A prototype system for early geometric configuration design

In this paper, we present a prototype system that has been developed to support geometric configuration of objects at the early stages of design. Guided by the general principle of minimum commitment, this system assists in the iterative development of alternative geometric configurations based on approximately or precisely defined information. The system has been evaluated in the context of computer enclosure design.     

A framework for reviewing domain specific conceptual models

Conceptual models are used in understanding and communicating the domain of interest during analysis phase of system development. As they are used in early phases, errors and omissions may propagate to later phases and may be very costly to correct. This paper proposes a framework for evaluating conceptual models when represented in a domain specific language based on UML constructs. The framework describes the main aspects to be considered when conceptual models are represented in a domain specific language, presents a classification of semantic issues and some evaluation indicators. The indicators can, in principle, identify situations in the models where inconsistencies or incompleteness might occur. Whether these are real concerns might depend on domain semantics, hence these are semantic, not syntactic checks. The use of the proposed review framework is illustrated in the context of two conceptual models in a domain specific notation, KAMA. With reviews based on the framework, it is possible to spot semantic issues which are not noticed by case tools and help the analyst to identify more information about the domain.     

Tolerances in computer-aided geometric design

In the design of discrete part shapes, the specification of tolerance constraints can have major consequences for product quality and cost. Traditional methods for tolerance analysis and synthesis are timeconsuming, and have limited applicability. This paper presents the results of research into the use of solid modeling technology for the automated solution of tolerancing problems. A linear programming method is presented for the solution of tolerance analysis problems on a worst-case basis. A Monte Carlo method is presented for both worst-case and statistical tolerance analysis. Both methods automatically derive all necessary geometric relationships from a solid model of the assembly. Example problems are solved using the experimental GEOTOL geometric design system.     

Visual knowledge specification for conceptual design: Definition and tool support

Current CAD tools are not able to support the conceptual design phase, and none of them provides a consistency analysis for sketches produced by architects. This phase is fundamental and crucial for the whole design and construction process of a building. To give architects a better support, we developed a CAD tool for conceptual design and a knowledge specification tool. The knowledge is specific to one class of buildings and it can be reused. Based on a dynamic and domain-specific knowledge ontology, different types of design rules formalize this knowledge in a graph-based form. An expressive visual language provides a user-friendly, human readable representation. Finally, a consistency analysis tool enables conceptual designs to be checked against this formal conceptual knowledge.In this article, we concentrate on the knowledge specification part. For that, we introduce the concepts and usage of a novel visual language and describe its semantics. To demonstrate the usability of our approach, two graph-based visual tools for knowledge specification and conceptual design are explained.     

A computerized optimization framework for the morphological matrix applied to aircraft conceptual design

This paper presents a formal mathematical framework for the use of the morphological matrix in a computerized conceptual design framework. Within the presented framework, the matrix is quantified so that each solution principle is associated with a set of characteristics such as weight, cost, performance, etc. Selection of individual solutions is modeled with decision variables and an optimization problem is formulated. The applications are the conceptual design of subsystems for an Unmanned Aerial Vehicle and an aircraft fuel transfer system. Both the system models and the mathematical framework are implemented in MS Excel.     

A framework for empirical evaluation of conceptual modeling techniques

The paper presents a framework for the empirical evaluation of conceptual modeling techniques used in requirements engineering. The framework is based on the notion that modeling techniques should be compared via their underlying grammars. The framework identifies two types of dimensions in empirical comparisons—affecting and affected dimensions. The affecting dimensions provide guidance for task definition, independent variables and controls, while the affected dimensions define the possible mediating variables and dependent variables. In particular, the framework addresses the dependence between the modeling task—model creation and model interpretation—and the performance measures of the modeling grammar. The utility of the framework is demonstrated by using it to categorize existing work on evaluating modeling techniques. The paper also discusses theoretical foundations that can guide hypothesis generation and measurement of variables. Finally, the paper addresses possible levels for categorical variables and ways to measure interval variables, especially the grammar performance measures.     

