Alan de Pennington

Requirements management : a representation scheme for product specifications

Product definition processes take a product specification (defining the requirements that the product must satisfy) and transform it into a product definition (defining, at least, the shape and material of the required product so that it can be manufactured). Recent advances in computer aided design technology have allowed product definitions to be captured electronically. Currently the resulting electronic product definitions are centred around representations of physical product structures and shape-related properties. The industrial need is now moving towards a desire to manage requirements in a plausible architecture. From this basis the products functional requirements can be identified and converted into physical elements which can be related to design intent/rationale; this requires the linking of elements of physical product structure and shape with elements of an electronic product specification. The research reported in this paper is focussed on the realisation of an electronic product specification. Such a specification must be defined in a way that allows relationships to electronic product definitions to be established. A product data model that supports the description of mechanical product specifications is presented and its functionality is demonstrated through a case study.

EVALUATION OF A 3D SHAPE GRAMMAR IMPLEMENTATION

The geometric design of the exterior appearance of consumer products is a principal consideration to retain brand identity. Architectural and engineering shape grammars had demonstrated shape computation as a formal and viable approach for supporting style conformance. However, most existing shape grammar implementations operated in limited experimental domains, and lacked support for complex three dimensional geometry, shape emergence and parametric shape rules. The aim of the reported research is to address these issues. Shape algebras are reduced in terms of shape operations with their basic elements which is generally applicable to shape computation. Specifically for algebra U13, exhaustive cases were enumerated for shape sum and shape difference operations. A U13 shape grammar implementation was developed to support both rectilinear and curvilinear basic elements in three dimensional space. Mathematical representations of basic elements were based on non-uniform rational b-splines and their reduced form. This allowed a simple yet exact notation which simplified support for maximal representation and its computation. Two cases studies, a Coca-Cola bottle grammar and a Head & Shoulder bottle grammar, were used to test the implementation.

Numerical Code Generation from a Geometric Modeling System

A geometric modeling system (GMS) can, in principle, model the geometric aspects of a manufacturing environment from an entire manufacturing cell through to the tooling details. It offers the capability of an unambiguous model of the component workpiece at all stages of manufacture, thus giving a representation of the stock to be removed by the material removal process. The conversion from a representation suitable for graphics to one more applicable to manufacture can be made. Preliminary studies suggest that a GMS having multiple representations and dimension and tolerance information, together with machinability data, will facilitate the selection of appropriate manufacturing processes and tooling to produce the specified geometry and surface finish. With minimal human intervention, a prototype system would give process planned N/C code, making use of available production engineering data. A further advantage of using the geometric modeler is that the N/C code generated can be verified for all types of invasive machining.

Constraint definition system: a computer-algebra based approach to solving geometric-constraint problems

Abstract During the computer-aided design of assemblies, or of single objects composed of primitive elements, the positions of their constituent parts must be determined. These parts can be positioned absolutely in terms of some coordinate system, or relatively in terms of the relationships or constraints that implicitly exist between their constituents. Despite having many advantages, the latter approach presents computational problems which have resulted in its limited acceptance. The paper describes a system which uses techniques from computer algebra to avoid these problems, and discusses its advantages and disadvantages.

A functional approach to redesign

This paper describes a methodology to assist in the identification of possible conceptual design variants during redesign. The approach is based on functional reasoning and involves: (1) the structural and functional analysis of an existing design; (2) the production of abstract representations of functions and design entities using conceptual graphs; and (3) design interrogation based on a functional tree approach. The research reported in this paper also focuses on the definition and the representation of elementary mechanical functions. Extended Backus-Naur Form (EBNF) notations are used to structure in a computable form, the relevant information (or design knowledge) conceptualised in either the conceptual graphs or the functional trees. EBNF syntax is also used to formulate rules which aid the partial automation of the reasoning process. The EBNF notations can be mapped to any programming language. A diaphragm valve is used as a case study to demonstrate the approach.

Offsetting in geometric modelling

Abstract The capabilities of current solid modelling systems are limited by the available representation schemes, geometric coverage, and types of operations allowed within a modelling system. Most of todays modellers can hardly do anything beyond graphic display and mass property calculation. Modelling systems need to extend their representations, geometry and operations to enable them to meet the requirements of the variety of engineering applications. This paper addresses the introduction of a class of operations called offsetting into solid modelling environments. A range of potential applications that could benefit from an offsetting utility has been identified, and a normal mathematical framework that rigorously characterizes the offsetting function is developed.

Advanced product planning: a comprehensive process for systemic definition of new product requirements

This paper reports results of research into the definition of requirements for new consumer products––specifically, electro-mechanical products. The research dealt with the derivation of design requirements that are demonstrably aligned with stakeholder needs. The paper describes a comprehensive process that can enable product development teams to deal with statements of product requirements, as originally collected through market research activities, in a systematic and traceable manner from the early, fuzzy front end, stages of the design process. The process described has been based on principles of systems engineering. A case study from its application and evaluation drawn from the power sector is described in this paper. The case study demonstrates how the process can significantly improve product quality planning practices through revision of captured product requirements, analysis of stakeholder requirements and derivation of design requirements. The paper discusses benefits and issues from the use of the process by product development teams, and identifies areas for further research. Finally, the conclusions drawn from the reported research are presented.

Towards an integrated description of product, process and supply chain

This paper draws upon learning from the aerospace, automotive and retail sectors to provide a framework for the modelling and simulation of supply chains, the processes that occur within them and the products that flow along them. The framework allows an integrated description of products and processes in a supply chain. Such a description could be used to support analyses and simulations that take account of the supply chain and its constituent products and processes. The framework itself is based on a data model that uses a single pattern for the representation of structured data. This pattern is used three times for supply chain, process and product. The descriptive capability of the framework is demonstrated through a case study that is taken from the packaging industry.

Computer Aided Design: An Early Shape Synthesis System

Today’s computer aided design systems enable the creation of digital product definitions that are widely used throughout the design process, for example in analysis or manufacturing. Typically, such product definitions are created after the bulk of [shape] designing has been completed because their creation requires a detailed knowledge of the shape that is to be defined. Consequently, there is a gulf between the exploration processes that result in the selection of a design concept and the creation of its definition. In order to address this distinction, between design exploration and product definition, understanding of how designers create and manipulate shapes is necessary. The research outlined in this paper results from work concerned with addressing these issues, with the long term goal of informing a new generation of computer aided design systems which support design exploration as well as the production of product definitions. This research is based on the shape grammar formalism.

Implications for Engineering Information Systems Design in the Product-service Paradigm

In an evolving business environment, many organizations are changing their product offering from the supply of predominantly physical goods to the delivery of product-service systems. The resulting need to support both physical goods and associated services throughout their lifecycles has a number of implications. This paper focuses on the changing requirements of engineering information systems caused by the need to represent both physical goods and associated services. Key characteristics that differentiate service offerings from physical goods are surveyed. The impact of these characteristics on the design of the engineering information systems that facilitate the delivery of product-service systems are outlined. The research reported in this paper draws together theories from engineering product definition and service blueprinting approaches that have traditionally been used to capture service products in the hospitality and financial sectors. Early results from the use of the service blueprinting method in defining technical services are presented and approaches to integrating product and service definitions are explored.