Simultaneous position and displacement sensing using two　bre Bragg grating sensors

摘要

Over the years, many shape sensing methods have been developed with technologies including optical bre, PZTand fringe projection. Among them, optical bres have gained a lot of attention due to their unobtrusive naturewhen either surface mounted or embedded in the structure. Optical bre Bragg gratings (FBG) are currentlyemployed for structural health monitoring in civil and aerospace systems and their shape sensing capabilitieshave been previously reported. In this paper, we propose a novel bre optic based shape sensor of an isotropiccantilever beam based on the principles of interferometry and FBG sensing. The method described in this paperuses a standard single core single-mode optical bre and the least number of sensors to estimate the shape,making it comparatively an inexpensive sensing method. On displacing the beam with an unknown magnitudeand at an unknown location along the beam, we are able to demonstrate that we can measure the shape of thedisplaced beam and the magnitude and location of the force applied. The analysis involves using a calibrationmethod and an iterative calculation to measure the two unknowns. An analytical model based on the knownbeam theories was used to assess the accuracy of the measurements. The preliminary analysis yielded an accuracyof ±1 mm and ±50 mm for the displacement and location, respectively.