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Increasing nonlinearity in today&rsquo, s grid challenges the conventional small-signal (modal) analysis (SSA) tools. For instance, the interactions among modes, which are not captured by SSA, may play significant roles in a stressed power system. Consequently, alternative nonlinear modal analysis tools, notably Normal Form (NF) and Modal Series (MS) methods are being explored. However, they are computation-intensive due to numerous polynomial coefficients required. This paper proposes a fast NF technique for power system modal interaction investigation, which uses characteristics of system modes to carefully select relevant terms to be considered in the analysis. The Coefficients related to these terms are selectively computed and the resulting approximate model is computationally reduced compared to the one in which all the coefficients are computed. This leads to a very rapid nonlinear modal analysis of the power systems. The reduced model is used to study interactions of modes in a two-area power system where the tested scenarios give same results as the full model, with about 70% reduction in computation time.

The inclusion of higher-order terms in small-signal (modal) analysis augments the information provided by linear analysis and enables better dynamic characteristic studies on the power system. This can be done by applying Normal Form theory to simplify the higher order terms. However, it requires the preliminary expansion of the nonlinear system on the normal mode basis, which is impracticable with standard methods when considering large scale systems. In this paper, we present an efficient numerical method for accelerating those computations, by avoiding the usual Taylor expansion. Our computations are based on prescribing the linear eigenvectors as unknown field in the initial nonlinear system, which leads to solving linear-only equations to obtain the coefficients of the nonlinear modal model. In this way, actual Taylor expansion and associated higher order Hessian matrices are avoided, making the computation of the nonlinear model up to third order and nonlinear modal analysis fast and achievable in a convenient computational time. The proposed method is demonstrated on a single-machine-infinite-bus (SMIB) system and applied to IEEE 3-Machine, IEEE 16- Machine and IEEE 50-Machine systems. This work was supported by TETfund, Nigeria

Today's power systems are strongly nonlinear and are becoming more complex with the large penetration of power-electronics interfaced generators. Conventional Linear Modal Analysis does not adequately study such a system with complex nonlinear behavior. Inclusion of higher-order terms in small-signal (modal) analysis associated with the Normal Form theory proposes a nonlinear modal analysis as an efficient way to improve the analysis. However, heavy computations involved make Normal Form method tedious, and impracticable for large power system application. In this paper, we present an efficient and speedy approach for obtaining the required nonlinear coefficients of the nonlinear equations modelling of a power system, without actually going through all the usual high order differentiation involved in Taylor series expansion. The method uses eigenvectors to excite the system modes independently which lead to formulation of linear equations whose solution gives the needed coefficients. The proposed method is demonstrated on the conventional IEEE 9-bus system and 68-bus New England/New York system.

International audience; The direct parametrisation method for invariant manifolds is a nonlinear reduction technique which derives nonlinear mappings and reduced-order dynamics that describe the evolution of dynamical systems along a low-dimensional invariant-based span of the phase space. It can be directly applied to finite element problems. When the development is performed using an arbitrary order asymptotic expansion, it provides an efficient reduced-order modeling strategy for geometrically nonlinear structures. It is here applied to the case of rotating structures featuring centrifugal effect. A rotating cantilever beam with large amplitude vibrations is first selected in order to highlight the main features of the method. Numerical results show that the method provides accurate reduced-order models (ROMs) for any rotation speed and vibration amplitude of interest with a single master mode, thus offering remarkable reduction in the computational burden. The hardening/softening transition of the fundamental flexural mode with increasing rotation speed is then investigated in detail and a ROM parametrised with respect to rotation speed and forcing frequencies is detailed. The method is then applied to a twisted plate model representative of a fan blade, showing how the technique can handle more complex structures. Hardening/softening transition is also investigated as well as interpolation of ROMs, highlighting the efficacy of the method.

This article presents the design strategy and experimental validation of a battery-free power supply for wireless sensor nodes (WSN) on an industrial study case. The power supply is based on the principle of vibration energy harvesting (VEH). The general architecture of the linear generator with electronic is presented. It is composed of commercially available components as a MIDE PPA 1014 piezoelectric cantilever beam and a LTC3588 circuit to extract and shape the electrical energy. The energy source comes from mechanical vibrations measured on the industrial environment in operation. A tunable mechanism of the resonance frequency is added in order to have a wider range of use than the natural range of a linear harvester.To adapt theVEH according with the source, it resonant frequency range can be tuned with a dedicated tip-mass. Then a fine adjustment within a range of about 20 Hz is set using both a moving clamping device and a temporarily wired electronic device working as a maximum power point finder (MPPF). To achieve a long lifetime, the storage is done using balanced supercapacitors. Two operational demonstrators are shown. The test benches as well as numerous experimental tests are presented. Shaped according to the industrial environment (49.0 Hz @ 2.7 m/s2), the VEH is capable of delivering continuously 100mA@3.3V with 200 mA peaks. When the power harvested ( 2.9 mW) is upper than the sensor average power, it offers the capability to store 17.5 J at 18.5 V. As a result, from this work, a WSN can successfully operate over a significantly long period of time despite fluctuations in the vibration source. This work was supported in part by the Internet Industriel des Objets et des Opérateurs (2IDO) Project through the Banque Publique d’Investissement (BPI) and in part by the Programme d’Investissements d’Avenir (PIA).

