Virtual prototyping and digital twin

The ability to perform autonomous mission planning is considered one of the key enabling technologies for uninhabited aerial systems. Subsequently, a big effort is made in the development of algorithms capable of computing safe and efficient routes in terms of distance, time, and fuel. In this paper an innovative 3-D planning algorithm is presented. The algorithm is based on considering the uninhabited aerial systems representation of real world systems as objects moving in a virtual environment (terrain, obstacles, and no fly zones), which replicates the airspace. Original obstacle avoidance strategies have been conceived to generate mission plans that are consistent with flight rules and with the vehicle performance constraints. Simulation test results show that efficient routes are computed in a few seconds.

We present a novel approach, called tangible digital master (TaDiMa), based on a flexible access to Product Lifecycle Management (PLM) database using a tangible/graphical user interface and augmented reality. We developed and tested a technical drawing template with automatically embedded markers for augmentation. We embedded the Mozilla FireFox engine into our annotation system for the integration of web 2.0 applications in the AR environment. We also extended the concept of web feed to PLM for notification of technical contents. We implemented a dynamic labelling management with view-driven filtering and placement. We also present a tangible management for layers visualization and users access by marked tokens. We validated the TaDiMa approach in a selection of possible scenarios for different PLM applications. The main benefit of the TaDiMa system is the easy and low-cost integration in the product lifecycle process. © 2009 Springer-Verlag.

Keywords: Industrial augmented reality , PLM , Tangible interfaces , Technical drawings and annotations

The chapter deals with developing small and cheap autonomous underwater vehicles, AUV, entrusted of extended manoeuvrability for surveying and docking missions, requiring accurate path tracking and attitude control, capable of travelling at low speed, down to the proper depth, to accomplish the assigned tasks with reliable autonomy and without relevant impact on the surroundings. The to day available AUVs, generally, make use of several propellers, distributed around the body, to achieve the desired mobility with full attitude control. The solution requires the closure of multiple loops between sensors and actuators, highly cross-coupled and dependent on dynamics non-linearity and marine surroundings disturbances. The prospected solution considers a properly shaped vehicle, to grant minimal drag for lowering power consumption. A single rear propeller has in charge propulsion and manoeuvring. The propeller can be oriented around two axes, say, pitch (for heaving) and yaw (for veering); the screw (hydrodynamic) torque is balanced by variable tilt fins, either, by counter-rotating vanes. A three degrees of freedom parallel-kinematics robotic wrist provides the joint path-and-attitude selection and the twist off-set, by driving the propeller assembly through three independent actuations. The devised submarine wobble-free autonomous navigator, SWAN, is a considerable upgrading of the vectored thrust planning, due to the innovative robotic actuation, permitting the joint heave and veer setting up, with the total balancing of the screw effect around the vehicle axis. The attitude preservation is important figure, each time the AUV's mission requires the accurate angular positioning of the carried instrumentation. The solution makes use of a ductrestricted propeller, with externally driven pitch-and-yaw bending and twist to counter-act the screw torque by continuous rotation, either, by tilted fins. The balancing wile assures local hover or docking, accomplished by active duct counter-rotation, while steady surveying missions exploit the reactive mode, for optimal efficiency. The through-out discussion of the prospected innovative robotic actuation is given, with characterisation of the basic functional and structural features, with account of the on-duty properties and of the conditioning design specification. This way, the noteworthy SWAN's peculiarities emerge, to equip advanced AUVs. The vectored control strategies are also discussed in the chapter. To that purpose, different AUV moving modes (approach to desirable point of space, approach to desirable point of space with desirable orientation, moving on the desirable spatial trajectory, etc.) are taken into consideration. The related examples algorithms, which operate on the heave and the veer setting and on the twist compensation, are investigated, for each navigation mode, also discussing the manoeuvrability abilities of the enhanced vectored propeller actuation, with added autonomy for docking and hovering. The chapter intends to provide full design and development frames of the advanced SWAN solution. The results, obtained by modelling the competing navigation modes, are addressed to document the effectiveness of the innovative robotic actuation, and to show how to work out the duty-oriented solutions, with the resort to the special purpose parallel wrist, in driving the manoeuvring thrust.

