This paper describes the development of a cost estimating methodology for predicting the cost of engineering design effort during the conceptual stages of product development. The research was carried out within a large European aerospace manufacturer whose traditional costing practices had become outdated. The main objective was to generate a suite of technical Cost Estimating Relationships (CERs) that integrate both quantitative and qualitative, non-recurring airframe engineering input, for the design process. Both the quantitative and qualitative design activities were separated during the CER development. At the end of the development process they were integrated to produce a final CER. The results demonstrate that these newly generated CERs can predict future design effort required, based on the typically limited product definition at the conceptual design stage.
Like most useful devices, magnetic bearing actuators have a large number of design parameters that must be selected in design optimization. The usual approach in the design of these devices is to limit the number of parameters by introducing relationships between them that are presumed consistent with optimal design, and then to iterate until a feasible design is found that meets all requirements. In the present work, the magnetic bearing actuator design is reformulated as a catalog selection problem and solved using a genetic algorithm (GA). The resulting designs are compared with solutions found using more conventional design procedures and are found to be superior. By challenging the embedded assumptions in the traditional design process, the GA approach reveals new and useful design concepts. In addition, the GA/catalog approach is more amenable to commercial design than is parametric optimization.
The objective of the presented approach is to increase productivity of the design process by informing designers about the correlations to parallel work and by practising collaborative work. A cooperative design process is support by a shared design database called the Active Semantic Network (ASN). The ASN is an active, distributed, and object-oriented database system that supports the definition of constraints that are evaluated by a rule-based approach. Constraints and locking conflicts are used to find out when the work of designers coincides and they have to adapt their work to results of colleagues. Additional to the support of information exchange, a cooperative transaction model provides several cooperation mechanisms to allow users to exchange partial results and share common data.
The present paper describes an innovative approach in computer-aided industrial design; despite the availability of sophisticated modelling tools, there are still critical issues to be faced in order to provide creative users with functionality really suited to their mentality and able to support them in more easily attaining a model with a certain aesthetic and emotional character and in its preservation during the required model modifications. Currently, the adopted computer-aided design tools offer functionality mostly based on low-level geometric elements, while designers would like to act on properties more directly connected with their design intent. In order to understand which properties are important, we deeply analysed the process followed by designers and computer-aided design operators for achieving the desired product. The possible relationships between shape geometry and aesthetic character have been investigated and a software prototype has been developed to demonstrate the validity of the research outcomes. The presented work has been mainly developed within the framework of a Research and Development project supported by the European Commission, named FIORES-II, which involved, beside several research institutions from different European countries, a wide and direct participation of industrial application companies, such as Alessi, BMW, Pininfarina, Saab, Formtech and Eiger.
This paper presents a methodology and a software that allows assemblies to be evaluated with respect to robustness and geometrical stability. The assembly robustness evaluation aims at detecting design and assembly solutions that are sensitive to variation and may cause problems later during production. It is based on Suh"s independence axiom, stating that in a good, uncoupled design, each functional requirement is satisfied by one and only one design parameter. The methodology enables the designer to evaluate the geometrical sensitivity of the assembly, what the sources of variation are, their importance for the overall robustness and in what order to improve the design. A possible result from the analysis may be that the concept must be changed in some way, either by changing the way parts are located with respect to each other or by using assembly fixtures for positioning. The software is implemented in a Microsoft Windows environment and has an IGES interface that enables the designer to import computer aided design (CAD) geometry from an arbitrary CAD system, and perform assembly robustness analysis.
The present paper describes a methodology and a software tool that allow assemblies to be evaluated and analysed with respect to degree of geometrical coupling and robustness on any hierarchical level of the assembly structure. Based on the assembly sequence and the mating conditions of a number of components fulfilling a number of functional requirements, a function means hierarchy with a pertinent set of relations between sub-assemblies, components and features is automatically generated and used for tolerance chain and stability analysis. Based on mating conditions and specified geometrical constraints, tolerance chains are automatically detected and presented in the structure. Geometrical couplings between sub-systems, components and individual features are detected and presented in stability matrices. The analysis tools assist in the iterative work of concept improvement and the decomposition of top-level geometrical constraints (tolerances on critical product dimensions) into bottom level feature constraints (tolerances on individual surfaces). The two analysis toots utilize the basic ideas in robust design and axiomatic design (the independence axiom), and can be used to compare and evaluate assembly concept solutions including different assembly fixturing solutions. The similarities between uncoupled robust assembly design and uncoupled robust tolerancing of individual parts are discussed and illustrated. Two examples are used to describe the methodology and the software tool.
