Reasoning Boolean operation based modeling for heterogeneous objects

A reasoning Boolean operation based CAD modeling approach applied to construct heterogeneous material objects is presented. This reasoning Boolean operation consists of a merging operation and an extracting operation, and it is executed according to the material-dominant information defined in the designed heterogeneous object database. In addition to the material-dominant Boolean union, subtraction, and intersection, a new Boolean complex_union operation is defined and introduced to the set of the reasoning Boolean operation. The Boolean complex_union ‘assembles’ the results of the material-dominant Boolean intersection and subtraction to form a new modeling assembly for the heterogeneous object. Due to the CAD-based nature, the thus formed heterogeneous model can be readily implemented with advanced CAD/CAE/CAM software for integrated design, analysis, and simulation. An example of such an application, its hierarchy of the model database, and the major steps of the model construction are described.     

Heterogeneous object modeling through direct face neighborhood alteration

Two recent advances—the use of functionally gradient materials in parts and layered manufacturing technology—have brought to the forefront the need for design and fabrication methodologies for heterogeneous objects. However, current solid modeling systems, a core component of computer-aided design and fabrication tools, are typically purely geometry based, and only after the modeling of product geometry, can a part's non-geometric attributes such as material composition be modeled. This sequential order of modeling leads to unnecessary operations and over-segmented 3D regions during heterogeneous object modeling processes.

To enable an efficient design of heterogeneous objects, we propose a novel method, direct face neighborhood operation. This approach combines the geometry and material decisions into a common computational framework as opposed to separate and sequential operations in existing modeling systems. We present theories and algorithms for direction face neighborhood alteration, which enables direct alteration of face neighborhood before 3D regions are formed. This alteration is based on set membership classification (SMC) and region material semantics. The SMC is computationally enhanced by the usage of topological characteristics of heterogeneous objects. After the SMC, boundary evaluation is performed according to the altered face neighborhood. In comparison with other solid modeling methods, the direct face neighborhood alteration method is computationally effective, allows direct B-Rep operations, and is efficient for persistent region naming. A prototype system has been implemented to validate the method and some examples are presented.     

An open platform of shape design optimization for shell structure

A general platform built on a computer-aided design (CAD) system is developed for parameterized shape design optimization of shell structure. Within the platform, parameterized surface modeling and computer-aided engineering (CAE) applications are embedded and seamlessly integrated with the CAD system through its application programming interface (API). Firstly, instead of the CAD system inherent surface modeling, a parameterized surface modeling for shell structure is fulfilled through integrating with parametric solid modeling of the CAD system. Thus, any dimensions for parametric solid modeling can be used to control shape modification of shell structure and serve as design variables for shape design optimization. Secondly, seamless integration of geometry modeling and finite-element modeling for shell structure is implemented. Finally, with integrated procedures of finite-element analysis and optimization algorithms, a general platform for parameterized shape optimization of shell structure is realized. Numerical examples are presented, and the results validate the effectiveness and efficiency of the platform. A shorten version of this paper was presented to the 7th World Congress of Computation Mechanics (WCCM 2006), July 16–22, 2006, Los Angeles, CA, USA.     

基于虚拟现实的三维园林景观设计仿真系统

现有的园林景观专业CAD软件对三维模型及虚拟仿真效果表达有限,只能进行二维施工图绘制.为解决动态景观特性,研发了虚拟现实技术的三维园林景观设计仿真系统,采用面向对象的参数化三维实体建模手段,实现了三维实体建模、设计场景的三维实时虚拟呈现、渲染图及动画制作、施工图绘制等功能,并探索了系统计算原理、实现方法及OpenGL扩展功能等相关技术.然后简要介绍了系统整体功能,详细论述了专业模块中的仿真过程.最后以工程实例验证了系统的有效性.     

Internet-enabled real-time collaborative assembly modeling via an e-Assembly system: status and promise

Collaborative CAD systems enabling collaboration in computer-aided design processes among distributed designers are gaining more and more attention. Yet, such systems, especially in support of collaborative assembly modeling, are hardly achievable. Targeting this gap, this paper addresses an Internet-enabled real-time collaborative assembly modeling system, named e-Assembly. This emerging system allows a group of geographically dispersed designers to jointly build an assembly model in real time over the Internet. In particular, this paper proposes a new assembly representation, called Collaborative Assembly Representation, for Internet-based collaborative assembly modeling. Also, collaborative assembly constraint satisfaction is addressed based on three coordination rules embedded in e-Assembly. Furthermore, the system architecture and realization of e-Assembly are provided. Finally, a prototypic implementation of e-Assembly is presented for demonstration and discussion.     

以网络为中心的协同特征造型

在网络化同步协同设计环境中,如何实现CAD系统之间的实时数据交换和模型同步,成为协同几何造型的关键问题。文中提出了一种新的复制式协同特征造型方法,该方法将现有的特征造型技术与分布计算、网络通信技术相结合,通过简单的造型消息交换来实现增量式协同造型,可以较好地满足几何模型实时同步的需要,而且也部分地解决了异构CAD软件之间的数据交换问题;并详细地介绍了协同造型通信协议、对象引用机制、以及分布式协同造型系统。     

A survey on CAD methods in 3D garment design

With the advance in virtual reality applications, garment industry has strived for new developments. This paper reviews state-of-the-art CAD methods in 3D garment design. A large range of techniques are selected and organized into several key modules which form the core of a 3D garment design technology platform. In each module, basic techniques are presented first. Then advanced developments are systematically discussed and commented. The selected key modules - digital human modeling, 3D garment design and modification, numerical integration of draping, 2D pattern generation, geometric details modeling, parallel computation and GPU acceleration - are discussed in turn. Major challenges and solutions that have been addressed over the years are discussed. Finally, some of the ensuing challenges in 3D garment CAD technologies are outlined.     