The propagation of an interface crack subjected to mixed mode I/II was investigated for two 2024-T351 aluminum thin layers joined by means of DP760 epoxy adhesive produced by 3M©. On the basis of beam theory, an analytical expression for computing the energy release rate is presented for the mixed-mode end loaded split (MMELS) test. The analytical strain energy release rate was compared by finite element (FE) analysis using the virtual crack closure technique (VCCT). Several fatigue crack growth tests were carried out in a plane bending machine to compare the experimental energy release rates to those of the analytical and FE solutions. Experimental results showed the relationship between the delamination modality and initial crack length rather than the applied load. The crack growth behavior showed stable crack growth followed by rapid propagation at the interface with the adhesive layer. © 2008 Elsevier Ltd. All rights reserved.

Keywords: Adhesive joint , Crack growth , Interface crack , MMELS specimen , Virtual crack closure technique

A three-dimensional finite-element simulation was conducted for a split-sleeve cold-expansion process in order to determine the residual stress field around an expanded hole. The commercial FEA software DEFORM-3D™, a Lagrangian implicit code designed for metal forming processes, was used to model the cold-expansion process of a fastener hole. The results show a through-thickness residual stress field in good agreement with the analytical solution developed by Guo. Moreover, the simulation has highlighted the effect of the split sleeve and the plate thickness on the residual stress field. © 2007 Elsevier B.V. All rights reserved.

Keywords: Cold-expansion of holes , Fastener holes , Finite-element simulation , Residual stress

The in terest 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. Copyright © 2008 by ASME.

A fully mechanical infinitely variable transmission (IVT) 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. Copyright © 2008 by ASME.

The efficacy of virtual reality (VR) as a design support technique is widely recognised by industries. However, the efficiency of the routine employment of VR into the product development process (PDP) still finds an obstacle in the poor integration of the tools employed. The use of VR still needs long and quite hard procedures to work effectively; the models have to be converted into a format that is compatible with VR systems and each task requires an effort to prepare the virtual environment or to post-process the results that depend on the complexity of the task. This work analyses some VR applications into the PDP and describes some ideas to effectively support the operator that prepares the virtual environment. These ideas have been tested by developing four software interfaces, able to create an easy data exchange link between VR and other design tools like CAD, CAE and computer aided control engineering (CACE). © 2007 Springer-Verlag London Limited.

Keywords: CACE , CAD , CAD-VR integration , CAE , Virtual prototyping , Virtual reality

The aesthetic impact of a product is an important parameter that makes the difference among products technologically similar and with same functionalities. Product shape, which is strictly connected to the aesthetic impact, has different meanings if seen from the design and the engineering point of view. The conceptual design of shape of aesthetic products is usually performed by designers at the beginning of the product development cycle. Subsequent engineering design and studies, such as structural and fluid-dynamic analyses, lead to several design reviews where the original shape of the object is often modified. The design review process is time consuming, requires the collaboration and synchronization of activities performed by various experts having different competences and roles, and is performed using different tools and different product representations. Then, computer aided tools supporting conceptual design and analysis activities within the same environment are envisaged. The paper presents the conceptual description of an environment named PUODARSI that allows designers to modify the shape of a product and evaluate in real-time the impact of these changes on the results of the structural and fluid dynamic analyses in an Augmented Reality (AR) collaborative environment. Main problems in integrating tools developed for different purposes, such as, haptic interaction, FEM and CFD analyses, AR visualization concern the feasibility of the integration, the data exchange, and the choice of those algorithms that allow all that while guaranteeing low computational time. The paper describes the main issues related to the choice of hardware and software technologies, and the PUODARSI system implementation. © The Eurographics Association 2008.