International audience; This article exhibits the sizing, modelling, and characterization of a power supply (output 3.3 V, 200 mA max, 11 days full autonomy) dedicated to power a wireless sensor node without battery but usable as simply as with a battery. This system is modular for various light levels (indoor and outdoor). It is easily integrable into a sensor node, using only commercial circuits. The choices of the photovoltaic surface (amorphous silicon,  5%, 35 cm²) and of the supercapacitors value (2x 25F, 2.7V) are explained for permanent operation, considering the solar potential and the consumption. An original part of the paper is devoted to issue of the startup, in which we demonstrate that after a particular preload, once installed, the device can start on request at the desired time (within 15 days) using as a trigger any light source, such as the LED of a mobile phone.

International audience; Identifcation and ftting is an important task in reverse engineering and virtual/augmented reality. Compared to the traditional approaches, carrying out such tasks with a deep learning-based method have much room to exploit. This paper presents SMA-Net (Spatial Merge Attention Network), a novel deep learning-based end-to-end bottom-up architecture, specifcally focused on fast identifcation and ftting of CAD models from point clouds. The network is composed of three parts whose strengths are clearly highlighted: voxel-based multi-resolution feature extractor, spatial merge attention mechanism and multi-task head. It is trained with both virtually-generated point clouds and as-scanned ones created from multiple instances of CAD models, themselves obtained with randomly generated parameter values. Using this data generation pipeline, the proposed approach is validated on two diferent data sets that have been made publicly available: robot data set for Industry 4.0 applications, and furniture data set for virtual/augmented reality. Experiments show that this reconstruction strategy achieves compelling and accurate results in a very high speed, and that it is very robust on real data obtained for instance by laser scanner and Kinect.

International audience; Industry 4.0 is leading to rethink how operational decisions are made within companies. In particular, it raises the question of the evolution of employee involvement and autonomy in operational decision-making in a Lean 4.0 context. Dealing with such issues within companies presents high stakes but also involves many risks and difficulties. Therefore, it is necessary to test these new Industry 4.0 autonomy models within our Evolutive Learning Factories by developing a suitable experimental protocol. This article proposes a typology of scenarios and case studies that will serve as a basis for future experiments to study these issues in a standardized work context. This first study framework confirmed that the decisions induced by all the problems and opportunities encountered at the operational level are numerous and varied. This research work is a first step and opens up much broader research perspectives on the contribution of Industry 4.0 technologies in implementing new models of autonomy at work.; L'industrie 4.0 amène à repenser la manière dont les décisions opérationnelles sont prises au sein des entreprises. Se pose notamment la question de l'évolution de l'implication et de l'autonomie des employés dans les prises de décision opération-nelles dans un contexte Lean 4.0. Traiter de telles problématiques au sein des entre-prises présente de forts enjeux mais comporte aussi de nombreux risques et diffi-cultés. Il convient donc de pouvoir tester ces nouveaux modèles d'autonomie 4.0 au sein d'Evolutive Learning Factories en développant un modèle expérimental adapté. Cet article propose une typologie de scénario d'études qui servira de base aux futures expérimentations permettant d'étudier ces problématiques dans un contexte de travail standardisé. Ce premier cadre d'étude a permis de confirmer que les déci-sions induites par l'ensemble des problèmes et opportunités rencontrés au niveau opérationnel sont nombreuses et variées. Ce travail de recherche constitue donc une première étape et ouvre des perspectives de recherche beaucoup plus larges sur l'ap-port des technologies de l'Industrie 4.0 dans la mise en oeuvre de nouveaux modèles d'autonomie au travail.

International audience; Manufacturing industry needs access to the data in order to realise its activities but also to generate new value-added knowledge. Nevertheless, it is confronted with a large and growing volume of heterogeneous data which limits its ability to exploit them optimally. Moreover, the data are distributed within different heterogeneous information systems, which limits the relationship exploration under the information retrieval process. Usually, the challenge is addressed by trying to manage and normalize the data structure in order to faster searching and exploiting them in a manufacturing context. For their part, the authors present i-Dataquest, an information retrieval system supported by (i) a graph-oriented model built from the structured and unstructured data of the company and (ii) a query system answering ‘what’ and ‘about what’ and (iii) generating three different results: a list of items, a list of property values and a list of sentences. The i-Dataquest prototype is built using Neo4J for the graph system generation, ConceptNet for lexical resource management and StandfordNLP for natural language processing. An evaluation of the prototype’s performance is conducted through a data set representing a drone manufacturer. The results show that the transformation of specific content such as tables in the graph and the semantic expansion of queries significantly improves the recall and precision measures. The results also suggest improving filtering less relevant results by considering particularly queries looking for a specific value.

Introduction: Since kinesthetic cues are not present in virtual environments, users have difficulty feeling the heaviness of virtual objects. To address this issue, pseudo-haptic approaches have been proposed to illusorily induce the weight of virtual objects through the user’s visual sensory system.Methods: In this paper, we used two methods to induce the impression of virtual objects’ heaviness. One relies on the direct modification of the control-display (C/D) ratio when lifting objects, and the other depends on controlling this ratio based on a velocity restriction. We innovatively measured each approach’s efficiency by analyzing physical work as an objective metric. In addition, we used Borg CR10 to measure users’ hand fatigue during the experimental phases.Results: Our findings are discussed in terms of individual lifting behavior in different pseudo-haptic methods. Furthermore, different virtual weight-lifting behaviors were compared to the same real-world weight-lifting behaviors.Discussion: According to our results, the direct control of the C/D ratio method provides virtual reality users with a more accurate weight perception than the velocity restriction one. Furthermore, with this first method, users’ lifting behavior was closer to the behavior when lifting real objects.