The design and production of aircraft structures is a highly cost-driven industrial activity. Advanced, more reliable cost-estimation techniques can help to improve competitiveness and reduce risk in the bidding phase. In this paper a design support framework will be presented that offers improved information and knowledge about new designs in an early stage of the development. The paper focuses on aircraft movables but similar frameworks can be built for other product families. The framework is based on the design and engineering engine architecture. The design and engineering engine formalizes the basic design cycle and comprises a multi-model generator (MMG) based on knowledge-based engineering principles that creates a smooth link between a parametric product model and different analysis tools, including a cost analysis tool. It will be shown that such an MMG can support the extraction of a cost engineering view on the product model that can be used in combination with proper cost-estimation relations to have more reliable cost information in an early stage of the design process. A cost analysis tool is presented that resembles a cost representation of a factory. The cost engineering view extracted by the MMG is fed into the cost analysis tool to give the designer an estimate of the cost consequences of his or her design choices. Emphasis is put on the influence of the choice of manufacturing concept on costs.
Selecting the best product concept is one of the most critical tasks in a new product development (NPD) environment. Making decisions at this stage becomes very difficult due to imprecise and uncertain product requirements. So, the evaluation process of determining the most satisfying conceptual design has been a very vital issue for companies to survive in fast-growing markets for a long time. Therefore, most companies have used various methods to successfully carry out this difficult and time-consuming process. Of these methods, an analytic hierarchy process (AHP) has been widely used in multiple-criteria decision-making problems (i.e. concept selection, equipment evaluation). In this study, however, we use an analytic network process (ANP), a more general form of AHP, due to the fact that AHP cannot accommodate the variety of interactions, dependencies and feedback between higher and lower level elements. Briefly, in this paper, an ANP-based approach is presented to evaluate a set of conceptual design alternatives in order to reach to the best concept satisfying the needs and expectations of both customers and company. In addition, a numerical example is presented to illustrate the proposed approach.
Annotation is a natural way for adding information to a specific representation. Most of the time these annotations remain informal and are considered as mere supports to a verbal exchange. We want to show in this paper that it is important to consider annotation as complex and composite elements that can play a central role in design co-operation. Relying on a strong empirical background especially based on ethnographic research and software developments in the truck manufacturing industry, we argue that providing annotation facilities within computer-aided design systems is not enough. We address here the cognitive side of the annotation, and we show how they can foster knowledge creation and participate to the development of shared understanding among design teams. We put on the hypothesis that annotation systems behave like natural languages, and we start exploring this metaphor. We then make a connection to the concept of communities of practice in order to position our work in a wider conceptual framework where the annotations are part of a 'shared repertoire'. The organization that can support the creation and maintenance of this 'shared repertoire' therefore becomes of prime importance. As a conclusion we propose to consider the annotation as the visible side of a larger and informal process, and propose to develop annotation functionalities of creating, storing retrieving new symbols associated with the creation of annotation glossaries suited for storing elements of the design context.
Large-scale engineering systems provide important functions to the human society. The involvement of multiple, competing functionality requirements and lots of resources has imposed high expectations, and at the same time challenges, for achieving reliable, affordable design. Axiomatic design approach has demonstrated its strength in various types of large-scale system design, including vehicles, aircrafts, manufacturing facilities, and so on. However, several obstacles are yet to be overcome in proper application of the axioms to a real-world design problem, by both researchers and practitioners. In this work, a systematic methodology is presented for applying Suh's axioms to evaluate and optimize large-scale engineering systems. When using the proposed methodology, design matrices are first obtained to map multiple, competing functionality requirements to their associated physical embodiments at different system hierarchical levels based on Axiom 1. An R / S analysis using surrogate modelling is then conducted on the design matrices to evaluate the existing system design. If the evaluation shows any areas for improvement, a combination of surrogate modelling-based R / S analysis and optimization is used to achieve a less functionally coupled design. An application in a nuclear reactor system design is used to demonstrate the use of the proposed methodology in dealing with real-world design problems. The results show that the proposed methodology provides a promising approach to efficiently evaluate and optimize a large-scale engineering system against multiple, competing design objectives.
