面向工程的专用产品参数化CAD系统的研究

 针对目前参数化CAD系统的不足，提出了面向工程的参数化思想，引入了功能约束，分析了对功能约束进行处理的3种方法．采用了基于特征的参数化造型方法，用应用层、描述层和图形层三层体系表达基于特征的参数化模型，将该模型作为参数驱动的基础．将设计中的约束分为3类：工程约束、适配约束和几何约束．通过适配约束在工程约束与几何约束间建立映射关系，使得参数化设计系统既可以受几何参数的驱动，又可以受工程参数的驱动，从而扩大了CAD技术对设计过程支持的范围。     

用于大平板测量的激光平面度仪

“激光平面度仪”是以空间自动安平的激光面作基准．以光电测头自动跟踪被测面．通过计算机控制和数据处理及输出的新型几何面型测量仪器。该仪器的研制成功,解决了平面测量过程“统一基准测量”这个国标难题;使得几何面型测量实现高精度智能化,并能带加工中心实现面型“光控加工”．论文对仪器工作原理、主要部件设计、仪器精度进行了分述和计算．     

画法几何在三维设计中的应用

对某些空间几何问题，采用画法几何的方法进行解题比用其它方法解题要简单快捷得多。但在三维设计环境中，采用传统的画法几何方法进行解题却有很大的局限性．针对三维设计中的一些难以解决的空间几何问题，尝试采用画法几何的方法，并应用三维造型中几何约束、基准平面等基本理论，将画法几何的应用领域拓展到三维设计环境中，探讨了“三维设计环境中的画法几何”的问题，从而避免了二维空间和三维空间的数据交换问题，提高了设计的效率。     

解构.重构思维下的仿生产品参数化生成研究

目的 在解构.重构思维下探索产品形态创新方法,发掘产品形态仿生设计的方案多样性。方法 阐述了解构.重构思维的理论应用、参数化设计方法应用流程。以自然花朵为实例研究,在搜集的牛津102与17花朵数据集中筛选出158张样本图片;首先通过Grabcut、Sobel、Canny等相关轮廓算法得出花朵平面轮廓,将特征轮廓进行解构分类后参数化表征;其次利用Rhino-Grasshopper软件重构花朵抽象三维模型,利用产品结构约束重构仿生产品;最后以灯具为例,调整参数后得到有花朵形态特征的产品形态重构群,得到基础仿生灯具模型,结构约束后得到仿生灯具三维模型。结论 该方法进一步探索了计算机辅助产品设计研究,实例表明自然花朵通过此方法可以生成大量具有创新性的形态初步模型,提高设计效率。     

多基准轴线对平面倾斜度误差的解析评定

根据被测要素与基准要素的几何关系，本文提出了一种评定轴线对平面任意方向倾斜度误差的算法。该算法通过坐标的旋转变换确定评定轴线，从而可以快速，准确地确定符合定义的倾斜误差值。     

涡轮叶片中隔肋转接段的参数化设计

目前在航空发动机涡轮叶片结构设计中存在的主要问题是结构分析和模型几何修改未能很好衔接，导致涡轮叶片的设计过程经常需要反覆，其设计修改过程繁琐、工作量大，影响了整体的设计。本文通过对隔肋转接段进行特征分析，提取并确定关键参数和约束条件，应用参数化设计特征建模技术，以程序设计的方式实现了隔肋转接段的参数化设计，达到了快速建模和快速修改的目标，同时也为涡轮叶片中复杂特征的参数化设计提供了借鉴。     

表面粗糙度参数Rz、Rmax、R1、R3z、RPc等的测量

在GB／T3505—2000《产品几何技术规范表面结构轮廓法表面结构术语、定义及参数》中定义了表面粗糙度幅度参数（纵坐标平均值）Ra、Rq、Rsk。Rku和间距参数、混合参数等,虽然该标准等效采用了ISO4287：1997《几何产品规范（GPS）表面特征：轮廓法表面结构的术语、定义及参数》,但这些参数远远不能满足我国目前工业生产的需要,特别是在涉外产品中常常会提出一些非标的表面粗糙度参数的技术要求,     

