面向制造的CAD/CAM系统--设计、加工编程软件Space-E

一、Space-E系统的基本构成 Space-E系统的造型功能提供了灵活的复合建模方式,即把严谨的实体造型和灵活的曲面造型相融合,提供了丰富的曲线曲面生成功能,以及多种快捷的实体生成功能,能够充分满足工业设计的需要,为用户提供自由直观的建模环境.     

Space-E在模具制造上的应用

一、前言Space-E是日立造船信息系统株式会社开发的GRADE系列模具CAD/CAM软件的最新产品,它基于Window平台,具有曲面造型、实体造型、工程图生成、塑料模设计和数控加工等功能。尤其在曲面造型和数控加工方面有许多独道之处。二、Space-E系统功能1．几何造型功能Space-E系统为模具造型提供了丰富的几何造型功能。如线框造型、曲面造型和实体造型功能。（1） 线框造型Space-E系统提供了各种直线、圆弧、样条曲线、二次曲线的基本线框造型功能;曲线投影、曲面与曲面求交、曲面边界线、曲面等参数线和偏移曲线等功能;曲线倒圆、倒…     

NURBS造型方法的研究与实现

本文通过ＮＵＲＢＳ造型方法关键技术的研究，在我校自主开发的超人（ＳｕｐｅｒＭａｎ）ＣＡＤ／ＣＡＭ集成系统中成功地实现了基于复合曲线ＮＵＲＢＳ蒙皮曲面的造型功能，双向蒙皮曲面的造型功能和ＮＵＲＢＳ曲线曲面的可控修形功能，建立了窒完全基于ＮＵＲＢＳ方法的ＣＡＤ／ＣＡＭ系统，大量的工程应用和实例验证，表明本研究的ＮＵＲＢＳ方法是一种适用于复杂外形产品设计与制造的，灵活有效的造型方法。     

汽车车身曲线曲面光顺处理方法的研究

本文根据车身曲线曲面的造型特点，提出了车身曲线曲面的光顺准则；重点介绍了用圆曲率法进行曲线曲面光顺的方法；还讨论了在实际车身曲面造型中，如何进行曲面光顺处理及检验曲面光顺的方法；最后介绍曲线曲面光顺方法在整车外表面设计中的应用。     

曲线曲面的定量造型方法

为了探索有效的曲线曲面造型的新方法,利用小波技术引进平均小波光顺率的概念,提出一种针对NURBS曲线曲面的定量造型方法.该方法把平均小波光顺率作为目标函数进行优化造型,同时由目标函数的值定量地评估优化造型结果的光顺情况.与传统方法相比,在曲线曲面造型过程中参考平均小波光顺率可以更方便地对曲线曲面进行造型设计.实例验证结果表明,文中方法在满足约束条件的情况下达到了满意的造型效果.     

NURBS曲线曲面的构形原理及其在产品造型中的应用

本文介绍了NURBS曲线、曲面的数学表达,给出了NURBS曲线和曲面的构形原理,在此基础上,推导了过滤曲面,进而获得了产品造型所要求的曲面。实践表明,应用NURBS曲面,使产品造型设计者能随心所欲地实现自己的设计意图。     

细分蒙皮曲面

对细分曲面在曲面造型中的应用进行了研究，并着重于蒙皮曲面造型技术．所提方法在传统的蒙皮曲面构造过程中引入细分方法，有效地避免了因截面曲线的相容性处理而产生的数据量激增的问题；最后生成的蒙皮曲面能够精确插值预先设计的截面曲线，并且可以在指定的截面曲线处产生折痕效果．     

基于STEP的曲线曲面造型技术

ＳＴＥＰ做为新一代的产品数据交换标准，正在被越来越多的ＣＩＭＳ系统所青睐，本文介绍了ＳＴＥＰ的特点，特别是对ＳＴＥＰ中做为曲线曲面造型系统设计基础的几何与拓扑集成资源作了较深入的解剖和分析，并在此基础上提出了一个基于ＳＴＥＰ的曲线曲面造型系统ＡＤＤＳＳ。     

