Mary T. Rogers

Expert form feature modelling shell

Abstract Contemporary geometric modellers are unsuitable for mechanical design because of mismatch in abstraction level. The databases of these modellers cannot be used to drive automated applications such as engineering analysis or process planning because of missing product information. The paper outlines an integrated system for design and applications; the system reasons in terms of form features. Object-oriented programming techniques support user definition of form features (volumetric shapes) that may be positioned and manipulated in a logical manner. A solid modeller interface generates equivalent solid representations in parallel with feature representations. Mechanisms for parameter inheritance and validity checking (cognition) are also discussed. The system is modular, which will allow it to be integrated with tolerance and material modellers that are currently under development. Artificial intelligence techniques have been applied to solid modelling, resulting in this powerful feature technology for creating flexible and integrated CAD systems for the next generation of engineering tools.

Assembly modeling as an extension of feature-based design

The advantages and limitations of procedural and declarative approaches for product modeling are discussed. Concepts are developed for modeling all levels of product relations with a uniform set of structures and relationships. It is shown that five basic structures,Part-of, Structuring relation, Degrees of freedom, Motion limits, andFit can be used to define relationships between assemblies, parts, features, feature volume primitives, and evaluated boundaries. Generic relations which facilitate constraint specification between target and reference entities are also presented. Methods for the derivation of the location of an assembly unit from high level constraint specifications, such as mating conditions, and techniques for determining the degrees of freedom, motion limits, and assemblability are required. This can be done by uni-directional parameter derivation in the procedural approach, or by symbolic geometric reasoning or numerical equation solution in the declarative approach. The former is less expensive, easy to implement, avoids conflicts, but leads to combinatorial explosion. The latter is general, flexible, decouples constraint specification from validation, but is expensive, and may require conflict resolution.

Database infrastructure for supporting engineering design histories

Abstract An engineering design history is a step-by-step account of the events and the states through which a design artifact evolved. Database technology has not yet provided adequate mechanisms for capturing and reusing design history information. This paper presents an infrastructure for computer-aided archiving and interrogation of engineering design histories. This framework combines research from software engineering, data engineering, and knowledge engineering to develop an environment for the capture and reuse of design histories. A Design Process Representation Language (DRL), is combined with ‘enhanced’ step models to capture design steps and design parameters. This high-level representation is translated into Data Definition Language (DDL) for operations on an object-oriented database. Advances in database technology that are required to fully support intelligent design history systems are discussed.

A heterogeneous, active database architecture for engineering data management

Abstract This paper presents an architecture for engineering data management that incorporates current work on engineering product standards as well as current work in database research. In particular, we present a framework that views an engineering design environment as an integrated, heterogeneous database system. Our integrated view of data makes use of PDES/STEP, presenting a framework for the representation of meta data that describes an object-oriented view of data and supports an object-oriented query language for the retrieval of data from multiple data sources. We also describe how the architecture makes use of active database technology to support n rule-based approach to constraint propagation and change notification. An additional aspect of the architecture presented in this paper is the design history component. We conclude by presenting an extended data management architecture that addresses the requirements for capturing information about the design process as part of the engineering data ...

Comparative study of procedural and declarative feature based geometric modeling

Two generic approaches to feature based geometric modeling appear to be evolving: procedural and declarative. The geometry of a feature can be created by unidirectional parameter derivation, as in the procedural approach, or by solving a set of simultaneous constraint equations, as in the declarative approach. The former is less expensive, easy to implement, avoids conflicts, but deals only with special cases, which leads to procedure explosion as new features are added. The latter is general, flexible, decouples constraint specification from validation, but is expensive, and may require conflict resolution. The declarative approach presented here takes advantage of two types of generic systems available commercially: geometric modeling core packages and constraint solvers.

An overview of the ASU engineering database project: interoperability in engineering design

The paper presents a work-in-progress report on work addressing interoperability in engineering design environments. The work is being conducted as a joint research effort between computer science and mechanical engineering researchers for the purpose of (1) creating a more productive environment for relating and accessing data in the engineering design process and (2) advancing database technology to adequately support interoperability issues in engineering design. The first six months of the project have primarily served as an organizational period, surveying database issues, learning about engineering design, and examining current efforts in engineering data exchange standards. The paper presents an overview of the research directions.<<ETX>>

A Testbed For Rapid Prototyping Of Feature Based Applications

Abstract The A.S.U. Features Testbed provides an infrastructure for rapid prototyping of feature based applications. The system has an open architecture in which users can define feature libraries for modeling their products and build knowledge bases for a variety of manufacturing applications. The Testbed is organized into two shells: one for feature based product definition, the other for feature based product evaluation or manufacturing planning. The product modeler allows one to integrate features, dimensions, tolerances, assembly data, geometry, topology, and design rules into a unified product description. The applications shell facilitates the creation of knowledge bases and reasoning procedures desired for the applications. In this chapter, we give a brief overview of the system and then discuss several applications that have been implemented. These include GT coding for machining, machinability evaluation, and composite panel forming. The Testbed can be used for two different purposes: (1) Organizations that want to evaluate feature based technology in conjunction with knowledge based applications can quickly do so in this integrated system. (2) feature related techniques and algorithms can be evaluated by software developers. Customization of the Testbed does not require any programming or re-compiling because the system is data-driven.

Metadata Extensions to an Object-Oriented Data Model for the Dynamic Capture of Engineering Design Histories

In this paper we present the Design History Data Model (DHDM), an extended object-oriented data model that explicitly supports the modeling and capture of engineering design histories. An engineering design history is a composite information structure that contains the evolution of engineering design specifications along with the design actions, constraints, and rationale that drove the design process. The capture and classification of engineering design activity is highly beneficial to future designers, assisting in design analysis, design maintenance, design learning, and design reuse. An advantage of the DHDM is that it incorporates a meta data and schema evolution component to support the capture of both pre-specified design activities and dynamic design activities. Pre-specifiable design specifications are those design tasks that are well-known and can be planned in advance of a design activity. Dynamic design involves the specification of design tasks as they actually occur using schema evolution. Modeling design activities is achieved through the use of process classes that are composed of subprocesses through the use of temporal aggregation concepts. Specific occurrences of design activities are modeled as instances of process classes. In addition to introducing the DHDM concepts, this paper describes a prototype implementation of the DHDM on the Itasca object-oriented database system. The prototype DHDM is evaluated with respect to constructibility, comprehensibility, and extensibility of the design history specification.