International audience; Virtual reality have advanced rapidly and are spreading in much of the world for huge numbers of application domains. However the cybersickness appears for many VR users and it is still a significant issue preventing them to feel free to use VR technology. In most of VR experience, the immersive display system can provoking much more self-motion perceived by eyes than the one given by vestibular systems. Through the sensory conflict theory, the mismatch in visual and vestibular sense causes sickness. In this paper a general framework for applying geometric simplification on the virtual scene is proposed with the aim of lowering the visually induced self-motion that can be quantified by optic flow analyzed on the rendered images. The synthetized image that includes original scene at central part and simplified scene at peripheral part, are rendered to VR users. The analyzed optic flow on the synthetized images is much less than the one given by the original images.

Feedback is often linked to rewards element in gamification to motivate users. However, there are more to feedbacks than rewards elements. Feedback can provide user with useful information and at the same time feedback from user are useful for an adaptive system. There has been lack of empirical basis for feedback design to maintain motivation in virtual reality environment especially for the less cognitively abled population such as stroke patients. This paper presents a review study on gamification, sensory feedback, and adaptive function with regards to the use of virtual reality in stroke rehabilitation. A further analysis was conducted on those work that involves gamification and virtual reality design principles. One major finding is the dominant use of visual feedback in the design as compared to auditory and haptics despite their potentials to encourage motivation and engagement. The literature findings will be used to inform future empirical research on virtual reality design for stroke rehabilitation. The idea is to investigate the effect of sensory feedback and the added value on motivation and engagement. Some plans on how to conduct such a study will be illustrated. This work was supported by French government funding managed by the National Research Agency under the Investments for the Future program (PIA) grant ANR-21-ESRE-0030 (CONTINUUM).

International audience; Enterprises now face a global, dynamic, and unpredictable economic environment. In response to quick changes of the demand, the production needs to have the ability to adapt rapidly to meet the production requirements. The Reconfigurable Manufacturing System (RMS) paradigm enables such capabilities. However, defining design and reconfiguration rules is highly challenging, as it requires a broad knowledge encompassing the inclusion of technological, production, and economic metrics, as well as an understanding of a reconfiguration strategy, determining the necessary reconfiguration frequency of the system. For now, no global methodology taking all those aspects into account has been proposed. This article presents an original framework for the design, evaluation, and reconfiguration of the Reconfigurable Production System (RPS). New metrics to measure reconfigurability are defined. The design approach consists in three main steps which are individually developed. The selection of the appropriated production system is based on the comparison of reconfigurability and productivity indicators. Finally, the reconfiguration strategy is presented. The methodology is applied on a case study from the automotive industry.

An original method for the simulation of the dynamics of highly flexible slender structures is presented. The flexible structures are modeled via a finite element (FE) discretization of a geometrically exact two-dimensional beam model, which entirely preserves the geometrical nonlinearities inherent in such systems where the rotation of the crosssection can be extreme. The FE equation is solved by a combination of harmonic balance (HBM) and asymptotic numerical (ANM) methods. The novel solving scheme is rooted entirely in the frequency domain and is capable of computing both the structure's frequency response under periodic external forces as well as its nonlinear modes. An overview of the proposed numerical strategy is outlined and simulations are shown and discussed in detail for several test cases.

International audience; This study proposes to investigate the effects of dry friction on the behaviour of a parametrically excited nonlinear oscillator using a pendulum as example. A harmonic balance method and time integration simulations are used to respectively compute and validate the solutions of the problem and their stability. The effects of dry friction on the behaviour of the system are discussed.

International audience; The aim of this contribution is to review and compare three different methods that have been proposed in order to derive reduced-order models for geometrically nonlinear structures, and relying on a nonlinear technique to better take into account the nonlinearities of the initial problem. The three methods are: implicit condensation, quadratic manifold derived with modal derivatives, and projection onto an invariant manifold, tangent at the origin to the linear eigenspace of the master modes. The methods are briefly reviewed theoretically and then compared with dedicated examples.

International audience; This paper proposes a new system-level application for monitoring out-of-step (OOS) events in power systems. As already known, amplitude-dependent frequency shift is a nonlinear phenomenon of electromechanical oscillations under large disturbances. The frequency shift indicates the system’s nearness to instability. This new tool utilizes the Normal Form method to identify the named phenomenon, leading to accelerated OOS detection. The proposed strategy is illustrated and compared to the equal-area criterion method in a single-machine-infinite-bus power system. Extensive tests on IEEE 3- and IEEE 50-machine power systems prove the efficacy and potential of the proposed method for online warnings of instability and ranking of vulnerable system modes.

