数字图像相关方法及其试验研究

发布时间：2018-08-17 09:40

【摘要】：数字图像相关方法由激光散斑术发展而来，是一种基于数字摄影技术与数字图像处理技术的非接触式光学测量方法，现已发展应用于多个领域。在土木工程测量中，以其非接触、高精度、全场测量等优点，很好的弥补了传统变形测量方法的不足，成为了一种令人瞩目的测量方法。本文以国内外在这一领域已有的研究成果为基础，围绕亚像素搜索精度与数字图像相关方法在土木工程测量中的应用而展开了研究。分析了常用亚像素搜索方法搜索精度的影响因素，提出相关最优区间；对二元三次曲面拟合法进行了改进，提高了亚像素搜索精度；并将数字图像相关方法应用于离面位移测量和悬臂钢梁振动模态测试研究中，，取得了较好的测量效果。总结了三种常用的亚像素搜索方法：曲面拟合法、梯度法、Newton-Raphon（N-R）法。利用计算机模拟散斑图，分析了图像质量、位移模式、计算方法选取对三种亚像素搜索方法搜索精度的影响，得到了模拟散斑图的最佳散斑颗粒尺寸、密度、最佳灰度值分布，最大应变与转角适用范围，以及三种亚像素搜索方法在不同噪音、位移、应变、旋转条件下的搜索精度。总结了曲面拟合法研究成果，对高斯曲面拟合、二元二次曲面拟合、二元二次多项式曲面拟合、二元三次曲面拟合等进行了搜索精度对比研究，并对其中计算精度最优的二元三次曲面拟合法进行了改进。在相关系数计算时引入距离加权系数，并将相关系数矩阵取对数后进行曲面拟合，得到了能与梯度法和N-R方法搜索精度相媲美的改进的曲面拟合方法。基于单目CCD的测量多用于平面内测量，而本文以针孔成像原理为基础，将数字图像相关方法应用于结构离面位移测量中。改进了基于单目CCD离面位移测量技术，并对噪音影响下离面位移测量精度进行了分析。塑料橡胶板变形实测结果表明，应用本文改进的方法可以得到较好测量效果。以数字图像相关方法动位移测量技术为基础，结合经典模态参数识别理论ITD法，对悬臂梁自然振动模态进行了测试。测得悬臂梁上各点位移时程数据，识别出模态参数，拟合出模态振型，得到了与理论值符合较好的一、二阶频率和一阶振型。为数字图像相关方法在土木工程测量中的进一步应用,作出了初步尝试。
[Abstract]:The digital image correlation method is developed by laser speckle technique. It is a non-contact optical measurement method based on digital photography and digital image processing technology. It has been applied in many fields. In civil engineering measurement, because of its advantages of non-contact, high precision and full-field measurement, it makes up for the shortcomings of traditional deformation measurement methods and becomes a remarkable measurement method. Based on the research results in this field at home and abroad, this paper focuses on the application of subpixel search accuracy and digital image correlation method in civil engineering survey. The factors affecting the search accuracy of common sub-pixel search methods are analyzed, and the correlation optimal interval is proposed, and the binary cubic surface fitting method is improved to improve the sub-pixel search accuracy. The method of digital image correlation is applied to the measurement of off-plane displacement and vibration modal test of cantilever steel beam, and good measurement results are obtained. Three commonly used subpixel search methods are summarized: surface fitting method and gradient method with Newton-Raphon (N-R) method. The effects of image quality, displacement mode and calculation method selection on the search accuracy of three sub-pixel search methods are analyzed by computer simulation of speckle pattern. The optimum speckle size, density and optimal gray value distribution of simulated speckle pattern are obtained. The application range of maximum strain and rotation angle, and the search accuracy of three sub-pixel search methods under different noise, displacement, strain and rotation conditions. The research results of surface fitting are summarized, and the search accuracy of Gao Si surface fitting, binary quadratic polynomial surface fitting and binary cubic surface fitting are compared. The fitting method of binary cubic surface which has the best calculation precision is improved. The distance weighting coefficient is introduced in the calculation of the correlation coefficient, and then the logarithm of the correlation coefficient matrix is taken to fit the surface. The improved surface fitting method, which is comparable to the search accuracy of the gradient method and the N-R method, is obtained. The measurement based on monocular CCD is mostly used in the in-plane measurement. In this paper, the digital image correlation method is applied to the off-plane displacement measurement of the structure based on the pinhole imaging principle. The off-plane displacement measurement technology based on monocular CCD is improved, and the accuracy of off-plane displacement measurement under the influence of noise is analyzed. The measured results of plastic rubber plate deformation show that the improved method can obtain better measurement results. Based on the dynamic displacement measurement technique of digital image correlation method and the classical modal parameter identification theory ITD method, the natural vibration modes of cantilever beam are tested. The displacement time history data of each point on the cantilever beam are measured, the modal parameters are identified, and the modal modes are fitted. The first, second order frequencies and the first order modes are obtained, which are in good agreement with the theoretical values. A preliminary attempt was made for the further application of digital image correlation method in civil engineering survey.
【学位授予单位】：长沙理工大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TU198

【参考文献】