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外文资料名称： Knowledge-Based Engineeri-
-ng Design Methodology
外文资料出处： Int.J.Engng Ed.Vol.16.No.1
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2.外文原文
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基于知识工程(KBE)设计方法
D. E. CALKINS
1. 背景
复杂系统的发展需要很多工程和管理方面的知识、决策，它要满足很多竞争性的要求。设计被认为是决定产品最终形态、成本、可靠性、市场接受程度的首要因素。高级别的工程设计和分析过程(概念设计阶段)特别重要，因为大多数的生命周期成本和整体系统的质量都在这个阶段。产品成本的压缩最可能发生在产品设计的最初阶段。整个生命周期阶段大约百分之七十的成本花费在概念设计阶段结束时，缩短设计周期的关键是缩短概念设计阶段，这样同时也减少了工程的重新设计工作量。
工程权衡过程中采用良好的估计和非正式的启发进行概念设计。传统 CAD 工具对概念设计阶段的支持非常有限。有必要，进行涉及多个学科的交流合作来快速进行设计分析(包括性能，成本，可靠性等)。最后，必须能够管理大量的特定领域的知识。解决方案是在概念设计阶段包含进更过资源，通过消除重新设计来缩短整个产品的时间。
所有这些因素都主张采取综合设计工具和环境，以在早期的综合设计阶段提供帮助。这种集成设计工具能够使由不同学科的工程师、设计者在面对复杂的需求和约束时能够对设计意图达成共识。那个设计工具可以让设计团队研究在更高级别上的更多配置细节。问题就是架构一个设计工具，以满足所有这些要求。 2. 虚拟(数字)原型模型
现在需要是一种代表产品设计为得到一将允许一产品的早发展和评价的真实事实上原型的过程的方式。虚拟样机将取代传统的物理样机，并允许设计工程师，研究“假设”的情况，同时反复更新他们的设计。真正的虚拟原型，不仅代表形状和形式， 即几何形状，它也代表如重量，材料，性能和制造工艺的非几何属性。设计人员希望设计的表述，将成为一个既有几何又有非几何属性的物理原型确切的表示。
产品表示法已经从二维的形状和几何的形式字形绘画的表示法移动向充分的三维几何模型表示法。设计工具，用于设计工程领域的需要，显然必须有刚才讨论的所有工具的属性。它必须结合计算机辅助设计系统的几何表示法，能做对程序语言的工程分析和代表设计知识在一个专家系统。一个真正的虚拟原型包含此全方位设计知识。
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3. 启用的技术设计 3.1. 知识类型
如同适用于 KBE 那样，知识能分成四种类型：
.事实， .程序， .判断， .控制。
在手册找到的形式化的知识例如原材料明细表，设计 data，ASTM 标准和设备规格被认为事实知识。算法的和操作的知识是程序上的知识的两种形式。数字的和非数字的解决问题一或者完成中的一些末端的过程是所有的算法的程序上的知识(APK)的原理。事实被 APK 通过工程和分析算法改变。有效的程序知识(OPK)被用于创造， 删除和运输事实。OPK 节目的例子是有限元素分析、优化和数据库管理系统[1]。经验法则和共同的实践是评断知识的实例。启发式，意见，经验，与合情推理中还包括判断的知识。逻辑和推理的形式原则是基本的判断知识的应用。控制知识元知识或知识有关知识，知识的其他类型的管理控制知识。仿造直系活动，意想不到的发展的预期，并且应付不确定性是所有特点控制知识[1]。 3.2. 基于知识的工程(KBE)
该技术允许一个真正的产品虚拟样机开发被称为基于知识的工程，或 KBE。KBE 是捕捉和对结构设计，其设计过程的知识方法。知识经济可以用来定义工程方法和程序[2]。在 KBE，产品结构树(拓扑学)是动态的，因此知识经济提供真正的工程自动化， 包括应用开发，几何造型，应用程序部署和工具的集成。基于知识工程是一种编程工具，用于开发一个虚拟原型设计顾问或为一个建立了产品设计，在给定的设计领域。
关于设计类的现有的知识在基于知识的工程学或设计被运用(KBE 或 KBD)并且被组织入能用数据库的格式由计算机。详细设计或虚拟原型，然后迅速开发基于知识的工程(KBE)的设计方法，通过对 23 位计算能力来开发数据库，和规则系统。该产品模型是在 KBE 环境下开发的虚拟样机。虚拟原型，如材料的所有几何特征或属性的产品，以及非几何属性，质量特性，应力和挠度特性等虚拟样机一旦被创建，它可以由设计者使用评估成功或设计配置的优点，然后修改。该产品模型表示后面的几何设计工程意图。在产品模型中包含的信息包括物理属性如几何，材料种类和功能限制。 3.3. 生成技术
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有三种 KBE 的工具，目前正在探索和发展类型。这些措施包括： 1．诊断方法(专家系统)。
2. 创造性的方法(设计顾问)/(设计检查)。 3. 生成方法(虚拟样机)。
专家系统是第一种类型的工具发达国家在工程领域的使用，这个工具用于诊断目的，例如分析汽车发动机出现故障。
第二类，设计顾问，更是目前的事态发展之一。它是用来反映了一个系统的设计过程，并告知约束和规则的基础上违反设计师与设计顾问所载的规则。设计师在这意见后行动并且做适当的变动。
第三类涉及到建立一个以该模型中的规则为基础的系统模型。这个模型，一个真正原型，然后起反应对在属性(几何或非几何)和再生原型的一个新的事例上的变化。这是用于被开发的类 KBE 的种类。
