Product design and engineering

The present paper deals with the manufacturing process of a railway carriage. In the first part of the paper, the authors focus on a "virtual railway factory" that uses a very innovative assembly cycle, if compared to the traditional manufacturing processes in the railway field. The case study refers to a railway carriage consisting of four modules, that are singularly set up of furnishings and other systems in dedicated workplaces. On one hand, the virtual simulation has highlighted several critical aspects to be improved, in order to achieve a greater feasibility and to reduce time and cost. On the other hand, the designers have been able to evaluate the movements of the parts and the assembly sequences of the components, by considering each geometric, functional and technological constraint and also some safety requirements. The second part of the paper deals with the simulation of the assembling operations and the analysis of tolerance chains, which have been performed through a Computer Aided Tolerancing system. In particular, the precision requirements have been also evaluated and we have compared the accumulation of dimensional and geometric deviations when using both rivets and traditional welds to fasten the modules. © 2009 Springer-Verlag.

Keywords: Computer Aided Tolerancing , Train design , Virtual manufacturing

A conically shaped Dielectric Elastomer (DE) linear actuator is presented which is obtained by coupling a DE film with a compliant mechanism. The compliant mechanism is designed, by means of a pseudo-rigid-body model, to suitably modify the force generated by the elastomer film. The resulting actuator provides a nearly constant force along the entire actuator stroke when the DE film is activated and returns to an initial rest position when the DE film is deactivated. Experimental activity fully validates the proposed concept. Possible applications of this kind of actuator are Braille cells, light weight robots and haptic devices. © 2009 IEEE.

Keywords: Compliant mechanisms , Dielectric elastomer actuators

In this paper, an overall description of the design of a robotic hand is discussed, with particular attention to the required sensory subsystem, its integration within the mechanical structure of the hand and the required control architecture. Different solutions for the joint configuration and the structure of the tendon network adopted for the transmission system are present together with three types of sensors applied on the finger and on the actuators. The integrated design of the hand finger and the sensors is reported and the motivations leading to this particular implementation are thoroughly addressed, taking into account both the mechanical constraints and the control requirements.

Keywords: Robot control , Robotic design , Robotic hands , Sensor systems , Sensors integration

The interest in actuators based on dielectric elastomer films as a promising technology in robotic and mechatronic applications is increasing. The overall actuator performances are influenced by the design of both the active film and the film supporting frame. This paper presents a single-acting actuator which is capable of supplying a constant force over a given range of motion. The actuator is obtained by coupling a rectangular film of silicone dielectric elastomer with a monolithic frame designed to suitably modify the force generated by the dielectric elastomer film. The frame is a fully compliant mechanism whose main structural parameters are calculated using a pseudo-rigid-body model and then verified by finite element analysis. Simulations show promising performance of the proposed actuator. © 2008 by ASME.

A fully mechanical infinitely variable transmission (1VT) based on the use of an oscillating inertia is described. The system includes a four-bar linkage mechanism, an epicyclic gear train and a pair of one-way clutches. The proposed IVT can be used in place of both gear-box and clutch in self-propelled vehicles. A basic model is used for a first attempt sizing of the transmission kinematic parameters. A more accurate model, achieved using Bond Graphs, is used to investigate the dynamic effect of inertias, one-way clutch compliance, and minor design changes in the kinematic parameters. Finally, simulations compare the behavior of a car fitted with a manual gear-box and the same car fitted with the proposed IVT. © 2008 by ASME.

This paper describes the nonlinear Finite Elements Analysis (FEA) of soft fingertips for robotic hands in contact conditions.The purpose is to test the reliability of FEA when designing fingertips with differentiated layer design, that is the adoption of a single elastic material, dividing the overall thickness of the pad into layers with different structural design (e.g.a continuous skin layer coupled with an internal layer with voids).The pads are shaped around a rigid core and their behavior is investigated under compressive contact loads.The applicability of various nonlinear hyperelastic constitutive models for predicting the pad behavior is explored under the hypothesis of large deflections.Two materials have been tested whose mechanical properties are determined experimentally.One of these materials can be used in rapid prototyping printers and its properties are presented for the first time.Experimental activity fully validates the proposed FEA models concerning homogeneous pads.At last two different and innovative pad geometries are proposed showing that FEA confirms to be a powerful tool for predicting the compliance of soft fingertips if the right hypothesis and simplifying assumptions are made.

Keywords: Contact mechanics , FE analysis , Robotic hand , Soft fingertip

Most of robotic soft pads studied so far were made with a thick layer of homogeneous material shaped around a rigid core; their behavior has been widely investigated in the literature, mainly under compressive contact load, showing typical non-linear relationship between contact deformation and applied load (the so called power law). This paper proposes differentiated layer design, that is the adoption of a single elastic material, dividing the overall thickness of the pad into layers with different structural design (e.g. a continuous skin layer coupled with an internal layer with voids). The purpose is to modify the actual pad compliance and the resulting power law; in particular, given the material and the allowable pad thickness, to increase the compliance with respect to a non structured pad. Some possible internal layer structures are described, compatible with rapid prototyping manufacturing. Their compressive behaviors are tested and comparatively evaluated showing that the concept can work and be exploited for useful application.© 2009 IEEE.

