Methodology for expert-system-based support of conceptual machine design

The cumulative requirements of design cannot be satisfied without the application of computer-based systems in the conceptual phase of design. The concept of intelligent CAD systems emerged at the beginning of the eighties. A practical implementation of an ICAD system can be based on an expert system with a specialized conceptual design methodology. Design prototypes may be generated by the systematic combination of known atomized building elements. To avoid combinatorial explosion, filtering is done on three levels. In the case of the pilot design expert system PANGEA, now being developed, the geometric modelling of prototypes is based on an extended B-rep scheme.     

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。     

A study on product modelling for integration of CAD/CAM

Modelling capability for products to be designed and manufactured plays an important role in order to effectively construct and utilize CAD/CAM systems. Product models should represent all the information about products, which is utilized in manufacturing processes. Therefore it is required that they describe functional structures of machine products, and include not only geometric information but also various non-geometric data, such as physical, technological and management data. Presently there do not seem to exist definite methods or theories for constructing product models. In this paper, we first investigate the whole manufacturing process, and propose a system structure for integration of CAD/CAM, in which product modelling plays a fundamental role. Then requirements for product modelling are studied thoroughly, and a new representation framework for product models is proposed. It consists of an object concept called frame, relations among frames and attributes, and it can incorporate the existing various modelling capabilities, such as solid modelling. We use this representation framework in combination with our solid modelling package GEOMAP-III, and show the effectiveness of this approach by performing illustrative design experiments.     

A CAD-CAE integration approach using feature-based multi-resolution and multi-abstraction modelling techniques

In spite of the widespread use of CAD systems for design and CAE systems for analysis, the two processes are not well integrated because CAD and CAE models inherently use different types of geometric models and there currently exists no generic, unified model that allows both design and analysis information to be specified and shared. In this paper, a new approach called the CAD/CAE-integrated approach is proposed and implemented by a feature-based non-manifold modelling system. The system creates and manipulates a single master model containing different types of all of the geometric models required for CAD and CAE. Both a solid model (for CAD) and a non-manifold model (for CAE) are immediately extracted from the master model through a selection process. If a design change is required, the master model is modified by the feature modelling capabilities of the system. As a result, the design and analysis models are modified simultaneously and maintained consistently. This system also supports feature-based multi-resolution and multi-abstraction modelling capabilities providing the CAD model at different levels of detail and the CAE model at various levels of abstraction.     

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.     

Visual language and graph-based structures in conceptual design

The paper deals with using design knowledge encoded in a visual language and graph-based structures to support the conceptual phase of designing. The visual language is based on the design conceptualization and composed of design diagrams being configurations of geometric primitives. A symbolic representation of design structures in terms of objects specified by the conceptualization and relations between them is defined, and then mapped into diagrams by a given realization. Diagrams are automatically transformed into the corresponding graph-based data structures. The knowledge stored in the graph representations of diagrams is translated into first-order logic formulas which describe generated design configurations. A proposed logic-based reasoning mechanism allows the design supporting system to check the compatibility of designs with the given requirements and constraints. The approach is illustrated by examples of designing configurations of transmission truss towers.     

概念设计模型和基于该模型的ICAD系统

围绕计算机辅助陶瓷产品概念设计的瓶颈问题和关键技术,一方面给出易于计算机表示的陶瓷产品的物元系统表示方法,提出陶瓷产品概念设计问题,特别是矛盾冲突问题,的物元系统模型化求解方法。另一方面基于以上模型化方法,设计开发了和谐化智能计算机辅助陶瓷产品概念设计系统。     

Object analysis patterns for embedded systems

Some of the most challenging tasks in building a software system are capturing, refining, and analyzing requirements. How well these tasks are performed significantly impacts the quality of the developed software system. The difficulty of these tasks is greatly exacerbated for the software of embedded systems as these systems are commonly used for critical applications, have to operate reliably for long periods of time, and usually have a high degree of complexity. Current embedded systems software development practice, however, often deals with the (requirements) analysis phase in a superficial manner, instead emphasizing design and implementation. This research investigates how an approach similar to the well-known design patterns, termed object analysis patterns, can be applied in the analysis phase of embedded systems development, prior to design and coding. Specifically, our research explores how object-oriented modeling notations, such as the Unified Modeling Language (UML), can be used to represent structural and behavioral information as part of commonly occurring object analysis patterns. This work also investigates how UML-based conceptual models of embedded systems, based on the diagram templates in the object analysis patterns, can be automatically analyzed using the Spin model checker for adherence to properties specified in linear-time temporal logic (LTL) using a previously developed UML formalization framework. We have applied these patterns to several embedded systems applications obtained from the automotive industry. This paper describes one of our case studies and illustrates how our approach facilitates the construction of UML-based conceptual models of embedded systems and the analysis of these models for adherence to functional requirements.     

