Intelligent computer-aided-design systems: a synergical approach of artificial intelligénce and engineering

A synergism has begun to surface from the artificial intelligence (AI) and engineering communities: an effort to apply AI techniques to engineering problem-solving activities, and to study problems arisen from various engineering fields as a way to develop AI theories and methodologies. This paper first discusses the needs of such a synergical approach and identifies in a broad perspective some AI techniques currently being applied to engineering. It then describes a system, called KREATOR, which applies qualitative reasoning, a subfield of AI, to computer-aided design (CAD). The key observation is that an engineer designer's qualitative knowledge can offer a good basis for the reasoning of device behaviors. Such knowledge, however, is not captured by conventional CAD systems for lack of good representations. KREATOR is a knowledge capturing scheme that allows the designers to record their qualitative knowledge of how mechanical devices behave, KREATOR then automatically generates qualitative simulations.     

A feature-based database evolution approach in the design process

Design data are assigned in geometric and non-geometric form in order to meet design requirements. These data and information must be encapsulated in a data structure that has significance for design applications in each design process phase. The main goal of this research is to find design data groups that represent each mechanical design phase, which will be called phase's design signature. In addition, current data should be an evolution of the geometric and non-geometric information of the previous design phase. In this paper, the purpose is to identify and model a set of design features that encapsulate the design data and their transformations which occurred during the mechanical design phases. This database must capture the designer's intents that can be modeled and implemented using feature-based model in the conventional CAD systems, object-oriented modeling, and Java classes.     

A conceptual approach for the die structure design

A large number of decisions are made during the conceptual design stage which is characterized by a lack of complete geometric information. While existing CAD systems supporting the geometric aspects of design have had little impact at the conceptual design stage. To support the conceptual die design and the top–down design process, a new concept called conceptual assembly modeling framework (CAMF) is presented in this paper. Firstly, the framework employs the zigzag function-symbol mapping to implement the function design of the die. From the easily understood analytical results of the function-symbol mapping matrix, the designer can evaluate the quality of a proposed die concept. Secondly, a new method—logic assembly modeling is proposed using logic components in this framework to satisfy the characteristic of the conceptual die design. Representing shapes and spatial relations in logic can provide a natural, intuitive method of developing complete computer systems for reasoning about die construction design at the conceptual stage. The logic assembly which consists of logic components is an innovative representation that provides a natural link between the function design of the die and the detailed geometric design.     

Using behavioral modeling technology to capture designer's intent

Ever since the introduction of geometric modeling technology in computer-aided design (CAD) systems, engineering designers have been able to speed up the design process and improve the design quality as well as collaborate on a design project with co-designers seated in different parts of the world. One of the recent emergences in the field of CAD tools is that of behavioral modeling (BM). It extends the capabilities of existing solid modeling applications by capturing the designer's knowledge in the computer model(s) of a design. It also assists the designer by iteratively checking model variances against designer specified constraints and goals so as to arrive at an optimum design during a reasonably short span of time. This article discusses the characteristics of its applications in a number of CAD systems. Some of the common characteristics include working within, or in conjunction with, 3D models and using behavioral features to embed design knowledge in a model. In the case of some high-end solid modelers, BM functionality has been combined with knowledge based engineering techniques.     

计算机辅助结构设计与分析的集成框架研究

针对计算机辅助结构设计和分析的集成问题,设计了一种基于统一模型库 方式的组件式CAD/CAE 集成框架,以结构CAD/CAE 集成模型库为框架底层,以几何造型、 可视化交互、第三方CAD、第三方CAE 等组件为中间组件层,以空间结构设计子系统、空 间结构分析子系统为上层应用层,提供空间实体建模、工程模型管理、多种有限元模型分析 与计算等功能,并应用于港口码头的结构设计及有限元分析。     

Adaptive CAD model (re-)construction with THB-splines

Computer Aided Design (CAD) software libraries rely on the tensor-product NURBS model as standard spline technology. However, in applications of industrial complexity, this mathematical model does not provide sufficient flexibility as an effective geometric modeling option. In particular, the multivariate tensor-product construction precludes the design of adaptive spline representations that support local refinements. Consequently, many patches and trimming operations are needed in challenging applications. The investigation of generalizations of tensor-product splines that support adaptive refinement has recently gained significant momentum due to the advent of Isogeometric Analysis (IgA) [2], where adaptivity is needed for performing local refinement in numerical simulations. Moreover, traditional CAD models containing many small (and possibly trimmed) patches are not directly usable for IgA. Truncated hierarchical B-splines (THB-splines) provide the possibility of introducing different levels of resolution in an adaptive framework, while simultaneously preserving the main properties of standard B-splines. We demonstrate that surface fitting schemes based on THB-spline representations may lead to significant improvements for the geometric (re-)construction of critical turbine blade parts. Furthermore, the local THB-spline evaluation in terms of B-spline patches can be properly combined with commercial geometric modeling kernels in order to convert the multilevel spline representation into an equivalent – namely, exact – CAD geometry. This software interface fully integrates the adaptive modeling tool into CAD systems that comply with the current NURBS standard. It also paves the way for the introduction of isogeometric simulations into complex real world applications.     

