【作者】 郭晨霞；

【导师】 杨瑞峰；

【作者基本信息】 中北大学 ， 仪器科学与技术， 2014， 博士

【摘要】 光纤环是干涉型光纤陀螺中传播两相向光波来产生SAGNAC相位差的部件，它由多匝光纤线圈绕制而成。光纤环的绕制长度及平均直径大小是影响光纤陀螺性能的重要因素，在光纤环的生产过程中，对光纤环的绕制长度进行精确测量既是光纤陀螺生产过程中的一个必要环节，也是精度保证的必要条件，因此开展光纤长度实时精确测量技术的研究具有重要的理论意义和工程实用价值。论文针对光纤的物理特性和光纤环的绕制特点，利用机器视觉非接触式测量方法，建立了光纤环绕制长度实时精确测量系统，解决了有骨架光纤环绕制长度的实时精确测量问题。基于在线测量对测量系统精度和速度的要求，论文从理论研究和实际应用两个方面，对基于视觉测量技术的光纤环绕制长度测量方法进行了深入研究，并对测量方法及相关处理算法进行了实验，验证了测量系统的可行性和实用性。论文主要研究内容及成果如下：1）根据透镜成像原理，结合光纤环绕制的特点及精确定位光纤成像位置的要求，建立了视觉成像系统；对系统的组成及构建过程中的软件设计、相机选择及固定方式等问题进行了科学分析。2）研究了视觉测量过程中的系统标定问题。基于多个自由平面的标定方法，针对光纤成像后形状特征，改进了常用的张正友标定方法，提出了更贴近被测物形状的圆阵列靶标标定摄像机内部参数的方法，且将圆阵列靶标置于与光纤环同轴的平面上标定摄像机外部参数，使得摄像机的成像模型适用于光纤长度测量，提高了光纤环绕制长度测量系统的测量精度。3）针对圆阵列靶标模板提出了相对应的标定特征点提取方法，并解决了标定特征点在成像后的坐标位置与其在世界坐标系中位置的对应问题。采用canny边缘检测算子提取平面靶标中圆阵列的轮廓、最小二乘椭圆拟合法求取椭圆的长、短半轴以及Hough变换累计数组方式提取圆阵列靶标上所有标定特征点的坐标。4）针对紧密绕制的光纤环成像图像难以用肉眼分辨成像清晰度的问题，在调整镜头焦距判断是否清晰成像的过程中引入图像清晰度评价方法来实时处理图像，确定清晰成像的聚焦位置，指导设置后续的光纤绕制图像采集参数。通过对准平面的合理选取，解决了光纤环绕制过程中随着绕制层数的增加导致光纤环绕制图像的清晰度与视觉系统景深之间的矛盾。5）针对光纤环绕制过程的特点，对传统运动目标检测方法进行了改进，使其适用于实时检测跟踪光纤环绕制图像。利用边缘检测算法，得到清晰反映新绕制的光纤位置图像，便于后续计算。6）针对光纤材质的特性及绕制过程中出现的绕制缺陷导致长度测量不准确的问题，提出采用光学几何成像方法精确测量光纤环绕制长度的方法。通过测量已知精确直径的光纤环承载主轴的直径，计算系统测量误差，验证了光纤环绕制长度测量方法的正确性。在解决以上关键技术问题的基础上，给出了光纤环绕制长度实时测量系统的测量精度为±0.076mm。更多还原

【Abstract】 Fiber coil is a component of interferometric fiber optic gyroscope (FOG), which is madeof multi-turn fiber coil to strength the SAGNAC phase difference by propagating two wavesin opposite direction. The winding length and the average diameter of fiber coil are theimportant factors to influence the performances of FOG. In the process of fiber coil winding,measuring length of fiber coil winding is not only a necessary step of producing FOG, butalso essential requirement of ensuring FOG accuracy. Therefore, the research on the real-timelength measurement technology of fiber coil winding is of important theoretical and practicalsignificance.The non-contact measurement method based on machine vision is applied to measure thelength of fiber in real time according to the physical characteristics of fiber. The measurementsystem is established to measure accurately the length according to the features of backbonefiber coil winding.The related algorithms are applied to measure the length of fiber coil winding in realtime based on the accuracy and speed in the process of measurement, the feasibility andpracticability of the measuring system is verified by experiments.The main research contents and results are shown as follows:1）The visual system was established according to the principle of lens imaging. Thesystem elements was chose by combining the characteristics of the fiber coil winding with therequirement of precisely locating the fiber position of images; then analyzing the systemcomposition and the software and the fixed way of camera.2）The calibration problem was researched and realized in the process of visualmeasurement. Based on the multiple freedom plane calibration method, the Zhang zhengyoucalibration method is improved according to the fiber shape in images; The improvedcalibration method is using a circular array target of more close to the measured fiber shape tocalibrate extrinsic parameters of camera, which is suitable for the optical fiber length measurement. In the process of the calibration, the circular array targets will be placed incoaxial with the fiber coil plane, which can improve the measurement accuracy of the system.3）The corresponding algorithm was proposed to extract feature points aiming at circulararray target template and solve the location problem of the calibration feature points. Thecanny edge detection operator was used to extract the outline of plane target in the circulararray. The least square ellipse fitting method was used to calculate long and short axis of theellipse. The cumulative array method of Hough transform was used to extract the outline ofplane target in the circular array.4）The image clarity evaluation methods were applied on solving image quality problemnot distinguished by the naked eyes in the process of adjusting the focus. The method can beused to determine the focusing position of clear imaging, which can instruct the subsequentimage acquisition. In acquainting fiber imaging, choose the suitable imaging plane to solvethe contraction between increase of the fiber winding lay and the limited the depth of field ofcamera which will cause out-of–focus image of fiber coil winding.5) The traditional moving target detection method was improved according to thecharacteristics of optical fiber winding. The improved method is more suitable to detect theprocess of fiber coil winding. The new fiber position is accurately detected in each imagewhich is suit to calculate the length of fiber subsequently.6) The geometrical optics imaging method was applied to accurately measure the lengthof fiber winding aiming at the characteristics of fiber and inaccurate length measurementproblem for winding defects. The measurement method is verified by measuring the knowndiameter of the fiber coil bearing spindle.The real measurement accuracy of the system achieves±0.076mm.更多还原