發(fā)布時間：2018-08-17 09:40

【摘要】：數(shù)字圖像相關(guān)方法由激光散斑術(shù)發(fā)展而來，是一種基于數(shù)字攝影技術(shù)與數(shù)字圖像處理技術(shù)的非接觸式光學(xué)測量方法，現(xiàn)已發(fā)展應(yīng)用于多個領(lǐng)域。在土木工程測量中，以其非接觸、高精度、全場測量等優(yōu)點，很好的彌補了傳統(tǒng)變形測量方法的不足，成為了一種令人矚目的測量方法。本文以國內(nèi)外在這一領(lǐng)域已有的研究成果為基礎(chǔ)，圍繞亞像素搜索精度與數(shù)字圖像相關(guān)方法在土木工程測量中的應(yīng)用而展開了研究。分析了常用亞像素搜索方法搜索精度的影響因素，提出相關(guān)最優(yōu)區(qū)間；對二元三次曲面擬合法進行了改進，提高了亞像素搜索精度；并將數(shù)字圖像相關(guān)方法應(yīng)用于離面位移測量和懸臂鋼梁振動模態(tài)測試研究中，，取得了較好的測量效果。 總結(jié)了三種常用的亞像素搜索方法：曲面擬合法、梯度法、Newton-Raphon（N-R）法。利用計算機模擬散斑圖，分析了圖像質(zhì)量、位移模式、計算方法選取對三種亞像素搜索方法搜索精度的影響，得到了模擬散斑圖的最佳散斑顆粒尺寸、密度、最佳灰度值分布，最大應(yīng)變與轉(zhuǎn)角適用范圍，以及三種亞像素搜索方法在不同噪音、位移、應(yīng)變、旋轉(zhuǎn)條件下的搜索精度。 總結(jié)了曲面擬合法研究成果，對高斯曲面擬合、二元二次曲面擬合、二元二次多項式曲面擬合、二元三次曲面擬合等進行了搜索精度對比研究，并對其中計算精度最優(yōu)的二元三次曲面擬合法進行了改進。在相關(guān)系數(shù)計算時引入距離加權(quán)系數(shù)，并將相關(guān)系數(shù)矩陣取對數(shù)后進行曲面擬合，得到了能與梯度法和N-R方法搜索精度相媲美的改進的曲面擬合方法。 基于單目CCD的測量多用于平面內(nèi)測量，而本文以針孔成像原理為基礎(chǔ)，將數(shù)字圖像相關(guān)方法應(yīng)用于結(jié)構(gòu)離面位移測量中。改進了基于單目CCD離面位移測量技術(shù)，并對噪音影響下離面位移測量精度進行了分析。塑料橡膠板變形實測結(jié)果表明，應(yīng)用本文改進的方法可以得到較好測量效果。 以數(shù)字圖像相關(guān)方法動位移測量技術(shù)為基礎(chǔ)，結(jié)合經(jīng)典模態(tài)參數(shù)識別理論ITD法，對懸臂梁自然振動模態(tài)進行了測試。測得懸臂梁上各點位移時程數(shù)據(jù)，識別出模態(tài)參數(shù)，擬合出模態(tài)振型，得到了與理論值符合較好的一、二階頻率和一階振型。為數(shù)字圖像相關(guān)方法在土木工程測量中的進一步應(yīng)用,作出了初步嘗試。
[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.
【學(xué)位授予單位】：長沙理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2013
【分類號】：TU198

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