工字型钢框架极限承载力分析的通用广义屈服函数

工字型钢构件空间受力下的精确广义屈服函数为隐式函数，不便使用，而现有的近似显式函数不能全面考虑截面几何参数的影响，在适用性和精度方面普遍存在问题。为此，通过合理选择工字型截面几何参数，研究建立了具有广泛适用性的工字型截面齐次广义屈服函数，据此提出了平面和空间受力下框架结构极限承载力分析的高效线弹性迭代方法。研究了工字型截面几何参数对广义屈服函数计算精度的影响；选择腹板面积与单翼缘面积之比γ₁和翼缘宽度与腹板厚度之比γ₂作为截面几何参数，通过回归分析建立了同时适用于平面和空间受力，且能够全面反映工字型截面几何特征的通用齐次广义屈服函数；通过有策略地缩减高承载单元的弹性模量，建立了工字型截面框架结构极限承载力分析的高效高精度线弹性迭代方法。通过对比分析验证了该方法具有良好的计算精度和效率以及较强的适用性。     

基于几何特征的不平整路面三维建模与分析研究

在对比利时路关键几何特征、特征的分布特点及其约束条件进行分析的基础上,提出了基于几何特征的参数化路面三维建模方法。通过比利时路三维理论模型与生成的三维随机路面融合,得到真实准确的比利时路三维模型;在建立标准化车辆振动模型的基础上,以IRI指数和车身振动加速度均方根值(RMS)作为评价指标,分析了比利时路的关键几何参数对车辆振动的影响。通过实测道路数据与所建立模型对比分析,验证模型的准确性;提出的道路三维建模方法可以扩展至卵石路、鱼鳞坑路、波纹路、搓板路等几乎所有不平整强化试验路面,为全面构建车辆虚拟试验场提供了一种参数可调、真实准确的道路三维建模途径。     

复杂线轮廓度误差坐标测量的数据处理方法

本文把平面上复杂轮廓的设计曲线能一地表示为参数矢函数描述，运用微分几何理论，导出被测工件上测点到设计曲线的距离函数，建立复杂发线轮廓度误差坐标测量的数据处理模型。文章对算法进行了精度分析，并且设计加工了一个凸轮试件，通过坐标测量，用本文方法精确、快速地计算出凸轮的轮廓度误差。     

A Conceptual Data Model of Datum Systems

A new conceptual data model that addresses the geometric dimensioning and tolerancing concepts of datum systems, datums, datum features, datum targets, and the relationships among these concepts, is presented. Additionally, a portion of a related data model, Part 47 of STEP (ISO 10303-47), is reviewed and a comparison is made between it and the new conceptual data model.     

激光型基准平台的研制

介绍了一种新型的激光型基准平台.该平台运用重力摆技术使光平台在一定范围内达到了自动安平的功能;运用激光在球面镜单根母线上的光学成像原理、光学补偿技术,解决了宽范围正交光平面的聚集问题;输出了两条正交的水平光基准面与垂直光基准面,通过水平旋转机构与支架升降机构实现了两基准面上、下、左、右位置的任意移动,并保持输出信号基本特性不变.     

Shape detection with vision: implementing shape grammars in conceptual design

Despite more than 30 years of research, shape grammar implementations have limited functionality. This is largely due to the difficult problem of subshape detection. Previous research has addressed this problem analytically and has proposed solutions that directly compare geometric representations of shapes. Typically, such work has concentrated on shapes composed of limited geometry, for example straight lines or parametric curves, and as a result, their application has been restricted. The problem of general subshape detection has not been resolved. In this paper, an alternative approach is proposed, in which subshape detection is viewed as a problem of object recognition, a sub-domain of computer vision. In particular, a general method of subshape detection is introduced based on the Hausdorff distance. The approach is not limited in terms of geometry, and any shapes that can be represented in an image can be compared according to the subshape relation. Based on this approach, a prototype shape grammar system has been built in which the geometry of two-dimensional shapes is not restricted. The system automates the discovery of subshapes in a shape, enabling the implementation of shape rules in a shape grammar. Application of the system is illustrated via consideration of shape exploration in conceptual design. The manipulations of sketched design concepts are formalised by shape rules that reflect the types of shape transformations employed by designers when sketching.     