International audience; Even if 3D acquisition systems are nowadays more and more efficient, the resultingpoint clouds nevertheless contain quality defects that must be taken into accountbeforehand, in order to better anticipate and control their effects. Assessing the quality of3D acquisitions has therefore become a major issue for scan planning. This paper presentsseveral quality metrics that are then studied to identify those that could be used to optimizethe acquisition positions to perform an automatic scan. From the experiments, it appearsthat, when considering multiple acquisition positions, the coverage ratio and score indicatorhave significant changes and can be used to evaluate the quality of the measurements. Differently,other indicators such as efficacy ratio, registration error and metrological characteristicsare insensitive to some acquisition positions

The aim of this contribution is to present numerical comparisons of model-order reduction methods for geometrically nonlinear structures in the general framework of finite element (FE) procedures. Three different methods are compared: the implicit condensation and expansion (ICE), the quadratic manifold computed from modal derivatives (MD), and the direct normal form (DNF) procedure, the latter expressing the reduced dynamics in an invariant-based span of the phase space. The methods are first presented in order to underline their common points and differences, highlighting in particular that ICE and MD use reduction subspaces that are not invariant. A simple analytical example is then used in order to analyze how the different treatments of quadratic nonlinearities by the three methods can affect the predictions. Finally, three beam examples are used to emphasize the ability of the methods to handle curvature (on a curved beam), 1:1 internal resonance (on a clamped-clamped beam with two polarizations), and inertia nonlinearity (on a cantilever beam).

International audience; ans ce papier, une méthode originale est présentée pour la simulation périodique de structures élancées hautement flexibles. Les structures flexibles sont discrétisées par éléments finis de poutres géométriquement exactes. Ensuite, le modèle est résolu par une méthode de résolution dans le domaine fréquentiel par continuation de solutions périodiques. La méthode proposée combine les principes de la méthode de l’équilibrage harmonique et la méthode asymptotique numérique. Cette étude vise à développer une méthode de résolution la plus efficace possible pour ces structures flexibles.

International audience; In this paper, a semi-passive nonlinear piezoelectric shunt absorber is presented, aiming at attenuating the vibration of a resonant elastic structure under external excitation. This is done by connecting the elastic structure to a nonlinear shunt circuit via a piezoelectric patch. The nonlinear shunt circuit consists of resonant circuit that includes a quadratic non-linearity. A particular tuning of the natural frequency of the shunt enables to create a two to one internal resonance. This generates a strong coupling between the mechanical mode and the electrical mode, leading to replace the mechanical resonance with a nonlinear antiresonance associated with an amplitude saturation, thus leading to an efficient vibration reduction. In this paper, we first propose a theoretical model that is expanded onto a suitable electromechanical modal basis and reduced to the two modes of interest, nonlinearly coupled by quadratic terms. Then, analytical solutions are obtained by the multiple scale method and compared to a reference numerical solutions stemming from the harmonic balance method. This enables to investigate the performance of the system in term of vibration absorption as well as giving design rules to tune the nonlinear shunt and to choose the free parameters of the system.

International audience; Virtual reality is a promising technology for training healthcare professionals in a safe simulation environment. In this work, we present the design and evaluation of an immersive simulator for training ultrasound-guided locoregional anesthesia operators. Eighteen anesthesiologists participated in a face and content validation study of the first prototype of the system. Responses to seven of the eleven questions on face validity were predominantly positive. The main raised issue concerns the fidelity of the needle haptic feedback, suggesting the use of a six degrees of freedom haptic feedback arm in the future prototypes. Responses to all six questions on content validity were predominantly positive. Participants find that the simulator is a promising training tool particularly suited for developing hand-eye coordination skills. These results support our design choices and suggest improvements for our simulator before its validation as a training tool.; La réalité virtuelle est une technologie prometteuse pour former les professionnels de santé dans un environnement de simulation sécurisé. Dans ce travail, nous présentons la conception et l'évaluation d'un simulateur immersif pour la formation de l’anesthésie locorégionale échoguidée. Dix-huit anesthésistes ont participé à la validation de l’aspect et du contenu du premier prototype du système. Les réponses à sept des onze questions sur la validité de l’aspect étaient positives. La problématique soulevée concerne la fidélité du rendu haptique de l'aiguille, suggérant l'utilisation d'un bras haptique à six degrés de liberté dans les futurs prototypes. Les réponses aux six questions sur la validité du contenu étaient positives. Les participants trouvent que le simulateur est un outil de formation prometteur particulièrement adapté pour développer les compétences de coordination œil-main. Ces résultats confortent nos choix de conception et suggèrent des améliorations pour notre simulateur avant sa validation comme outil de formation.

Closed-form formulations are difficult to find when the material behavior law is nonlinear. A linear approximation, on the other hand, has a very narrow range of validity. In this communication, the Normal Form (NF) method is employed to solve a 1-D nonlinear magnetodynamic problem. The discrete model is formulated in a state-space form suitable for NF applications. The resulting system is then expanded on a linear mode basis to cubic order. Analytical solutions are obtained using the NF technique and compared to traditional solutions. The results show the cubic polynomial adequately approximates the problem, and the NF solution is valid for some range of magnetic field intensity. This work is a part of the CE2I project, co-financed by the European Union, the European Regional Development Fund (ERDF), the French State, and the Hauts-de-France Region.

