基于哈希的二维工程 CAD 图纸检索技术

针对企业在设计创新过程中大量采用已有计算机辅助设计(CAD)图纸进行设计重 用的情况,提出了一种基于哈希的二维工程 CAD 图纸检索方法。首先基于环形分割算法提取 工程 CAD 图纸中每个组件对象几何特征;基于传统 LBP 算子提出了一种局部拓扑矢量量化模 式(T-LVQP),实现对各个组件拓扑特征的提取;然后基于协方差描述符融合几何特征和拓扑特 征,通过 LBG 算法将所有组件按照几何特征分组后得到工程 CAD 图纸的特征向量表达;最后 通过迭代量化哈希算法生成图纸的哈希序列。实验结果表明,该算法检索速度快、准确度高, 对于二维工程 CAD 图纸具有较好的检索效果。     

集成环境中基于特征顺序的产品建模方法研究

ＣＡＤ系统输出的基于特征的产品数据,实际上是一个静态的特征序列的描述,百忽略了特征在“拼装”成零件时,所遵循的顺序规律。在对特征分类的基础上,研究了基本形状特征之间的空间关系、拼装所遵循的规律,提出了基于特征关系矩阵及其有向夫环图的描述方法,建立具有动态性的和层次性的产品特征的数据模型。详细讨论了由ＣＡＤ系统数据转化为集成系统内部层次模型过程中所涉及的主要问题,包括特征之间的关系、特征关系矩阵的建     

Principled Modeling and Automatic Classification for Enhancing the Reusability of Problem Solving Methods of Expert Systems

Software reuse is widely believed to be a key to improving software productivity and quality in conventional software. In expert systems, much of the knowledge has been compiled (i.e., compressed and restricted into effective procedures) and this makes reusability difficult. One of the issues in modeling expert systems for enhanced reusability is capturing explicity the underlying problem solving designs. Principled knowledge representation schemes have been used to model components of complex software systems. However, the potential for applying these principled modeling techniques for explicitly capturing the problem solving designs of expert systems has not been fully explored. To overcome this omission, we use an Artificial Intelligence knowledge representation scheme for developing an ontology of the software components to facilitate their classification and retrieval. The application of our ontological approach is of both theoretical and practical significance. This method facilitates the reuse of high-level design. We illustrate the application of principled domain modeling using two real world applications of knowledge-based systems.     

A survey of digital design reuse

As integrated circuit technologies advance toward higher performance, greater densities, and increasing system complexity, CAD tools and design methodologies struggle to keep pace. Managing the formidable complexity of the design process is one of the main challenges to IC design. Disseminating design reuse is central to bringing the design effort's complexity back to a manageable size. Effective reuse, though, takes more than just gathering predesigned components in a library. Reuse-oriented policies and strategies must permeate the entire design process, from the methodologies themselves to the final designs. In this article, we provide a brief overview of the state of the art in design reuse for digital systems. We also discuss the challenges posed to this discipline by the recent trend toward integrating processor cores in high-volume application specific integrated circuits     

Automating the analysis of design component contracts

Software patterns are a new design paradigm used to solve problems that arise when developing software within a particular context. Patterns capture the static and dynamic structure and collaboration among the components in a software design. A key promise of the pattern‐based approach is that it may greatly simplify the construction of software systems out of building blocks and thus reuse experience and reduce cost. However, it also introduces significant problems in ensuring the integrity and reliability of these composed systems because of their complex software topologies, interactions and transactions. There is a need to capture these features as a contract through a formal model that allows us to analyze pattern‐based designs. In this paper, we provide an overview of a formal framework for ensuring the integrity of the compositions in object‐oriented designs by providing mathematically rigorous modeling and analysis techniques for object‐oriented systems comprising pattern‐based designs as the basic building blocks or design components. A case study related to a hypermedia Web‐based application has been presented to illustrate our approach in distributed systems. Copyright © 2005 John Wiley & Sons, Ltd.     

