一种适用于特征造型的参数化设计方法

本文提出了一种面向特征造型的参数化设计方法，该方法对三维几何约束在初始设计阶段采用高层表示，并基于面向特征造型的高层几何约束模型与约束传播实现尺寸驱动几何，从而能够有效地支持特征设计，初始设计。     

面向三维变量设计的可变特征模型

本文提出了一个面向三维变量设计的产品形状可变特征模型，其中包括特征树，特征表有特征约束关系图等新概念，用于描述设计过程中的形体模型和特征间的相互内在联系，从而不仅可作参数化设计，还支持更广泛意义上的变量设计。     

基于活动约束系统的变量化设计

在变量化设计过程中设计对象可以看作是一个几何约束系统,这个系统由几何元素以及作用于几何元素之间的各种约束关系构成。一个复杂的设计对象所对应的几何约束系统往往包含大量几何元素和约束关系,如果不加区别地把所有的几何元素和约束关系纳入变量化求解的范围,则很难满足交互设计的需要。而另一方面几何约束系统又往往是稀疏系统：（1）作用于任一几何元素的约束很少;（2）与任一约束相关的几何元素很少。基于这一事实给出了一种预处理策略从原始几何约束系统中搜索得到一个规模较小的活动约束系统,变量化求解在活动约束系统上进行。该方法已在自行研制的参数化造型系统GEMS5．0中实现。     

基于自由度分析的耦合几何约束求解

针对目前的CAD软件不能求解复杂耦合几何约束的问题,提出一种基于自由度分析的耦合几何约束求解方法.通过添加部分约束,将这些约束的值作为迭代变量,再对复杂约束耦合问题进行约束聚合;将没有被用到的约束作为迭代的目标函数进行计算,大大减少了传统方法中解决复杂约束耦合问题所需要的变量数,提高了计算过程的稳定性.在最坏情况下,对不同数量的聚合体构成的复杂约束耦合模式所需要添加的变量数进行了讨论,从原理上成功地解决了复杂耦合几何约束问题.该方法可以用复杂聚合模式作为几何设计的基本元素,较好地解决了二维几何约束求解问题.     

基于几何推理的布局设计新方法

面向约束的布局设计问题一直是布局研究的热点．本文提出了一个基于几何推理的布局设计生成算法，其最大优点就是充分利用参数化设计的优点，建立了影响布局设计的变量之间的关系．该算法具有较强的柔性，易于扩充，并支持约束一致性检测和影响布局设计参变量的局部修改．算法已在作者研制的车身内布置设计系统中得到了较好的应用．     

从二维草绘到三维变量化设计

该文提出了一个从二维草绘开始的三维变量化几何模型的建立方法，详细介绍了变量约束，关系布尔运算的机理与方法，并进一步分析了针对已建立的几何模型进行变量化设计的途径及有关注意事项。     

基于灰度差分不变量的点特征匹配

本文提出了一种新的基于灰度差分不变量的点特征匹配方法。首先，利用灰度差分不变量获得点集之间的初始匹配；然后，利用初始匹配快速、稳健地估计图象之间的唯一几何约束－对极几何约束；最后，利用对极几何约束改进初始匹配。大量的实际图象实验表明，本文所提出的匹配算法有非常快的运算速度和很高的匹配正确率。     

基于标识的特征造型原型系统的研究与实现

从特征造型软件开发的角度对参数化特征造型的一些关键技术进行了研究，并在ACIS几何平台上开发了一个参数化特征造型原型系统GDS。讨论了GDS的关键技术：基于标识的特征表示模型，标识子系统、统一二、三维约束的基于子图的草图设计及约束求解方法、基于约束依赖图的特征编辑算法等。     

基于子图的草图设计和约束求解

提出了一种基于子图的拟序列化草图设计方法。基于标识的约束模型统一了二维、三维约束,使得每个几何元素对应唯一的标识,几何元素之间的约束关系表示为标识之间的约束,这些约束被分为结构约束和尺寸约束。提出了基于序列化设计过程的约束求解方法。实验表明,该技术可快速有效地进行参数化草图设计和特征编辑。     

一种新的几何约束结构及其射影不变量

几何不变量，特别是射影不变量，是基于单视点灰度图像识别三维物体的一条有效途径．但理论研究表明，只有特定的几何约束结构，才具有射影不变量．所以，研究并发现这种几何约束结构就具有十分重要的意义．该文提出了一种新的由相邻3平面上5条直线组成的几何约束结构及其所具有的射影不变量．该结构较Sugimoto提出的几何约束结构简单，可从结构同样复杂的物体中获得更多的几何不变量，有利于提高物体识别的稳定性；同时，由于该结构大量存在于由多面体组合而构成的人造物体及地面建筑物中，因此它非常适合这类物体的识别．实验验证了文中提出的几何约束结构具有不随物体成像视点改变的射影不变量．     

SEMANTIC CONSTRAINT MODELER FOR 2D AND 3D GEOMETRY

Design changes for 2D & 3D geometry are the most important features in the process ofproduct design.Constraint modeling for variationl geometry based on geometric reasoning is one ofthe best approaches for this goal.However,it is difficult for the proposed systems to maintain orhandle the consistency and completeness of the constraint model of the design objects.To changethis situation,a semantic model and its control approach are presented,aiming at the integrationof the data,knowledge and method related to design objects.Aconstraint definition system for in-teractively defining the semantic model and a prototype modeler based on the semantic model arealso implemented to examine the idea which is extended to 3D geometric design too.     

