Virtual prototyping and digital twin

This paper presents the development of an underactuated prosthetic hand that offers a cost-effective, functional, and human-like alternative for individuals with upper limb amputations. The design and virtual prototyping of the hand focus on achieving a size, weight, and appearance that closely resemble a human hand, aiming to enhance user acceptance. The prosthetic hand consists of ten degrees of freedom (DoF), with four of them being actuated. Among these, three degrees of actuation (DoA) are controlled by electric motors and a tendon transmission system, while the remaining DoA is manually actuated by the user through a spring plunger. The underactuated design incorporates compliant hinges based on springs and a mechanism that decouples the motors from the fingers, enabling more natural movements and greater adaptability to different objects. By incorporating a tendon transmission system and manual thumb actuation, users can easily accomplish basic grasping tasks without relying on complex control systems. To evaluate the gripping abilities and maximum gripping force of the hand, a virtual prototype has been created and tested in different grasping scenarios. This assessment allows for performance evaluation and refinement of the design. To improve affordability and accessibility for a wider range of users, the prosthetic hand has been designed with a focus on cost-effective components and widespread utilization of additively manufactured parts.

This paper presents the design and virtual prototyping of a constant force gripper for food handling and harvesting, aimed at reducing the production costs associated with manual labor performed by human workers. The gripper has been designed using advanced Computer-Aided Design (CAD) software to be easily fabricated using additive manufacturing techniques. The solution involved the use of a lumped compliant element to obtain the desired constant force output, resulting in a gripper that is easily maintainable and cost-effective. The use of a constant force mechanism eliminates the need for dedicated sensors and complex control algorithms to avoid object damage, as completely closing the grasp is sufficient for every operation. The optimization of the compliant element shape has been crucial for achieving the desired constant force output and has required a Matlab software optimization framework using the pseudo-rigid body model equations and an fmincon algorithm. The virtual prototyping approach, using a flexible multi-body dynamics software, has enabled fast and easy testing of the CAD design, leading to an optimized final design with high performance and precision. The study results have demonstrated the potential of virtual prototyping for the design and optimization of advanced robotic systems in cost-sensitive industries, particularly in the food harvesting sector.

Keywords: Compliant Element , Computer Aided Engineering , Constant Force Device , Food Harvesting , Virtual Prototyping

Lattice structures for engineering applications are patterns of unit cells designed to make a larger functional structure. Research on lattice structures ranges in many fields, from mechanical characterization and cell and pattern designs in respect of their applications, to the manufacturing process and its final shape control. From the manufacturing point of view, some kinds of lattice structures can be infeasible when approached with traditional manufacturing methods. It may offer an inevitable limitation of their adoption. However, advancements in Additive Manufacturing (AM) have solved this manufacturing issue to a great extent, allowing to obtain major complexity of the cells that can be achieved. The topology, shape of the unit cell, and the characteristics of its replication pattern allow us to obtain many kinds of structures in respect of the different engineering requirements and manufacturing constraints. Nevertheless, the necessity of new or dedicated CAD-CAE approaches arises to manage the domains of multiscale modeling. These are some of the advantages and disadvantages that may arise while approaching the design of a component using lattice structures. The aim of this paper is to provide an overview that integrates the most recent applications of lattice structures with their related design and manufacturing issues so that, from a practical design point of view, any state-of-the-art improvements may be established in respect of the related field of applications. In this article, engineers and researchers may find a practical summary of the capabilities and processes of lattice structures that are currently available from a design and development point of view.

Keywords: additive manufacturing , cellular structures , design methodologies , functionally graded materials , lattice structures , TPMS

As technology advances, we are surrounded by more complex products that can be challenging to use and troubleshoot. We often turn to online resources and the help of others to learn how to use a product's features or fix malfunctions. This is a common issue in both everyday life and industry. The key to being able to use a product or fix malfunctions is having access to accurate information and instructions and gaining the necessary skills to perform the tasks correctly. This paper offers an overview of how artificial intelligence, digital twins, and the metaverse-currently popular technologies-can enhance the process of acquiring knowledge, know-how, and skills, with a focus on industrial maintenance. However, the concepts discussed may also apply to the maintenance of consumer products.