One of the recent research topics in the area of design and virtual prototyping is offering designers tools for creating and modifying shapes in a natural and interactive way. Multimodal interaction is part of this research. It allows conveying to the users information through different sensory channels. The use of more modalities than touch and vision augments the sense of presence in the virtual environment and can be useful to present the same information in various ways. In addition, multimodal interaction can sometimes be used to augment the perception of the user by transferring information that is not generally perceived in the real world, but which can be emulated by the virtual environment. The paper presents a prototype of a system that allows designers to evaluate the quality of a shape with the aid of touch, vision and sound. Sound is used to communicate geometrical data, relating to the virtual object, which are practically undetectable through touch and vision. In addition, the paper presents the preliminary work carried out on this prototype and the results of the first tests made in order to demonstrate the feasibility. The problems related to the development of this kind of application and the realization of the prototype itself are highlighted. This paper also focuses on the potentialities and the problems relating to the use of multimodal interaction, in particular the auditory channel. ©2008 IEEE.

Keywords: Audio & visual sensors and displays , Haptic , Humancomputer interaction

This work studies how a nonlinear kinematic model aimed for cyclic plasticity could be put into effect and used within a FEM code. A correct modeling of cyclic elasto-plastic behavior can be exploited in low-cycle fatigue life investigation as well as in manufacturing problems related to springback prediction. The chosen formulation has been proposed by Chaboche, and it is implemented in most of the commercial codes used for nonlinear FEM simulations. At first, a procedure for the proper identification of unknown material model parameters has been put forward. This calibration, based on the data collected from experimental low-cycle fatigue tests, has been performed by means of an inverse method. Laboratory tests differ according to the type of material under investigation. A classification can be operated distinguishing between specimens obtained from bulk materials or from sheet metals. For the former, standard tension-compression tests have been performed, while for the latter, a dedicated testing equipment for three-point bend cyclic tests has been devised. Then, further experimental tests have been run to check model transferability: different strain per cycle amplitudes, asymmetric strain cycling and different stress triaxiality levels have been investigated. For each of these tests, experimental vs. FEM results have been analyzed to show the level of agreement that has been reached. © 2008 Springer Science+Business Media B.V.

Keywords: Cyclic plasticity , Inverse methods , Kinematic hardening , Parameter identification , Transferability tests

The interest of both the academics and industrials for the UASs (Uninhabited Aerial Systems) has been significantly growing for the last ten years. Technological developments in their design are opening the way for their exploitation in a wide range of applications. Nevertheless, the expected benefits are not yet fully exploited due to the still significant number of accidents. Several researches have demonstrated that the absence of vehicle decisional capacity is among the most important causes of such accidents. One of the proposed solutions is to increase the vehicle ability to perform autonomous mission planning. In this paper a planning algorithm for UASs mission is presented. Such algorithm has been designed following an heuristic approach in order to rapidly provide a robust solution to mission planning problem in evolving scenario. Original obstacle avoidance strategies have been conceived in order to generate mission plans which are consistent with flight rules and with the vehicle performance constraints. Simulation test results show that very efficient routes are computed in a few seconds. Copyright © 2008 by the American Institute of Aeronautics and Astronautics, Inc.