Computer-Aided Design (CAD) constitutes an important tool for industrial designers. Similarly, Virtual Reality (VR) has the capability to revolutionize how designers work with its increased sense of scale and perspective. However, existing VR CAD applications are limited in terms of functionality and intuitive control. Based on a comparison of VR CAD applications, ImPro, a new application for immersive prototyping for industrial designers was developed. The user evaluations and comparisons show that ImPro offers increased usability, functionality, and suitability for industrial designers. TUMCREATE Phase 2, funded by the National Research Foundation (NRF) Singapore under its Campus for Research Excellence and Technological Enterprise (CREATE) programme

International audience; A system composed of two cubic nonlinear oscillators with close natural frequencies, and thus displaying a 1:1 internal resonance, is studied both theoretically and experimentally, with a special emphasis on the free oscillations and the backbone curves. The instability regions of uncoupled solutions are derived and the bifurcation scenario as a function of the parameters of the problem is established, showing in an exhaustive manner all possible solutions. The backbone curves are then experimentally measured on a circular plate, where the asymmetric modes are known to display companion configurations with close eigenfrequencies. A control system based on a Phase-Locked Loop (PLL) is used to measure the backbone curves and also the frequency response function in the forced and damped case, including unstable branches. The model is used for a complete identification of the unknown parameters and an excellent comparison is drawn out between theoretical prediction and measurements.

International audience; In this paper, both vibration reduction and task accuracy improvement for flexible redundant manipulators, using the resolution of redundancy, is addressed. The exciting force of flexural motion, which is induced by the motion of the manipulator, causes undesired deflection at the end-effector. The null space inherent in redundancy feature is exploited to damp out the vibration while maintaining the end-effector posture. In order to exploit all the degrees of freedom in the null space, a feedback control design based on torque optimization has been introduced using analytical method for the redundancy resolution. The simulation analysis is presented to test the effectiveness of the proposed approach.

International audience; The collaborative robot (cobot) is a technology contributing to the industrial revolution Industry 4.0. Indeed, cobots’ flexibility and their easy-to-use solutions fill a gap with traditional robots to robotize manufacturing of products with low volume and high mix profiles. Parts needed to manufacture a product must first be presented to the cobot, so that afterwards it can perform operations such as assembly. The paper classifies the current part presenters. Then, a methodology is proposed to select the best presenter based on the characteristics of the parts and the workstation. To be aligned with markets requiring a high mix of products frequently renewed, the development times for part presenter design and for cobot programming are new data to select the best presenter. Indeed, at every part redesign, the part presenter changes and the cobot is reprogrammed. These two times are depreciated based on the lifespan quantity of the part. Lifespan quantity is the number of the same parts, which are dropped-off on the part presenter during the part’s lifespan, i.e. until its redesign. A concrete industrial use case is explained to test the methodology. Results conclude that a tray pattern is the best part presenter, except for parts with low lifespan quantity. Lifespan quantity of the part appears to be a significant parameter when deciding the best part presenter.

International audience; Collaborative robots have open new ways of designing assembly processes, thanks to their ability to share work space with operators. not only may they support the economical performance, but they can also improve the overall ergonomics. Building on existing work on task allocation problems, the authors study further the collaboration opportunities between operator and robot, namely cooperation phases (type of collaboration where both operator and robot act on the same work piece). This work proposes anewformulation of the related problem, and solutions are sought through heuristics methods, to investigate whether concurrent usage of different collaboration modes delivers better performance. The results indicate that cooperation mode enables higher process performances while controlling ergonomic risks. With a concern for real-life application, it has been applied on a real case study to verify its applicability.

International audience; Parametrically excited oscillators are used in several domains, in particular to improve the dynamical behaviour of systems like in the case of the parametric amplification or parametric energy harvesting. Although dry friction is often omitted during system modelling due to the complexity of its nonsmooth nature, it is sometimes necessary to account for this kind of damping to adequately represent the system motion. In this paper, it is proposed to investigate the effect of dry friction on the dynamical behaviour of a nonlinear parametric oscillator. Using the pendulum case as example, the problem is formulated according to a Mathieu-Duffing equation. Semi-analytical developments using the harmonic balance method and the method of varying amplitudes are used to find the solutions of this equation and their stability. These results are validated thanks to a comparison with time integration simulations. Effects of initial conditions on the basins of attractions of the solutions are also studied using these simulations. It is found that trivial and nontrivial solutions of the oscillator including dry friction are not connected, giving birth to isolated periodic solutions branches. Thus, both initial displacement and phase between the excitation and the oscillator displacement must be carefully chosen to reach periodic solutions. Finally, a method based on the energy principle is used to find the critical forcing amplitude and frequency needed to obtain the birth of nontrivial solutions for the nonlinear parametric oscillator including dry friction.

International audience; Glancing Angle Deposition (GLAD) is a technique used in Physical Vapor Deposition (PVD) to prepare thin films with specific properties. During the deposition process, a tilt is introduced between the sputtered atoms flux and the normal of the substrate surface. By shadowing effect, this induces tilted nano-columns that affect the properties of the coating. To predict these properties, several existing tools simulate the different steps of the PVD deposition. First, a simulation of the sputtering of atoms from a metallic target is made, followed by the computation of the atoms transportation from the target to the substrate. Finally, the growth of the film is computed. All these simulations use point based representation to represent the deposited atoms. However, such representation is not suited for classical finite elements analysis (FEA).In this paper, a methodology for generating FEA meshes from the points produced by film growth simulation is presented. Two major scientific challenges are overcome. Firstly, how to segment the ”film” point cloud into a collection of individual “columns” and secondly, how to generate the meshes of the columns that are approximately represented by points. The point cloud segmentation is computed through neighbourhood notion. The mesh is obtained as an implicit surface by the marching cubes algorithm and smoothed by a Humphrey’s class Laplacian algorithm. Numerical simulations based on the generated FEA meshes will be conducted using Abaqus FEA software.