Keywords: computer-aided design , cyberphysical system design and operation , eXtended reality , maintenance , metaverse

Power converters and semiconductor devices are spreading their application fields, due to new renewable energy and automotive frameworks. In the electrified vehicles context, the even more stringent requirements, both in terms of performances and reliability, pose new challenges in the design phase of power switches. This paper analyzes, by means of finite-element simulations, a low-voltage power semiconductor system-in-package devoted to automotive applications, which integrates a MOSFET-based half bridge and a controller. Three simulation physical domains integrated in a unique flow are considered: thermo-mechanical, electromagnetic, and thermal numerical models. The aim is to develop a new comprehensive methodology which starts with a thermo-structural simulation of the package, then computes the on-state resistance and parasitic components to assess the electrical behavior of the package. Finally, a simulation check is made to verify if the power device performances are thermally consistent with applicative conditions.

Nowadays, battery design must be considered a multi-disciplinary activity focused on product sustainability in terms of environmental impacts and cost. The paper reviews the design tools and methods in the context of Li-ion battery packs. The discussion focuses on different aspects, from thermal analysis to management and safety. The paper aims to investigate what has been achieved in the last twenty years to understand current and future trends when designing battery packs. The goal is to analyze the methods for defining the battery pack's layout and structure using tools for modeling, simulations, life cycle analysis, optimization, and machine learning. The target concerns electric and hybrid vehicles and energy storage systems in general. The paper makes an original classification of past works defining seven levels of design approaches for battery packs. The final discussion analyzes the correlation between the changes in the design methods and the increasing demand for battery packs. The outcome of this paper allows the reader to analyze the evolutions of the design methods and practices in battery packs and to understand future developments.

Keywords: Battery modeling , Design for X , Design methods , Design optimization , Li-ion batteries

Additive manufacturing allows the creation of geometries otherwise impossible to achieve through traditional technologies in mechanical components. These geometries can be obtained using algorithms to optimize the mass distribution. Topology Optimization algorithms are one of the tools most applied in design for additive manufacturing and lightweight engineering. These optimization techniques require Finite Element Method tools to evaluate and compare the mechanical behavior of different geometrical solutions. The optimization results are closely related to boundary conditions, objectives, and constraints. Therefore, one of the issues is the necessity to evaluate different parameter settings to improve the result in terms of light weight, strength, and easy printability. This article shows a working method for using topological optimization to lighten a connecting rod. The resultant model is optimized considering Additive Manufacturing.

Keywords: additive manufacturing , connecting rod , design for additive manufacturing , lightweight engineering , topological optimization

In the presented work, a parametric multibody simulation model is presented that is capable of predicting the friction torque and kinematics of tapered roller bearings. For a highly accurate prediction of bearing friction, consideration of solid and lubricant friction is mandatory. For tapered roller bearings in particular, the friction in the contact between the rolling element and raceway is of importance. Friction forces in the contact between the rolling element end face and inner ring rib as well as roller cage pocket contacts are also considered in the model. A large number of tests were carried out to validate the model in terms of the simulated frictional torque. Influencing variables such as speed, axial load, radial load, and temperature were investigated. The simulation results show good agreement with the measured friction torque, which confirms that the model is well suited to predict frictional torques and therefore the kinematics of tapered roller bearings.

Keywords: dynamic simulation , experimental validation , friction , modelling , multi body simulation , power losses , rolling bearing , tapered roller bearings , tribology

The operation of Tapered Roller Bearings (TRBs) in partially and fully flooded lubricated systems involves relevant lubricant flows; the axial flow rate from the small end to the large end of a TRB is renowned as pumping effect. This effect, which has been studied since the 1970s, affects the cooling process, the static pressure on seals, and the load-independent power losses (PLB0). Then, it influences the design of lubricant supply system. Over the years, analytical formulations to estimate oil flow rates and resistant torques in TRBs have been developed exploiting simplified theories. However, for non-ideal operating conditions, the above formulations may provide incorrect information. To this respect, the development of new tools to support the design of TRBs lubrication systems is needed. Nowadays, novel numerical and experimental techniques allow more detailed analysis of oil behaviors within TRBs. The first goal of the present paper is to introduce Computational Fluid Dynamics (CFD) methods to model and simulate TRBs in the OpenFOAM® environment. In this way, it is possible to estimate fluxes and resistant torques exploiting relatively low computational resources. The second goal is to describe experimental campaigns aimed at measuring loadindependent power losses (PLB0), the oil distribution, and the lubricant velocity field. The latter, exploiting Particle Image Velocimetry (PIV) techniques. Thus, the CFD results can be compared with the experimental ones.

