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Contrôle in situ et modélisation du procédé de moulage de composites liquides – Suivi non-intrusif du degré de polymérisation
No full textInternational audienceContrôle in situ et modélisation du procédé de moulage de composites liquides – Suivi non-intrusif du degré de polymérisatio
Caractérisation au choc de composites : endommagement et effet de la géométrie
No full textInternational audienceCaractérisation au choc de composites : endommagement et effet de la géométri
Friction identification in suspended cable-driven robots using current-controlled actuation and force sensing
No full textInternational audienceThis paper presents an experimental framework for identifying friction parameters in cable-actuated systems representative of suspended Cable-Driven Parallel Robots (CD-PRs). The proposed method combines current-controlled actuation with dual force sensing-using both a dynamic load cell and a static strain gauge-to estimate motor inertia, viscous friction, static friction, and suspended mass. A linear dynamic model is identified via regression from time-resolved current and velocity data. Experimental validation under quasi-static and dynamic conditions demonstrates repeatability, with mass estimates accurate to within 1% of ground truth. Observations reveal tension asymmetries and hysteresis effects induced by friction, which explain the residual platform sway often observed under conventional position control. These findings underscore the need for friction-aware modeling and real-time tension feedback in control strategies. The proposed identification approach provides a scalable method for characterizing frictional dynamics in underactuated or suspended CDPR configurations
Stochastic programming for the design and configuration planning of reconfigurable assembly lines under demand uncertainty
No full textInternational audienceReconfigurable assembly lines are designed to deal with the production requirements of all variants of a product family. These lines are generally composed of serial workstations, each made up of a set of resources performing the same set of tasks. Such a structure can be dynamically adjusted to respond to changes in demand volume by modifying the allocation of tasks or resources across workstations. Since reallocating tasks can be costly and operationally complex, reallocating resources is often preferred. In this work, we consider a set of configurations that share the same assignment of tasks but differ by the number of resources assigned to the workstations. Different demand scenarios are examined, in which the volume of demand varies at each period, and it is necessary to plan configurations for each period to meet demand. The performance of this strategy highly depends on the initial assignment of tasks. To address this challenge, we propose an integrated approach that combines task assignment optimization with configuration planning. A stochastic integer linear programming model is developed, minimizing the expected number of resources used. Preliminary experimental results show that, as the number of periods and scenarios increases, solving the model with a commercial solver becomes computationally expensive. Thus, a simulated annealing algorithm is proposed to efficiently handle large-size instances. Numerical experiments are conducted to evaluate both the proposed model and the metaheuristic. The findings will be presented during the conference
Hea thin films as protective barrier against carbon diffusion during sps
No full textInternational audienceThe production of metal parts by powder metallurgy using the Spark Plasma Sintering (SPS) process, results in a fine and homogeneous microstructure with a chemical composition close to that of the initial powder. In this process, the sintering is performed by the simultaneous application of a pulsed current, making it possible to heat the powder, and of a uniaxial pressure
Passive neck stiffness and range of motion for males and females from early to late adulthood
No full textInternational audienceMETHODS : Eighty participants aged 20 to 79 years (nearly even distribution), who self-reported no history of significant health conditions and with no neck pain, were recruited. Two custom apparatus were used to support participants in relaxed lying. Their head was rotated to maximum ROM; applied moment and head-torso motion were recorded. Muscle activation was monitored in real-time to ensure electromyographic signals from agonist muscles remained below a passive threshold. Stiffness was determined from the moment-angle data within each of three zones, with zone boundaries delineated to maximize moment-angle linearity within each zone. The age and sex effects on passive stiffness and ROM were assessed using generalized linear models for flexion and extension, and linear mixed models for lateral bending and axial rotation.RESULTS : Passive neck ROM decreased by 0.2° per year of age in lateral bending and axial rotation for males and females, and extension ROM for males was 5.8° lower than for females. Passive stiffness in lateral bending (zone 1 and 2: 0.9 and 3.5 Nmm/°/year; zone 3: 3%), axial rotation (zone 1 and 2: 1%; zone 3 for males and females: 1.9 and 0.9 Nmm/°/year) and some zones in extension (zone 2: 0.8 Nmm/°/year; males in zone 3: 2.7 Nmm/°/year) increased with age, and males had higher stiffness than females in lateral bending (zone 1 and 2: 22.3 and 43.9 Nmm/°; zone 3: 35%) and axial rotation (zone 1 and 2: 49% and 35%).CONCLUSIONS: Passive neck ROM decreased with age in lateral bending and axial rotation, while passive neck stiffness tended to increase with age in all motions but flexion. Extension ROM was higher for females, and lateral bending and axial rotation stiffness at lower angles were higher for males.CLINICAL SIGNIFICANCE: The neck ROM, stiffness, and moment-angle corridors developed in this study provide benchmarks for clinical assessment of cervical spine function, and can assist the development of surrogate and computational models incorporating minimal muscle activation, for injury simulation and clinical skill training