Keywords: Experimental analysis , Fingertip design , Robotic hands , Soft fingers

A novel design for a Dielectric Elastomer (DE) actuator is presented. The actuator is obtained by coupling a conically shaped DE film with a compliant mechanism. The compliant mechanism is designed to suitably modify the force generated by the elastomer film. The resulting actuator provides a nearly constant force along the entire actuator stroke when the DE film is activated and quickly returns to an initial rest position when the DE film is deactivated. The electromechanical properties of the DE film are measured experimentally. The sizing of the compliant mechanism is obtained through a pseudo-rigid-body model and subsequently verified through finite element analysis. Simulations show that the designed actuator works as desired. Possible applications of this kind of actuator are MRI compatible devices, haptic devices and Braille cells. ©2009 IEEE.

Keywords: Compliant mechanisms , Dielectric elastomer actuators

The interest in actuators based on dielectric elastomer films as a promising technology in robotic and mechatronic applications is increasing. The overall actuator performances are influenced by the design of both the active film and the film supporting frame. This paper presents a single-acting actuator, which is capable ofsupplying a constant force over a given range of motion. The actuator is obtained by coupling a rectangular film of silicone dielectric elastomer with a monolithic frame designed to suitably modify the force generated by the dielectric elastomer film. The frame is a fully compliant mechanism whose main structural parameters are calculated using a pseudo-rigid-body model and then verified by finite element analysis. Simulations show promising performance of the proposed actuator. © 2009 by ASME.

In this paper, an overall description of the design of a robotic hand is discussed, with particular attention to the required sensory subsystem, its integration within the mechanical structure of the hand and the required control architecture. Different solutions for the joint configuration and the structure of the tendon network adopted for the transmission system are present together with three types of sensors applied on the finger and on the actuators. The integrated design of the hand finger and the sensors is reported and the motivations leading to this particular implementation are thoroughly addressed, taking into account both the mechanical constraints and the control requirements.

Keywords: Robot control , Robotic design , Robotic hands , Sensor systems , Sensors integration

A novel mathematical procedure is proposed, which makes it possible to optimize lozenge-shaped dielectric-elastomer-based linear actuators for known materials and desired force/stroke requirements. Simulation results are provided which both demonstrate the efficacy of the novel procedure with respect to traditional design approaches and show that simpler, cheaper, lighter and better- behaved lozenge-shaped actuators can be conceived which do not require any integration of compliant frame elements. © 2009 Springer-Verlag Berlin Heidelberg.

Adaptive manufacturing systems achieve intelligence and adaptation capabilities through the close interaction between mechanics, electronics, control and software engineering. Mechatronic design of intelligent manufacturing behaviours is of paramount importance for the final performances of complex systems and requires deep integration between mechanical and control engineering. Virtual Commissioning environments offer engineers new opportunities for the design of complex intelligent behaviours and for the enhancement of the performance of adaptive manufacturing systems. This paper discloses a systematic design method focused on interdisciplinary behavioural simulations: Virtual Commissioning tools are used to virtually explore new solution spaces for an effective mechatronic optimization. The results, achieved by applying the method in reengineering a module of an automotive sensor manufacturing line, are finally presented. © 2009 Springer-Verlag.

Keywords: Computer aided engineering , Mechatronic design , Virtual commissioning

Fine porcelain products get their peculiar characteristics at the end of their thermal process. During the firing, the product is subjected to shrinkage and a considerable amount of the material mass becomes viscous, causing the product shape to be modified due to the own object weight. As the final object shape is a relevant characteristic for both usability and aesthetics of the commercial product, the activity purpose was to devise a methodology to automatically detect the raw product shape required to match a provided final geometry. Such a methodology has been implemented by means of commercial CAD/FEM tools and should be used in porcelain products design. The research consists of three parts. During the first one an extensive experimental campaign has been carried out in order to model the behavior of the heat treated material; by using the experimental data a numerical model of the material behavior has been built. in the second part the model reliability has been tested by means of a set of FE analysis. Such an analysis simulates the effects of stresses caused by the real industrial firing process. in the end, during the third part, inverse firing process FE simulations have been performed. These simulations will allow the designer to know the raw-product geometry, in order to obtain the expected finished product. .Copyright © 2008 by ASME.

Simulation and other computer aided tools are often used in automotive design, since the design process is strictly oriented to the optimization of the performances through an iterative synthesis and analysis cycle aimed to understand the effects of changes in the geometry and layout of the various components. The search for the optimal performances is at the moment carried out empirically by the "trial and error" approach because parameters and constraints are too many for a global optimization of the vehicle dynamics to be performed. Nevertheless it is possible to introduce in the current design process some optimization algorithms or tools that can guide the designer in the decision process. This paper presents a methodology, applied to the conceptual design of the upright for a Formula SAE prototype, in which a multi-body simulator, CAD and a topological optimization tool are sinergically employed in order to support the suspension design.

