Real-time deformed shape estimation of a wind turbine blade using distributed fiber Bragg grating sensors

Abstract

This study presents a real-time shape estimation technique based on measured strains at multiple points. For the measurement of multiple strain data, fiber Bragg grating (FBG) sensors are used because of their excellent strain accuracy and multiplexing capability with minimal mechanical loading. The displacement-strain relation of a blade structure is systematically formulated using a finite element model, where the locations and directions of the FBG sensors are taken into account. Because there could be unavoidable modeling uncertainties, the operational modal analysis is also introduced to construct a displacement-strain transformation matrix. In the laboratory, the developed technique is applied to a wind turbine blade in which the FBG sensors are embedded. The blade deformation is reconstructed using the proposed method when the blade is subjected to static and vibratory loadings. At the same time, a stereo pattern recognition system consisting of eight cameras directly captures the deformation of the blade to validate the estimated blade shapes. For various loading cases, the estimated results of the blade shape agree very well with the reference measurements.