Development and performance evaluation of real-time geometric error compensation through position feedback modification in 5-axis machining
No full textInternational audienceGeometric errors in amachine tool structure are mainly responsible for the volumetric error in theworkspace. They occur at the attachment of each link between axis joints, but also along each axis in their joint frame. Reducing the impact of these errors is a key factor in guaranteeing the functional requirements of high value-added parts. Unlike mechanical correction, software compensation strategies are often chosen for their ease of implementation and versatile nature. In this study, a correction method by modifying the position measurement in real time is introduced and compared to compensation tables. The reaction response of the numerical controller (NC) to the modification of its position feedback is studied, and a 5-axis machining experiment to validate the proposed solution is performed. The principle of the experiment is to impose a virtual volumetric error in the workspace by modifying a machining program, then to test separately the ability of compensation tables and the proposed method to correct the chosen virtual geometric errors. The aim is to obtain a corrected workpiece similar to the one machined with a nominal program. In this way, it is not necessary to identify the geometric errors of the machine’s structure to test the performance of software compensationmethods. The machined workpieces feature geometries that are easy to control, but the tool paths generated to produce them were complex enough to challenge the compensation methods. The ability of the proposed solution to correct the virtual volumetric error introduced by a modified machining program is evaluated at 98%. Indeed, roundness measurements show that over 99% of the added error has been corrected, with residuals lower than 5 μm. Furthermore, the joint trajectories monitored during machining are studied through a contouring error estimation. Nominal and compensated trajectories are 98% similar with the proposed solution, compared with 35% for compensation tables
Environment Spatial Restitution for Remote Physical AR Collaboration
No full textInternational audienceThe emergence of spatial immersive technologies allows new ways to collaborate remotely. However, they still need to be studied and enhanced in order to improve their effectiveness and usability for collaborators. Remote Physical Collaborative Extended Reality (RPC-XR) consists in solving augmented physical tasks with the help of remote collaborators. This paper presents our RPC-AR system and a user study evaluating this system during a network hardware assembly task. Our system offers verbal and non-verbal interpersonal communication functionalities. Users embody avatars and interact with their remote collaborators thanks to hand, head and eye tracking, and voice. Our system also captures an environment spatially, in real-time and renders it in a shared virtual space. We designed it to be lightweight and to avoid instrumenting collaborative environments and preliminary steps. It performs capture, transmission and remote rendering of real environments in less than 250ms. We ran a cascading user study to compare our system with a commercial 2D video collaborative application. We measured mutual awareness, task load, usability and task performance. We present an adapted Uncanny Valley questionnaire to compare the perception of remote environments between systems. We found that our application resulted in better empathy between collaborators, a higher cognitive load and a lower level of usability, remaining acceptable, to the remote user. We did not observe any significant difference in performance. These results are encouraging, as participants' observations provide insights to further improve the performance and usability of RPC-AR
Evaluating Noise Emissions of Endourological Lasers: A Comparative Analysis of Ho:YAG, Tm:YAG, and Thulium Fiber Laser Systems
No full textInternational audienceObjective:To evaluate the noise levels of Holmium:YAG (Ho:YAG), Thulium Fiber (TFL), and pulsed Thulium:YAG (p-Tm:YAG) lasers across various settings, focusing on compliance with safety thresholds and potential impact on communication in the operating room (OR).Materials and Methods: Noise measurements were taken in an empty OR using sound meters placed 1 m from the laser source. Ambient noise, standby, ready, and lasering modes at three settings (0.2 J-50 Hz, 0.5 J-20 Hz, and 1 J-10 Hz) were measured. Background noise was adjusted logarithmically, and sound emissions were weighted on dBA. Eleven laser models across Ho:YAG, TFL, and p-Tm:YAG systems were analyzed using descriptive and inferential statistics.Results: Noise levels varied significantly by system and setting. All lasers produced <55dBA during standby/ready modes. During lasering, the Rocamed MH01 (Ho:YAG), RevoLix (Tm:YAG), and IPG Urolase PRO (TFL) were the quietest. The Quanta Cyber Magneto (Ho:YAG), Dornier Thulio (Tm:YAG), and EMS Laserclast (TFL) reached the highest noise levels, up to 66.06dBA. All lasers complied with NIOSH (85dBA) and OSHA (90dBA) limits, though several exceeded the 55dBA threshold for high-concentration tasks.Conclusion: Endourological lasers produce <55dBA in standby/ready modes but may exceed this during lasering, potentially impacting communication and focus in the OR. While occupational noise risks are minimal, attention to noise emissions is crucial for optimizing surgical team performance. Future studies should explore noise impact on surgical outcomes