Virtual prototyping and digital twin

This paper presents a new method for optimizing the layout position of several Industrial Robots (IRs) placed within manufacturing work-cells, in order to execute a set of specified tasks with the minimum energy consumption. At first, a mechatronic model of an anthropomorphous IR is developed, by leveraging on the Modelica/Dymola built-in capabilities. The IR sub-system components (namely mechanical structure, actuators, power electronic and control logics) are modeled with the level of detail strictly necessary for an accurate prediction of the system power consumption, while assuring efficient computational efforts. Secondly, once each IR task is assigned, the optimal work-cell layout is computed by using proper optimization techniques, which numerically retrieve the IR base position corresponding to the minimum energy consumption. As an output to this second development stage, a set of color/contour maps is provided, that depicts both energy demand and time required for the task completion as function of the robot position in the cell to support the designer in the development of an energy-efficient layout. At last, two robotic manufacturing work-cells are set-up within the Delmia Robotics environment, in order to provide a benchmark case study for the evaluation of any energy saving potential. Numerical results confirm possible savings up to 20% with respect to state-of-the-art work-cell design practice.

Virtual prototyping enables the validation and optimization of mechanical devices similar to physical testing, saving time and costs in the product development, especially in case of heavy machines with complex motions. However, virtual prototyping is usually deployed only at the end of the design process, when the product architecture has already been developed. The present paper discusses the introduction of virtual prototypes since the conceptual design stage as “Virtual Concepts”, in which coarse models of machinery design variants are simulated to interactively evaluate several solutions and support best design choices. Virtual concept modeling and interactive preliminary validation, along with its later integration into a virtual prototype, are expressly investigated using multi body dynamics software. A verification case study concerning a large vibrating screen is presented, in order to demonstrate that dynamic virtual concepts can enable an easier and effective interactive evaluation of the design variants, thus increasing the design process predictability. Finally, current challenges to be solved for the practical adoption of virtual concept simulations as an integral part of the industrial design process are critically discussed.

Keywords: CAD based simulation , Design process , Vibrating screen , Virtual concepts , Virtual prototyping

Quick-Release Hooks (QRHs) are connection devices for chains or metal ropes, which can be unfastened under full-load conditions by using a limited opening force. Despite their widespread use, the scientific literature about the mechanical behaviour of QRHs is rather limited. This paper deals with the kinematic and quasi-static analysis of a class of QRHs, based on a spring-loaded four-bar mechanism operating in the proximity of a singularity configuration. The quasi-static analysis allows to estimate the opening force as a function of the mechanism geometry and of the safety spring's features. At last, a multibody model of the system is developed, in order to validate the analytical model and to evaluate the influence of friction in revolute joints.

Keywords: Multibody modelling , Quasi-static analysis , Quick-release hook

The actual use of Industrial Robots (IR) for assembly systems requires the exertion of suitable strategies allowing to overcome shortcomings about IR poor precision and repeatability. In this paper, the practical issues that emerge during common “peg-in-hole” assembly procedures are discussed. In particular, the use of passive Remote Center of Compliance (RCC) devices, capable of compensating the IR non-optimal performance in terms of repeatability, is investigated. The focus of the paper is the design and simulation of a flexure-based RCC that allows the prevention of jamming, due to possible positioning inaccuracies during peg insertion. The proposed RCC architecture comprises a set of flexural hinges, whose behavior is simulated via a CAE tool that provides built-in functions for modelling the motion of compliant members. For given friction coefficients of the contact surfaces, these numerical simulations allow to determine the maximum lateral and angular misalignments effectively manageable by the RCC device.

Keywords: Compensation Strategies , Compliant Flexures , Peg-in-hole assembly , RCC Device , Robotic assembly , Virtual Prototyping

The paper presents the design of an onshore Wave Energy Converter (WEC) named ALETTONE (At Least Energy Thanks To Neptune), which is characterized by a low cost mechanical architecture based on a four-bar linkage with mobility in a vertical plane. The lower link is a floating rocker arm moved by the hydrostatic and hydrodynamic forces exerted by the sea water, whereas the upper rocker arm is connected to a rotating electric generator via a transmission composed of either a single or a pair of one-way clutches coupled to a speed multiplier gearbox. Due to its simplicity, this WEC concept seems to be an interesting solution for energy generation in isolated locations. After a description of the overall design, the dynamic model of the system is presented, along with simulation results in case of monochromatic and panchromatic waves.