KBE 利用生成技术来获取通用产品设计信息，包括几何和拓扑结构，产品结构的发展及制造工艺设计规则。生成建模地图功能规格，该产品的详细陈述。一个生成模型的优点是，由于产品需求的变化，外观设计的表述是立即更新，直接影响到所有输出。因此，KBE 是一种动态的对象模型，其中对外观设计的表述是不断更新。知识工程的方法设施为迅速生成模型生成新的功能规格设计的工程设计和制造知识获取。相对于传统的设计工具，KBE 提供真正的设计与自动化设计协助。在设计过程期间，KBE 是系统的连续的再设计的一种健壮设计技术。 3.4. KBE 的代表性产品
当前 KBE 软件是基于面向对象非诉讼程序设计语言，比如 LISP 语言。因此，设计资料无须下令在模型正确，因为它会制订该命令本身。面向对象编程工程对象的概念，用于表示的特点，无论几何和非几何，实际物理对象。对象不是被动的，但可以反应其他对象。一个对象可以创建和存储信息和采取行动应对外部刺激。一个对象可以从另一个信息需求对象，或者将信息发送到另一个对象。
KBE 实现了真正的并行工程攻克了一系列的捐助领域的专门知识在一个组织。这可以包括代表从设计，工程，模具和其他制造业领域。KBE 的供应商有一个捕捉行之有效的方法和编纂这种产品信息的范围。通常情况下，KBE 的开发将与方法顾问学习“知识捕获”进程的第一个发展项目，然后将转让和应用这些技能后续项目。 3.5. KBE 工具
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有许多不同的软件工具可用于 KBE 发展。当中包括 ICADTM，TKSolverTM，设计 LinkTM，ProEngineerTM，STONEruleTM 和智能 ElementsTM。所有这些集成了至少 1 现代 CAD 系统提供一个当代集成设计系统。 Unigraphics 系统，CATIATM，支持EngineerTM， IDEASTM 和自动 CADTM 是一些选择。 这些软件工具用于开发domainspecific 这两个知识工程的方法设计工具，设计顾问和虚拟样机。 3.6. 生成虚拟样机(GVP 公司)
这种虚拟原型的方法奠定了基础的 KBE 描述，是基于对 KBE 的智能 CAD 软件的使用[5]。智能 CAD 使用为元设计，这是设计工具设计在一个产品模型的形式。该产品模型是产品结构，工程分析，产品成本，设计标准，管理准则，材料特性，制造约束和进程计划的框架。它能够输出设计报告，表示该产品的设计状态。该报告可以包括例如：分析，3 个数据的三维几何模型，材料，成本报告和指示草案。GVP 公司的捕获和自动化功能设计的规则和方法的理解在工程过程。在 GVP 公司为工程师提供了有效的替代功能选择和操作。工程师添加他们的判断力，优化设计，最终系统。
阿生成虚拟样机(GVP 公司)是一个系统既是模型的几何和非 24 D.尔金斯等。一个产品(一个对象)的几何属性中嵌入了 KBE 的模式。它存储知识在组成一个产品模型系统设计和制造工程的规则，同时解决几何和非几何的问题。阿生成虚拟原型是这些设计规则的组合，其中包括对工程指令用于创建的设计，也就是车辆的几何形状。生成虚拟样机的代表背后的几何设计工程意图。它可以存储诸如几何和材料规格，以及过程和性能信息产品信息。
生成虚拟样机的范例被定义如下：
生成：生成或自动产生这一虚拟原型的实例，以响应输入状态向量。采取输入规范说明，运用相关的做法并且自动地引起设计。当要求改变时，设计与所有表现产品一起立刻被更新。
虚拟的影响，虽然没有实际的事实： [1]基于计算机模型原型：原来的模式，或一个具体的例子类型。 3.7. 设计规则
KBE 是基于知识的设计使用形式的设计规则，设计规则构成了一个对象的核心。设计规则包括 4 种基本类型：
1. 启发式：包括实验的经验规则和最佳做法。通常是基于企业文化设计的启发。
这些都是的类型，如果(条件为真)，然后(行动推荐)。
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2. 经验设计规则：这些规则根据从实验性数据被开发的曲线适合的表示。元模型
技术用于开发复杂系统的模型。
3. 立法限制：这些都是组成法律或工程的既定规则标准。
4. 物理定律：首次原则为基础的分析或数值模式的形式。也被称为参数的规则。
这些规则通常是使用报表模型解决简单的算法。
设计规则用于合成中的知识基础知识，如何在给定的模型建立知识。设计规则来定义和涉及双方在知识经济模式的属性。工程师的方法和过程由这些规则仿造。设计规则类型包括：
.计算 .条件句 .查寻数据库 .固定 .变量 .引用
.执行外部程序 .选择 .优化。
Knowledge-Based Engineering (KBE) Design Methodology
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BACKGROUND