Interactive design of 3D models with geometric constraints

In this paper, an interactive graphical approach for the design of parameterized part-hierarchies is presented. Primitive solids can be grouped into compound objects, and multiple instances of a compound object can be used in further designs. Geometric relations between primitives and instances are specified by geometric constraints between their local coordinate systems. The user can specify and edit a model by direct manipulation on a perspective or parallel projection with a mouse, whereas a procedural model representations is automatically generated via visual programming. The obtained twoview approach offers two concurrent interface styles to the end-user and enables the combination of an intuitive direct manipulation interface with the expressiveness of a procedural modeling language.     

An ontology-based support for product conceptual design

The research presented in this paper is a follow-up of our prior work involving the development of a graphical modeling tool to support designers at the conceptual design stage. To close the loop for supporting designers in generating design concepts flexibly, fast, and easily, an ontology-based approach for knowledge management that works along with the graphical modeling tool is discussed. Ontology and databases for the tool are developed to promote the systematic capture of design knowledge and efficient reuse of the design knowledge selection. In order to locate the proper information and query the data from the databases, the relationship between the ontology and databases, the data analysis process, ontology enrichment, and the ontology-based query engine are built to offer users multiple design results according to users’ requirements. A tire design example is presented to demonstrate the proposed approach. The ontology-based method described in this paper can help retrieve and save the complex relations, support the reasoning, integrate heterogeneous data resources and offer users more accurate, proper and comprehensive data.     

A form verification system for the conceptual design of complex mechanical systems

This paper presents a summary of research into the development and implementation of a domain-independent, computer-based model for the conceptual design of complex mechanical systems [1]. The creation of such a design model includes the integration of four major concepts: (1) the use of a graphical display for visualizing the conceptual design attributes: (2) the proper representation of the complex data and diverse knowledge reguired to design the system; (3) the integration of quality design methods into the conceptual design: (4) the modeling of the conceptual design process as a mapping between functions and forms. Using the design of an automobile as a case study, a design environment was created which consisted of a distributed problem-solving paradigm and a parametric graphical display. The requirements of the design problem with respect to data representation and design processing were evaluated and a process model was specified. The resulting vehicle design system consists of a tight integration between a blackboard system and a parametric design system. The completed system allows a designer to view graphical representations of the candidate conceptual designs that the blackhoard system generates.     

Information frameworks for conceptual engineering design

An information modeling approach is used to gain an understanding of the information and decision content of conceptual engineering design. Information frameworks are presented that attempt to represent the key decisions made during conceptual design. Elements of the frameworks are derived from results from design theory and methodology and decision theory. Using a number of products, the frameworks are demonstrated in simulated design situations. The models provide an explicit, generic and consistent perspective for identifying the information content of conceptual designs.     

A conceptual model for the logical design of temporal databases

Although widely advocated as a tool for the conceptual modelling of data, the Entity-Relationship (E-R) model [4] and its extensions are generally lacking in constructs to model the dynamic nature of the real world, making them inadequate for designing temporal databases. This research first extends the E-R model to a Temporal Event-Entity-Relationship Model (TEERM), by introducing events as an additional construct. Second, a method is proposed for mapping this conceptual model into a temporal relational model for the logical design of temporal relational databases with a corresponding set of integrity constraints. The model is illustrated with an example and evaluated using a set of criteria proposed by ^{Batini et al. [2]}. The model appears to be expressive, simple and easy to use, and should, therefore, aid the temporal database design process significantly.     

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.     

A system for desktop conceptual 3D design

In the traditional design process for a 3D environment, people usually depict a rough prototype to verify their ideas, and iteratively modify its configuration until they are satisfied with the general layout. In this activity, one of the main operations is the rearrangement of single and composite parts of a scene. With current desktop virtual reality (VR) systems, the selection and manipulation of arbitrary objects in 3D is still difficult. In this work, we present new and efficient techniques that allow even novice users to perform meaningful rearrangement tasks with traditional input devices. The results of our work show that the presented techniques can be mastered quickly and enable users to perform complex tasks on composite objects. Moreover, the system is easy to learn, supports creativity, and is fun to use.     

Constraint-based functional design verification for conceptual design

In the early stages of mechanical product design, designers not only need to determine the physical structure of the design, but also need to verify that the design functions properly with the allowable values or ranges of values of the relevant design attributes. Existing work on design verification is either aimed at specific design problems, which are generally carried out at the downstream design stages, or aimed at deriving design behavior using a behavioral simulation approach. Functional design verification has largely been neglected by the research society. To tackle this problem, we propose a generic constraint-based approach that is based on a comprehensive functional design model. A number of strategies are proposed for the approach, including strategies for design variables reduction, variable dependency graph development, constraint propagation, and dynamic verification of a design over an assigned set of attributes (variables). The approach is implemented as part of a functional modeling design environment. A simple design verification case is presented to illustrate our approach.     