Assembly tolerance chains are often the root cause for low geometrical robustness and high manufacturing costs. This paper presents a framework for function means modeling in configuration design that allows for modeling and analysis of geometrical couplings, and detection of potential tolerance chains. Requirement decomposition is described, and geometrical couplings on different hierarchical assembly levels are modeled, analyzed and explained. The treatment of sub-assemblies is especially described. The presented framework includes the use of locating schemes for positioning parts in assemblies. A general positioning system for modeling datum frames and locating schemes for parts and sub-assemblies are presented and used. An automotive example is used to show how an overall geometrical product constraint is decomposed into locating schemes on individual parts and how potential tolerance chains are detected. Finally, geometrical coupling quantification and the use of fixtures as a mean for breaking tolerance chains are discussed. The proposed framework enables potential tolerance chains to be detected already in the configuration design phase. By detecting potential tolerance chains in very early configuration design, design solutions with low robustness, needing tight tolerances to fulfill their functional requirements, may be avoided.
The transplanting accuracy of a rice transplanter for picking, conveying and transplanting seedlings mainly depends on the trajectory as well as the return motion of the hoe. The trajectory of the hoe has to be optimized in treating seedlings for a prevailing soil condition. For better transplanting accuracy, a planetary-gear-train system, instead of the four-bar linkage system is used to design a transplanting mechanism. This study proposes a theoretical design method for a transplanting mechanism; the method designs non-circular gears of a planetary-gear-train system for the hoe to trace a prescribed trajectory. An optimization method was used to determine the arm length and tool length; inverse kinematics to determine the configuration angles of the two links and the roll contact condition in transmitting motion between the gears; and a linearization approach to obtain the shapes of the gears. Based on the proposed method, the shapes of the gears and the lengths of the tools of the planetary-gear-train system are determined for three prescribed trajectories. A commercialized package program (ADAMS) is used to carry out a kinematic simulation to confirm that the gear-train system configured from the proposed method is adequate for the transplanting mechanism.
This paper reports on a study in which virtual reality representations of a car were compared with concept sketches and a real car as a means for customer evaluations. Early communication with customers is important in order to identify customer needs and to achieve response on design solutions. Physical prototypes are often used for these purposes, but they are costly to produce, inflexible in modifications, and expensive and fragile to carry, which has lead to an increased interest for the use of virtual reality prototypes. However, knowledge is scarce of how different types of product representations may influence customers' understanding of a product concept. The study indicated that the different product representations resulted in small differences in the participants' understanding of the car, despite the greater degree of realism in the virtual reality representations and, of course in the real car, compared with the sketches. The study indicates that there are other factors to consider than the degree of realism in the product representations for efficient product evaluations with customers; for example, that the participants are well familiar with the type of product, but also with the type of representation technology.
The strategic importance of global competitiveness of the machine tool industry in Japan is steadily increasing, and therefore machine tool manufacturers require effective corporate strategy to achieve sustainable competitive advantages. Strengths, Weaknesses, Opportunities and Threats (SWOT) analysis is one of the most effective approaches used for analysing strategic management policy of an organization. However, the use of conventional SWOT analysis is based on the qualitative analysis and has no means of determining the importance of each SWOT factor. In this study, a newly structured SWOT analysis has been proposed for weighting and rating individual SWOT factors using the pairwise comparison matrices. As a result, effective industrial strategy planning for the machine tool industry can be carried out by applying the proposed method.
Taguchi concepts have been developed into an engineering method of quality improvement referred to as Quality Engineering in Japan and as Robust Design in the West, which is a disciplined engineering process that seeks to find the best trade-off of a product design. A safety optimization framework using Taguchi concepts is proposed in this paper. An example is used to demonstrate the application of the framework in maritime safety studies. Following a brief review of Taguchi concepts and techniques used in Robust Design, this paper discusses how the Taguchi concepts such as "quality loss function", "signal-to-noise ratio", "orthogonal arrays", "degree of freedom" and "analysis of variance" may be synthesized in maritime safety engineering studies. Brainstorming, an integral part of the Taguchi philosophy, is also briefly discussed. Orthogonal arrays are used to study many parameters simultaneously with a minimum of time and resources to produce an overall picture for more detailed safety-based design and operational decision-making. The signal-to-noise ratio is employed to measure quality; in this case, risk level. The loss function is considered as an innovative means for determining the economic advantage of improving system safety or operational safety. Noise factors are considered as any uncontrollable or uncontrolled variables or any other undesired influences. Control factors are the variables that are set by the designers that will characterize the performance as well as safety level of a system throughout its life cycle. The outcomes of this paper may provide the fundamental knowledge for safety analysts to utilize the Taguchi concepts and methodologies. A hypothetical example with simple analysis techniques is used to illustrate how the Taguchi method can be used to extract from expert judgements those factors the experts judge as most vital when they perform risk estimation for a ship with the purpose of determining insurance rates.
