异构CAD系统集成技术综述

异构CAD系统集成是实现协同产品开发的重要环节.首先讨论基于几何数据交换的异构CAD系统集成方法,论述几何数据交换方法本身存在的问题、几何数据交换相比其他方法的不足;然后从参数化特征信息交换的核心问题、代表性研究工作和特征信息交换工具3个方面入手,分析基于参数化特征信息交换的异构CAD系统离线集成,并对基于操作命令交换的CAD系统在线集成工作进行介绍.最后对该领域未来的发展趋势进行了总结.     

一种含设计意图的3D模型数据实时交换格式

为了在不同商用3D CAD系统之间实现含设计意图的几何模型数据的网上实时交换,提出了一种基于XML描述的数据交换格式,可将参考面的定位数据与局部坐标、组成轮廓草图的图元数据与约束关系、特征的构建形式与构建过程以层次结构化的方式包含在交换数据中,满足了同构与异构CAD系统之间实时交换含设计意图的数据之需要.     

特征交换框架下奇异特征的处理

在实体建模中,奇异特征的存在阻碍了基于特征的数据交换的顺利进行。针对该问题,提出一种在特征交换框架下基于几何操作的奇异特征交换方法,通过将奇异特征转化为一组与之等价的几何操作实现奇异特征的交换。实验结果表明,该方法能有效解决异构CAD系统间奇异特征的交换问题。     

CAD数据交换与互操作性的研究

针对目前三维CAD数据的交换状况,分析了基于标准模型和专用接口等两种主要CAD数据交换技术.以STEP标准为例,阐述了基于标准模型的CAD交换技术的架构和实际交换过程中遇到的数据丢失问题.专用接口是点对点的交换,是最原始的解决CAD数据交换的方法,涉及到各个CAD软件的商业利益,在CAD软件众多的情况下,使得CAD数据交换异常复杂.这两种CAD数据交换方法存在一个重大缺陷,即产生的都是"哑"模型,在非原CAD系统中无法对其进行编辑,极大地阻碍了CAD数据的交换.同步建模技术采用概念设计的理念和非历史特征的建模方法,不仅加速了模型设计,也较好地解决了CAD数据的交换问题.     

异构CAD系统间中性语义特征数据交换

提出了一种基于中性语义特征转换的异构CAD系统间数据交换方法,该方法采用“中性语义特征转换器”将不同系统间的造型信息转换为统一的数据信息格式,并通过中性语义转换库实现了不同系统间操作命令的4种映射关系。此外,还实现了异构CAD系统间零件的同步协同传输。最后,将该文提到的思想初步应用在理工大学自主开发的HUSTCAIDS与UG间的异构协同设计中,证明该理论的可行性。     

电力应用系统数据交换平台

现代企业资源具有分布式、异构性、跨领域协同工作等特点。通过分析电力行业电力应用系统的现状,针对各系统间缺乏规范化和标准化的数据共享机制,信息资源难以共享,数据交换率低效等问题,提出了基于SOA架构,以XML作为异构系统之间数据交换的标准格式,以Web Service作为各系统数据交换的标准接口的数据交换平台,解决各系统间的数据的交换和共享。经过实际应用表明,本平台极大的方便了各电力应用系统之间数据的交换与共享,大大的提高了企业的运营效率。     

CAD/PDM系统间数据双向集成技术和应用研究

针对CAD/PDM系统间点对点集成存在的维护困难等问题,提出了一种以中间集成平台为基础的CAD/PDM系统间数据双向集成解决方案。方案包括：CAD/PDM系统间数据双向集成业务流程建模、CAD/PDM系统中的BOM和关联图文档数据表现形式、基于中间集成平台的CAD/PDM数据集成模式、嵌入式适配器、XML数据交换协议、消息机制,以及具有消息机制的SolidWorks/Mit-PDM嵌入式适配器软件开发。以某夹具产品的设计数据交换为例,验证了所提出方式的正确性。实际应用表明：该方案具有较好的柔性和扩展性,能实现异构CAD/PDM系统间的双向数据交换集成。     

集中式异构数据交换模型的研究和设计

本文首先研究电子政务中基于集中式的异构数据交换模型的体系结构,然后提出了一种基于XML、WebService的跨平台、松散耦合的异构数据库间安全数据交换系统模型,将交换的层次提高到直接的政务业务交换。最后给出了一个使用该数据交换模型的应用实例。     

电子政务系统中的数据交换和共享服务平台设计

就电子政务系统中的数据交换和共享服务平台设计展开了相关的分析与探讨,阐述了目前电子政务系统中的数据交换问题,就数据交换的网络结构予以深入研究,并设计出了一种扩展性能较强的电子政务数据交换平台系统,从而促成了异构数据库间的可视性交换, “信息孤岛”问题迎刃而解.     