To improve roller bearing efficiency, it is essential to identify the sources of power losses and quantify them in the design stage, considering different influencing factors. For oil-lubricated bearings, load-independent power losses ((Formula presented.)) can be the dominant source of dissipation, especially for high-speed and abundant lubrication. In the present work, (Formula presented.) of a 32208 tapered roller bearing were measured experimentally under various operating conditions; that is, different rotational speeds, temperatures, and geometries of the oil reservoir. A numerical tool, based on computational fluid dynamics, to estimate (Formula presented.) and provide useful insights to investigate their causes has been developed in the OpenFOAM® environment. Numerical and experimental results show excellent agreement in most of the operating conditions investigated. Oil flows, (Formula presented.) contributions of different bearing components, and computational effort are discussed in the article.

Keywords: CFD , experimental validation , hydraulic power losses , lubrication , OpenFOAM^® , Tapered roller bearing

To enhance the bearings' efficiency, it is essential to determine and quantify the sources of power loss in the design stage. In oil-lubricated bearings, load-independent power losses (PLB0 ) can be a significant factor in energy dissipation. This study examines the PLB0 of a double-row Tapered Roller Bearing (32312-A) under different operating conditions, namely various speeds, viscosities, and lubrication conditions, i.e. Feed Lubrication (FEED-L) and Full-Flooded Lubrication (FLO-L). In this respect, a numerical tool based on Computational Fluid Dynamics has been developed within the OpenFOAM® environment. Results highlight that the estimated PLB0 in FLO-L can be an order of magnitude higher than the ones evaluated in FEED-L. The PLB0 in FEED-L are almost exclusively due to inertial effects (99%) and the PLB0 in FLO-L are for the 70% caused by viscous effects. Additionally, it has emerged that the lubricant viscosity has a huge impact on PLB0 for both lubrication conditions. For instance, in the studied configurations, doubling the viscosity can lead to an increase of up to 180% for FEED-L and up to 500% for FLO-L. Moreover, in FEED-L, the flow rate has a significant effect on PLB0 ; on average, doubling the flow rate leads to an increase in PLB0 of more than 15%.

Keywords: Bearing Efficiency , CFD , Hydraulic Power Loss , Lubrication , Open Source , Rolling-Element Bearing

This study aims to investigate the impact of laser beam shaping on metal mixing and molten pool dynamics during laser beam welding of Cu-to-steel for battery terminal-to-casing connections. Four beam shapes were tested during LBW of 300 µm Cu to 300 µm nickel-plated steel. Both experiments and simulations were used to study the underlying physics. A CFD model was firstly calibrated against experiments and then deployed to explore the effect of the increasing ring-to-core diameter, as well as a tandem laser spot configuration. The study showed that metal mixing is influenced by the keyhole dynamics and collapse events, but also there is an intricate interplay between keyhole geometry, fluid dynamics via Marangoni forces and buoyancy forces. Notably, the buoyance forces due to the different densities of steel and Cu, along with the recoil pressure contribute to the upward flow of steel towards Cu, and hence impact meaningfully the material mixing. The study pointed-out that the selection of a custom ring-to-core diameter and ring-to-core power is a decision with a trade-off between the need of stabilising the keyhole dynamics and the need to reduce the mixing. Findings indicated that 350 µm ring and 90 µm core with 30% of ring power (weld configuration C3) resulted in more stable dynamics of the keyhole, with significant reduction of collapse events, and ultimately controlled migration of steel towards Cu. Additionally, the pre-heating approach with the tandem beam only led to local fusion of Cu and no significant improvement in keyhole stability was observed.

Keywords: Battery pack manufacturing , CFD simulation , Cu-to-steel welding , Laser beam shaping , Metal mixing and molten pool dynamics

The automotive production sector plays a significant role in the energy consumption of all the industrial sphere, which currently represents approximately 38% of the total global energy use. Especially in production sites with several manufacturing lines working in parallel, the occurrence of failures and anomalies or sudden changes in the production volume may require a re-scheduling of the entire production process. In this regard, a digital twin of each phase of the process would give several indications about the new re-scheduled manufacture in terms of energy consumption and the control strategy to adopt. Therefore, the main goal of this paper is to propose different modeling approaches to a degreasing tank process, which is a preliminary phase at automotive production sites before the application of paint to car bodies. In detail, two different approaches have been developed: the first is a physics-based thermodynamic approach, which relies on the mass and energy balances of the system analyzed, and the second is machine learning-based, with the calibration of several artificial neural networks (ANNs). All the investigated approaches were assessed and compared, and it was determined that, for this application and with the data at our disposal, the thermodynamic approach has better prediction accuracy, with an overall mean absolute error (MAE) of 1.30 °C. Moreover, the model can be used to optimize the heat source policy of the tank, for which it has demonstrated, with historical data, an energy saving potentiality of up to 30%, and to simulate future scenarios in which, due to company constraints, a re-scheduling of the production of more work shifts is required.