Solid modeling

Solid modeling deals with the representation, design, visualization. and analysis of models of 3D parts. While the embodiment of solid modeling technology in contemporary commercial CAD systems is finally beginning to fulfil the old promise of providing major improvements in the productivity of the manufacturing industry, solid modeling research remains in its infancy. Recent developments focus on advanced design paradigms, topological and geometric extensions of the domain and the performance and reliability of the fundamental algorithms. The current trend follows two paths: capitalizing on the concepts of features, constraints, and model parameterization, which provide a more intuitive and suitable design vocabulary than the traditional edges, faces, or Boolean operations; and incorporating information about the tolerances, assembly relations, and mechanical properties of parts and assemblies, which provides a suitable product database for the development of analysis and planning applications. We selected the articles in the special issue carefully, choosing from among the papers presented at the 1993 ACM/IEEE Second Symposium on Solid Modeling and Applications     

Functional integration in CAD systems

This paper examines the issue of integration in CAD systems and argues that for integration to be effective, it must address the functional aspects of a CAD system. It discusses the need for integrated systems and, within a structural engineering context, identifies several facets of integration that should be targeted. These include 2-D drafting and 3-D modelling, graphical and nongraphical design information, the CAD data structure and its user interface, as well as integration of the drafting function with other engineering applications. Means of achieving these levels of integration are briefly discussed and a prognosis for the future development of integrated systems explored. Particular attention is paid to the emergence (and potential role) of ‘product models’ which seek to encapsulate the full range of data elements required to define completely an engineering artefact.     

Product design logic for an intelligent product modelling system

Recent research in CAD systems has been conducted to realize intelligent processing. Several CAD systems and product modelling systems have been developed using AI techniques. However, in order to develop more intelligent CAD systems, the design logic which connects the functional requirement to the geometric and the technological information of the designed product must be evaluated.

A product model used in such intelligent CAD systems has to include not only the geometric and the technological information of the product but also the designer's thought process which explains the design logic.

Design logic is generally divided into two parts. One is the generalized design logic which is commonly used in the conceptual design of mechanical products. The other is the product specified design logic which is used in the fundamental and detailed design phase. Different logic is applied to each product. This type of design logic is often used in modification design and compilation design, where the dimensions of parts have to be modified according to different functional requirements. When the dimensions and accuracies of the products are defined in connection with the functional requirements through design logic, the CAD system can automatically make decisions according to the given requirements. In this paper, suitable presentation formats and processing functions for these two types of design logic are discussed.

The importance of design logic in product modelling is proven through several case studies in this paper. As a conclusion, the intelligent product modelling system is developed, which should expedite the progress of design automation in the near future. In conceptual design, the design logic is processed in the modelling system and the product structure, with the technological information decided automatically from the functional requirement. Automation in the detailed design phase is also facilitated by the modelling system using the product specified design logic in the product model.     

A decision-support method for information inconsistency resolution in direct modeling of CAD models

Direct modeling is a very recent CAD paradigm that can provide unprecedented modeling flexibility. It, however, lacks the parametric capability, which is indispensable to modern CAD systems. For direct modeling to have this capability, an additional associativity information layer in the form of geometric constraint systems needs to be incorporated into direct modeling. This is no trivial matter due to the possible inconsistencies between the associativity information and geometry information in a model after direct edits. The major issue of resolving such inconsistencies is that there often exist many resolution options. The challenge lies in avoiding invalid resolution options and prioritizing valid ones. This paper presents an effective method to support the user in making decisions among the resolution options. In particular, the method can provide automatic information inconsistency reasoning, avoid invalid resolution options completely, and guide the choice among valid resolution options. Case studies and comparisons have been conducted to demonstrate the effectiveness of the method.     

