Integrated and Intelligent Database Systems for Plant Engineering Framework

This paper gives an overview of an integrated and intelligent database system for a plant engineering framework. We have integrated existing two-dimensional (2D) CAD systems, a three-dimensional (3D) CAD system, and a relational database system which stores engineering information such as design conditions, maintenance histories, and inherent properties. By integrating these systems, the infrastructure for concurrent engineering has been realized. As for design knowledge, we treat object-oriented programming as a useful knowledge representation method. We analyze the plant structure and functional requirements of the system, and then represented them by using the hierarchical Class structure. Design knowledge accompanies the Class, so we represent it using Method. As a design automation system, we develop an automated design check system. This is implemented by using the Common Lisp Object System. These systems are the main parts of the plant engineering framework, and are utilized in the practical design. We intend to develop a mechanical/electronic design framework using the same approach.

Collaborative Engineering Based on Knowledge Sharing Agreements

The design of products by multi-disciplinary groups is a knowledge intensive activity. Collaborators must be able to exchange information and share some common understanding of the information’s content. The hope, however, that a centralized standards effort will lead to integrated tools spanning the needs of engineering collaborators is misplaced. Standards cannot satisfy the information sharing needs of collaborators, because these needs cannot be standardized. This paper discusses the design and use of a shared representation of knowledge (language and vocabulary) to facilitate communication among specialists and their tools. The paper advances the opinion that collaborators need the ability to establish and customize knowledge sharing agreements (i.e. mutually agreed upon terminology and definitions) that are usable by people and their machines. The paper describes a formal approach to representing engineering knowledge, describes its role in a computational framework that integrates a heterogeneous mix of software tools, and discusses its relationship to current and emerging data exchange standards. This work is supported by ARPA contract DAAA 15-91-C0104 as part of the SHADE project. (CDR TR# 19940912)

Information Needs in Agile Manufacturing

In this paper we discuss the special information technology needed to support the emerging trend of agile manufacturing. Specifically, we address product data exchange standards, tools for efficient searches of product databases, and information models for the processing capabilities of manufacturing plants. The implementation of the product and plant information models is also discussed. Finally, we outline the role of these models in an ongoing study on the design-for-manufacture of electromechanical devices in an agile manufacturing environment.

An Assembly Constraint Model for Parameterized Mechanical Systems

This paper (1) introduces Natural Assembly Relationships (NARs) to model assembly constraints between parts and (2) analyzes the constraint relationships that are defined using NARs for parameterized mechanical assemblies. The NARs are expressed as first order predicates using primitive features as arguments, such as planar and cylindrical surfaces. The concept of Basic Parameters Set is introduced as the design parameters in CAD systems, which, together with a set of form feature constraint relationships, maintains maximal consistency with original design meanings. Based on NARs, part parameters, and primitive features, design parameter chains can be constructed for closed loop assemblies. From these chains, constraint equations can be derived, which are the basis for change propagation and information management for mechanical system design.

Mechanical System Information Management in a Shared Multidisciplinary Environment

This paper describes the information model and data management methods developed for the global database of a Concurrent Engineering environment for mechanical system design and evaluation. The environment considered has a CAD system and four CAE applications. The information model supports these engineering disciplines through multiple, unrestricted product composition hierarchies and a shared product definition. The dependency between the shared product definition and application models and between attributes of the parameterized, shared product definition are analyzed. The data management method employs a versioning policy that maintains consistent representations and history of the design as it undergoes design change transactions.

An Authorization Mechanism for a Document Database

A programmable authorization mechanism for an engineering document database is described. The database stores documents and their versions in a commercial relational database. Documents and other objects contain user-defined attributes. Release and approval procedures of the documents are described by means of state graphs that specify the possible states of a document and the transitions between them. The system consists of centralized server and client programs, which communicate with the server using a specific protocol. The database administrator must be able to formulate rules that tell who is allowed to do particular database operations; rules that tell which operations are allowed in particular document states; and rules that describe consistency invariants between attributes. These rules are expressed by means of authorization procedures written in a special language. Whenever the server receives an operation request, it executes the corresponding authorization procedure. The system can thus be easily adapted to an organization without actually modifying the client or server programs.

Identification of Dynamics Bodies From Part Mating Conditions

A method to automatically identify bodies for Dynamics Analysis based on a given set of arbitrary parts and their mating conditions has been developed. The use of this method is considered within the context of Concurrent Engineering design of mechanical systems, where an entity translator from a shared global database to a Dynamics database is intended to automatically identify the bodies for rapid Dynamics model setup and simulation. A simplified formulation of the mating conditions that reduces the number of equations needed with respect to previous research is presented. The importance of detecting the equations associated with redundant constraints, in order to obtain the set of bodies, is presented. The method has been demonstrated by using some examples.

EXPRESS-P: Extending EXPRESS for Process Modeling and Monitoring

The upcoming ISO standard EXPRESS has been defined as a data specification language for the use within STEP. EXPRESS supports the modeling of static structural relationships and consistency constraints whereas the applicability of EXPRESS for the modeling of behavior is very limited. Thus, at present there is an ongoing discussion by which means EXPRESS should be extended with. In this paper, we present EXPRESS-P. EXPRESS-P is an extension of EXPRESS by the concepts of the formal languages SDL (CCITT Standard), Estelle (ISO Standard), and GRAPES-86. Within these approaches a system is described as a network of communicating concurrent agents. In addition to the language, we introduce graphical means for this extension (System and Process Diagrams). Finally, we give a practical example by modeling an injection molding process in order to demonstrate the applicability of EXPRESS-P.

The Technology of Language and How Advances Will Affect Product Modeling and Design

Design and CAE are being influenced by a number of business factors that heighten the importance of communication, and, thus, language. Among these factors are: globalization of product and component markets, electronic commerce via EDI, competitive demands for shortened development cycles, and increased accountability for design through the entire product life cycle. Engineering management reflects these business factors in such trends as: outsourcing of design work on a global basis, subcontracting of construction and/or manufacturing engineering, and simultaneous engineering across disciplines. This paper explores the oncoming revolution in language technology from the viewpoint of its potential effects on CAE. Some brief introductory observations are made on the importance and current status of language as it relates to design. Next, the philosophical and practical language barriers to further progress in object-oriented CAE are laid out. Finally, an agenda is proposed whereby these barriers can be overcome. Progress for CAE will be driven by the information needs of the end users of engineering’s products. This progress will be fed by technology advances and economic forces external to engineering design, yet it will take the form of a metalanguage unique to the field. Reaching our future aspirations for CAE will require the encouragement and cooperation of the commercial, professional, and governmental sectors, because the creation of a new language is a complex and costly proposition.

Tools and Methods for Performance Evaluation of RDBMS Applications

The goal of our research is to predict performance of applications using ORACLE RDBMS and then to propose tools to optimize performance. The performance we are interesting in, is the performance as perceived by users. We then specially study user’s transactions response time. Our method is based on measurement, and the first step was to measure performance on existing applications using ORACLE RDBMS. We have developed several software tools: - user simulator - application generator - workload application generator - measurement tools to measure user transactions response time and system activity during a transaction execution. The second step consisted in data collection and data analysis of measures. The data analysis, based on statistic methods, has permitted to extract the most influent factors and to understand how they can enhance applications performance (Rumpler and Polo, 1993). We are now able to present the most part of these results. The last step will consist in building the rules of an expert system for configuration and tuning assistance of ORACLE RDBMS applications. We also analyse the impact of operating system (UNIX) parameters on performance, and these information will complete our expert system possibilities. The present paper will describe precisely this research with tools developed, methods used, and results.