基于XML的战略网络信息平台研究与实现

如何建立战略网络信息平台,实现组织间异构数据库的信息交换,是战略网络有效运行和效率提高的关键所在。该文在分析XML的特点基础上,提出了基于XML的战略网络的信息交换平台总体框架,论述了基于XML的战略网络信息平台的作用、异构数据交换的方法原理和实现过程,以期解决组织间异构数据库的数据交换和共享问题。     

An approach to identify design and manufacturing features from a data exchanged part model

Due to the large variety of CAD systems in the market, data exchange between different CAD systems is indispensable. Currently, data exchange standards such as STEP and IGES, etc. provide a unique approach for interfacing among different CAD platforms. Once the feature-based CAD model created in one CAD system is input into another via data exchange standards, many of the original features and the feature-related information may not exist any longer. The identification of the design features and their further decomposition into machining features for the downstream activities from a data exchanged part model is a bottleneck in integrated product and process design and development. In this paper, the feature panorama is succinctly articulated from the viewpoint of product design and manufacturing. To facilitate feature identification and extraction, a multiple-level feature taxonomy and hierarchy is proposed based on the characteristics of part geometry and topology entities. The relationships between the features and their geometric entities are established. A litany of algorithms for the identification of design and machining features are proposed. Besides, how to recognize the intersecting features or compound features based on the featureless chunks of geometry entities is critical and the issue is addressed in the paper. A multi-level compound feature representation and recognition approach are presented. Finally, case studies are used to illustrate the validity of the approach and algorithms proposed for the identification of the features from CAD part models in neutral format.     

A constructive approach to calculate parameter ranges for systems of geometric constraints

Geometric constraints are at the heart of parametric and feature-based CAD systems. Changing values of geometric constraint parameters is one of the most common operations in such systems. However, because allowable parameter values are not known to the user beforehand, this is often a trial-and-error process. We present an approach for automatically determining the allowable range for parameters of geometric constraints. Considered are systems of distance and angle constraints on points in 3D that can be decomposed into triangular and tetrahedral subproblems, by which most practical situations in parametric and feature-based CAD systems can be represented. Our method uses the decomposition to find critical parameter values for which subproblems degenerate. By solving one problem instance for each interval between two subsequent critical values, the exact parameter range is determined for which a solution exists.     

A novel CRDT-based synchronization method for real-time collaborative CAD systems

CRDT (Conflict-free Replicated Data Type) has been proposed as an alternative synchronization mechanism for collaborative text editing systems in recent years. However, CRDT-based synchronization methods for collaborative systems with sophisticated objects, such as collaborative CAD (Co-CAD) systems, are rarely investigated in previous literatures. How well CRDT-based synchronization methods for Co-CAD systems could perform remains unknown. This paper presents a novel CRDT-based synchronization method to maintain eventual consistency for the feature-based CAD model. Firstly, three operation relations are defined as the dependency-conflict relation, the mutual exclusive relation and the compatible relation in context of the feature-based CAD systems. Secondly, a feature-based conflict detection mechanism is proposed to detect the three relations. Thirdly, a feature-based conflict resolution approach under the CRDT framework is presented to solve the conflicts. Fourthly, the time complexity and the space complexity are analyzed in theory. Finally, case studies of collaborative modeling procedures verify the correctness and feasibility of the proposed method.     

Isogeometric topology optimization using trimmed spline surfaces

In the present work, a new spline based topology optimization using trimmed spline surfaces and the isogeometric analysis is proposed. In the proposed approach, the trimmed surface analysis which can treat topologically complex spline surfaces using trimming information provided by CAD systems is employed for structural response analysis and sensitivity calculation in the topology optimization. The outer and inner boundaries of design models are represented by a spline surface and trimming curves. Design variables used in this approach are the coordinates of control points of a spline surface and those of trimming curves. New sensitivity formulations for the control points in the trimmed surface analysis are proposed and their efficiency and accuracy are verified. The creation of new inner fronts during optimization is allowed for the topological flexibility. An inner front merging algorithm is also presented. The proposed spline based topology optimization is used to solve some benchmarking problems. Design space dependency which is one of serious shortcomings in conventional topology optimization approaches is naturally eliminated by the proposed spline based optimization. Design dependent load problems which are difficult to treat with conventional grid based topology optimization methods are easily dealt with by the proposed one. It is also shown that post-processing effort for converting to CAD model is eliminated by using the same spline information in numerical analysis and design optimization.     