流曲线曲面的概念和构造方法

给出了一种新的曲线曲面－流曲线曲面概念及其构造方法。给出了用多项式和Ｂｅｚｉｅｒ控制网构造流曲线曲面的基本方法和约束条件，这种流曲线曲面方法可用于计算机辅助几何设计和图形学中曲线表示和设计，特别是船体外型的造型和设计。     

CADDS系统在汽车仪表板及其模具三维造型／数控加工中的应用

介绍利用ＣＡＤＤＳ５软件成功地完成了汽车仪表板造型设计和模具数控加工的过程。着重介绍ＣＡＤＤＳ５软件中曲面造型（ＮＵＲＢＳ）、参数化设计和数控加工模块在开发过程中显示出的灵活、准确、可靠等特点。证明在复杂曲面产品开发过程中，ＣＡＤ／ＣＡＭ技术具有传统方法不可比拟的优点。     

Partition of unity parametrics: a framework for meta-modeling

We propose Partition of Unity Parametrics (PUPs), a natural extension of NURBS that maintains affine invariance. PUPs replace the weighted basis functions of NURBS with arbitrary weight-functions (WFs). By choosing appropriate WFs, PUPs yield a comprehensive geometric modeling framework, accounting for a variety of beneficial properties, such as local support, specified smoothness, arbitrary sharp features and approximating or interpolating curves. Additionally, we consider interactive specification of WFs to fine-tune the character of curves and generate non-trivial effects. This serves as a basis for a system where users model the tools used for modeling, here weight-functions, in tandem with the model itself, which we dub a meta-modeling system. PUP curves and surfaces are considered in detail. Curves illustrate basic concepts that apply directly to surfaces. For surfaces, the advantages of PUPs are more pronounced; permitting non-tensor WFs and direct parameter space manipulations. These features allow us to address two difficult geometric modeling problems (sketching features onto surfaces and converting planar meshes into parametric surfaces) in a conceptually and computationally simple way.     

曲面实体造型中曲线和曲面交点的求解

求交是曲面实体造型系统中影响拼合算法效率和稳定性的重要因素，而求交算法又是和曲面的几何表示密切相关的。ＮＵＲＢＳ虽然能统一表示所有曲面，但却给二次曲面的求交带来了不必要的复杂性。二次曲面经常在机械零件的设计中被用来描述轴、孔、槽等几何特征，因此它们的求交算法应具有高精度、高效率和高稳定性。为此，对一种实用的二次曲面表示方法——几何法进行了深入研究后，给出了构成二次曲面轮廓的几种二次曲线和空间四次曲线与二次曲面交点的求法。     

基于层状纹理切片表示法的短毛造型系统

提出了一个真实感短毛的实时绘制与造型系统。该系统采用快速的层状纹理切片技术进行毛发表示,保证了真实感短毛绘制和造型的实时性。在毛发造型方面,系统采用倒伏向量场和长度标量场来控制模型表面短毛的形态变化,并提供了多种造型工具,如梳理、吹风、引力棒、插值、扰动等。利用这些造型工具,用户可以灵活、直观地对短毛形态进行编辑与设计。系统还提供了一个毛发纹理生成器,使用户可以通过设计毛发纹理来对毛发的粗细、疏密和颜色等属性进行整体控制。实验结果表明,本文系统具有较强的短毛造型能力,并具有非常好的可操作性和用户交互性。     

Interactive 3D garment design with constrained contour curves and style curves

This paper presents interactive techniques to design 3D garments conveniently and precisely with constrained contour curves and style curves. Contour curves, including silhouette curves and cross section curves, are used for garment surface modeling. Style curves, including seam lines, dart lines, notch lines and grain lines, are introduced for designing patterns on the triangular garment surfaces. Contour curves are extracted automatically from the boundaries of garment sub-meshes. The definitions and resolving rules of various constraints are introduced for editing the contour curves conveniently. Style curves are generated by projecting control points onto 3D garment triangular surfaces. In order to draw the style curves validly, some constraints are also introduced according to the craft requirements of pattern design. Furthermore, the effects of style curves in pattern flattening are analyzed, which can guide the designer to draw style curves more reasonably and enhance the pattern design quality. Finally, some examples are given to show that our methods can make the 3D garment design more flexible and friendly, and style curves can be applied into design patterns on 3D triangular surface for shoes, toys and so on.     

