Abstract
In this paper, Rayleigh backscattering sensors (RBS) are used to realize shape sensing of beam-like structures. Compared to conventional shape sensing systems based on fibre Bragg grating (FBG) sensors, RBS are capable of continuous lateral sensing. Compared to other types of distributed fibre optic sensors (FOS), RBS have a higher spatial resolution. First, the RBS’s strain sensing accuracy is validated by an experiment comparing it with strain gauge response. After that, two shape sensing algorithms (the coordinate transformation method (CTM) and the strain-deflection equation method (SDEM)) based on the distributed FOS’ input strain data are derived. The algorithms are then optimized according to the distributed FOS’ features, to make it applicable to complex and/or combine loading situations while maintaining high reliability in case of sensing part malfunction. Numerical simulations are carried out to validate the algorithms’ accuracy and compare their accuracy. The simulation shows that compared to the FBG-based system, the RBS system has a better performance in configuring the shape when the structure is under complex loading. Finally, a validation experiment is conducted in which the RBS-based shape sensing system is used to configure the shape of a composite cantilever-beam-like specimen under concentrated loading. The result is then compared with the optical camera-measured shape. The experimental results show that both shape sensing algorithms predict the shape with high accuracy comparable with the optical camera result.
Highlights
The usage of composites in air-foil and wind turbine blades has dramatically reduced the weight of these structures and, increased their deflections largely
The simulation shows that compared to the fibre Bragg grating (FBG)-based system, the Rayleigh backscattering sensors (RBS) system has a better performance in configuring the shape when the structure is under complex loading
The simulated results show that when applying the strain deflection equation method (SDEM) algorithm with the FBG sensor in a real air-foil loading, the error can go up to around 30% compared to the theoretical solution
Summary
The usage of composites in air-foil and wind turbine blades has dramatically reduced the weight of these structures and, increased their deflections largely. Various sensing technologies exist for monitoring the geometrical shape of a wing structure, such as the strain sheet measuring method, the vision measurement method, the photo elastic method, the laser scan measuring method and the three-coordinate measuring method [2,3,4,5,6], their instalments require enormous space. They are only suitable for the ground testing of the wing shape and not applicable for the real-time monitoring of the aerodynamic shape of a morphing wing during flight [7]. Fibre optic sensors (FOS), due to their advantages such as immunity from electromagnetic interference, low weight and small size, which can be largely embedded in airplanes to form a sensor network, are generally viewed as the technology with the highest potential for the continuous
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