Keywords: Four-bar mechanism , Multibody simulation , Onshore generation , Wave energy converter

According to recent researches, it is desirable to extend Industrial Robots (IR) applicability to strategic fields such as heavy and/or fine deburring of customized parts with complex geometry. In fact, from a conceptual point of view, anthropomorphic manipulators could effectively provide an excellent alternative to dedicated machine tools (lathes, milling machines, etc.), by being both flexible (due to their lay-out) and cost efficient (20-50% cost reduction as compared to traditional CNC machining). Nonetheless, in order to successfully enable highquality Robotic Deburring (RD), it is necessary to overcome the intrinsic robot limitations (e.g. reduced structural stiffness, backlash, time-consuming process planning/optimization) by means of suitable design strategies and additional engineering tools. Within this context, the purpose of this paper is to present recent advances in design methods and software platforms for RD effective exploitation. Focusing on offline methods for robot programming, two novel approaches are described. On one hand, practical design guidelines (devised via a DOE method) for optimal IR positioning within the robotic workcell are presented. Secondly, a virtual prototyping technique for simulating a class of passively compliant spindles is introduced, which allows for the offline tuning of the RD process parameters (e.g. feed rate and tool compliance). Both approaches are applied in the design of a robotic workcell for high-accuracy deburring of aerospace turbine blades.

Keywords: Engineering methods , Industrial robotics , Intelligent factory , Virtual prototyping

Quick-Release Hooks (QRH) are particular accessories for connecting chains or metal ropes, that can be remotely unfastened under full-load conditions via application of an external force with limited magnitude. Despite their widespread use, and aside from a number of patents, the scientific literature related to QRH performance is rather limited. This paper reports about the modelling of a class of QRH, which relies on the use of a four-bar linkage mechanism operating in the proximity of a singularity configuration. Design graphs depicting the main functional parameters are reported. At last, a multibody model of the system is developed, which validates the analytical results while providing an insight of the frictional forces effect on the device modelling and performance.

Keywords: Kinematic analysis , Multibody modelling , Parameter design , Quick-release hook , Static analysis

Orthodontic treatments based on removable thermoplastic aligners are becoming quite common in clinical practice. However, there is no technical literature explaining how the loads are transferred from the thermoformed aligner to the patient dentition. Moreover, the role of auxiliary elements used in combination with the aligner, such as attachments and divots, still needs to be thoroughly explained. This paper is focused on the development of a Finite Element (FE) model to be used in the design process of shape attributes of orthodontic aligners. Geometrical models of a maxillary dental arch, including crown and root shapes, were created by combining optical scanning and Cone Beam Computed Tomography (CBCT). Finite Element Analysis (FEA) was used to compare five different aligner's configurations for the same tooth orthodontic tipping movement (rotation around the tooth's center of resistance). The different scenarios were analyzed by comparing the moment along the mesio-distal direction of the tooth and the resulting moment-to-force ratio (M:F) delivered to the tooth on the plane of interest. Results evidenced the influence of the aligner's configuration on the effectiveness of the planned orthodontic movement.

Keywords: Anatomical modelling , Numerical analysis , Orthodontic aligner , Orthodontic tooth movement

In the present work, the effect of Eruption Guidance Appliances (EGAs) on TemporoMandibular Joint (TMJ) disks stress level is studied. EGAs are orthodontic appliances used for early orthodontic treatments in order to prevent malocclusion problems. Commercially available EGAs are usually produced by using standard sizes. For this reason, they are not able to meet all the specific needs of each patient. In particular, EGAs are symmetric devices, while patient arches generally present asymmetric conditions. Thus, uneven stress levels may occur in TMJ disks, causing comfort reduction and potential damage to the most solicited disk. On the other hand, a customized EGA could overcome these issues, improving the treatment effectiveness. In this preliminary study, a Finite Element (FE) model was developed to investigate the effects of a symmetric EGA when applied to an asymmetric mouth. Different misalignment conditions were studied to compare the TMJ disks stress levels and to analyze the limitations of a symmetric EGA. The developed FE model can be used to design patient-specific EGAs, which could be manufactured by exploiting non-conventional techniques such as 3D printing.

Keywords: Eruption guidance appliance (EGA) , FE model , Patient-specific orthodontic appliance , TMJ disks stress , TMJ disorders

Tactile interaction consists in providing the user of a Virtual Reality (VR) system with sensations related to touch, mainly during the evaluation and the manipulation of virtual objects. In some cases the term tactile is used to refer to mechanical stimulation of the skin, which -together with the kinaesthetic sense- creates the haptic feedback. For these reasons, the tactile devices are strictly related to the haptic interfaces. Therefore, in order to give a complete and exhaustive overview of the interfaces related to touch, we have analysed the different categories of devices, such as vibrotactile interfaces, force feedback devices, local and full shape displays. Nowadays, a larger number of applications have been developed for tactile and haptic interaction in Virtual Reality. These applications belong to various fields: Medicine (chirurgical simulators, rehabilitation), Education (display of physical or mathematical phenomena), Industry (virtual prototyping, training, maintenance simulations), Entertainment (video games, theme parks), Arts and Creation (virtual sculpture, virtual instruments), etc. Hereafter the State of the Art related to the tactile and haptic technologies is presented.