A new constructive approach to constraint-based geometric design

In the paper, a new constructive approach to solving geometric constraints in 2-D space is presented. Constraints are employed on lines and points only, but more sophisticated geometric elements like Bézier curves and ellipses can also be constrained by mapping them onto auxiliary lines and points. The algorithm is based on local propagation, but first, the problem is transformed into a form that guarantees success of employing this simple technique. The most important steps are substitution of complex constraints with sets of simpler ones and insertion of redundant constraints by solving triangles and determining sums and differences of adjacent angles. In this way, various well-constrained problems with a few exceptions are solved, over-constrained scenes and input data contradictory to some well-known mathematical theorems are detected, and the algorithm is proved successful in many under-constrained cases as well.     

A graph-theoretic approach to conceptual design with functional perspectives

This paper explores the concepts of concurrency in design and develops an approach that involves reliability and other functional perspectives at the conceptual design stage. The paper uses graph theory to represent a product and define the relationships between its components. It employs the graph-theory concepts of the “tree” and the “forest” to represent a functional design artefact and idle condition, respectively.

The approach presented in the paper provides a more refined visualisation of the energy flow and is applicable to numerous designs including sliding gears, clutches, overrunning clutches and flywheels, amongst others. It can be used to concurrently modify the design taking into consideration various constraints, e.g. expected mechanical failures and cost considerations. A case study is presented to illustrate the benefits of the approach discussed in the paper.     

From conceptual models to schemata: An object-process-based data warehouse construction method

Data warehouse modeling is a complex task, which involves knowledge of business processes of the domain of discourse, understanding the structural and behavioral system's conceptual model, and familiarity with data warehouse technologies. The suitability of current data warehouse modeling methods for large-scale systems is questionable, as they require multiple manual actions to discover measures and relevant dimensional entities and they tend to disregard the system's dynamic aspects. We present an Object-process-based Data Warehouse Construction (ODWC) method that overcomes these limitations of existing methods by utilizing the operational system conceptual model to construct a corresponding data warehouse schema. We specify the ODWC method, apply it on a case study, evaluate it, and compare it to existing methods.     

A framework for an automotive body assembly process design system

This paper describes a framework for an automotive body assembly process design system. It is a computer-aided intelligent system that can automatically generate the optimal joint types and assembly sequences for the best dimensional quality. The backbone of this system is the Case-Based Reasoning (CBR) methodology, which works by searching through a case library created from previous designs whose identifying features resemble the current case. Algorithms for initial solution generation, dimension chain generation, joint design selections, assembly sequence generation, and tolerance analysis and optimization are developed. Based on the framework, a software tool called Body Build Advisor, or BBA, is developed. The software allows process designers to analyze candidate assembly schemes and achieve the best assembly process design prior to having detailed knowledge of geometry of the parts, and thus is ideal for architectural process design. In addition, the system has the advantage of an open structure that can be easily modified and adapted to accommodate existing assemblies and to suggest areas for improvement.     

A framework for digital sunken relief generation based on 3D geometric models

Sunken relief is a special art form of sculpture whereby the depicted shapes are sunk into a given surface. This is traditionally created by laboriously carving materials such as stone. Sunken reliefs often utilize the engraved lines or strokes to strengthen the impressions of a 3D presence and to highlight the features which otherwise are unrevealed. In other types of relief, smooth surfaces and their shadows convey such information in a coherent manner. Existing methods for relief generation are focused on forming a smooth surface with a shallow depth which provides the presence of 3D figures. Such methods unfortunately do not help the art form of sunken reliefs as they omit the presence of feature lines. We propose a framework to produce sunken reliefs from a known 3D geometry, which transforms the 3D objects into three layers of input to incorporate the contour lines seamlessly with the smooth surfaces. The three input layers take the advantages of the geometric information and the visual cues to assist the relief generation. We have modified the existing techniques of line drawings and relief generation, and then combine them organically for this particular purpose.