The development of complex systems requires a sequence of engineering and management decisions which must satisfy many competing requirements. Design is recognized as the primary contributor to the final product form, cost, reliability and market acceptance. The high-level engineering design and analysis process (conceptual design phase) is particularly important since the majority of the life-cycle costs and overall quality of the system are determined during this phase. The major opportunities for cost savings occur in the earliest phases of a product design. Approximately seventy per cent of the life- cycle costs are frozen by the end of the conceptual design phase, Fig. 1. The key to shortening the design cycle is to shorten the conceptual design phase, which will also reduce the amount of engineering in the redesign stage.
The engineering trade-off process during conceptual design is undertaken using good estimations and informal heuristics. Current traditional CAD tool support is extremely limited for the conceptual design phase. There is need to rapidly conduct design analyses involving multiple disciplines communicating together (trading off such things as performance, cost, reliability, etc.). Finally, it is necessary to be able to manage a large amount of domain-specific knowledge. The solution is to commit more resources at the conceptual design stage to reduce the cycle time by eliminating redesign.
All of these factors argue for an integrated design tool and environment that can help make decisions early in the design synthesis (conceptual design) process. This integrated design tool will enable a diverse and multi-disciplinary team of engineers, designers and stylists to achieve consensus of design intent under complex design requirements and increased design constraints. The design tool should allow the design team to examine more configurations at greater levels of detail. The problem then is to develop an architecture for a design tool that meets all of these requirements. VIRTUAL (DIGITAL) PROTOTYPE MODEL
What is needed is a way to represent the product design process to obtain a true virtual prototype which would allow the early development and evaluation of a product. The virtual prototype would replace traditional physical prototypes and allow the design engineer to examine `what-if' scenarios while iteratively updating their designs. A true
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virtual prototype would not only represent the shape and form, i.e. the geometry, it would also represent non-geometric attributes such as weight, material, performance and manufacturing processes. Designers want a design representation that will be an exact representation of a physical prototype with both geometrical and non-geometrical attributes.