Bridging qualitative spatial constraints and feature-based parametric modelling: Expressing visibility and movement constraints

We present a concept for integrating state-of-the-art methods in geometric and qualitative spatial representation and reasoning with feature-based parametric modelling systems. Using a case-study involving a combination of topological, visibility, and movement constraints, we demonstrate the manner in which a parametric model may be constrained by the spatial aspects of conceptual design specifications and higher-level semantic design requirements. We demonstrate the proposed methodology by applying it to architectural floor plan layout design, where a number of spaces with well defined functionalities have to be arranged such that particular functional design constraints are maintained. The case-study is developed by an integration of the declarative spatial reasoning system CLP(QS) (CLP(QS) – a declarative spatial reasoning system. www.spatial-reasoning.com.) with the parametric CAD system FreeCAD.     

基于物元动态系统分析的智能化模型化概念设计

针对计算机辅助概念设计的瓶颈问题和关键技术,一方面应用物元动态系统分析方法给出陶瓷产品的物元系统表示方法,提出了陶瓷产品概念设计中矛盾冲突和矛盾冲突解决的物元系统模型化方法。另一方面提出面向CIMS的CAD的和谐化智能化研制思想,开发了和谐化智能化计算机辅助陶瓷产品概念设计系统。     

Automation in the design of EDM electrodes

Plastic parts, especially those designed for consumer electronics products, are becoming more compact and freeform in shape. This requires the construction of compact and delicate geometric features in the injection moulds that produce these parts. It is now common practice to employ electric discharge machining (EDM) whenever the conventional machining process fails to machine such delicate features. Although CAD/CAM systems are widely used in mould design and manufacturing, and specific commercial CAD/CAM systems that are customized for injection mould applications are also available, there are still no intelligent CAD tools that address the specific requirements of EDM electrode design. The aim of this research is to develop an intelligent CAD tool that supports EDM electrode design. This CAD tool uses a new technique that recursively splits the EDM region into sub-regions until machinable electrodes can be constructed. The CAD tool has been implemented and integrated into a commercial CAD/CAM system, and 40 different real designs has been used to test its capability in handling a wide variety of geometric shapes. Performance data show that the efficiency of the design process can be improved by at least 50%, with a potential to achieve 85% through improved implementation and further research.     

Expert tutoring system for teaching mechanical engineering

This paper describes the work undertaken, at the Higher Technical School of Industrial Engineers of Gijón, for the development of computer aided systems, in the line of expert systems, concentrating research, and development in the field of mechanical design. We are using this software as an integrated tool in our work for teaching machine design. Models to develop the software of several components are defined, and their application methodology is also presented.

An application which tackles the problem of configuration design, applied to mechanical transmission is also described in this article. The failure of machine elements in mechanical design, frequently occurs due to poorly detailed projects.

The developed work is applied to the design of configurations for mechanical systems, by means of an intelligent program which incorporates the process of geometric design, the calculation of mechanical elements, the selection in electronic databases and the output of CAD plans.

Configuration design is a type of design problem where the different elements (which make up the system, mechanism or machine project object), are selected from databases and connected in order to complete the requirements (functionality, specifications, and established restrictions) outlined in the problem.     

Manufacturing cost modelling for concurrent product development

This research work aims to develop an intelligent knowledge-based system that accomplishes an environment to assist inexperienced users to estimate the manufacturing cost modelling of a product at the conceptual design stage of the product life cycle. Therefore, a quicker response to customers’ expectations is generated. This paper discusses the development process of the proposed system for cost modelling of machining processes. It embodies a CAD solid modelling system, user interface, material selection, process/machine selection, and cost estimation techniques. The main function of the system, besides estimating the product cost, is to generate initial process planning includes generation and selection of machining processes, their sequence and their machining parameters. Therefore, the developed system differs from conventional product cost estimating systems, in that it is structured to support concurrent engineering. Manufacturing knowledge is represented by hybrid knowledge representation techniques, such as production rules, frames and object oriented. To handle the uncertainty in cost estimation model that cannot be addressed by traditional analytical methods, a fuzzy logic-based knowledge representation is implemented in the developed system. Based on the analysis of product life cycle, the estimated cost included material, processing, machine set-up and non-productive costs. A case study is discussed and demonstrated to validate the proposed system.     

