Product design and engineering

A fuzzy method to handle vagueness and imprecision in the description of requirements for multi-attribute decision making (MADM) problem is presented. This method is applied to design of an apron conveyors to collect and transfer scraps. The aggregation function for the overall evaluation is obtained utilising the Taguchi loss functions.

A prst step towards a semi-immersive Virtual Reality (L!R) interface for Finite Element Analysis (FEA) is presented in this paper. During recent years, user interfaces of FM solvers have matured from characterbased command-line driven implementations into easy-touse graphical user interfaces (GUS). This new generation of GUIs provides access to intuitive and productive tools for the management and analysis of structural problems. Many pre-And post-processors have been implemented targeting the simplification of the manmachine interface in order to increase the ease of use and provide better visual analysis of FEA solver results. Nevertheless, none of these packages provides a real 3Denabled interface. The main objective of this project is to join state-of-The-Art visualization technology, VT devices, and FM solvers into the integrated development environment VRFM.

Keywords: 3D Modeling , Finite Element Analysis , Interactive Modeling , Simulation. , Virtual Reality

This paper describes the preliminary results of the research work currently ongoing at the University of Parma, and partially carried out within a basic research project funded by the European Union. The research work aims at applying the techniques used in gesture analysis and recognition for understanding human skill performed for non rigid object grasping and manipulation. The various grasping gestures have been classified on the basis of some quantitative features extracted from the hand gesture analysis. Finally, it is planned to map the formalized skill into a robotics system, that will be able to grasp and manipulate non rigid objects, also facing unexpected situations.

A computer visualization application has been presented for fuzzy evaluation of windscreen wiper systems which must satisfy several requirements. Some requirements are modelled by fuzzy sets and a compensating arithmetic mean is utilized for computing an overall performance. A computer animation of wiper mechanism motion and rainfall is shown, which enables to experts, drivers and passengers to evaluate the degree of satisfaction and correctness of judgements. This fuzzy evaluation approach is illustrated by considering five `subjective' requirements (driver and passenger visibility, wiped surface, visibility and trouble sensations), and for three design alternatives (traditional single and double wiped systems and variable course system) the results are shown.

Current research trends are extending from partially integrated product and process modeling to life cycle modeling, in order to provide a framework and methodologies based on a holistic approach for the support of sustainable product development. Within given scope we are interested to investigate, if feature technology, introduced in the late seventies and developed over the paste twenty years provides the potential, if further enhanced, to be used as a means to provide basic integration for geometry related processes and models over different product life cycle stages. In a first approach, feature neighborhoods are developed and introduced as an extension, to foster evaluation of disassembly / reassembly on grounds of feature-based product descriptions. An attempt to support product maintenance and material recycling within life cycle modeling while investigating structural dimension and limits of improved feature models as a means of geometrybased model integration.

This paper presents novel interaction techniques and tools to support direct manipulation of flexible material models. We discuss interaction techniques and tools at two different levels: definition of the object/environment model, and manipulation of the digital environment as it was real to modify and validate the model.

This work presents a set of methods for simplifying finite element (FE) models without reducing their accuracy in terms of global static and dynamic behavior. The methods were developed to simplify the FE models of carbodies in white without affecting their static and low-frequency dynamics. The simplified models allow structural variations to be theorized and simulated, while accurately representing physical reality.

An innovative concept has been developed in which the dynamic behaviour of a cylindrical cam mechanism is modified using inertial compensation techniques. Elastic and magnetic compensation systems are incorporated in the experimental acoustic and acceleration analysis procedure. Both compensation systems have a remarkable effect on the reduction of the noise and vibration levels produced by the impact between the cam follower and the groove inversions. However, individually they both have different influences on the groove junctions. Generally they both have a considerable effect on the integral cam mechanism in terms of reducing emitted sound levels. The results also show that the difference in emitted sound levels before and after modification is approximately 3 dB. This conclusion means that the difference of the equivalent sound level is roughly equal to a reduction of about thirty percent below the original level with the compensation devices in position.