An experimental proof of concept of a new semi-passive nonlinear piezoelectric shunt absorber, introduced theoretically in a companion article, is presented in this work. This absorber is obtained by connecting, through a piezoelectric transducer, an elastic structure to a resonant circuit that includes a quadratic nonlinearity. This nonlinearity is obtained by including in the circuit a voltage source proportional to the square of the voltage across the piezoelectric transducer, thanks to an analog multiplier circuit. Then, by tuning the electric resonance of the circuit to half the value of one of the resonances of the elastic structure, a two-to-one internal resonance is at hand. As a result, a strong energy transfer occurs from the mechanical mode to be attenuated to the electrical mode of the shunt, leading to two essential features: a nonlinear antiresonance in place of the mechanical resonance and an amplitude saturation. Namely, the amplitude of the elastic structure oscillations at the antiresonance becomes, above a given threshold, independent of the forcing level, contrary to a classical linear resonant shunt. This paper presents the experimental setup, the designed nonlinear shunt circuit and the main experimental results.

International audience; In the context of optimization and cycles reduction for product design in industry, digital collaborative tools have a major impact, allowing an early stage integration of multidisciplinary challenges and oftentimes the search ofglobal optimum rather than domain specific improvements. This paper presents a methodology for improving participants’ implication and performance during collaborative design sessions through virtual reality (VR) tools, thanks to intention detection through body language interpretation. A prototype of the methodology is being implemented based on an existing VR aided design tool called DragonFly developed by Airbus. In what follows we will first discuss the choice of the different biological inputs for our purpose, and how to merge these multi-modal inputs a meaningful way. Thus, we obtain a rich representation of the body language expression, suitable to recognize the actions wanted by the user and their related parameters. We will then show that this solution has been designed for fast training thanks to a majority of unsupervised training and existing pre-trained models, and for fast evolution thanks to the modularity of the architecture.

Today virtual reality technologies is becoming more and more widespread and has found strong applications in various domains. However, the fear to experience motion sickness is still an important barrier for VR users. Instead of moving physically, VR users experience virtual locomotion but their vestibular systems do not sense the self-motion that are visually induced by immersive displays. The mismatch in visual and vestibular senses causes sickness. Previous solutions actively reduce user's field-of-view and alter their navigation. In this paper we propose a passive approach that temporarily deforms geometrically the virtual environment according to user navigation. Two deformation methods have been prototyped and tested. The first one reduces the perceived optic flow which is the main cause of visually induced motion sickness. The second one encourages users to adopt smoother trajectories and reduce the cybersickness dose value. Both methods have the potential to be applied generically., Posters, Ruding Lou, Richard So, and Dominique Bechmann

Centralized electrical networks induce a dependency of local territories for their power supply. However, thanks to microgrids, territories can increase their decision-making autonomy to design a network that matches their values. Technological and management choices are critical to minimize microgrids negative impacts on their environment. Influence of the latter on the design space is rarely discussed whereas extending the design space would help to find innovative microgrids. The purpose of this paper is to find several microgrids with various performances and parameters that are compromises between economic, technical and environmental objectives. The solutions’ variety therefore extends the decision-makers’ design space. A tool has been developed to answer this goal. Design parameters are both technological and management parameters. A physical modelling is implemented in a sequential simulation of the microgrid operation. The performance of the simulation allows to use genetic algorithms to perform multi-objective non-weighted optimizations. Two twoobjective optimizations are performed. Results show how the solutions’ diversity in terms of performances and parameters helps the user choosing innovative microgrids. Especially, it underlines the potential of this approach to find microgrids with close performances but different parameters. This work was supported by the Region Provence-Alpes-Côte d’Azur, France

Industrial cobotics is presented as a way of business competitiveness by combining human skills and decision making with robotic advantages. The place and safety of humans in cobotic (collaborative robotic) systems are the subjects of much discussion. This article provides a qualitative overview of the main multidisciplinary fields related to the place of human operators during the design process of humans–robots’ systems and discusses paths for effective consideration of the human challenge during this kind of design projects. The added value of this article is its multidisciplinary aspect. Readers will find in this article a technological overview of cobotics, different methodologies and design models focused on final users, interesting examples of evaluation indicators potentially adapted to an effective consideration of humans during the design process of cobotic systems (economic, technical, and human) and guidelines seeking to support cobotic system designers to succeed considering final users during the design process. This work has been supported by the French National Research Agency (ANR) as part of the research project HECTTOR: Humans Committed to Organisations and Work Transformations in the « Factories of the Future » through cobotisation—(ANR-17-CE10-0011)

International audience; A reduced-order modelling to predictively simulate the dynamics of piezoelectric structures with geometric nonlinearities is proposed in this paper. A formulation of three-dimensional finite element models with global electric variables per piezoelectric patch, and suitable with any commercial finite element code equipped with geometrically nonlinear and piezoelectric capabilities, is proposed. A modal expansion leads to a reduced model where both nonlinear and electromechanical coupling effects are governed by modal coefficients, identified thanks to a non-intrusive procedure relying on the static application of prescribed displacements. Numerical simulations can be efficiently performed on the reduced modal model, thus defining a convenient procedure to study accurately the nonlinear dynamics of any piezoelectric structure. A particular focus is made on the parametric effect resulting from the combination of geometric nonlinearities and piezoelectricity. Reference results are provided in terms of coefficients of the reduced-order model as well as of dynamic responses, computed for different test cases including realistic structures.

