本文選題：空間網(wǎng)格結(jié)構(gòu) + 自由形態(tài)　； 參考：《浙江大學(xué)》2014年博士論文

【摘要】：自由形態(tài)空間網(wǎng)格結(jié)構(gòu)的網(wǎng)格設(shè)計是一項十分復(fù)雜的工作,而目前大部分網(wǎng)格設(shè)計的研究都是針對某個具體工程,無法直接應(yīng)用到或指導(dǎo)其他結(jié)構(gòu)的網(wǎng)格設(shè)計。針對此問題,本文深入研究自由形態(tài)空間網(wǎng)格結(jié)構(gòu)的網(wǎng)格設(shè)計,提出一種面向自由曲面的網(wǎng)格設(shè)計新方法,發(fā)展了已有的網(wǎng)格生成方法和網(wǎng)格優(yōu)化技術(shù),實現(xiàn)了自由形態(tài)點云的網(wǎng)格設(shè)計。 本文結(jié)合已有研究,給出了自由形態(tài)空間網(wǎng)格結(jié)構(gòu)的定義,回顧了自由形態(tài)空間網(wǎng)格結(jié)構(gòu)的的應(yīng)用現(xiàn)狀,闡述了網(wǎng)格設(shè)計的內(nèi)涵,總結(jié)了網(wǎng)格生成方法和網(wǎng)格優(yōu)化方法的研究現(xiàn)狀。 當前的自由曲面造型技術(shù)以B樣條方法為基礎(chǔ),本文闡述了B樣條、B樣條曲線曲面以及非均勻有理B樣條(NURBS)的定義和重要性質(zhì)；介紹了B樣條曲線曲面的正向計算和反向映射的計算方法；解析了CAD/CAM/CAE領(lǐng)域普遍應(yīng)用的IGES接口文件的數(shù)據(jù)格式,以獲取各類建模軟件中構(gòu)造的自由曲面信息,用于網(wǎng)格設(shè)計。 基于空間網(wǎng)格結(jié)構(gòu)對網(wǎng)格的要求,提出了一種自由曲面網(wǎng)格生成的新方法—等參線分割法。該方法的基本原理是利用B樣條曲面的張量積特性,通過提取等參線,將二維的曲面網(wǎng)格劃分問題,降為一維的曲線分割問題。為實現(xiàn)等參線分割,建立了等參線等弦長分割算法。 基于等參線分割法分別對簡單自由曲面和復(fù)雜邊界自由曲面進行網(wǎng)格生成。依據(jù)邊界輪廓形狀,將簡單自由曲面歸納為四邊形邊界曲面、三角形邊界曲面和圓形邊界曲面三類,針對每種曲面設(shè)計不同形式的網(wǎng)格,發(fā)展了相應(yīng)網(wǎng)格形式的生成算法。介紹了復(fù)雜邊界自由曲面的生成途徑,以及與之相關(guān)的重要定義；建立了曲面邊界線的分類準則、提出了分類方法,結(jié)合物理空間與參數(shù)域內(nèi)邊界線之間的關(guān)系,提出了復(fù)雜邊界曲面網(wǎng)格生成的基本方法,并探討了網(wǎng)格的細部優(yōu)化方法,完善了網(wǎng)格生成算法流程。 發(fā)展了面向3D掃描點云的網(wǎng)格生成方法,在點云上直接剖分網(wǎng)格。基于有限元中廣泛應(yīng)用的波前推進法(AFT),針對點云的數(shù)據(jù)特點,引入搜索盒數(shù)據(jù)結(jié)構(gòu)以建立起離散數(shù)據(jù)點之間的拓撲關(guān)系,提出了點云初始邊界的搜索方法,完善了前沿推進過程中生成新節(jié)點的算法,形成了應(yīng)用于點云的網(wǎng)格生成方法。在此基礎(chǔ)上,進一步研究了網(wǎng)格的優(yōu)化調(diào)整方法。提出了包括Delaunay優(yōu)化和Laplacian優(yōu)化兩個步驟的優(yōu)化流程,并通過對Laplacian優(yōu)化方法的改進,克服傳統(tǒng)Laplacian優(yōu)化網(wǎng)格收縮的缺陷。提出了針對線約束和點約束的網(wǎng)格調(diào)整方法。采用兩種不同工藝制作實物模型,展示了基于3D掃描的自由形態(tài)空間網(wǎng)格結(jié)構(gòu)幾何設(shè)計全過程。 根據(jù)上述理論與方法編制了自由形態(tài)空間網(wǎng)格結(jié)構(gòu)網(wǎng)格設(shè)計程序FreeMesh。該系統(tǒng)包括前處理模塊,網(wǎng)格設(shè)計模塊和后處理模塊。其中,網(wǎng)格設(shè)計模塊是程序的主體,完成了自由曲面的網(wǎng)格設(shè)計和自由形態(tài)點云的網(wǎng)格設(shè)計兩大功能。 通過理論推導(dǎo)、數(shù)值模擬以及程序系統(tǒng)的編制,證明了本文所提出的自由形態(tài)空間網(wǎng)格結(jié)構(gòu)網(wǎng)格設(shè)計方法是可行且有效的,能為實際工程應(yīng)用提供技術(shù)支持。最后,論文提出并討論了今后有待解決的若干問題。
[Abstract]:The grid design of free form space grid structure is a very complicated work. At present, most of the research of grid design is aimed at a specific project and can not directly apply or guide the grid design of other structures. In this paper, the grid design of free form space grid structure is deeply studied, and a kind of surface is proposed. The new method of grid design for freeform surface has developed the existing grid generation method and grid optimization technology, and realized the grid design of free form point cloud.
In this paper, the definition of free form space grid structure is given in this paper. The application status of free form space grid structure is reviewed, the connotation of grid design is expounded, and the research status of grid generation method and grid optimization method is summarized.
The current free form surface modeling technology is based on the B spline method. This paper describes the definition and important properties of B spline, B spline curve and surface and non-uniform rational B spline (NURBS), introduces the forward calculation and reverse mapping calculation method of B spline curve and surface, and analyzes the IGES interface file which is widely used in the CAD/CAM/CAE field. Data format is used to obtain freeform information in various modeling software for grid design.
Based on the requirement of space grid structure to the grid, a new method of generating free surface mesh - isoparametric line segmentation is proposed. The basic principle of this method is to use the tensor product characteristics of B spline surface and extract isoparametric lines to divide the two-dimensional surface mesh into one dimension curve segmentation problem, and to realize isoparametric segmentation. A string length segmentation algorithm, such as isoparametric line, is established.
Based on the isoparametric line segmentation, the simple free-form surface and the complex boundary free-form surface are generated. According to the shape of the boundary contour, the simple free-form surface is divided into three kinds of quadrilateral boundary surface, triangular boundary surface and circular boundary surface, and different forms of grid are designed for each surface, and the corresponding grid forms are developed. The generation method and the important definition related to the complex boundary free-form surface are introduced, the classification criterion of the surface boundary line is established, the classification method is put forward, and the basic method of generating the complex boundary surface mesh is put forward by combining the relationship between the physical space and the boundary line in the parameter domain, and the fine grid is discussed. The optimization method of the Department has improved the grid generation algorithm flow.
The grid generation method for 3D scanning point cloud is developed, and the grid is directly dissecting on the point cloud. Based on the wave front propulsion method (AFT) widely used in the finite element, the search box data structure is introduced to establish the topological relation between the discrete data points, and the search method of the initial boundary of the point cloud is proposed. The algorithm of generating new nodes in the process has formed a grid generation method applied to point cloud. On this basis, the optimization and adjustment method of grid is further studied. The optimization process of two steps including Delaunay optimization and Laplacian optimization is put forward, and the traditional Laplacian optimization grid is overcome by improving the Laplacian optimization method. A mesh adjustment method for line constraints and point constraints is proposed. Two different processes are used to make the physical model, and the whole process of geometric design of free form space grid structure based on 3D scanning is presented.
According to the theory and method mentioned above, a free form space grid structure grid design program FreeMesh. is developed. The system includes the pre processing module, the grid design module and the post-processing module. Among them, the grid design module is the main body of the program. It completes the two functions of the grid design of free surface and the grid design from the form point cloud.
Through theoretical deduction, numerical simulation and programming system, it is proved that the free form space grid structure grid design method proposed in this paper is feasible and effective, and can provide technical support for practical engineering applications. Finally, the paper puts forward and discusses some problems to be solved in the future.
【學(xué)位授予單位】：浙江大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2014
【分類號】：TU399