A new generation of aircraft piston engines is currently being introduced on the market. These new engines come directly from the huge experience achieved in the motorcycle and automotive racing and production. However direct use of automotive power unit is not advisable, since car engines work mainly in the first quarter of the power output, while sport motorcycles are used in a very "light" way, with the engines that span several times through the entire range of power outputs and rpm. The other problem is fuel. Aircraft spark ignition engine for ultralight and light aircrafts may continue to use automotive gasoline, while diesel engines for light up to cargo aircraft should use jet(A1) and jp4. However, the large experience obtained from racing/high-performance motorcycles, racing/high-performance cars and common rail engines cannot be ignored. Thousand of hours and billion of Euros have been spent for this development and the results are interesting. This paper tries to calculate the future aircraft engine performance from the many experimental data already available on a certain type of combustion chamber or better from a well defined and experimented cylinder unit. On the other side the "lean-thinking" approach to aircraft engine design may be not applicable. The lean thinking approach tends to prefer the time-to-market to the optimization of the engine unit. With engines that will probably stay on the market for 30 years this approach is not convenient. An important optimization during the design phase is possible with modern CAD tools. Mass and cost reduction may easily reach the 30%. On the other side the "brain storming approach" is not applicable to the heavily-constrained aircraft-engine design, where it is common that inapplicable solutions and ideas seem to be the best during the initial phase even to experts. Our research team developed three different families of engines: the first family uses the cylinder unit of a well proven motorcycle engine, which comes directly from racing and was sold in tenth of thousands in the world market. These spark ignition engines have 4 up to 16 cylinders (Figg. 1, 2), with power from 150 HP to 800 HP. This type of engines have very brilliant power to weight ratios with not superlative fuel consumptions. They are conceived for ultralight aircrafts and helicopters, tilt rotor, tilt shaft and tilt motor power lift V/STOL aircrafts. The second cylinder unit comes directly from the 2 valves FIAT 1900 jtd, that is one of the best two valves turbocharged common rail diesel available on the market. These units span from 4 up to 16 cylinders with power outputs from 175 HP (Fig. 3) up to 1000 HP. They run with jp4, jp8 or jet (A1) and can be bolted directly to the original engine mount of existing light aircraft like Cessna 172/182/337 or can be used in new light aircrafts. The third one is an originally conceived twin combustion chamber diesel family with output power from 600 HP to 4000 HP (hybrid engine) originally conceived for the Hercules C130J, ATR42 or ATR72 aircrafts (Figg. 4, 5). Our hybrid engine is composed by two separate engines: the VD007 diesel and a turboshaft. Each engine moves a separate contra rotating propeller. In ordinary flight the turboshaft works as a turbocharger. In this case the rear propeller is nearly idle. During take off or emergency the turboshaft combustion chamber is activated and additional power is available. In this case pitch is given to the rear propeller that outputs additional useful thrust. All these engines use only the thermo-fluid-dynamics and a few parts of the original cylinder unit, since aircraft application need extended modifications and, in many cases, complete redesign. However on all these engines a large amount of experimental, road and reliability data are available. Their direct application in the aircraft field is a plain mistake, since automotive and motorcycle are very different, but it is not the case to discard all this data that are available for free. For this reason innovative simulation methods were used to obtain engine performance envelope, with the possibility to choose the most convenient off-design solution on a certain aircraft, depending on the use and on the requirements. It is also possible to obtain reliability data for the aircraft FADEC (Full Authority Digital Engine Control) that controls all these new units. It is important to underline that airborne FADECs should be completely different from ground borne FADECs since in the aircraft application recovery strategies are to be chosen by the well trained pilot, while in the automotive field recovery is usually applied automatically in order to preserve engine integrity. A new method for the determination of the engine performance envelope is introduced as an example on the turbo/hybrid diesel unit for the C130J; this engine is called VD007. This approach has been successfully applied on the small diesel jtd family and also to the spark ignition family. © 2008 by the American Institute of Aeronautics and Astronautics, Inc.

The work presented in this paper refers to the implementation of a product development process based on the use of virtual model of the human body to design specific custom-fit product, such as a prosthesis socket (interface between the residual limb and the mechanical part of the prosthesis). It considers the integration of advanced ICT tools coming from the reverse engineering, the physics-based modelling and simulation, and the rapid prototyping fields. The paper describes problems related to the implementation of each step within a real socket development process. © Springer-Verlag Berlin Heidelberg 2007.

