基于特征的三维变量设计模型及形体重构

本文提出了一个适用于微机的基于特征的三维变量设计模型及形体重构方法，通过引入特征及约束的概念使变量设计成为可能，而特征树的应用克服了以往利用ＣＳＧ树进行三维变量设计的不足。该方法保存的信息还能用于后序加工。     

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。     

三维特征造型系统中装配与零件设计的联动*

为了在现有系统的基础上实现变量化设计,研究了三维特征造型系统中的层次化单元装配模型,在此基础上加入了装配单元对变量化设计的改进,进一步实现了装配设计和零件设计的联动,有效地进行了变量化设计,并且在装配设计模块中给出了具体的应用实例。     

钣金件自动展开新方法

在对钣金件特征研究和"零厚度"假设的基础上,提出一种钣金件自动展开新方法.对钣金件进行特征分类,基于特征设计进行钣金件特征造型,并通过特征树的形式存储特征之间的关系,最后对特征树进行中序遍历得到钣金件的展开图.并将上述方法应用在SMCAD(Sheet-Metal CAD)系统中.结果表明,该方法能方便快捷的实现钣金件自动展开,并使钣金件设计和展开摆脱了对三维平台的依赖,展开过程更为简洁.     

面向设计重用的工程零件设计特征模型构建

随着CAD技术的蓬勃发展和广泛引用,设计重用受到了越来越多的关注,然而由于缺乏有效的底层模型表征,现有的三维CAD模型检索算法普遍存在难以支持设计重用的问题.针对设计重用需求,提出一种设计特征模型的表征结构及构建方法.通过扩展特征树的设计模型表征结构,准确地刻画设计模型中不同粒度、不同形式的特征及特征间的关联关系,有效地捕捉模型中包含的设计语义;通过人工交互定义主形状特征和辅形状特征、系统自动建立特征间关系的方式构建设计特征模型,确保模型表征的唯一性及稳定性.实验结果表明,文中提出的设计特征模型表征结构及构建方法能够有效地捕捉工程零件中包含的设计语义,进而支持面向设计重用的检索.     

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。     

基于特征综合的植物建模方法

研究顾基于推理创建植物三维模型的方法,选择了一种很典型的植物－－树,研究面向特征综合的集成形状和语义的树表达模型,提供了综合形状和语义的三维树模的生成方法,以及相应的模拟树四季形状变化的模型,同时,将上述方法和模型在树的综合生成实验系统中予以实现。     

基于语义的三维CAD模型可重用区域自动提取

针对产品设计中的局部检索重用需求,提出一种基于语义分析的可重用区域自动提取方法。通过采用扩展特征树表征三维CAD模型,准确刻画设计模型中不同粒度、不同形式的特征及特征间的关联关系,有效捕捉模型中包含的设计语义;通过分析局部区域的设计重用性,提出局部区域可重用性度量函数,并以扩展特征树的表征结构为输入,依据局部区域的可重用性自动提取候选可重用区域;通过进一步评价候选可重用区域的重用率确定最终可重用区域,以确保可重用区域的有效性及合理性。实验结果表明,依据本方法提取获得的可重用区域符合设计重用语义,能有效支持产品设计阶段的局部检索重用。     

金银花MDA2000V2--设计人员的好帮手

金银花系MDA2000V2作为一个三维CAD系统,采用了先进的三维参数化、变量化特征造型技术和领先的ACIS几何造型内核,是国内自主版权的优秀三维C A D设计系统之一.金银花MDA2000V2具有的三维零件特征造型功能和二维工程图自动生成功能,极大地解除了传统绘图方式对设计思路的束缚,将机械设计人员带入广阔的三维设计空间.     

基于知识的设计过程保存与重构

提出基于知识的广义特征信息模型和记录设计历史的广义特征CSG树的表示方法.通过对设计知识与广义特征的封装,构建了广义特征信息模型,在该模型基础上用CSG树的方法表示了设计过程.广义特征信息模型和广义特征CSG树存储于XML格式的广义特征信息表中,实现了设计过程的保存.通过对广义特征信息表的导入和解析,重构了设计过程,实现了设计过程和设计知识的重用.最后给出了在涡轮叶片设计中的实例.     

Recognizing manufacturing features from a design-by-feature model

This paper presents a methodology for recognizing manufacturing features from a design feature model. The common feature-feature interacting relationships are categorized. A feature recognition processor first translates the design feature model of a part into an intermediate manufacturing feature tree by handling design features according to their properties and the interacting relationships between features. Through combination, decomposition, and (tool approach direction) TAD-led operations, alternative interpretations of manufacturing feature model for the part are then generated, and the manufacturing feature tree is updated and extended with AND/OR operators to store these interpretations. Finally, a single interpretation with the lowest machining cost will be selected in the manufacturing feature tree. The proposed processor can support a dynamic and effective recognition process of manufacturing features during the design stage of a part. By defining the interactions between volumetric features elaborately, and utilizing design features and auxiliary information, the processor can recognize manufacturing features from complex parts. The processor recognizes not only some essential manufacturing features but also replicate, compound and transition features defined in STEP. The alternative interpretations can be used for a generic manufacturing application environment.     