Product conceptualization is widely accepted as a key activity in new product development. In product conceptualization, customer requirements play a crucial role. In today's competitive and globalized business environment, one decisive factor for a company to out-perform its competitors is its ability to incorporate customer preferences in new product development projects. This study aims at establishing an effective measure for evaluating demographic customer characteristics and detecting demographic customer differences in product conceptualization. For this purpose, an environment based on a four-domain modelling paradigm and a three-phase process is proposed. In this environment, a design knowledge hierarchy is postulated for representing design knowledge and a Kohonen association algorithm is adopted for evaluating the customer requirements elicited from diverse demographic customer groups based on a two-level decision-making scheme. A case study on wood golf club design is used to illustrate the proposed approach.
We focused on designer's drawings to determine how designers made images of a design object from given keywords. We thought that difficult keywords would give us good clues to understanding the designers' creative thinking process. An experiment was held to examine designers' creative thinking. The subjects were assigned a task to design 'a chair which gives a sad image'. Subjects' drawings were evaluated and words on sketches were structured into meaning hierarchy. From the results, we found that when the design goal was difficult to convert to the forms, the designer tried decomposing the meaning of the design goal into an adequate level to be able to image forms. Based on this study, we present a model of a thinking path for understanding the creative thinking process of design.
Feature recognition techniques have been developed in the past that dealt with parameterizing regular features. In response to the availability of free form shape, researchers have turned to free form features. Some of the methods developed for features can be re-used in the free form domain, but many methods have to be developed anew. In this paper it is argued that there is a need for a general framework to provide a common point of reference for new methods and to increase the cohesion between such methods. An initial framework is proposed for the definition of features and for one of the possible applications of features, feature recognition. Two existing free form feature recognition methods are analysed with regard to the framework, in order to critically review the proposed framework as well as the two methods.
Design function deployment is a prescriptive design system. It combines the benefits offered by quality function deployment, concurrent engineering, design models and methods, and computer-aided engineering. It has a unique chart structure to store the information generated at different stages of the design process. This paper explains design function deployment using a chair as an example.
Computer aided engineering has gained increasing significance in product development processes and research in recent years. Simulation techniques and CAE methods are becoming more and more significant as strategic success factors. While the finite element method and multibody system simulation are state-of-the-art in many fields of application, structural optimisation methods are not so widely used. Although much progress in development has been achieved in recent years, their successful application is often still time-consuming and sometimes not even possible. Further research work and development is necessary to improve both the capabilities of structural optimisation methods and their usability. The research work presented in this paper is a contribution towards producing an integrated structural optimisation process, introducing a new shape optimisation approach. The new process allows an integrated investigation of dynamically loaded parts in complex mechanical systems and a straightforward optimisation with respect to fatigue. Coupling effects between optimisation operations and system dynamics are fully covered. Finite element analysis (FEA), multibody system simulation (MBS), fatigue analysis and shape optimisation are tied together into a fully automated process. The whole optimisation loop, which is an iterative procedure, incorporates all these analysis steps and is implemented in a straightforward, batch-oriented manner using well-known standard software. Since the whole process involves several different analysis types, the resulting setup is rather complex and the reader may not be familiar with all the terms arising within the context. Therefore, some essential aspects of each of the stages involved in the process are explained, to provide the reader with important concepts. An academic example is discussed in depth, to illustrate and clearly outline the potential of this method. The results clearly show the importance of covering fatigue aspects in shape optimisation problems of parts in dynamic systems. In particular, the interaction between the dynamic properties of the part and the overall system, as well as its implications on the optimisation process are demonstrated. Finally, a more complex application, namely the optimisation of a passenger car suspension arm, is presented. This example demonstrates the applicability and feasibility of the optimisation process for real world problems.
In 2002 the UK Department of Health and the Design Council jointly commissioned a scoping study to deliver ideas and practical recommendations for a design approach to reduce the risk of medical error and improve patient safety across the National Health Service (NHS). The research was undertaken by the Engineering Design Centre at the University of Cambridge, the Robens Institute for Health Ergonomics at the University of Surrey and the Helen Hamlyn Research Centre at the Royal College of Art. The research team employed diverse methods to gather evidence from literature, key stakeholders, and experts from within healthcare and other safety-critical industries in order to ascertain how the design of systems--equipment and other physical artefacts, working practices and information--could contribute to patient safety. Despite the multiplicity of activities and methodologies employed, what emerged from the research was a very consistent picture. This convergence pointed to the need to better understand the healthcare system, including the users of that system, as the context into which specific design solutions must be delivered. Without that broader understanding there can be no certainty that any single design will contribute to reducing medical error and the consequential cost thereof.