基于3D CAD模型的设计结构矩阵自动化生成系统

设计结构矩阵DSM已成为许多研究和实践领域中复杂系统建模和分析的工具。但是,DSM的构建却面临很大的困难,因为每个产品的分解和结构关系可以有不同的解释,因此不能以标准模式构建。这使得DSM的快速生成难以实现,从而延长了产品设计周期。介绍了一种基于CAD模型的DSM自动生成系统。首先,使用SolidWorks API提取SolidWorks平台中CAD模型的结构特征树中的顶层部件的Mates特征信息,并将其按特定顺序排列并存储在数据库中。其次,分析组装的部件之间的几何关系,以确定各种配合的类型对部件之间的连接关系的影响程度,并建立了相应的分析和比较规则。最后,使用Visual Basic成功完成了DSM自动生成系统的设计。同时,本文以一些CAD模型为例,验证了所开发系统的可行性和可靠性。     

Model formulation as a problem-solving task: Computer-assisted engineering modeling

A central purpose of knowledge acquisition technology is to assist with the formulation of domain models that underlie knowledge systems. In this article we examine the model formulation process itself as a problem-solving task. Drawing from AI research in qualitative reasoning about physical systems, we characterize the model formulation task in terms of the inputs, the reasoning subtasks, and the knowledge needed to perform the problem solving. We describe the elements of a high-level representation of modeling knowledge, and techniques for providing intelligent assistance to the model builder. Applying the results from engineering modeling to knowledge acquisition in general, we identify properties of the representation that facilitate the construction of knowledge systems from libraries of reusable models. © 1993 John Wiley & Sons, Inc.     

A goal-based framework for contextual requirements modeling and analysis

Requirements engineering (RE) research often ignores or presumes a uniform nature of the context in which the system operates. This assumption is no longer valid in emerging computing paradigms, such as ambient, pervasive and ubiquitous computing, where it is essential to monitor and adapt to an inherently varying context. Besides influencing the software, context may influence stakeholders’ goals and their choices to meet them. In this paper, we propose a goal-oriented RE modeling and reasoning framework for systems operating in varying contexts. We introduce contextual goal models to relate goals and contexts; context analysis to refine contexts and identify ways to verify them; reasoning techniques to derive requirements reflecting the context and users priorities at runtime; and finally, design time reasoning techniques to derive requirements for a system to be developed at minimum cost and valid in all considered contexts. We illustrate and evaluate our approach through a case study about a museum-guide mobile information system.     

A hierarchical approach on assembly sequence planning and optimal sequences analyzing

Assembly sequence planning (ASP) is a critical technology that bridges product design and realization. Deriving and fulfilling of the assembly precedence relations (APRs) are the essential points in assembly sequences reasoning. In this paper, focusing on APRs reasoning, ASP, and optimizing, a hierarchical ASP approach is proposed and its key technologies are studied systematically. APR inferring and the optimal sequences searching algorithms are designed and realized in an integrated software prototype system. The system can find out the geometric APRs correctly and completely based on the assembly CAD model. Combined with the process APRs, the geometric and engineering feasible assembly sequences can be inferred out automatically. Furthermore, an algorithm is designed by which optimal assembly sequences can be calculated out from the immense geometric and engineering feasible assembly sequences. The case study demonstrates that the approach and its algorithms may provide significant assistance in finding the optimal ASP and improving product assembling.     

超二维环境下尺寸驱动和参数设计的研究

超二维环境的最大特点在于使用了二维数据表示三维模型，实现了不建立三维模型直接对三维模型的各向投影进行参数设计，直接修改复杂工程图，由于相对三维工程实体，纯二维数据信息量不足，而按以往方法用多视图来弥补，又因视图间缺乏必要联系，无法建立和描述三维信息，因而，超二维模型引入视图投影信息，使之具有一定的三维信息。通过结合当前尺寸驱动和参数设计的现状，在超二维环境下，引和高等画法几何学多视图间的投影原理，     

Representational Reasoning and Verification

Formal approaches to the design of interactive systems rely on reasoning about properties of the system at a very high level of abstraction. Specifications to support such an approach typically provide little scope for reasoning about presentations and the representation of information in the presentation. In contrast, psychological theories such as distributed cognition place a strong emphasis on the role of representations, and their perception by the user, in the cognitive process. However, the post-hoc techniques for the observation and analysis of existing systems which have developed out of the theory do not help us in addressing such issues at the design stage. Mn this paper we show how a formalisation can be used to investigate the representational aspects of an interface. Our goal is to provide a framework to help identify and resolve potential problems with the representation of information, and to support understanding of representational issues in design. We present a model for linking properties at the abstract and perceptual levels, and illustrate its use in a case study of a ight deck instrument. There is a widespread consensus that proper tool support is a prerequisite for the adoption of formal techniques, but the use of such tools can have a profound effect on the process itself. In order to explore this issue, we apply a higher-order logic theorem prover to the analysis. Received May 1999 / Accepted in revised form July 2000     

基于意图捕捉的适时智能辅助设计技术*

在设计师需要的时候提供适时、必要而不冗余的设计资源,是智能辅助设计软件系统最基本的特征。设计师意图的实时捕捉正是提供适时、必要资源的基础。通过研究设计过程中的人机交互行为,建立MultiAgent工作模型, 利用Agent从人机操作交互、上下文内容推理以及设计师的习惯符号化等方面实现设计师意图的捕捉,在此基础上构建一个顺应设计师设计思维发展和工作进程的智能辅助设计平台。