Measurement of morphing wing deflection by a cross-coherence fiber optic interferometric technique

Abstract

A fiber-optic interferometric technique aimed at measuring the deflection of aircrafts' morphing wings is presented. The wing deflection induces a strain in the sensing fiber optic coils that are firmly fixed onto the wing. A change of the phase angle of the light propagating through the fiber is measured by an 'all-in-fiber' Michelson interferometer based on a 3×3 fiber-optic coupler. Two light sources of different coherence lengths and wavelengths are simultaneously used to ensure a wide measurement range and high accuracy. A new technique for determination of the zero deflection point using the cross-correlation of the two interferograms is proposed. The experiments performed on a specimen made of a carbon-fiber-reinforced plastic honeycomb structure demonstrated a relative uncertainty <1% and a precision of about 0.06°in the measuring range ±5°of the morphing wing deflection.

Recent researches on morphing aircraft technologies in Japan and other countries

“…Both CFD and wind tunnel test results showed an increase of laminar flow region with a design optimization delaying the transition location. Tomić et al presented a fiber-optic interferometric technique for a measurement of deflections of an aircraft's morphing wing (Tomić et al, 2018). The proposed technique achieved an accurate deflection measurement in their experiments.…”

Fibre-optic measurement of strain and shape on a helicopter rotor blade during a ground run: 2. Measurement of shape

“…Shape conveys information about a structure that is easily visualized and interpreted, and its measurement [1,2] has applications that span medicine [3], robotics [4], aerospace [5] and civil engineering [6]. The capability for shape measurement could also be a key enabling technique for future advances, for example for shape morphing aerospace structures [7][8][9]. The shape of an object may be deduced indirectly from strain measurements made at strategic locations, processed using straindeformation retrieval methods [10,11].…”