Keywords: Human body modeling , Physics-based simulation , Product customization , Prosthesis design

A physics-based cloth modelling system has been proposed, targeted at the virtual prototyping of garments of real interest and production. The system should allow designers to validate their styling/design choices on a digital apparel model before (or in place of) any physical prototyping. Taking into account the design complexity of real tailored apparel, CAD apparel models can be defined incorporating information about tailoring/assembly features. A graphical interface allows a user to create his/her garment by interactively specifying design elements such as layers, seams, pockets, constraints, aesthetic and functional lines. A discrete Newtonian particle-based model is considered for physics-based cloth simulation, originally defined for single textile layers and then extended to real-shaped apparel, by taking into account structural properties of materials and the previously defined design/ assembly rules. Several garment models are proposed as test cases, designed for real apparel manufacturing and simulated on virtual mannequins. Copyright © 2007 Inderscience Enterprises Ltd.

Keywords: Apparel design , Cloth modelling , ODE solvers , Particle-based modelling , Tailoring features , Virtual simulation

In this paper, we describe a framework which helps designers visualize and verify the results of robotic work cell simulation in a Virtual Environment (VE). The system aims at significantly reducing production costs and error sources during manufacturing processes. The means to achieve these goals are the development of a prototypical VE for the support of robots planning tasks, reuse of animation events, and the implementation of customization tools for animation elements and their behavior. By using advanced Virtual Reality (VR) techniques, the system is also able to direct the focus of the observer to interesting events, objects and time-frames during robotic simulations in order to highlight the Human Robot Interaction within the manufacturing systems. © The Eurographics Association 2007.

Virtual Reality and related technologies are becoming a common practice in the design industry in general and more specifically in the automotive field. By the joined use of virtual prototyping methodologies it is possible to achieve the reduction of the time-to-market, as well as the costs deriving from the creation of physical prototypes. Ergonomics tests conducted in Virtual Reality environments can be successfully used to influence the design of products. We have set up a mixed reality environment that allows us to simulate and test postural aspects as well as various levels and modalities of users' interaction. In order to achieve a performing interaction, correct registration and visualization parameters must be carefully set for preventing possible interaction errors, such as pointing with precision to the assigned target. The paper presents a methodology for tuning stereoscopic properties of the mixed reality environments used for ergonomic tests of a car interior in order to achieve correct visualization and positioning parameters. The environment includes a virtual human controlled by an optical motion tracking system, physical objects onto which the graphic virtual environment is superimposed, and a rotatory haptic device for controlling the car on-board infotainment. interface. © The Eurographics Association 2007.

The field of computer graphics is greatly increasing its overall performance enabling consequently the implementation of most of the product design process phases into virtual environments. The deriving benefits of using virtual practices in product development have been proved intrinsically highly valuable, since they foster the reduction of time to market, process uncertainty, and the translation of most prototyping activities into the virtual environment. In this paper we present the developed platform in mixed environment for ergonomic validation. Specifically we defined a methodology for testing both aspects related to design and ergonomic validation by allowing the tester to interact visually and physically with the car dashboard control devices and related interface by the mean of a rotatory haptic device. By experimental session it has been highlighted that it is possible gathering qualitative data about the design, and finding typical occlusion problems, but also quantitative data can be collected by testing the infotainment interface and the consequent users' distraction during the device use. © Springer-Verlag Berlin Heidelberg 2007.

Keywords: Ergonomic analysis , Mixed environments , Tactons

The main purpose of the present study was to optimize a prototype hexapod robot, called Gregor I, through reverse engineering techniques. The robot is based on experimental observations of the cockroach with regard to mechanical design and the locomotion control strategy. This paper reports on the design phase of a hexapod robot, where the basic geometry of the system is defined through solid modeling and improved through kinematic and dynamic studies, using multi-body software. The dynamic simulation environment made it possible to study the performance of the system under different working conditions. Guidelines for an optimization process of the hexapod structure were drawn from these analyzes, aimed at the improvement of specific characteristics: speed, payload and climbing capabilities. Finally, the robot model and the robot prototype were compared.