用于光纤光栅曲线重建算法的坐标点拟合

以光纤布拉格光栅(FBG)曲线传感器在结肠中的形状检测为背景,提出了一种基于Frenet标架的坐标点拟合算法来提高光纤光栅曲线重建算法的精度。首先,将相互之间呈90°的四根光纤光栅贴在一根形状记忆合金(SMA Styrene Maleic Anhydride)基材周围,形成一根直径为3mm,长度为900mm的光纤光栅曲线传感器。接着,将该曲线传感器分别放置在毫米方格纸以及圆柱体上进行二维和三维曲线的重建。通过曲线重建软件读出每个数据采集点的重建坐标值,并与通过方格纸读出的标准坐标值对比得出重建误差,从而得出两种坐标点拟合方法的优劣。结果表明:使用基于Frenet标架的坐标点拟合算法可有效提高重建精度。对提出的算法与常用的曲线重建算法进行了比较,结果显示:在接近光纤光栅应变极限的情况下,使用基于Frenet标架的坐标点拟合算法在单方向上能够比原算法平均减小约3.5%~5.5%的误差,为进一步提高光纤光栅形状传感系统的精度奠定了基础。

Coordinate point fitting in FBG curve reconstruction algorithm

To detect the shape of a Fiber Bragg Grating(FBG) sensor in a colon, a coordinate fitting method based on Frenet frame was proposed to improve the precision of the FBG curve reconstruction algorithm. Firstly, four FBGs perpendicular to each other were clinged to one Shape Memory Alloys(SMA) substrate. Hence, one FBG curve sensor with a diameter of 3 mm and a length of 900 mm was formed. Then, this sensor was put on a millimeter-square graph paper and a cylinder respectively to accomplish the reconstruction of 2D and 3D curves. Furthermore, every reconstructed value of data collection points was read from the curve reconstruction software and reconstruction errors were acquired by the contrast between the reconstructed values and the standard values read from the coordinate paper. Finally, the merit degree between two fitting methods was obtained. Experimental results show that the proposed coordinate fitting method based on Frenet frame effectively improves the reconstruction accuracy. When the FBG achieves their ultimate strain, the proposed fitting method can reduce the average error by 3.5%-5.5% at single direction, which lays a foundation for the precision upgrading of the FBG curve sensing system.