Part design using manufacturing features

This paper presents a methodology by which manufacturability data is used to drive the design process. The system allows a designer to determine the features to be considered. He provides the basic geometric parameters for each feature and passes them to the modeling system for instantiations. Tolerances and surface finish allow the system to derive manufacturing implications used by the designer to review the design. The physical parameters, in addition to the processing information, lead to an integrated model which may be used by both the designer and the manufacturing personnel. This procedure may be invoked at any level of the design process and contribute to a final manufacturable design. The philosophy employed in the development of this work is to define manufacturing features as instances of generic ones with specific properties and processing methods. The design features obtain their geometric superclasses from a commercially available package of solid primitives thus allowing for the part to be graphically displayed.     

产品反求工程中基于几何特征及约束的模型重建

由于大多数机械零件产品都是按一定特征设计制造的,同时特征之间具有确定的几何约束关系,因此,在产品的模型重建过程中,一个重要的目标即是还原这些特征以及它们之间的约束,具体方法是首先进行特征识别,将测量数据分块,然后基于特征约束建立优化数学模型,在建模过程中寻求满足特征参数目标函数下的约束最优解,使重建模型更为准确、接近原型。     

Automatic and a priori refinement of three-dimensional meshes based on feature recognition techniques

This work presents the general evolution of CAD/CAM systems for a better integration of all functions involved in the design and manufacturing process of mechanical parts (simultaneous engineering). We are proposing here an approach of the automatic three-dimensional mesh generation problem featuring a pre-optimization scheme based on the “a priori” evaluation of a dual geometric model (CSG–Exact B-Rep) in order to identify, directly and automatically, geometric features causing stress concentration. We provide more precise knowledge on how geometric features are identified and used in order to calculate a nodal density field across the parts that is more interesting for analysis or representation purposes.     

Conceptual design, manufacturability evaluation and preliminary process planning using function-form relationships in stamped metal parts

A large number of design decisions are made during the conceptual design of a part. However, there are few representation and reasoning tools for decision support during conceptual design. The conceptual design stage is characterized by a lack of complete geometric information. Existing geometric modelers require complete geometric information, while a functional reasoning methodology using a <verb, noun > representation is typically too terse. In this paper, we present a new representation called sketching abstraction for conceptual design, using the function-form relations in a design. The functionally critical part of the geometry is presented using a set of functional features, while the rest of the geometry is abstracted as a set of linkages. Part functionality is correlated with the sketching abstraction using data structures called function-form matrices. The sketching abstraction is annotated using a set of primitives, and a set of grammar rules are used to extract canonical relationships between the functional features. The sketching abstraction can be used for extracting designs that are geometrically dissimilar but functionally similar, thus providing the designer with ideas for design alternatives. The sketching abstraction can also be used to carry out domain-dependent manufacturability evaluation checks. A further use of sketching abstractions is to initiate the development of a process plan for manufacturing. Sketching abstractions are related to the solid model of a part. Thus, this representation provides a link between pure functional and pure geometric representations. The domain of application is stamped metal parts. We present the part functionality and the features used in this domain. We also illustrate the use of sketching abstractions for conceptual design, manufacturability evaluation and preliminary process planning.     

一种基于曲率的边折叠简化算法

针对目前三角网格简化算法在低分辨率的状态下往往丢失模型重要几何特征,从而导致视觉上的失真问题,提出了一种改进的边折叠三角网格简化算法。在Garland算法基础上引入了近似曲率的概念,并将其加入到二次误差测度中,使得二次误差测度在能够度量距离偏差的情况下,能够反映模型局部表面几何变化。实验结果表明改进的算法有效保持了模型的细节特征,简化效果更好。     

A feature-based database evolution approach in the design process

Design data are assigned in geometric and non-geometric form in order to meet design requirements. These data and information must be encapsulated in a data structure that has significance for design applications in each design process phase. The main goal of this research is to find design data groups that represent each mechanical design phase, which will be called phase's design signature. In addition, current data should be an evolution of the geometric and non-geometric information of the previous design phase. In this paper, the purpose is to identify and model a set of design features that encapsulate the design data and their transformations which occurred during the mechanical design phases. This database must capture the designer's intents that can be modeled and implemented using feature-based model in the conventional CAD systems, object-oriented modeling, and Java classes.