International audience; This paper deals with the assembly line balancing issue. The considered objective is to minimize the weighted sum of products’ cycle times. The originality of this objective is that it is the generalization of the cycle time minimization used in single-model lines (SALBP) to the multi-model case (MALBP). An optimization algorithm made of a heuristic and a tabu-search method is presented and evaluated through an experimental study carried out on several and various randomly generated instances for both the single and multiproduct cases. The returned solutions are compared to optimal solutions given by a mathematical model from the literature and to a proposed lower bound inspired from the classical SALBP bound. The results show that the algorithm is highperforming as the average relative gap between them is quite low for both problems.

Animal welfare has become an increasingly important concern in the sports field. Learning horse-drawn carriage driving requires much time and effort for both the drivers and the horses because the associated gestures to avoid harming the horses are difficult to acquire. This raises the need to develop realistic simulation environments for future drivers. To this end, two haptic interface prototypes were designed, coupled with dedicated simulation software. The first was developed based on a SPIDAR haptic device and implemented simple behaviors of the carriage. A user study demonstrated interest in such a simulator, which led to the design of a second prototype, on a different architecture than the first prototype, for integrating more precise laws of horse behavior such as mood and allowing a more subtle control of forces. An evaluation with driving learners revealed that the simulator was capable of not only producing sensations close to reality but also improving the interaction between the trainer and the learner. This work was supported by the Ifce and SAHn under grant no. 2016-17-007.

Virtual reality (VR) is a computer-based technology that can be used by professionals of many different fields to simulate an environment with a high feeling of presence and immersion. Nonetheless, one main issue when designing such environments is to provide user interactions that are adapted to the tasks performed by the users. Thus, we propose here a task-centred methodology to design and evaluate these user interactions. Our methodology allows for the determination of user interaction designs based on previous VR studies, and for user evaluations based on a task-related computation of usability. Here, we applied it on the hazard identification case study, since VR can be used in a preventive approach to improve worksite safety. Once this task and its related user interactions were analysed with our methodology, we obtained two possible designs of interaction techniques for the worksite exploration subtask. About their usability evaluation, we proposed in this study to compare our task-centred evaluation approach to a non-task-centred one. Our hypothesis was that our approach could lead to different interpretations of user study results than a non-task-centred one. Our results confirmed our hypothesis by comparing weighted usability scores from our task-centred approach to unweighted ones for our two interaction techniques. Conseil régional de Bourgogne-Franche-Comté (reference: CDBOBI)

International audience; In the last decade, the potential of Micro Aerial Vehicles (MAVs) has generated an enormous interest in this technology and numerous applications have therefore been proposed in military and civilian fields. More recently, researchers have begun to work on a new and miniaturized generation called Flapping Wing Nano Aerial Vehicles (FWNAVs) who could be particularly promising for the indoor inspection. Before to be able to use efficiently these FWNAVs, there are however significant scientific and technical challenges to solve due to the scaling down. These include aerodynamics of low Reynolds number flow, small-scale power generation and power storage, navigation and communication, propulsion and control as well as manufacturability. This paper sets out the potential applications of such FWNAVs and reviews some of the challenges related to aerodynamics, stability, and design trends.

The objective of this PhD is to review the design of the current prototype in order to increase its lift, so as to take off.; L’objectif de cette thèse est de revoir la conception du prototype actuel pour accroître sa portance, dans l’idée de procéder au décollage du nano drone.

International audience; This communication aims to present a cross-perspective – robotics, industrial engineering, sociology and ergonomics – research project experience dealing with development of collaborative robotics in SMEs. Our conviction is that Industry 4.0 must imply: (1) “departitioning” of disciplines involved in the design of work situations and (2) construction of hybrid approaches for understanding and transforming work. In this communication, we propose to relate such an experience on the basis of a research project - funded by the French National Agency for Research (ANR), and focused on transformation of French Small and Middle Companies (SMC’s) in relation to introduction of Collaborative Robotics. Collaborative Robotics is of particular interest for us as it embeds promises and pitfalls of articulation between technologies and work. However, these promises may be discussed and tempered by confronting them to actual design issues, work organization and transformation of work management.

International audience; This communication discusses the resulting changes in the field of design project management generated by the industry of the future and its promises, with a special focus on collaborative robotics. Among the guiding issues of this work, we will focus on the importance of including such an intention to cobotize some or all of the tasks initially assigned to human operators, during the strategic stakes of the design process and to instruct and support it by the potential contributions of a bottum up approach centered on the real activities, mobilized and deployed during the realization of the tasks which are objects of cobotization. This discussion is based on an industrial case study, aimed at assisting a finishing workstation (the last stage of a production process) for fragile mechanical parts used in the manufacture of metal parts for the aeronautics sector.

