本文選題：蜂窩芯測量 + 外形輪廓測量��； 參考：《西南交通大學(xué)》2017年碩士論文

【摘要】：隨著航空制造技術(shù)的日益發(fā)展,現(xiàn)代飛機正朝著高性能、高減重、以及低成本的方向發(fā)展。蜂窩芯結(jié)構(gòu)是現(xiàn)代飛機上采用的一種新型填充復(fù)合材料,具有重量輕、穩(wěn)定性好、強度高特點。但蜂窩芯結(jié)構(gòu)較為復(fù)雜,類似蜜蜂巢穴呈空心六方晶格,有規(guī)則的排列。蜂窩芯類零件上下表面是密集排列的孔,側(cè)面為切割后不完整的蜂窩孔壁。壁厚占蜂窩芯外形輪廓的總表面積比例較小,且壁厚較薄。結(jié)構(gòu)特殊性給該類零件加工質(zhì)量測量帶了來較大困難。針對這情況,分析了現(xiàn)階段較為典型的數(shù)字化測量技術(shù),針對蜂窩芯結(jié)構(gòu)的外形輪廓和孔特征分別提出較優(yōu)的測量方案,并將兩種不同的測量數(shù)據(jù)進行了融合研究,主要工作內(nèi)容如下:1.針對蜂窩芯外形輪廓測量,提出了一種基于三維光學(xué)掃描的測量方案。首先在蜂窩芯表面緊密貼合一覆蓋層,以覆蓋層的外形輪廓間接反映蜂窩芯的外形輪廓。采用三維光學(xué)掃描采集覆蓋層外形點云數(shù)據(jù),通過計算點云的法矢,然后在法矢方向偏置覆蓋層厚度,從而獲得蜂窩芯的外形輪廓數(shù)據(jù)。最后通過實例驗證了測量方法的可行性。在計算點云數(shù)據(jù)法矢的過程中,采用計算點云k鄰域,以k鄰域建立微切平面得到法矢的方法,文中改進了點云k鄰域的搜索算法,提高了點云數(shù)據(jù)法矢的計算速度。2.提出了一種基于三坐標測量機的蜂窩芯孔特征測量方法。首先計算孔截面內(nèi)包含孔壁最小測量范圍,然后利用測針在此范圍內(nèi)采樣測量,不斷逼近零件孔壁獲得近似孔壁點,通過近似孔壁點擬合獲得精確的孔心坐標。根據(jù)三坐標測量機測針參數(shù)、蜂窩芯參數(shù)以及孔特征理論數(shù)據(jù)對測量過程的極限誤差進行了分析。3.三維光學(xué)掃描數(shù)據(jù)與三坐標測量數(shù)據(jù)的精確融合。在測量過程中引入靶標球,用三坐標測量機和光學(xué)掃描儀分別對靶標球進行測量,根據(jù)不同測量數(shù)據(jù)中的球心位置計算得到數(shù)據(jù)的變換矩陣,實現(xiàn)數(shù)據(jù)的融合。在計算三維光學(xué)測量數(shù)據(jù)的靶標球心過程中,按照球體特性先對球體數(shù)據(jù)進行初步提取,然后引入了 RANSAC算法,精確提取球體數(shù)據(jù),提高了球心的計算精度。研究成果表明:有效的解決了蜂窩芯外形輪廓及孔特征的測量難題,提高了測量效率和測量精度,并實現(xiàn)了不同測量數(shù)據(jù)的精確融合。
[Abstract]:With the development of aeronautical manufacturing technology, modern aircraft are developing towards high performance, high weight loss and low cost.Honeycomb core structure is a new type of filled composite material used in modern aircraft, which has the characteristics of light weight, good stability and high strength.But honeycomb core structure is more complex, similar to honeybee nest with hollow hexagonal lattice, regular arrangement.The upper and lower surface of honeycomb core parts are densely arranged holes, and the side is incomplete honeycomb hole wall after cutting.The ratio of wall thickness to the total surface area of honeycomb core profile is small, and the wall thickness is thin.The structural particularity makes it difficult to measure the machining quality of this kind of parts.In view of this situation, this paper analyzes the typical digital measurement technology at the present stage, puts forward better measuring schemes for the outline and hole characteristics of honeycomb core structure, and studies the fusion of two kinds of measurement data.The main work is as follows: 1.A measurement scheme based on three-dimensional optical scanning is proposed for the profile measurement of honeycomb core.Firstly, a covering layer is tightly attached to the honeycomb core surface, and the contour of the honeycomb core is indirectly reflected by the outline of the cover layer.The contour data of honeycomb core are obtained by calculating the normal vector of the point cloud and biasing the thickness of the cover layer in the normal vector direction.Finally, the feasibility of the measurement method is verified by an example.In the process of calculating the normal vector of point cloud data, the method of computing point cloud k neighborhood and establishing a micro-tangent plane by k neighborhood is used to obtain the normal vector. In this paper, the search algorithm of point cloud k neighborhood is improved, and the computing speed of normal vector of point cloud data is improved.In this paper, a method for measuring the characteristics of honeycomb core holes based on CMM is proposed.First, the minimum measurement range of the hole wall is calculated in the section of the hole, and then the sample measurement is made by using the needle in this range, and the approximate hole wall point is obtained by continuously approaching the hole wall of the part, and the exact coordinates of the hole center are obtained by fitting the approximate hole wall point.The limit error of the measuring process is analyzed according to the needle parameters, honeycomb core parameters and the theoretical data of hole characteristics of CMM.Accurate fusion of 3D optical scanning data and 3D measurement data.The target ball is introduced into the measurement process, and the target sphere is measured by CMM and optical scanner respectively. The transformation matrix of the data is calculated according to the position of the ball center in different measurement data, and the data fusion is realized.In the process of calculating the spherical center of 3D optical measurement data, the spherical data is extracted preliminarily according to the characteristics of the sphere, and then the RANSAC algorithm is introduced to accurately extract the spherical data, which improves the accuracy of the calculation of the spherical center.The research results show that: the problem of measuring the contour and hole characteristics of honeycomb core is solved effectively, the measuring efficiency and precision are improved, and the accurate fusion of different measurement data is realized.
【學(xué)位授予單位】：西南交通大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TB33

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