Design and analysis of large strain fiber Bragg grating sensor for straightness monitoring of scraper conveyor in coal mine

To address the issues of low monitoring accuracy and even breakage of optical fiber grating sensors used for monitoring the straightness of scraper conveyors in vertical directions due to significant fluctuations in the coal seam floor, this study focuses on the 5502 working face of Shuozhou Coal & Electricity Qianjing Coal Industry Co., Ltd., Jineng Holding Group. The study begins with an analysis of the bending posture and the mechanism of vertical bending in scraper conveyors. Through theoretical calculations, the maximum allowable strain range that meets the requirements for straightness monitoring is determined. Subsequently, a design approach combining theoretical calculations and simulation verification is employed to determine the structure and material, selecting aluminum-magnesium alloy as the structural material. The relationship between the axial strain of the large-strain structure and the grating segment is studied. Three different micro-strains are applied to the large-strain structure, and data is fitted using Matlab to summarize the variation patterns. The sensitivity coefficient K is found to be 2.36, meeting the theoretical requirement of K> 2. This proves that the designed large-strain sensor can achieve a maximum allowable strain of 6000με for optical fiber gratings, which is sufficient for the straightness monitoring needs of the working face in the vertical direction.