异构CAD系统协同框架与互操作

协同CAD通过网络支持不同地域的设计人员实时地完成产品设计或决策任务,以提高群体协同工作效率;异构CAD系统协同将分布的不同的CAD系统,如ProE、UG、SolidWork等业界比较成熟且是主流的商业CAD系统,集成在一个框架平台下,从而支持人们更方便地协同工作;文章讨论了异构CAD系统协同的体系结构与共享感知问题,提出了一个支持共享感知的复制式系统结构模型;进一步将现有商业CAD系统引入到该模型中,给出了一个基于构件的协同CAD中间件框架模型,讨论了中间件接口和CAD系统的互操作。     

Interface programs to enable full 3-D geological modeling with a combination of AutoCAD and SURFER

The interface programs presented in this paper are capable of connecting gridding- and contouring software (SURFER) and a 3-D CAD system (AutoCAD) to enable true 3-D modeling in a standard MS-DOS environment. The results of the contouring package can be passed to the CAD system for postprocessing as full 3-D information; independent 2-D information stored in the CAD system can be sent to the contouring package to be overlaid on 3-D models     

一种面向方案设计的装配建模表示方法

ＣＡＤ系统对方案设计支持的关键是建立独立于几何细节而又表达的功构关系的装配模型,本文试图运用逻辑装配单元的定义来实现产品功能需求和结构表现间的有效关联,分别讨论了方案设计中功能描述和几何构形表示方式,形式化表达了方案设计的逻辑造型和装配建模过程,给出了支持自顶向下方案设计的装配模板定义,为方案设计的计算机辅助实现作了有益的尝试。     

基于ACIS平台的大型三维CAD系统的设计与开发

该文介绍了一个基于ACIS平台的大型三维CAD系统的设计、开发与应用。分别介绍了该系统的交互系统、造型系统和渲染系统的设计与实现。设计了一个栈式命令处理系统，便于实现异常复杂的用户交互命令。简要介绍了特征造型功能在ACIS平台上的实现。在ACIS框架上自选算法，重新设计了渲染引擎，扩展了渲染数据结构和功能，克服了ACIS提供的渲染引擎的局限性，得到了独特的渲染效果。最后介绍了本系统的应用情况。     

基于特征和知识的注塑模CAD/CAE集成化研究

重点讨论了利用特征造型技术和人工智能技术进行CAD／CAE集成的方法，并对系统集成的关键技术进行了研究。在对产品建模过程中，针对问题的不同特点采用不同的方法对知识进行提取和推理，最终目的是提高注塑模设计的自动化程度，实现设计－分析的自适应。     

机器人专用VLSI芯片及其设计系统

本课题目标是建立一个机器人VLSI专用芯片设计系统,并进行ROCO芯片(用于机器人正、反运动学,雅可比矩阵和动力学的实时计算)的设计和验证。     

基于特征的三维参数化产品造型系统ZD－MCAD Ⅱ

本文介绍了浙江大学人工智能研究所在产品造型研究基础上完成的一个面向机械产品设计的实用化计算机辅助设计（ＣＡＤ）系统ＺＤ－ＭＣＡＤⅡ。首先我们结合实际从事ＣＡＤ系统的经验提出了一套开发实用化、商品化ＣＡＤ系统的设计方法学，然后介绍了ＺＤ－ＭＡＣＤⅡ的系统结构以及总体功能，并就某些重要的模块的结构及实现进行了广泛的讨论。     

工程布局CAD系统设计与实现

针对工程布局设计的复杂性,提出了开放式的工程布局设计CAD系统的结构框架,讨论了实现该系统的关键方法,包括自动化设计进程建模、基于功能特征的待布物和布局空间几何近似建模、布局知识和布局约束的表达、布局方法应用.基于该系统框架,实现了计算机辅助工程布局设计原型系统,并以车辆动力舱布局设计为背景,对原型系统的有效性进行了验证.     

从工业界的角度看CAD技术的研究主题与发展方向

回顾了现有CAD系统所采用的主流、成熟技术,包括特征造型技术,基于历史的造型、参数化设计以及组件技术．从工业界的角度分析了当前CAD技术的若干研究主题,包括CAD与互联网、曲面造型、数据交换、从二维到三维、概念设计与早期设计等．并展望了未来的CAD系统,包括未来的计算环境、未来的机械CAD、未来的数据共享以及未来的零件造型技术。     

Logic-based 2D geometric modeling in a CAD environment

This paper examines the use of predicate logic for deductive construction of geometric models. The process of logical inference and its use for geometric modeling is examined. The logic-based definition of a retaining wall is presented, the implementation of a logic-based CAD system using a commercial software is briefly discussed and its use is illustrated.