Keywords: Cylindrical cam mechanism , Elastic system , Inertial compensation , Instantaneous power level , Magnetic system , Shuttle

In the present paper, a procedure is described whereby the elastic properties of a ceramic material are evaluated during a biaxial flexure test. The disk specimen is supported on three points and loaded by a uniform pressure on the opposite face. The whole displacement field undergone by the upper face, measured by a digital speckle interferometer, is approximated by a set of polynomials whose weights depend on the elastic properties. This dependence, previously determined by finite element analysis, is exploited to derive the values of the elastic properties from the displacement field experimentally detected. The procedure proposed was applied to a silicon carbide specimen.

Keywords: Biaxial flexural test , Ceramic material , Elastic properties , Speckle interferometry , Zernike polynomials

Multiple input devices are increasingly used in user interfaces to make human-computer communication more efficient and effective. Interface designers have not only to decide on which input modes should be supported, but also how to fuse them into a single representation format that can be processed by the underlying application system. Drawing appropriate decisions requires, however, a sufficient understanding of the properties of fusion itself. While others have informally characterized input fusion as a transformation between information types, the purpose of the paper is to explore fusion by means of formal process modelling. That is, fusion processes are defined in a formal framework which supports proof of the existence of necessary properties following directly from the process definitions. The presented approach can be applied to analyse and compare fusion processes in existing systems, as well as an aid for interface designers, who have to verify the behaviour of their systems.

Keywords: Ambiguity , Formal methods , Fusion , Multimodal interfaces

Due to life cycles of artifacts, which become shorter, rapid prototyping development and tight feedback among product requirements, design, and manufacturing are gaining increasing importance. Classical rapid prototyping technologies such as computer-numerically-controlled (CNC) machinery, which remain still time consuming and expensive, are getting superseded by a growing propensity to apply new solid freeform fabrication (SFF) technologies, which became commercially available since 1987. Although, being on the market for only less than a decade, remarkable progress in various directions such as accuracy, used materials, through-put, and equipment costs, has been achieved in SFF technologies. However, there are still several technological as well as methodological problems left. Within given scope, we would like to tackle some, taken from the methodological field, which seems still weakly developed compared to existing technology. Within our approach we apply feature-based models and techniques, realized within typed attributed entity (TAE) structures. In particular, we are interested in the handling of additional fabrication relevant form structures and the automatic determination of fabrication parameters. To verify developed methodologies and to demonstrate the applicability of our taken approach, several selected parts, taken from precision machinery engineering and aerospace engineering were modeled and processed. An implemented prototype environment and a stereolithography apparatus (SLA) were used for integrated knowledge handling, computation and SFF fabrication.

The errors in the kinematic parameters of robots, due to the machining and to the assembly of the mechanical links, affect the positioning accuracy of robots. To obtain good accuracy these errors must be limited. In order to limit the positioning error it is important to carefully choose dimensional tolerances. Thus to obtain an optimum design of robots it is important to relate the positioning accuracy to the design tolerances, and then to manufacturing cost. This paper presents a method to synthesize the design tolerances of spatial robots, using a parameter that settles a relation between the cost and the positioning error. This method was implemented and tested on the Delta robot. Delta is a four degrees of freedom (dof) robot with a parallel structure, conceived for the manipulation of lightweight objects at fast working rhythms. After a statistical analysis of the effects of manufacturing tolerances and of the angular position of drives on the position accuracy, the method was applied obtaining optimal design and assembly tolerances to reach an assigned positioning accuracy.

User interfaces of current 3D and virtual reality environments require highly interactive input/output (I/O) techniques and appropriate input devices, providing users with natural and intuitive ways of interacting. This paper presents an interaction model, some techniques, and some ways of using novel input devices for 3D user interfaces. The interaction model is based on a tool-object syntax, where the interaction structure syntactically simulates an action sequence typical of a human's everyday life: One picks up a tool and then uses it on an object. Instead of using a conventional mouse, actions are input through two novel input devices, a hand- and a force-input device. The devices can be used simultaneously or in sequence, and the information they convey can be processed in a combined or in an independent way by the system. The use of a hand-input device allows the recognition of static poses and dynamic gestures performed by a user's hand. Hand gestures are used for selecting, or acting as, tools and for manipulating graphical objects. A system for teaching and recognizing dynamic gestures, and for providing graphical feedback for them, is described. © 1994, Taylor & Francis Group, LLC. All rights reserved.

