experimental modal analysis · Operational modal analysis · Wind tunnel experiments 1.1 Introduction The field of structural dynamics has a set of applications that is in a constant expansion due to the advances in mechanical design procedures and testing protocols and structural health monitoring schemes applied to engineering structures involved in the considerably diverse universe of mechatronic systems, for example the specific case of wind turbines that involve supporting structures and blades that are subjected to harmonic excitation product of their natural interaction with the air in normal or nominal operating conditions. In this context, modal analysis and modal testing are powerful technological tools with a solid theoretical and experimental background [1–4] widely applied to the validation of the mathematical models of the dynamic response of the mechanical systems. In both of the two main presentations of modal analysis: experimental modal analysis (EMA) and operational modal analysis (OMA) the mechanical design engineer have a reliable source of information about the dynamic nature of the system or constituting part of it, like the case of the blades, a vital part of a wind turbine for an energy generation system. In this work, we present experimental results of a modal analysis procedure performed on a wind turbine blade designed for small power applications. The test was performed in the two common formats: experimental modal analysis at laboratory conditions and operational modal analysis in real life-like operational conditions, the latter were simulated by wind tunnel experiments with turbulence generated by using a fixed pattern grid. We use velocity measurements in the analysis to determine the natural frequencies and modal damping factors. L. G. Trujillo-Franco ( ) Licenciatura en ingeniería mecánica automotriz, Universidad Politécnica de Pachuca, Zempoala, Hidalgo, México e-mail: luis.trujillo@upp.edu.mx H. F. Abundis-Fong División de Estudios de Posgrado e Investigación, Tecnológico Nacional de México/I.T. Pachuca, Pachuca de Soto, Hidalgo, Mexico e-mail: hugo.af@pachuca.tecnm.mx R. Campos-Amezcua Tecnológico Nacional de México/Centro Nacional de Investigación y Desarrollo Tecnológico, Interior Internado Palmira S/N, Col. Palmira, Cuernavaca 62490, Mexico e-mail: rafael.ca@cenidet.tecnm.mx R. Gomez-Martinez Instituto de Ingeniería, Universidad Nacional Autónoma de México, Mexico City, CDMX, Mexico e-mail: RGomezM@iingen.unam.mx © The Society for Experimental Mechanics, Inc. 2021 B. Dilworth (ed.), Topics in Modal Analysis & Testing, Volume 8, Conference Proceedings of the Society for Experimental Mechanics Series, https://doi.org/10.1007/978-3-030-47717-2_1 1
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