Product representation has moved from the 2-D orthographic drawing representation of the shape and form of the geometry, to full 3-D model representation of the geometry. The design tool that is needed for the design engineering domain, clearly must have attributes of all of the tools just discussed. It must combine the geometrical representation of the CAD systems, be able to do the engineering analysis of the procedural languages and represent the design knowledge as in an expert system. A true virtual prototype contains this full range of design knowledge. ENABLING TECHNOLOGIES FOR DESIGN Types of knowledge
. Knowledge’, as applied to KBE, can be divided into four types [1]： . facts, . procedures, . judgments, . control.
Formalized knowledge found in handbooks such as material specifications, engineering data， ASTM standards, and equipment specifications is considered factual knowledge. Algorithmic and operative knowledge are the two forms of procedural knowledge. Numeric and non-numeric procedures for solving a problem or accomplishing some end are all elements of algorithmic procedural knowledge (APK). Facts are transformed by APK through engineering and analysis algorithms.Operative procedural knowledge (OPK) is used to create, delete, and transport facts. Examples of OPK programs are finite-element analysis, optimization, and database management systems [1].Rules of thumb and common best-practices are examples of judgment knowledge. Heuristics， observations, experience, and plausible reasoning are also included in judgment knowledge. Logic and the formal principles of reasoning are fundamental to judgment
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knowledge application.Control knowledge is metaknowledge or knowledge about knowledge. The other types of knowledge are managed by control knowledge. Pattern directed actions, anticipation of unexpected developments, and dealing with uncertainties are all features of control knowledge [1]. Knowledge-based engineering (KBE)
The technology that allows the development of a true virtual prototype of a product is known as
knowledge-based engineering, or KBE. KBE is the methodology for capturing and structuring knowledge about a design and its design process. KBE may be used to define engineering methods and procedures [2]. In KBE, the product structure tree (topology) is dynamic, so that KBE offers true engineering automation including application development, geometric modeling, application deployment and tools integration. Knowledge-based engineering is a programming tool used to develop a virtual prototype or a design advisor for the design of an established product in a given design domain. Dym, et al. [3] and Gonzalez, et al.[4] provide valuable overviews of KBE.
Existing knowledge about a class of designs is utilized in knowledge-based engineering or design (KBE or KBD) and organized into a database format usable by computers. Detailed designs or virtual prototypes are then rapidly developed Knowledge- Based Engineering (KBE) Design Methodology 23 through the use of digital computing power, developed databases, and systems of rules. The product model which is developed in the KBE environment is a virtual prototype. A virtual prototype has all of the geometric characteristics or attributes of the product as well as the non-geometric attributes such as materials, mass properties, stress and deflection characteristics, etc. Once the virtual prototype is created, it can be used by the designers to evaluate the success or merit of the design configuration, and then modify it if desired. The product model represents the engineering intent behind a geometric design. The information contained in a product model includes physical attributes like geometry, material type and functional constrains. Generative technology
There are three types of KBE tools that are currently being explored and developed. These include：
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1. Diagnostic approach (expert system).
2. Creative approach (design advisor)/(design checking). 3. Generative approach (virtual prototype).
The expert system was the first type of tool developed for use in the engineering domain.This tool is used for diagnostic purposes such as analyzing a malfunctioning automobile engine.
The second type,design advisor,is the one to more current developments.It is used to follow the design process of a system, and advise the designer of constraint and rules violations based on rules contained with the design advisor. The designer then acts on this advice and makes appropriate changes.
The third type involves developing a model of the system based on rules contained with the model. This model, a virtual prototype, then reacts to changes in attributes (either geometric or non-geometric), and regenerating a new instance of the prototype. This is the type of KBE that is used in the classes developed.