Keywords: artificial neural network , automotive production process , digital twin , model predictive control , paint shop , physics-based model

In recent decades industrial development has led to increasingly sophisticated machinery and systems, which require complex maintenance routines. Consequently, maintenance operators may not have the sufficient skills to perform recovery procedures properly and quickly, so that the need of assistance from the manufacturer's after-sales service or companies specialized in maintenance services. Such actions usually lead to very long recovery times, high maintenance costs, and a temporary drop in production. In this scenario, we should consider that Industry 4.0 is making available innovative technologies, such as Augmented Reality (AR), suitable for improving the skills and competencies of operators without burdening their cognitive load, and consequently wellbeing. However, technologies must be selected, designed, and used according to the users' needs to be effective and useful. The paper presents a user experience (UX)-driven methodology for designing user-centric AR applications for complex maintenance procedures. The methodology was applied to a real industrial case concerning the management of CNC machines in a plant producing tractors components, where a smartphone-based AR application was designed and tested with users. The satisfactory results highlighted the potential benefits of AR in industry and specifically in maintenance.

Keywords: Augmented Reality , Industry 4.0 , Maintenance , Operator 4.0 , User experience design

Due to the rising digitalization in the past few years, even more data can be collected from smart products and sensors to describe the real world, goods, environments, and newly humans including those mutual interactions. Digital twin (DT) has become a key word in engineering, society, and medicine, which is also a hot topic in research for creating virtual data-driven replicas of real objects and simulating their behaviors to predict and optimize the entire system functioning. DTs can mirror the physical entities throughout their lifecycle and create real-time connections between the physical and virtual worlds to monitor and control physical objects from any location. Physical objects can be any living or non-living object, such as humans, machines, robots, cars, buildings, plants, food, or economy. Numerous papers related to DT in various industries have been presented, but very few are focusing on the human-related aspects and the quality of the human machine interaction. In this context, how to shape a human-centric digital twin (HCDT)? The paper states the needs of a human-centric approach in the design and development of DT and presents a set of significant applications of HCDT in different fields, from industry to medicine, from economics to society, discussing the positioning of the HCDT concept in the landscape of transdisciplinary engineering, which is also subject of a workshop during the conference.

Keywords: Digital Twin , Human-centric approaches , Human-machine interaction , Transdisciplinary Engineering

Within the EUROfusion roadmap for the technological development of the European-DEMOnstration (EU-DEMO) reactor, a key point has been identified in the discontinuous operation (pulse-dwell-pulse) of the machine. Water Cooled Lithium Lead (WCLL) Breeding Blanket (BB) Primary Heat Transfer Systems (PHTSs) adopt technology and components commonly used in nuclear fission power plants, whose performances could be negatively affected by the above mentioned pulsation, as well as by low-load operation in the dwell phase. This makes mandatory a full assessment of the functional feasibility of such components through accurate design and validation. For this purpose, ENEA Experimental Engineering Division at Brasimone R.C. aims at realizing STEAM, a water operated facility forming part of the multipurpose experimental infrastructure Water cooled lithium lead -thermal-HYDRAulic (W-HYDRA), conceived to investigate the water technologies applied to the DEMO BB and Balance of Plant systems and components. The experimental validation has the two main objectives of reproducing the DEMO operational phases by means of steady-state and transient tests, as well as performing dedicated tests on the steam generator aiming at demonstrating its ability to perform as intended during the power phases of the machine. STEAM is mainly composed of primary and secondary water systems reproducing the thermodynamic conditions of the DEMO WCLL BB PHTS and power conversion system, respectively. The significance of the STEAM facility resides in its capacity to amass experimental data relevant for the advancement of fusion-related technologies. This capability is attributable to the comprehensive array of instruments with which the facility will be equipped and whose strategic location is described in this work. The operational phases of the STEAM facility at different power levels are presented, according to the requirements of the experiments. Furthermore, a preliminary analysis for the definition of the control strategy for the OTSG mock-up was performed. In particular, two different control strategies were identified and tested, both keeping the primary mass flow constant and regulating the feedwater mass flow to follow a temperature set-point in the primary loop. The obtained numerical results yielded preliminary feedback on the regulation capability of the DEMO steam generator mock-up during pulsed operation, showing that no relevant overtemperature jeopardized the facility integrity, thanks to the high system responsivity to rapid load variations.

