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A new deformation monitoring method for a flexible variable camber wing based on fiber Bragg grating sensors

This work presented an indirect method to monitor the deformation of the flexible variable camber wing using attached fiber Bragg gratings. To measure the transverse strains resulting from deformation of flexible variable camber wing, two groups of fiber Bragg grating sensors were attached on both upper and lower surfaces of the metal sheet, which was used to replace the traditional hinges. When the flexible variable camber wing was actuated by the lower surface’s pneumatic artificial muscle actuators, the upper surface would undergo the tensile deformation. A redshift could be observed from the reflective wavelength of the fiber Bragg grating sensors located on the upper surface. On the contrary, a blueshift could also be observed from the lower surface due to the compressive deformation. The comparison of the results with those obtained from strain gauges demonstrated the reliability of fiber Bragg grating sensors. Then, the vertical displacement and deflection angle of the flexible variable camber wing were obtained through the von Karman strain–displacement relation. A finite element model of the flexible variable camber wing was developed to simulate the variation of strain and displacement, which is caused by deformation of the metal sheet. A good agreement could be seen from the vertical displacements among the fiber Bragg grating strain sensors, finite element model, and direct measurements with laser range-finders.