KBE uses generative technology to capture generic product design information, including geometry and topology, product structure development and manufacturing processes as design rules. Generative modeling maps functional specifications to a detailed representation of the product. The advantage of a generative model is that as the product requirements change, the design representation is immediately updated directly affecting all outputs. Thus, KBE is a dynamic object model wherein the representation of the design is continually updated. KBE methodology facilities the capture of engineering and manufacturing knowledge into a generative model by rapidly generating new designs from functional specifications. In contrast to the conventional design tools, KBE offers true design automation vs. design assistance. KBE is a robust design technology for continuous redesign of a system during the design process. KBE product representation
Current KBE software is based on an object-oriented non-procedural design language such as LISP. As a result, the design information need not be ordered correctly within the model, as it will work out the order itself. Object-oriented programming works on the concept of objects that are used to represent the characteristics, both geometric and non-
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geometric, of actual physical objects. Objects are not passive, but can react with other objects. An object can create and store information and act in response to external stimuli. An object can demand information from another object, or send information to another object.
KBE enables true concurrent engineering by capturing the domain expertise of a range of contributors in an organization. This can include represent atives from design, engineering, tooling and other areas of manufacturing. KBE vendors have a well- established methodology for capturing and codifying this range of product information. Often, KBE developers will collaborate with methodology consultants to learn the `knowledge capture' process on a first development project and then will transfer and apply those skills to follow-on projects. KBE tools
There are a variety of software tools available for KBE tool development. Included are ICADTM, TKSolverTM, Design LinkTM, ProEngineerTM,STONEruleTM and Smart ElementsTM. All of these are integrated with at least one of the contemporary CAD systems to provide a contemporary integrated design system. Unigraphics,CATIATM, Pro- EngineerTM, IDEASTM and Auto-CADTM are some of the options.
These software tools are used to develop domain-specific design tools of the two KBE approaches,design advisor and the virtual prototype. Generative virtual prototype (GVP)
The virtual prototype approach forms the basis of the KBE classes described, and is based on the use of the KBE software ICAD [5]. ICAD is used for metadesign, which is the design of design tools in the form of a product model. The product model is the framework for the product structure, engineering analysis, product cost, design standards,regulatory codes, material characteristics, manu-facturing constrains and process plans. It is able to output a design report that represents the design state of the product. This report can include for example： data for analysis, 3-D geometric models,bills of material, cost reports and manufacturing instructions. The GVP captures and automates the functional design rules and understood methodologies of the engineering process. The GVP provides functionally valid alternatives for engineers to select and manipulate. The
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engineers add their judgement to optimize final systems designs.
A generative virtual prototype (GVP) is a system model that represents both the geometric and non-D. Calkins, et al.24 geometric attributes of a product (an object) which are embedded in the KBE model. It stores knowledge about a system in a product model composed of design and manufacturing engineering rules,which address both geometric and nongeometric issues. A generative virtual prototype is a combination of these design rules and includes a set of engineering instructions used to create the design,that is, the vehicle geometry. The generative virtual prototype represents the engineering intent behind the geometric design. It can store product information such as geometry and material specifications as well as process and performance information.
The generative virtual prototype paradigm is defined as follows：
Generative： generate or automatically produce an instance of the virtual prototype in response to an input state vector. Take input specifications, apply relevant procedures and generate a design auto-matically. When the requirements change, the design is updated immediately along with all of performance outputs.
Virtual： in effect although not in actual fact： a computer based model Prototype： original model or example of a particular type. Design rules
KBE is based on the use of design knowledge in the form of ‘design rules’. The design rules form the kernel of an object. Design rules comprise four basic categories： 1. Heuristics： comprised of experimental rules of thumb and ‘best practices’.Usually based on corporate culture design heuristics. These are of the type, If (condition is true), then (action recommended).
2. Empirical design rules： these rules are based on curve-fitted expressions that are developed from experimental data. Meta-model technology used to develop models of complex systems.
3. Legislated constraints： these are comprised of rules established by law or by engineering standards.
4. Laws of physics： based on first principles in the form of analytical or numerical models. Also known as parametric rules. These rules are usually simple algorithms that
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would be solved using spreadsheet models.
Design rules are used to synthesize the knowledge in the knowledge base and to establish how the knowledge is used in a given model. The design rules are used to both define and relate the attributes in a KBE model. The methods and processes of an engineer are mimicked by these rules. Design rule types include： . calculations . conditionals . look-up databases . fixed . variable . references
. execute external programs . selections . optimizations.
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