This work describes an integrated method of 3D modelling algorithms with a modal approach in a multibody environment which provides a slimmer and more efficient simulation of flexible component contacts realistically reproducing system impacts and vibrations. A non-linear numerical model of the impulse contact forces based on the continuity approach of Lankarani and Nikravesh is developed. The model developed can evaluate deformation energy taking into account the material's characteristics, surface geometries and the velocity variations of the bodies in contact. ADAMS®-type modelling is applied to the sliding contacts of the links of a chain and its mechanical tensioner (“blade”) in the timing of an internal combustion engine. The blade was discretized by subdividing it into smaller components inter-connected with corresponding centres of gravity through 3D General Forces. Static and dynamic tests were performed to evaluate the stiffness, damping and friction parameters for the multibody model and to validate the methodology.

Keywords: Flexible body , Friction forces , Hysteresis damping , Impact , Slip

In the last decades the main focus for improvements in Power Electronics was mainly addressed on chip technology. Therefore, Power Electronic performance depends by a high ratio on package technologies and on their interconnections. In particular, the automotive industry has high requirements regarding cost efficiency, reliability and compactness. Increasing power densities, cost pressure and more stringent reliability target for modern power semiconductors are making thermal system optimization more and more important in relation to electrical optimization. This article will give an overview of the new methodological approach leaded by Finite Element (FE) simulation for new packages and interconnection solution ideas. A viscoplastic creep modelling is adopted for the solder taking into account time, temperature and stress dependences in Thermal Cycle. A parametric study is performed by changing geometrical solutions. The results obtained from the modelling has been used to form design guidelines that were also matched with experimental data.

Keywords: Finite Element Modeling , Power Electronics , Solder Joint , Viscoplasticity

This paper presents the determination of the vibration impact of the helicopter structural components and skin repairs in terms of frequency characteristics. To address this issue, a 3D Finite Element Method (FEM) model of 349 Gazelle helicopter has been developed in ABAQUS and the frequency analysis is conducted. The results on the natural frequencies of the full structure reasonably match with the literature giving confidence in the baseline model. The main advantage of this FEM model is that, it can be used to predict the natural frequencies of the full structure, precisely. In addition, the material properties and conditions of the components can be updated based on the applied conditions during the repair and maintenance period. Thus, the model gives a comprehensive design tool for analysing the frequencies of the helicopter with differing components. The effective variations in the frequency changes due to repair are predicted numerically. The discussion of these results helps in developing leads to improved selection of replacement materials and their properties.

This research focuses on the integrated simulation of helicopter-pilot system to predict pilot's physiological and psychological responses to the vibration. This paper describes the approach of integration of helicopter structural model to the aerodynamic forcing function and to the pilot-seat model. The physiological and psychological responses at 5 Hz are calculated based on vibration transmission ratio of the pilot's body segments. The pilot's Physiological responses including heart rate, highest blood pressure, lowest blood pressure, respiration rate and saliva secretion quantity are presented. Tired eyes, irritation, dizziness, yawning, sleepiness and headache as psychological reactions are provided. The integrated simulation approach of helicopter-pilot system can be used for pilot health and comfort assessments, helicopter structural and cockpit and seat design.

The associated risk for a patient taking advantage of Helicopter Emergency Medical Services (HEMS) mainly relates to vibrations. To this aim, especially in case of trauma and serious illness and long travels, aspects related to the vibrations effects on the patient needs to be properly investigated, taking into account the particular features of the helicopter used for HEMS. The purpose of this paper is the integrated simulation of vertical vibration at the supine patient's body, lying down on a rescue litter, in HEMS. Here, a 3D structural model of a reference helicopter, the Aerospatiale Gazelle, has been developed in ABAQUS and integrated with a dynamic model where aerodynamic forcing functions due to rotor are modelled. The accelerations at the litter location in the helicopter structural model are recorded and used as inputs to the supine patient's body model in MATLAB. The Multi-Body (MB) model of the patient's body consists of three interconnected masses of the head-neck, torso-arms and pelvis-legs. The simulation is carried out for single manoeuvre and the vibration information is extracted at the three body segments. This predictive approach of integrated simulation of the helicopter-patient is an effective tool in investigating of biodynamic response of the patient in HEMS. The benefits of this approach are reducing the risk and costs of running the experiments, providing suggestions on redesigning of litters and controlling the vibration on the litters in HEMS.