Similarity assessment of 3D mechanical components for design reuse

Duplicate designs consume a significant amount of resources in most new product development. Search of similar parts for a given query part is the key to avoid this problem by facilitating design reuse. Most search algorithms convert the CAD model into a shape signature and compute the similarity between two models according to a measure function of their signatures. However, each algorithm defines the shape signature in a different way, and thus has its own limitations in discriminating 3D parts. This paper proposes a search scheme that successfully complements various shape signatures in similarity assessment of 3D mechanical components. It considers form-feature, topological, and geometric information in component comparison. Such an integrated approach can effectively solve the feature intersection problem, inherited in any feature-based approaches, and capture the user's intent more precisely in the search, which geometry-based methods fail to accomplish. We also develop a set of algorithms that performs the component comparison in a polynomial time. The proposed scheme is implemented in a product design environment consisting of commercial CAD and PDM systems. The result demonstrates the practicality of this work in automatic search of similar mechanical components for design reuse.     

Content-based assembly search: A step towards assembly reuse

The increased use of CAD systems by product development organizations has resulted in the creation of large databases of assemblies. This explosion of assembly data is likely to continue in the future. In many situations, a text-based search alone may not be sufficient to search for assemblies and it may be desirable to search for assemblies based on the content of the assembly models. The ability to perform content-based searches on these databases is expected to help the designers in the following two ways. First, it can facilitate the reuse of existing assembly designs, thereby reducing the design time. Second, a lot of useful designs for manufacturing, and assembly knowledge are implicitly embedded in existing assemblies. Therefore a capability to locate existing assemblies and examine them can be used as a learning tool by designers to learn from the existing assembly designs. This paper describes a system for performing content-based searches on assembly databases. We identify templates for comprehensive search definitions and describe algorithms to perform content-based searches for mechanical assemblies. We also illustrate the capabilities of our system through several examples.     

Constructing Minimum Connected Dominating Sets with Bounded Diameters in Wireless Networks

Connected Dominating Sets (CDSs) can serve as virtual backbones for wireless networks. A smaller virtual backbone incurs less maintenance overhead. Unfortunately, computing a minimum size CDS is NP-hard, and thus most researchers in this area concentrate on how to construct smaller CDSs. However, people neglected other important metrics of network, such as diameter and average hop distances between two communication parties. In this paper, we investigate the problem of constructing quality CDS in terms of size, diameter, and Average Backbone Path Length (ABPL). We present two centralized algorithms having constant performance ratios for its size and diameter of the constructed CDS. Especially, the size of CDS computed by the second algorithm is no more than 6.906 times of its optimal solution. Furthermore, we give its distributed version, which not only can be implemented in real situation easily but also considers energy to extend network lifetime. In our simulation, we show that in average the distributed algorithm not only generates a CDS with smaller diameter and ABPL than related work but also suppresses its size well. We also show that it is more energy efficient than others in prolonging network lifetime.     

LdShake support for team-based learning design

Some educational innovation initiatives require practitioners to team up on the design of new learning activities. However, existing learning design tooling does not integrally support their tasks. Some tools enable authoring of designs, while other tools support sharing and commenting of learning design ideas, but none of them offers an integrated provision of technological features to support the work of design teams specifically. The requirements include team formation, the storage and retrieval of designs, and the promotion of interaction in the co-creation of designs. The LdShake platform has been conceived to enable sharing and co-editing of learning designs. This paper introduces LdShake’s technological features and evaluates to what extent they support the aforementioned requirements. A first evaluation context is focused on learning design, while a second one is devoted to devising research ideas. The results obtained in the two contexts are complementary, pointing out distinct affordances and user behaviors (e.g., on browsing designs) that depend on the characteristics of each context, while also bringing to light the relevance of LdShake’s social network related features. Overall, the design considerations proposed and the evaluation results obtained contribute toward an improved understanding of how to support networked teams.     