Variational Modeling of Free-form Curve and Surface Using Wavelet Basis Functions

Variational modeling approach is often used to interactively design free-form curves and surfaces. Traditionally, a variational problem can be transformed to the optimization of control points. Unfortunately, as the number of basis functions grows, the local support property of B-spline often makes the computation of an optimization system time-consuming. To solve this problem, wavelet basis instead of B-spline basis is used to represent the curves or surfaces. Because the wavelet basis is a hierarchical basis with multiresolution property, the coarse wavelet basis can be used to describe the overall shape of the curves/surfaces, while the finer wavelet basis used to describe the details of the curves/surfaces. Thus, the computing speed of the optimization system can be raised greatly.     

An approach of designing and controlling free-form surfaces by using NURBS boundary Gregory patches

Designers require a means of designing complex free-form surfaces easily and intuitively. One general approach to designing such surfaces is to first define a curve mesh consisting of characteristic lines, such as cross sections and boundary curves, then to interpolate the curve mesh using free-form surfaces. NURBS surfaces are widely used but make the interpolation of an irregular curve mesh difficult. This has been a major limiting constraint on designers. In this paper, we propose a new surface representation that enables the smooth interpolation of an irregular curve mesh with NURBS curves and surfaces.     

Image‐based modeling of 3D objects with curved surfaces

This paper addresses an image‐based method for modeling 3D objects with curved surfaces based on the non‐uniform rational B‐splines (NURBS) representation. The user fits the feature curves on a few calibrated images with 2D NURBS curves using the interactive user interface. Then, 3D NURBS curves are constructed by stereo reconstruction of the corresponding feature curves. Using these as building blocks, NURBS surfaces are reconstructed by the known surface building methods including bilinear surfaces, ruled surfaces, generalized cylinders, and surfaces of revolution. In addition to them, we also employ various advanced techniques, including skinned surfaces, swept surfaces, and boundary patches. Based on these surface modeling techniques, it is possible to build various types of 3D shape models with textured curved surfaces without much effort. Copyright © 2007 John Wiley & Sons, Ltd.     

UNISURF,from styling to tool-shop

Since 1965, CAD has replaced the conventional system for defining free-form curves and surfaces. UNISURF, which has been widely used in the French car industry for designing car bodies since 1975, is briefly described.     

飞机液压刹车系统数字仿真研究

该文以某飞机机型为研究对象,对液压刹车系统的建模、控制方法以及系统仿真作了深入的研究。在考虑飞机防滑刹车系统的特点和各组成部分物理特性的基础上,建立了系统仿真的整体数学模型;采用PBM控制思想完成了控制回路的设计,并在MATLAB6．1／SIMULINK仿真环境下进行了系统仿真分析与研究。另外给出了干、湿两种跑道的仿真结果,并进行了刹车性能的比较分析。该文的仿真结果曲线与真实刹车物理试验曲线基本吻合,从而证明了建模的合理性。所进行的数字仿真也为刹车系统的设计和研究提供了一定的理论依据。     

An Extended Rounding Operation for Modeling Solids with Free-Form Surfaces

An extended rounding operation can be an excellent tool for modeling solids with free-form surfaces. Using the rounding operation, the edges and vertices of a solid can be locally rounded, and those parts of the solid are changed to free-form surfaces. As a user, you put in information about edges that should be rounded and the radii of curves generated by the operation. This facility has been implemented in our solid modeling system, Desiqnbase.