An image evaluation approach for parameter-based product form and color design

The parameter-based technique provides an efficient and valid means of constructing 3-D geometric models in many CAD software systems. However, its use is generally restricted to the design of mechanical components with regular configurations, and it is not ideally suited to product form and color design. This paper proposes a rapid conceptual design approach, which creates color-rendered forms and combines parameter-based features with fuzzy neural network theorems and gray theory to predict their image evaluation. Two evaluation models (Evaluation Model I and Evaluation Model II) are developed and applied in a case study of an electronic door lock design. Model I uses a fuzzy neural network to predict the overall image, while Model II uses a gray clustering operation for the color image evaluation and two fuzzy neural networks for the form image evaluation and the overall image evaluation. The results show that the image prediction capability of Model II is superior to that of Model I (RMSE: 0.062 versus 0.105). Furthermore, the overall image evaluation is dominated by the door lock's color rather than by its form (RMSE: 0.071 versus 0.162). The dominance of color in determining the image evaluation may be due to the specified image words, form evolution restrictions, or the membership grade ranges of the test color samples and the test form samples, etc. Having established the superiority of Model II, it is applied to develop a consultative design interface integrated with a professional CAD system in order to demonstrate the effectiveness of the proposed product design and image evaluation approach. The design system presented in this study enables a designer to predict the likely image tendencies of a designed product without the need to create and test a prototype model. Hence, he or she can make any design parameter modifications necessary to ensure that the finished product meets its specified image goals.     

Systems modelling for sustainable building design

To support performance-oriented modelling for sustainable building design, one must both model geometric interdependencies in a parametric way and include non-geometric physical, environmental, and economic design reasoning. For this purpose, this paper examines the use of Systems Modelling Language (SysML) to model systems for sustainable building design and develops a method called Parametric Systems Modelling (PSM). Selected diagrams demonstrate the application of the method for performance-oriented building design and show generic models of typical requirements, design structures, internal processes, and item flows of energy and resources in a systems view. An exemplary implementation of a parametric system, which handles the trade-off between investments in both building envelope and heat generation technology, illustrates the use and benefit of systems modelling for decision-making. Further considerations address integrating systems modelling into the CAD/BIM-based design process.     

THE OBJECT-ORIENTED INTELLIGENT PROGRAMMING IN CAD/CAM

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CAD for process plants: an update

We review the availability of CAD software for the process design activities of physical properties generation, unit operation design, flowsheeting and dynamic flowsheet simulation. Similarly we look at CAD software for materials control, piping documentation and pipe stressing. We report conclusions drawn from our research into the provision and use of CAD turnkey systems for producing schematics at the conceptual design phase, and for equipment specification, layout, piping design and 3D modelling at the engineering design phase.By reviewing the shortcomings of current CAD systems along with developing CAD technology, we were able to specify the requirements of the next generation of process plant CAD.     

面向智能CAD的分层构造自动型方法

本文着重对由抽象符号转化成具体形体的技术作了研究，提出了分层构造的自动造型方法．它支持直接由抽象的设计方案自动生成设计结果的三维表示，因而更适合于以辅助方案设计为核心的智能ＣＡＤ系统．一个基于该自动造型方法的椅子智能ＣＡＤ实验系统已在浙江大学人工智能研究所投入运行．     

Integrated distributed intelligent system for process-control system design

In process-control system design, the Computer Aided Design (CAD) techniques have evolved a new generation of design techniques. This also paves the way for implementing Computer Integrated Manufacturing Systems (CIMS). However, the key issue to accomplishing the objectives in CAD is the automation of conceptual design. This paper first introduces the fundamentals of conceptual design for process-control system design. Then, a strategy to solve the problems in conceptual design is proposed. The associated system configuration and software implementation platform for developing intelligent systems for process control system design are presented. Finally, an application case is studied.     

Learning studies in the use of computer aided design systems for discrete-parts manufacture

Two-dimensional computer aided engineering design systems are recognized as having limitations in comparison with the alternative three-dimensional techniques of solid modelling. The mathematically sounder approach of solid modelling permits far greater integration between the activities of functional design, design analysis and manufacturing. However, the existing methods of specifying design geometry within typical solid modelling systems are deficient in that they relate more to the mathematical needs of the computer system than they do to the needs of the designer. CAPE-LUT (Computer Aided Production Engineering-Loughborough University of Technology) is a prototype system which provides a machining analogy so that geometric and manufacturing ideas can be expressed through familiar engineering terminology, to provide detail designs and outline process plans. CAPE-LUT is an experimental vehicle only and the system has been used to investigate the hypothesis that a 'manufacturing features' approach to design and manufacture is easy to learn, accurate and fast in use, and acceptable to practising designers and manufacturing engineers. This paper describes the experimental work, which provides statistical evidence that the manufacturing features method is significantly easier to learn than a similar CAD system that has a purely geometric interface. It is also shown that CAPE-LUT performed well when used by experienced subjects and was acceptable to a large number of practising engineers.