Abstract data views: an interface specification concept to enhancedesign for reuse

The abstract data view (ADV) design model was originally created to specify clearly and formally the separation of the user interface from the application component of a software system, and to provide a systematic design method that is independent of specific application environments. Such a method should lead to a high degree of reuse of designs for both interface and application components. The material presented, extends the concept of ADV's to encompass the general specification of interfaces between application components in the same or different computing environments. This approach to specifying interfaces clearly separates application components from each other, since they do not need to know how they are used, or how they obtain services from other application components. Thus, application components called abstract data objects (ADOs), are designed to minimize knowledge of the environment in which they are used and should be more amenable to reuse     

An educational exercise examining the role of model attributes on the creation and alteration of CAD models

Computer-aided design (CAD) is a ubiquitous tool that today’s students will be expected to use proficiently for numerous engineering purposes. Taking full advantage of the features available in modern CAD programs requires that models are created in a manner that allows others to easily understand how they are organized and alter them in an efficient and robust manner. The results of a class-based exercise are presented to examine the role of model attributes on model creation, alteration, and student perception. Two popular CAD programs are used for the exercise: SolidWorks and Pro|Engineer. General results from both programs are reported. Fewer more complex features are found to be correlated with reduced modeling time. Simple features are shown to be positively correlated with the number of features retained without change. More complex features are found to be negatively correlated with the number of new features. Student perceptions of model quality and intuitiveness are positively correlated with the amount of feature reuse. Student survey data shows a preference for simpler features, the naming of features, and the use of reference geometry. The results do not allow for a generic approach regarding feature complexity to be prescribed. Overall, properly conveying design intent is shown to be positively correlated with design retention and negatively correlated with alteration time.     

Knowledge graph construction for product designs from large CAD model repositories

Product Design based Knowledge graphs (KG) aid the representation of product assemblies through heterogeneous relationships that link entities obtained from multiple structured and unstructured sources. This study describes an approach to constructing a multi-relational and multi-hierarchical knowledge graph that extracts information contained within the 3D product model data to construct Assembly-Subassembly-Part and Shape Similarity relationships. This approach builds on a combination of utilizing 3D model meta-data and structuring the graph using the Assembly-Part hierarchy alongside 3D Shape-based Clustering. To demonstrate our approach, from a dataset consisting of 110,770 CAD models, 92,715 models were organized into 7,651 groups of varying sizes containing highly similar shapes, demonstrating the varied nature of design repositories, but inevitably also containing a significant number of repetitive and unique designs. Using the Product Design Knowledge Graph, we demonstrate the effectiveness of 3D shape retrieval using Approximate Nearest Neighbor search. Finally, we illustrate the use of the KG for Design Reuse of co-occurring components, Rule-Based Inference for Assembly Similarity and Collaborative Filtering for Multi-Modal Search of manufacturing process conditions. Future work aims to expand the KG to include downstream data within product manufacturing and towards improved reasoning methods to provide actionable suggestions for design bot assistants and manufacturing automation.     

ODMixed: A tool to obtain optimal designs for heterogeneous longitudinal studies with dropout

ODMixed is a computer program to obtain optimal designs for linear mixed models of longitudinal studies. These designs account for heterogeneous correlated errors and for data with dropout. Designs are compared by using relative efficiencies, e.g., between a D-optimal design for homogeneous data and another for heterogeneous data or between a D-optimal design for complete data against another that optimizes designs when data is missing at random. Two examples are worked out to illustrate how researchers could use this computer program to profit of optimal design theory at the planning stage of longitudinal studies.     

Selecting and parameterising components using knowledge based configuration and a heuristic that learns and forgets

In this paper we suggest the use of knowledge based configuration in connection with CAD systems to enhance the ability of reusing models of CAD components and to automate solution processes especially of variational design problems. Configuration systems can support design engineers in choosing components and in checking consistency. We have investigated how configuration mechanisms can be applied to the design of engineering products and introduce our heuristic relevant knowledge first (RKF). This heuristic solves many of the problems which occur with configuration in engineering domains which continuously change, e.g. as a consequence of innovation. We conclude with the presentation of experiments performed with RKF.     