基于曲率特征混合分类的高密度点云去噪方法

为解决复杂曲面点云在平滑去噪中存在的问题,提出基于曲率信息混合分类的特征保持点云平滑算法．该方法将平面投影与双边滤波算法相结合,采用主成分分析法对点云的局部曲率特性进行评价,使用线性组合混合分类方法将数据分为平面、次特征、富特征类型以及组合类型．针对不同特征邻域类型,提出平面类型的投影平滑方法、次特征和富特征类型的变参数双边滤波法平滑方法的线性组合方法实现点云数据的平滑去噪．将该方法用于激光三维高分辨率人体扫描系统所得到的高密度点云数据,实验结果表明该方法能够在有效光顺点云的同时保持其表面的几何特征,且简化了法向调整的繁杂运算．     

AutoCAD 中基于超图约束驱动参数化设计的实现

 使用超图表示约束模型,采用基于超图约束驱动的几何推理约束满足法进行参数化设计,几何实体的计算基于特征点。作者结合在ＡｕｔｏＣＡＤ上开发参数化设计模块的实践,得出该方法能处理多实体约束关系（如面积约束）,提高求解效率,降低时间复杂度。     

Enriched machining feature-based reasoning for generic machining process sequencing

This paper presents an enriched machining feature (EMF)-based reasoning approach to generic machining process sequencing for distributed process planning (DPP). An EMF is represented by combining its machining volume with surface, geometric and volume features, as well as other technological information needed to machine the feature. The information embedded in the EMF is retrieved progressively for machining sequence generation. Following an introduction of EMF and its representation scheme, the problems in determining machine-independent feature groups (set-ups) in DPP and their machining sequences to be followed for a given part are investigated. Based on the EMF concept, five reasoning rules are formulated and the algorithms developed. As the set-ups and sequences are generated based on manufacturing constraints and datum references but separated from specific resources, they are generic and applicable to machine tools with varying configurations and capabilities. This approach is further validated through a case study.     

几何公差控制角度偏差及角度公差分析

针对角度尺寸公差不能控制平面与平面之间的角度,而采用几何公差控制可能会导致角度偏差失去控制等问题,引入了被测要素附加贴切要素符号,实现用几何公差精准控制被测平面与基准面之间角度偏差,并给出了几何公差与角度公差的换算方法;针对装配层平面与平面之间角度偏差控制及累积计算问题,研究了多个零件装配后的角度尺寸链画法和角度尺寸链偏差累积计算方法;最后,以某型号电动木材切割机为例实现了用几何公差控制角度累积偏差以及各个零件上相关特征的几何公差与角度公差的转换,并分析计算了角度累积偏差。研究结果可为平面与平面之间的角度公差的分析控制及图样标注提供借鉴和参考。     

Representation of function-form relationship for the conceptual design of stamped metal parts

Design representation of parts during conceptual design stage has been a challenging task because of the incompleteness of the information available. Traditional geometric design requires too much information on the geometric attributes, and does not consider the functionality of the part any more than that provided by individual features. Functional design in the form of verb, noun representation does not have adequate correlation with the geometric design. In this article, we propose a new form of the design representation of parts during conceptual design. The representation is calledsketching abstraction. In this representation, the discretionary geometry of the part that has functional relevance is captured using functional features, while the non-discretionary geometry is represented using a linkage mechanism. The functional features are related to the part function using data structures calledfunction-form matrices. The sketching abstraction is annotated with a set of primitives, and a grammar has been developed that parses the sketch to extract a set of canonical relationships between the functional features. These relationships can be used to extract part designs that are functionally similar but geometrically dissimilar. The sketching abstraction has a relationship with the solid model of the part as well. Thus we attempt to bridge the gap between function and form representations and provide the designer with a tool that can be used for generating design alternatives. We illustrate the theory developed in the domain of stamped metal parts.     

Feature-based geometric reasoning for process planning

We present a framework based on Domain Independent Form (DIF) features for automatic evaluation of manufacturability and process planning for machining. The framework enables interpretation of a common product model with respect to each task in the transition from design to manufacture. A key idea here is to generate the interpretation suitable for each task in two steps. In the first step, DIF features that are defined through feature enumeration are automatically extracted from the geometric model. The extracted DIF features are then mapped into features meaningful for individual tasks through geometric reasoning based on domain dependent knowledge. The formal approach to feature definitions and separation of the domain specific reasoning from the general geometric reasoning enable us to overcome the bottlenecks reported in features technology. Work reported in this paper has been funded in part by grants from Aeronautical Development Agency and the Department of Science and Technology.