基于实体的特征反求技术研究

反求工程是当今CAD建模技术的一种重要途径,它极大地提高了设计人员的设计效率.然而仅包含曲面信息的三维重构限制了反求工程与CAD/CAPP/CAM系统的集成.针对这一问题,本文提出了基于多色图表示子特征之间空间约束关系的集合运算思路,可以较好地得到反求实体的特征信息以及特征树的结构利于其后的CAD模型的再设计、设计分析和加工.     

支持进化的计算机辅助设计环境

介绍一个支持进化的计算机辅助设计环境。多Agent系统的结构为设计人员在该环境下的协作及资源共享提供了支撑框架，基于树结构的遗传算法为拓宽设计人员的思维空间提供了一种工具。文中用一个手机设计实例描述了该环境中进化设计的过程。该实例用基于数学表达式二叉树的遗传算法及数学软件工具MATLAB生成形状草图，用基于特征的设计产品树产生可选的部件组合。由于进化过程由设计人员引导，因此可以较快地实现令人满意的结果。     

基于形状索引的DoG特征结合GPRT的人脸关键点检测算法

针对传统人脸对齐算法效率较低的问题,提出一种基于形状索引的高斯差分(DoG)特征与高斯过程回归树(GPRT)的人脸关键点检测算法。首先,由高斯过程回归树的内核测量两个输入之间的相似性,并表示为两个输入进入相同叶子的树木数。然后基于高斯过程回归树模型提取形状索引DoG特征,并进一步完成GPRT的特征设计。最后从局部视网膜模式中采集滤波回应来增加稳定性,实现对抗几何差异的鲁棒性。在LFPW人脸数据库上验证结果表明该方法能够取得良好的性能表现,证明了基于形状索引的DoG特征与GPRT的人脸关键点检测算法的有效性。     

Applications of quadtree, octree, and binary tree decomposition techniques to shape analysis and pattern recognition

The binary tree, quadtree, and octree decomposition techniques are widely used in computer graphics and image processing problems. Here, the techniques are reexamined for pattern recognition and shape analysis applications. It has been shown that the quadtree and octree techniques can be used to find the shape hull of a set of points in space while their n-dimensional generalization can be used for divisive hierarchical clustering. Similarly, an n-dimensional binary tree decomposition of feature space can be used for efficient pattern classifier design. Illustrative examples are presented to show the usefulness and efficiency of these hierarchical decomposition techniques.     

基于循环映射模型的概念设计自动化策略研究

建立了由主体特征和接口特征组成的功能特征模型,以及基于“需求域-功能域-原理解域循环映射”的概念设计模型;在此基础上提出了适用于计算机处理的概念设计与／或树形式化表达方法,探讨了相应的求解算法,开发了一个支持功能设计和功能求解的复合功能概念设计自动化原型系统,并以木材加工机械的概念设计为例进行了验证．     

An integrated form-feature-based design system for manufacturing

Much of the knowledge that is applied in or communicated between design and manufacturing activities is primarily shape based or shape indexed. Previous attempts to acquire and organize shape knowledge have been mostly concentrated on feature recognition from solid models, group technology (GT) coding schemes, and feature-based modeling. This paper presents the development of an efficient form-feature-based modeling system, and addresses the important issue of utilizing feature information for manufacturing, which has not been extensively discussed by previous work. In this paper we first present a Euler operator-based approach for efficient and effective form-feature encoding and manipulation in a feature-based design environment. Subsequently, a hybrid representation scheme called enhanced CSG tree of feature (ECTOF), which integrates feature model with solid model in a tree structure, is discussed. A feature interference resolution methodology to maintain the correct and consistent feature information in an ECTOF is also deliberated. Finally, we present a machinability-checking module, which employs global accessibility criteria to analyze a feature's machinability on a three-axis machining center. By developing feature interference resolving and machinability testing techniques and integrating with an efficient feature-based design system, this research makes the development of an integrated feature-based design and manufacturing system possible.     

Fast Feature‐Oriented Visual Connection for Large Image Collections

Deriving the visual connectivity across large image collections is a computationally expensive task. Different from current image‐oriented match graph construction methods which build on pairwise image matching, we present a novel and scalable feature‐oriented image matching algorithm for large collections. Our method improves the match graph construction procedure in three ways. First, instead of building trees repeatedly, we put the feature points of the input image collection into a single kd‐tree and select the leaves as our anchor points. Then we construct an anchor graph from which each feature can intelligently find a small portion of related candidates to match. Finally, we design a new form of adjacency matrix for fast feature similarity measuring, and return all the matches in different photos across the whole dataset directly. Experiments show that our feature‐oriented correspondence algorithm can explore visual connectivity between images with significant improvement in speed.