Keywords: DEMO components assessment , DEMO water technologies , experimental installation , RELAP5 thermal-hydraulic analysis , STEAM facility

Power modules development is becoming more and more important for switching applications, to improve electric and reliability performances. This paper presents an experimental-numerical method to characterize the reliability behavior of ACEPACKTM SMIT package, a top side-cooled module designed with a half bridge topology, which employs high-voltage silicon MOSFETs. The experimental test involves power cycling to study the reliability and thermal behavior. Then, a finite-element based model is developed to simulate test conditions, to calculate temperature behavior inside the package.

The unsteady flow characteristics and responses of the UAS-S45 airfoil with a morphing trailing edge shape at high angles of attack undergoing deflections are investigated at a Reynolds number of 2.4 × 106. The flexible trailing edge was simulated using a computational fluid dynamics approach using a dynamic mesh and user-defined functions. The goal was to achieve a dynamically deflected trailing edge in an unsymmetrical airfoil and assess the influence of unsteady morphing trailing edge deflection on transient forces and flow field unsteadiness. The steady aerodynamic characteristics of the morphing deflection and the conventional deflection was initially studied. Then, the unsteady aerodynamic characteristics of the morphing wing was investigated as the trailing edge deflects at different rates. The dynamic flow responses to downward deflections are studied using the turbulence model. The time histories of the lift and drag coefficient responses exhibit a proportional relationship between the morphing frequency and the slope of response at which these parameters evolve. Coefficients of lift, drag, and moment of the deflected trailing edge airfoils were compared to those of the reference airfoils for various angles of attack. The numerical results show that the transient lift coefficient in the deflection process was higher than that of the static case at different angles of attack. The transient lift coefficient were higher as the deflection frequency increased. It was also revealed that the trailing edge deflection did not favor the flow reattachment. In addition, the dynamic mesh strategy, cell quality, and the proposed method of deforming the morphing trailing-edge was presented

Keywords: computational fluid dynamics (CFD); aerodynamics , Dynamic Mesh , Frequency analysis , Morphing Trailing Edge

A leading challenge in the assembly process of aircraft skin panels is the precise control of part-to-part gaps to avoid excessive pre-tensions of the fastening element which, if exceeded, impair the durability and the response under dynamics loads of the whole skin assembly. The current practice is to measure the gap in specific points of the assembly with parts already at their final location, and then be-spoke shims are machined and inserted between the mating components to fill the gap. This process involves several manual measurement-fit-adjust quality loops, such as loading parts on the assembly frame, measuring gaps, off-loading parts, adding be-spoke shims and re-positioning parts ready for the fastening operation—as a matter of fact, the aircraft is re-assembled at least twice and therefore the current practice has been proved highly cost and time ineffective. Additionally, the gap measurement relies on manual gauges which are inaccurate and unable to follow the actual 3D profile of the gap. Taking advantage of emerging tools such as in-line measurement systems and large-scale physics-based simulations, this paper proposes a novel methodology to predict the part-to-part gap and therefore minimise the need for multiple quality loops. The methodology leverages a physics-driven digital twin model of the skin assembly process, which combines a physical domain (in-line measurements) and a digital domain (physics-based simulation). Central to the methodology is the variation model of the multi-stage assembly process via a physics-based simulation which allows to capture the inherent deformation of the panels and the propagation of variations between consecutive assembly stages. The results were demonstrated during the assembly process of a vertical stabiliser for commercial aircraft, and findings showed a significant time saving of 75% by reducing costly and time-consuming measurement-fit-adjust quality loops.

Keywords: Aircraft skin panels , Digital twin , Morphing mesh , Multi-stage assembly simulation , Physics-based modelling , Virtual shimming

This work proposes a geometric approach to inverse kinematics of hyper-redundant manipulators used for remote maintenance of nuclear fusion reactors. The approach is particularly suited to be adopted in real-time human-in-the-loop control strategies involving high-frequency control feedback and requiring safe interaction between the manipulator and the in-vessel environment. The capability of the inverse kinematic method to find a solution for a set of different robot end-effector poses, inside a toroidal environment, was tested on the HyRMan kinematics, i.e. the Hyper Redundant Manipulator developed in the framework of the Divertor Tokamak Test (DTT) project. The simulation tests were aimed at assessing performance of the proposed method in terms of accuracy in the end-effector positioning, computational burden, distance from obstacle, distance from joint angles and torque limits and success rate of the task execution. The achieved results were compared to the ones obtained through an iterative method proposed in literature, i.e. the one based on the computation of the Jacobian pseudo-inverse, demonstrating overall higher performance of the proposed approach and comparable ability to safely avoid obstacles and joint limits.

Keywords: Hyper-Redundant Manipulators , Inverse Kinematics , Nuclear Fusion , Remote Maintenance