Keywords: Integrated approach , Multi-body , Topological optimization

The problem of integrating topological optimization tools in product development process (PDP) is becoming more and more urgent since nowadays they are widely employed in several engineering fields (civil, aeronautics, aerospace, automotive). The interest for these tools is due to their capacity to better mechanical properties through a global optimization of the product in terms of weight, stiffness, resistance and cost. In particular, there is a lack of specific tools for automatic feature recognition on voxel models generated by the topological optimization tools. Our paper presents an innovative methodology that allows the integration of topological optimizers in the product development process by means of a wise and rational knowledge management and an efficient data exchange between different systems. The target has been reached through the implementation of CAD automation modules which decrease the working time and give the possibility to effectively schematize the designer's knowledge. Copyright © 2008 by ASME.

CAD reconstruction of anatomical regions from computerized tomography (CT) scans is a very common approach in orthopaedic biomechanics. The CAD model is discretized into finite volume sub-domains and finite element (FE) analyses are performed in order to predict the distribution of stresses generated by applied loads. However, quality and reliability of numerical results depend on the level of accuracy reached in the meshing process. This paper analyzes some critical parameters that may affect the overall efficiency of the CT-FEM transformation process: scan threshold range, object size, and complexity. An optimization procedure for minimizing geometric errors on size and shape of reconstructed objects is presented. Finally, accuracy of stress predictions is evaluated for FE models that include known amounts of geometric errors. Compression and bending loads are considered. Results show that geometric and stress errors rapidly decrease as the objects to be reconstructed become larger in size. Optimal threshold ranges can be identified clearly for both an epoxy-resin benchmark model and a real bone specimen cut from a human lumbar vertebra. This allows geometric errors to be reduced significantly. © 2009 World Scientific Publishing Company.

Keywords: CT scanning , FEM , Geometric errors , Mesh generation , Reconstruction of geometry , Stress errors

This paper describes a mixed reality application for the assessment of manual assembly of mechanical systems. The application aims at using low cost technologies and at the same time at offering an effective environment for the assessment of a typical task consisting of assembling two components of a mechanical system. The application is based on the use of a 6-DOF interaction device that is used for positioning an object in space, and a haptic interface that is closer to reality and is used for simulating the insertion of a second component into the first one while feeling a force feedback. The application has been validated by an expert user in order to identify the main usability and performance problems and improve its design. © 2009 Springer Berlin Heidelberg.

Keywords: Haptic-based interaction , Virtual Manual Assembly , VR system evaluation

Exploring how to enhance and assist the design process with the support of new Information and Communication Technologies is a growing field of research. The analysis of the design processes of aesthetic shapes highlights open issues that make the processes inefficient and generate some questions about how to improve the process performances. Examples of questions are: how to generate more and better ideas, how to become more creative and how to exploit at best people know-how. The research presented in this paper reasons about issues related to aesthetic shapes perception and proposes some solutions at the basis of future design tools based on new ways of working and new ways of interaction. copyright © 2008by ASME.

The design of complex industrial products requires more knowledge than the one that a single person can possess. A successful industrial design entails a collaborative activity between designers and engineers during which they share their specialized knowledge accepting and interpreting their points of view through a multi-disciplinary and collaborative methodology. In particular, this paper focuses on issues related to the knowledge creation, management and enrichment for industrial collaborative design in virtual environment. The idea is to endow the virtual environment, used to create the 3D models and to carry out the analysis, with a knowledge management (KM) module able to gather information about different versions of the product and simulation analysis data. Moreover, this KM module includes an annotation tool used to support annotation-based collaboration between designers and engineers through which they can exchange impressions, ideas, and comments in order to achieve a shared solution about an industrial design issue. © 2009 Springer-Verlag Berlin Heidelberg.

This paper describes a haptic device whose aim is to render the contact with a continuous and developable surface by means of the representation of a geodesic trajectory. Some preliminary tests conducted with industrial designers have showed that the trajectories performed while exploring the surface of a style product, for a qualitative evaluation, follows some particular trajectories that may be mathematically described as geodesic curves. In order to represent these particular curves a haptic strip based on a modular servo-controlled mechanism has been developed. Each module of mechanism allows us to control both the curvature and the torsion. This device, in respect to the commercial existing haptic devices, allows a hand-surface contact with the virtual model in real scale without artifacts, by self-deforming its shape in order to conform to the mathematical curve to render. The strip is 900 mm long and has 9 control points for bending and 8 control points for torsion. Due to these characteristics, it allows us to render exploration trajectories of several kinds of product shapes and dimensions. In order to allow users to fully explore an object surface, we have mounted the strip on a platform consisting of two MOOG-FCS HapticMaster devices, which permits 6DOF orientation of the strip and force feedback control. The paper describes the mechanism of the strip and the 6DOF platform starting from the empirical observations of the exploration of surfaces and highlights the problems encountered and the solutions adopted.