In a design of industrial product, its shape that influences the rigidity and vibratory characteristics as well as productivity is determined by trial-and-error-based experimentation or simulation. The NURBS representation is used widely in computer-aided design/computer-aided manufacturing (CAD/CAM) systems because it offers good capabilities for representation of sculptured surfaces, reduction of the amount of numerical control data, and control of the cutter pass and cutting speed. Thereby, it realizes a smooth surface and high efficiency of manufacturing. Therefore, once a finite element method based on the NURBS representation is established, we may integrate it into a comprehensive CAD/CAM/computer-aided engineering tool for product design. From that point of view, this study addresses the formulation of a finite shell element that perfectly forms the product shape represented by the NURBS surface. The NURBS surface, which is originally defined by a control point scheme, is represented by interpolating the nodal points on the surface. The function for this interpolation is used for the shape function. The explicit derivation of the shape function also allows formation of a mass matrix to solve dynamic problems. The method presented here is applied to several bending analyses of plates and shells to demonstrate the effectiveness and good accuracy of the method. Results suggest that this method offers a useful tool for product shape design.
Engineering, design science is a young scientific discipline. Its status and its realm have not yet been firmly established. The present paper intends to contribute to the clarification of the concept of engineering design science. Starting from a few basic models (a general interaction model of technical action, a model of the structure of action in general and a model of the basic design cycle), the contours of a science of engineering design are explored step by step. This results, first, in recognizing 'engineering design epistemology' (the science of engineering design science) as a metadiscipline with respect to engineering design science proper; and second, in viewing 'engineering design methodics' (the collection of design methods designers dispose of) as an indispensable tool-kit for the designer, as an essential object of engineering design science too, but yet not belonging itself to engineering design science. It is therefore in this treatise sharply distinguished from engineering design methodology, which does belong to engineering design science. This distinction is generally not made in the literature. In the realm of engineering design science proper, the following regions are identified: 'engineering design phenomenology', 'engineering design methodology' and 'engineering design ontology'. A stratification model for the context of engineering design science is presented, and the various items are discussed. The intimate relation between engineering design science and natural science is briefly entered into.
From the abstract of the whole treatise preceeding Part 1 of this paper (J. Eng. Des., 2000, vol. 11, no. 4, 377397) we recall that a stratification for the context of engineering design science was constructed, consisting of 5 levels, viz. general epistemology, engineering design epistemology, engineering design science, engineering design methodics and engineering design practice. The levels of general epistemology and of engineering design epistemology were briefly discussed, and a start was made in discussing the level of engineering design science proper, which would subsequently address I: The action subject of engineering design , II: The action object of engineering design, III: The action process of engineering design, and IV: Engineering design ontology. Part 1 ended with the discussion of "The action subject of engineering design", so consequently Part 2 starts with discussing "The action object of engineering design". The next item, "The engineering design process" is discussed from two aspects, viz. "Engineering design phenomenology" and "Engineering design methodology". This item, "The engineering design process" clearly forms the kernel of the paper. After two short paragraphs on "Engineering design ontology" (belonging to engineering design science) and "Engineering design methodics" (the tool kit of the engineering designer, but as such not belonging to engineering design science), the paper ends with a logical analysis of the relation between engineering design science and natural science, for which the metaphor of a Siamese Twin clearly presents itself.
The techniques used for the design of circuits for space applications are not different from those used for commercial applications. However the technology and the fabrication processes must be oriented to obtain an average life of the circuit and/or component higher than the expected service offered from the satellite. For these applications the Monolithic Microwave Integrated Circuit (MMIC) design techniques must satisfy requirements that include also specifications such as the reliability and the final production yield. In this paper a MMIC design technique, oriented to the optimisation of the production yields, is proposed. This method, based on a sensitivity analysis, i.e. on the circuit behavior for value variations of passive elements from their nominal value, and on the contemporary determination of the production yields, allows the identification the circuit elements to obtain high production yield. Moreover it allows an appropriate choice of the circuit topology. As example, this technique has been applied to design a MMIC to employ on a Synthetic Aperture Radar (SAR) in X band.