Ontology-based feature mapping and verification between CAD systems

Data interoperability between computer-aided design (CAD) systems remains a major obstacle in the information integration and exchange in a collaborative engineering environment. The use of CAD data exchange standards causes the loss of design intent such as construction history, features, parameters, and constraints, whereas existing research on feature-based data exchange only focuses on class-level feature definitions and does not support instance-level verification, which causes ambiguity in data exchange. In this paper, a hybrid ontology approach is proposed to allow for the full exchange of both feature definition semantics and geometric construction data. A shared base ontology is used to convey the most fundamental elements of CAD systems for geometry and topology, which is to both maximize flexibility and minimize information loss. A three-branch hybrid CAD feature model that includes feature operation information at the boundary representation level is constructed. Instance-level feature information in the form of the base ontology is then translated to local ontologies of individual CAD systems during the rule-based mapping and verification process. A combination of the Ontology Web Language (OWL) and Semantic Web Rule Language (SWRL) is used to represent feature classes and properties and automatically classify them by a reasoner in the target system, which requires no knowledge about the source system.     

基于特征的CAD数据交换方法研究

分析了现有产品数据交换方法的基本特点并指出其不足之处,提出了一种基于特征的CAD数据交换方法,这种以定义造型功能映射集合为基础的新方法实现了不同CAD系统之间高效的数据交换,可保存高层设计意图。在Inventor和SolidWorks上初步实现了拉伸、旋转、扫描、圆角等几种特征数据交换,验证了方法的可行性。     

Parametric exchange of round shapes between a mechanical CAD system and a ship CAD system

Interoperability among heterogeneous Computed-Aided Design (CAD) systems is an important issue. With the advent of global outsourcing, collaborative design has expanded from inside the enterprise to parts suppliers. This paper introduces a method for design data exchange between shipyards and equipment suppliers. These parties usually use different CAD systems, because they want to select the most suitable one for their jobs. CAD systems provide modeling functionality that is based on distinct modeling units. Therefore, to exchange design data, one must map between these two distinct sets of modeling units. Some modeling units can be directly mapped and converted, and other modeling units that cannot be directly mapped (such as the fillet feature in a mechanical CAD system) are converted by the indirect mapping procedure proposed in this paper. The proposed method is demonstrated with case studies between TransCAD and the AVEVA Marine system.     

建筑结构CAD数据交换技术研究

随着ＣＡＤ技术的发展,ＣＡＤ在建筑工程的应用越来越广泛。本文在分析国内建筑结构ＣＡＤ应用现状的基础上,对结构ＣＡＤ如何有效地利用建筑ＣＡＤ的设计成果作了深入研究,提出了基于构件识别和工程数据库管理的建筑与结构ＣＡＤ之间进行数据交换的技术。     

Feature-based spline optimization in CAD

In this paper, an advanced method for CAD-based spline structure optimization is investigated. The method is based on the combination of the commonly known parameter-based spline shape optimization and a recently presented feature-based structure variation concept for commercial CAD tools. The aim is to extend common parameter-based spline shape variation by the additional possibility to automatically add and remove control points or entire splines directly in CAD space. Such advanced spline modification provides a new level of flexibility in general geometry-based structural optimization. Using these splines to build CAD models, entirely new structures may be automatically generated during an optimization run through this newly gained flexibility in spline manipulation. The idea is to roughly define a continuous design space by basic splines and to gradually increase their shape complexity by control point number variation during optimization. Thus, operating on a knowledge-lean initialization—a design space bounded by basic splines and filled with material—this combination further extends the search and solution spaces of CAD-based structural optimization. The paper provides an outlook towards automated geometry-based structure creation combining nowadays commercial CAD software and a dedicated variation and optimization framework for geometry-based structural optimization.     

有限元领域中多态模型误差分析方法

基于特征造型技术的三维CAD系统目前已广泛应用于产品设计,同时CAE在产品设计与优化中也起到了越来越重要的作用.而有限元是最为广泛使用的CAE方法之一.由CAD系统建立的模型在进行有限元分析之前,通常需要根据分析需要对模型进行简化,如何分析模型简化前后对有限元计算结果的影响程度是CAD模型到CAE模型自动转化的首要步骤.将模型因特征的简化而形成的各种状态的模型称为多态模型.针对确保一定分析精度,节省计算资源的需求,根据有限元误差理论提出了分析不同简化模型对有限元分析结果造成的误差的方法,且通过数据实例得到验证,根据误差分析方法提出模型误差层次的概念,为有限元领域中多态模型的生成提供了新的思路.