International audience; Truss lattice structures are intricate geometries, whose fabrication has recently been simplified by the development of Additive Manufacturing (AM) technologies. These lightweight geometries present great volume densities and surface-to-occupancy ratios, which makes them ideal for thermal dissipation applications. This paper introduces a new framework for the parametric design of graded truss lattice structures that maximize passive cooling. It exploits the results of a semi-analytic formulation and analysis of the volume density and surface-to-occupancy ratio of state-of-the-art unit cells. In particular, it comes out that any truss lattice structure presents an optimal beam diameter over unit cell size ratio that maximizes its surface-to-occupancy value. This value and the ratio for which it is reached are identified and compared for the most common unit cells. The unit cell with the maximal surface-to-occupancy ratio is then identified, along with its set of optimal parameters, taking into account additive manufacturing constraints. The validation of this optimal geometry is performed by populating pre-defined design spaces of both academic and industrial case studies. An orientation strategy and a parametric gradation approach are also proposed to further optimize the generated heat sinks and maximize passive cooling. These results are very helpful to support decision making during the parametric design of a heat sink and to identify, a priori, the optimal unit cell, its control parameters, its orientation and its gradation strategy. The generated geometries are compared with traditional heat sink structures through static heat dissipation simulations, in order to demonstrate their interest.

International audience; Currently, the content-based retrieval is a problem of major interest in several different fields and, focusing on mechanical engineering, many approaches exist to compare and retrieve single CAD parts, to evaluate shape similarity, to extract features and to segment models. However, most of the proposed approaches do not take into account all the key characteristics of an assembly model, such as the relationships between its components, and the different levels according to which two assembly models can be considered similar, i.e. either globally, partially, or locally. For these reasons, the retrieval of CAD assembly models still faces challenges to fully satisfy designers’ expectations. The aim of this paper is to review the state-of-the-art of works addressing the CAD assembly model retrieval and to identify future challenges and possible research directions. Firstly, the paper highlights the user requirements for CAD assembly model retrieval and proposes a set of criteria for analyzing the available methods grouped into the following macro-categories: objective, assembly characterization, assembly descriptor, query specification and type of similarity. Secondly, it describes and characterizes the available methods by organizing them according to the adopted criteria. Finally, it discusses the open issues and future challenges.

International audience; This paper introduces a new approach for the generation of as-scanned point clouds of CAD assembly models. The resulting point clouds incorporate various realistic artifacts that would appear if the corresponding real objects were digitalized with a laser scanner. Such a virtual Reverse Engineering technique can produce a huge amount of realistic point clouds much faster than using classical time-consuming Reverse Engineering techniques on real physical objects. Here, there is no need to use a laser scanner and the post-processing steps are automatic. Using this technique, it is easy to create large databases of point clouds automatically segmented and labeled from the CAD models and which can be used for supervised machine learning. The proposed approach starts by generating a triangle mesh wrapping the CAD assembly model to be reverse engineered. The resulting watertight mesh is then sampled to obtain a more realistic distribution of points. The occlusion phenomenon is then simulated using a hidden point removal algorithm launched from several viewpoints. A misalignment procedure can optionally be used to simulate the fact that in real-life Reverse Engineering the position and orientation of the laser scanner and/or real object would have been changed to get a different scanning viewpoint. The virtual Reverse Engineering process ends by generating noise and by inserting outliers. The approach is illustrated and validated on several industrial examples.

International audience; Tuned dynamic absorbers are usually used to counteract vibrations at a given frequency. Presence of non-linearities causes energy-dependent relationship of their resonance and antiresonance frequencies at large amplitude of motion, which consequently leads to adetuning of the absorber from the targeted frequency. This paper presents a procedure to track an extremum point (minimum or maximum) of nonlinear frequency responses, based on a numerical continuation technique coupled to the harmonic balance method to follow periodic solutions in forced steady-state. It thus enable to track a particularantiresonance. The procedure is tested and applied on some application cases to highlight the resonance and antiresonance behavior in presence of geometrically non-linear and/or inertial interactions.

International audience; The problem of minimum distance calculation between line-segments/capsules, in 3D space, is an important subject in many engineering applications, spanning CAD design, computer graphics, simulation, and robotics. In the latter, the human robot minimum distance is the main input for collision avoidance/detection algorithms to measure collision imminence. Capsules can be used to represent humans and objects, including robots, in a given dynamic environment. In this scenario, it is important to calculate the minimum distance between capsules ef ciently, especially for scenes (situations) that include a high number of capsules. This paper investigates the utilization of QR factorization for performing ef cient minimum distance calculation between capsules. The problem is reformulated as a bounded variable optimization in which an af ne transformation, deduced from QR factorization, is applied on the region of feasible solutions. A geometrical approach is proposed to calculate the solution, which is achieved by computing the point closest to the origin from the transferred region of feasible solutions. This paper is concluded with numerical tests, showing that the proposed method compares favorably with the most ef cient method reported in theliterature.

Technological advances, promoted by the Industry 4.0 paradigm, attempt to support the reconfigurability of manufacturing systems and to contribute to adaptive operational conditions. These systems must be responsive to significant changes in demand volume and product mix. In this paper, a hybrid optimisation approach is suggested to solve sequencing and assignment problems of reconfigurable assembly lines, where mobile robots collaborate with human operators. The objectives are: i) to define a schedule of jobs, ii) to assign tasks to the mobile robots, and iii) to decide the allocation of robots to workstations, in order to minimise the number of robots required. Preliminary results show that the proposed methodology can make an efficient robot allocation under high demand variety. In addition to that, the hybrid optimisation approach can be adapted to other configurations of assembly systems, which demonstrates its applicability to solve problems in other contexts.