面向复用成本优化的构件重构方法

构件需要在其复用期间进行持续的优化改进和重构,消除设计需求与复用需求之间的差异,在保证有用性的前提下改善可用性.为此,提出一种面向复用成本优化的、基于局部性原理与实例集分解的构件重构方法.首先给出一种基于特征的构件模型,着重探讨基于可变点的复用机制,并在此基础上研究构件复用成本的构成要素、优化策略与优化目标,即通过提高构件固定部分的比例降低复用成本.探讨了构件复用过程中存在的时间/空间局部性,依据构件实例复用频度的差异,将具有高复用频度的实例分离出来形成(半)实例化构件,以降低构件复用过程中的实例化成本与实现成本.进而提出一种基于贪心策略的构件实例分解算法实现近似最优化,并通过实例验证其有效性.该方法通过将构件特征间依赖关系分解为构件实例间依赖关系,将构件的部分实例化工作由复用阶段提前到设计阶段来完成,将若干可变特征转化为固定特征,从而避免了构件频繁复用时的多次实例化,以降低复用成本.     

A feature-based fixture design methodology for the manufacturing of aircraft structural parts

In fixture design for the manufacturing of aircraft structural parts, there are various challenges and serious problems in industry, such as difficulty in design knowledge capture and reuse, and the arbitrary or non-standard nature of design, which influence the efficiency and quality of fixture design. This paper proposes a feature-based fixture design methodology in which previous fixture design cases and design rules are described in association with features and thus the design knowledge is integrated with geometric information of aircraft structural parts, which are the main concern of this project. In this methodology, machining features of the structural parts and their associated attributes are identified by feature recognition technique from the 3 dimensional (3D) part models defined based on model-based definition (MBD) technique. The feature-based part information models are then established and are used to retrieve previous fixture design cases and design rules stored in the knowledge base. Fixture designers will choose the appropriate retrieved design cases as the starting point for new fixture design or use previous designs to assess his/her current design. In this way the process of new fixture design can be improved. In the current stage of the research, a prototype feature-based fixture design system based on CATIA for the manufacturing of aircraft structural parts has been developed and used by a large airplane manufacturer.     

基于自编码器的特征迁移算法

近年来,栈式自编码网络（stacked auto-encoder,SAE）在大规模数据集上表现出优异的图像分类性能。相对于其他图像分类方法中手工设计的低级特征,SAE的成功归因于深度网络能够学习到丰富的中级图像特征。然而,估计上百万个网络参数需要非常庞大的带标签的图像样本数据集。这样的性质阻止了SAE在小规模训练数据上的许多应用。在这篇文章中,提出的算法展示如何将SAE在大规模数据集上学习到的图像表示有效地迁移到只有有限训练数据的视觉识别任务中。实验部分设计了一个方法来复用在MNIST数据集上训练得到的隐藏层,以此计算在MNIST-variations数据集上的中级图像表示。实验结果展示了尽管两个数据集之间存在差异,但是被迁移的图像特征能够使得模型的分类性能得到极大的提升。     

特征的自动识别规则与提取

在对箱体类零件的加工特征及特征参数进行了分析,归纳和总结,在特征实体造型进行了研究的基础上,制定了各类特征的合理的识别规则和 识别算法,及提取的信息模型,实现了对复杂箱体类零件的加要特征信息自动提取,及CAD／CAPP系统的信息自动传递。     

A behavioral analysis and verification approach to pattern-based design composition

Integrating software components to produce large-scale software systems is an effective way to reuse experience and reduce cost. However, unexpected interactions among components when integrated into software systems are often the cause of failures. Discovering these composition errors early in the development process could lower the cost and effort in fixing them. This paper introduces a rigorous analysis approach to software design composition based on automated verification techniques. We show how to represent, instantiate and integrate design components, and how to find design composition errors using model checking techniques. We illustrate our approach with a Web-based hypermedia case study.