Novel 3-D input devices are taking the place of traditional 2-D input devices in current 3-D graphical user interfaces. Among them, hand-input devices seem intuitive and powerful for performing tasks in 3-D environments. They offer the possibility to interact by means of hand gestures, i.e. in a natural way, close to human habits of interacting with the surrounding world. This paper describes a system supporting hand gestures for interacting with 3-D user interfaces. The system provides a visual programming environment for the design of gesture languages, defined as a collection of hand gestures. Moreover, a system for interpreting a gesture language, where gestures are performed by a user wearing a hand-input device, and for providing graphical feedback during the interaction, is presented. © 1994 Academic Press Limited.

The effect of boron on sintering of austenitic stainless steel was studied with reference to atmosphere (nitrogen-hydrogen mixtures) and temperature conditions. Specimens were characterised by the usual microstructural techniques and the boron distribution in the microstructure was also studied by means of Auger electron spectroscopy and secondary ion mass spectroscopy. In addition, tensile tests were carried out to verify the influence of the process parameters on the mechanical properties of the materials. Boron strongly enhances sintering by liquid phase formation only when the process is carried out in pure hydrogen at a temperature higher than 1200°C. In those conditions a eutectic reaction between austenite and a complex boride of the type (Fe, Cr, Mo)2B occurs favouring densification through the well known mechanisms of liquid phase sintering. A very low fraction of residual porosity is obtained. Conversely, the presence of nitrogen in the sintering atmosphere impedes boron–steel interaction and sintering is inhibited. The liquid phase sintered specimens exhibit a dense microstructure which should provide good corrosion resistance. PM/0631. © 1994 Maney Publishing.

This paper presents the theoretical basis of an innovative method in which the structure's experimental modal parameters (modal frequencies and shapes) in air are used in calculating its modal parameters in water, knowing only the structure's external geometry and position in water. The formulas will serve to develop the software in the second, forthcoming, phase of the work.

This work was carried out as part of a project aimed at evaluating the dynamic behavior of robot structures in water. A procedure for predicting the structure's modal parameters in water using its modal parameters in air as a starting point is described and applied. The results, presented for simple structures but fully applicable to more complex ones, show that the problem of the structure-fluid coupling can be solved with limited calculation resources.

In user interfaces of modern systems, users get the impression of directly interacting with application objects. In 3D based user interfaces, novel input devices, like hand and force input devices, are being introduced. They aim at providing natural ways of interaction. The use of a hand input device allows the recognition of static poses and dynamic gestures performed by a user's hand. This paper describes the use of a hand input device for interacting with a 3D graphical application. A dynamic gesture language, which allows users to teach some hand gestures, is presented. Furthermore, a user interface integrating the recognition of these gestures and providing feedback for them, is introduced. Particular attention has been spent on implementing a tool for easy specification of dynamic gestures, and on strategies for providing graphical feedback to users' interactions. To demonstrate that the introduced 3D user interface features, and the way the system presents graphical feedback, are not restricted to a hand input device, a force input device has also been integrated into the user interface. © 1993 Eurographics Association

Keywords: Interactive techniques , novel graphic applications , novel input devices

An Auger Electron Spectroscopy study of vacuum and hydrogen sintered martensitic stainless steel is presented, aimed at interpreting the influence of the atmosphere on the sintering process. The spectroscopic analysis, carried out on the surfaces of both powder grains and pores in the sintered specimens, allows for comparison of their chemical states and discussion of the chemical-physical processes which are active during sintering and hence responsible for the destabilization of oxides that cover the powder surface. Some noticeable differences between the two atmospheres are pointed out concerning the sintering mechanisms, and a correlation with some technological properties of pieces is proposed.

Laser beam penetrations have been carried out on URANUS 45 duplex stainless steel sheets, varying the beam power as well as the traverse speed. The microstructural results, in terms of bead geometry, microhardness and austenite content, have been related to the working parameters, with the support of an analytical thermal model of laser beam welding.