【摘要】：隨著制造業(yè)的持續(xù)快速發(fā)展,傳統(tǒng)的正向工程已經(jīng)難以滿足人們的需求,反求工程越來越廣泛的被應(yīng)用到新產(chǎn)品開發(fā)設(shè)計中。反求工程不僅可以大幅度縮短新產(chǎn)品的開發(fā)設(shè)計周期,也可以大大降低研發(fā)的成本。在反求工程中,快速、準(zhǔn)確地獲取目標(biāo)物體的三維幾何數(shù)據(jù)是極為關(guān)鍵的一步,但是對于具有復(fù)雜內(nèi)腔輪廓的零部件,數(shù)據(jù)測量方式受到了相應(yīng)的限制,從測量精度和成本兩個方面考慮,本文提出了一種基于斷層輪廓成像三維模型重構(gòu)的方法進行數(shù)據(jù)采集,是將CCD相機通過連接件與數(shù)控加工中心集成為一體,安裝高分辨率的鏡頭與LED環(huán)形光源,并配有可拆卸的遮光桶,將用包埋體包裹后固定于機床工作臺上的被測工件,使用數(shù)控加工中心進行高精度逐層切削成像,得到斷層輪廓圖像。之后對斷層圖像進行圖像預(yù)處理、邊緣檢測、亞像素細分等技術(shù)進行處理,從而得到被測件的三維點云數(shù)據(jù),再對三維點云數(shù)據(jù)進行點云精簡、分割、三角網(wǎng)格化處理,最后通過曲線曲面擬合得到被測物體的三維重構(gòu)模型。本文研究內(nèi)容為:(1)CCD獲取斷層輪廓圖像的試驗研究通過搭建試驗平臺,對被測件進行預(yù)處理之后,根據(jù)試驗設(shè)備的工作參數(shù)來選擇合適的拍攝條件進行數(shù)據(jù)采集試驗,通過對比和分析試驗結(jié)果,確定最佳的拍攝條件以獲取高質(zhì)量的斷層圖像。在確定了拍攝條件的基礎(chǔ)上,進行完整的三維模型重構(gòu)試驗的圖像采集。本文共采集斷層輪廓圖像249層,共2490張。(2)圖像的預(yù)處理以及邊緣檢測技術(shù)首先根據(jù)采集的原始數(shù)據(jù),研究了圖像的預(yù)處理技術(shù),即平滑去噪、灰度平均法以及中值濾波;然后,通過研究已有的邊緣檢測算法canny算法和log算法,在此基礎(chǔ)上提出一種改進的canny算法,一定程度上提高了邊緣檢測精度;最后通過亞像素細分算法進一步提高邊緣檢測精度,相比較像素級的邊緣檢測精度,亞像素細分算法精度提高了50%。(3)點云數(shù)據(jù)的處理研究了點云數(shù)據(jù)的處理,包括點云數(shù)據(jù)的精簡、點云數(shù)據(jù)的分割和點云數(shù)據(jù)的三角網(wǎng)格化等。首先研究了點云數(shù)據(jù)精簡的方法,如均勻采樣法、包圍盒法以及基于網(wǎng)格的方法,本文采用了一種基于曲率的點云精簡算法,并通過實例驗證了此算法的可行性;最后研究了網(wǎng)格三角剖分算法,提出了一種新的點云數(shù)據(jù)三角網(wǎng)格化算法。(4)曲面擬合和三維重構(gòu)對曲面擬合進行了研究,包括曲面擬合理論基礎(chǔ),nurbs曲面擬合以及曲面的拼接。使用imageware、ug軟件用基于特征曲線的重構(gòu)、輪廓線疊加擬合重構(gòu)和nurbs曲面擬合重構(gòu)三種不同方法對經(jīng)處理的三維點云進行曲面擬合,得到了被測件的三維重構(gòu)模型,通過對重構(gòu)誤差的分析得到nurbs曲面擬合重構(gòu)的重構(gòu)精度最高。最后從數(shù)據(jù)采集、邊緣檢測精度和曲面重構(gòu)精度三方面提出了改進重構(gòu)精度的集中可行性方案。
[Abstract]:With the continuous and rapid development of manufacturing industry, the traditional forward engineering has been difficult to meet the needs of people. Reverse engineering is more and more widely used in the development and design of new products. Reverse engineering can not only greatly shorten the development and design cycle of new products, but also greatly reduce the cost of R & D. In reverse engineering, obtaining the 3D geometric data of the target object quickly and accurately is a very important step, but for the parts with complex inner cavity contour, the measurement method of data is limited accordingly. Considering the accuracy and cost of measurement, this paper presents a method of 3D model reconstruction based on fault contour imaging for data acquisition, which integrates CCD camera with NC machining center by connecting parts. Installed with high resolution lens and LED ring light source, and equipped with removable shading barrel, will be wrapped in embedded body and fixed on the machine tool workbench measured workpiece, using numerical control machining center for high-precision layer-by-layer cutting imaging. The contour image of the fault is obtained. Then the image pre-processing, edge detection and sub-pixel subdivision are carried out to obtain the 3D point cloud data, and then the 3D point cloud data is simplified, segmented and triangulated. Finally, the three-dimensional reconstruction model of the measured object is obtained by curve and surface fitting. The research contents of this paper are as follows: (1) the experimental research of CCD to obtain the image of fault contour by building a test platform, after pre-processing the tested parts, according to the working parameters of the test equipment to select the appropriate shooting conditions for the data acquisition test, Through the comparison and analysis of the experimental results, the best shooting conditions are determined to obtain high-quality tomography images. On the basis of determining the shooting conditions, a complete 3-D model reconstruction experiment of image acquisition is carried out. In this paper, a total of 2490 slices of slice contour images are collected. (2) pre-processing and edge detection techniques of images are firstly studied according to the original data collected, namely smoothing denoising, gray-level averaging and median filtering. Then by studying the existing edge detection algorithms canny algorithm and log algorithm an improved canny algorithm is proposed which improves the edge detection accuracy to a certain extent. Finally, the sub-pixel subdivision algorithm is used to further improve the edge detection accuracy. Compared with the pixel-level edge detection accuracy, the sub-pixel subdivision algorithm improves the accuracy by 50%. (3) the point cloud data processing is studied. Including point cloud data simplification, point cloud data segmentation and point cloud data triangulation and so on. Firstly, point cloud data reduction methods, such as uniform sampling method, besieged box method and grid-based method, are studied. A curvature-based point cloud reduction algorithm is adopted in this paper, and the feasibility of this algorithm is verified by an example. Finally, the mesh triangulation algorithm is studied and a new triangulation algorithm for point cloud data is proposed. (4) the surface fitting is studied by surface fitting and 3D reconstruction, including the theoretical basis of surface fitting. Nurbs surface fitting and surface stitching. By using imageware,ug software, three different methods of reconstruction based on characteristic curve, superimposed contour fitting and nurbs surface fitting are used to fit the surface of the processed 3D point cloud, and the three-dimensional reconstruction model of the tested part is obtained, which is based on the feature curve reconstruction, the contour superposition fitting reconstruction and the nurbs surface fitting reconstruction. The reconstruction accuracy of nurbs surface fitting reconstruction is the highest by analyzing the reconstruction error. Finally, from three aspects of data acquisition, edge detection accuracy and surface reconstruction accuracy, a centralized feasible scheme to improve the reconstruction accuracy is proposed.
【學(xué)位授予單位】：太原理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TP391.41

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