Keywords: Helicopter Emergency Medical Service , HEMS , Simulation , Structural model , Supine patient's body , Vertical vibration

Purpose - This paper aims to describe a methodology to optimize the trajectory of unconventional airship performing a high-altitude docking manoeuvre. Design/methodology/approach - The trajectories are based upon Bezier curves whose control points positions are optimized through particle swarm optimization algorithm. A minimum energy strategy is implemented by considering the airship physical properties. The paper describes the mathematical model of the airships, the trajectories modelling through Bezier's curves and the optimization framework. A series of test cases has been developed to evaluate the proposed methodology. Findings - Results obtained show that the implemented procedure is able to optimize the airship trajectories and to support their in-flight docking; a strong influence of the wind speed and course on the trajectories planning is highlighted. Research limitations/implications - The wind speed considered in these simulations depends only on altitude, and gusts effect has been neglected. Practical implications - The proposed model can support the study of unconventional airship trajectories and can be useful to evaluate best in-air docking strategies. Originality/value - The paper addresses the problem of trajectory optimization for a class of new air vehicles with an heuristic approach.

Keywords: Airship , Bezier curves , Green transportation , Heuristic algorithms , Trajectories optimization

This work analyses the effect of friction in suspension components on a race car vertical dynamics. It is a matter of fact that race cars aim at maximising their performance, focusing the attention mostly on aerodynamics and suspension tuning: suspension vertical and rolling stiffness and damping are parameters to be taken into account for an optimal setup. Furthermore, friction in suspension components must not be ignored. After a test session carried out with a F4 on a Four Poster rig, friction was detected on the front suspension. The real data gathered allow the validation of an analytical model with friction, confirming that its influence is relevant for low frequency values closed to the car pitch natural frequency. Finally, some setup proposals are presented to describe what should be done on actual race cars in order to correct vehicle behaviour when friction occurs.

Keywords: friction , Passive suspension , suspension system , validation

The automotive steering system inevitably presents internal friction that affects its response. This is why internal friction phenomena are carefully monitored either by OEMs and by vehicle manufacturers. An algorithm to predict the mechanical efficiency and the internal friction of a steering gear system has been developed by the ZF-TRW Technical Centre of Gardone Val Trompia and the University of Brescia, Italy. It is focused on mechanical steering gear of the rack and pinion type. The main contributions to the overall friction have been identified and modelled. The work is based on theoretical calculation as well as on experimental measurements carried out on a purpose-built test rig. The model takes into account the materials used and the gear mesh characteristics and enables the prediction of the steering gear friction performance before the very first prototypes are built.

Keywords: Friction , Rack and pinion , Steering , Steering feel , Vehicle dynamics

Induction cooktops are very efficient systems, but, their energy consumption should be reduced using a temperature controller for optimizing the electrical power. Such controllers are already widely spread in several applications (air conditioning, ovens, etc.). Induction cooktops work with discrete levels of power, and, therefore, the user can select and modify the requested power level during the cooking. This paper presents the Hardware-In-The-Loop simulation to develop an active temperature controller, which optimizes the energy management of the water boiling using an induction cooktop. A thermal and induction model has been developed in MATLAB/Simulink® framework, while a discrete PID controller has been implemented inside a physical ATMEGA processor and tested within the Hardware-In-The-Loop platform.

Keywords: Hardware-In-The-Loop , Induction Heating , Temperature Controller , Water Boiling

In Europe, kitchen hoods currently come with an energy label showing their energy efficiency class and other information regarding the energy consumption and noise level, as established by the European Energy Labelling Directive. Because of recent regulations, designs of cooker hoods must consider new issues, such as the evaluation of the energy efficiency, analysis of the energy consumption, and product lifecycle impact. Therefore, the development of eco-driven products requires Ecodesign tools to support eco-innovation and related sustainability improvements. The scope of the proposed research is to define a method and an agile and affordable platform tool that can support designers in the early estimation of product energy performance, including the calculation of energy efficiency indexes. The approach also considers the use of genetic algorithm methods to optimize the product configuration in terms of energy efficiency. The research context concerns large and small productions of kitchen hoods. The paper describes the methodological approach within the developed tool. The results show a good correlation between real efficiency values and calculated ones. A validation activity has been described, and a test case shows how to apply the proposed approach for the design of a new efficient product with an A-class Energy Efficiency Index.

Keywords: Ecodesign , Energy label , Knowledge-based engineering , Optimization , Product configuration , Virtual prototyping