【參考文獻】

中國期刊全文數(shù)據(jù)庫 前10條

1 李娜;陸金鈺;羅堯治;;基于能量法的自由曲面空間網(wǎng)格結(jié)構(gòu)光順與形態(tài)優(yōu)化方法[J];工程力學(xué);2011年10期

2 王英姿;IGES文件中裁剪曲面的剖析及正確顯示方法[J];工程圖學(xué)學(xué)報;2005年05期

3 宋建民;席平;胡畢富;王一多;;自由曲面上曲線物理空間和參數(shù)空間互相轉(zhuǎn)換算法[J];工程圖學(xué)學(xué)報;2009年01期

4 劉曉;駱少明;呂惠卿;;超限映射法的四邊形網(wǎng)格劃分技術(shù)研究[J];廣東工業(yè)大學(xué)學(xué)報;2006年01期

5 葉曉平,季勁松,單巖,童水光;IGES格式中裁剪曲面信息的解析[J];機電工程;2001年03期

6 關(guān)振群 ,宋超 ,顧元憲 ,隋曉峰;有限元網(wǎng)格生成方法研究的新進展[J];計算機輔助設(shè)計與圖形學(xué)學(xué)報;2003年01期

7 李娜;陸金鈺;羅堯治;;利用張力薄膜平衡特性構(gòu)造自由曲面空間結(jié)構(gòu)[J];計算機輔助設(shè)計與圖形學(xué)學(xué)報;2010年07期

8 關(guān)振群,隋曉峰,顧元憲,李云鵬;復(fù)雜三維組合曲面的有限元網(wǎng)格生成方法[J];計算力學(xué)學(xué)報;2003年04期

9 董辰世,汪國昭;一個利用法矢的散亂點三角剖分算法[J];計算機學(xué)報;2005年06期

10 陳濤,李光耀;平面離散點集的邊界搜索算法[J];計算機仿真;2004年03期

中國博士學(xué)位論文全文數(shù)據(jù)庫 前2條

1 李欣;自由曲面結(jié)構(gòu)的形態(tài)學(xué)研究[D];哈爾濱工業(yè)大學(xué);2011年

2 李娜;空間網(wǎng)格結(jié)構(gòu)幾何形態(tài)研究與實現(xiàn)[D];浙江大學(xué);2009年

，

本文編號：2071322