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Contrôle du châssis pour la technologie de conduite autonome
No full textThis dissertation explores the development of an advanced control strategies for the intelligent chassis control system design, which acts as the nexus between driver/ADAS/autopilot and physical chassis components. It aims to create a comprehensive framework for designing and integrating global chassis control strategies, ensuring optimal vehicle performance across various driving scenarios. Emphasis is placed on generating and distributing a global yaw moment control signal among a redundant set of actuators for enhanced path tracking, stability, and lateral guidance. Key aspects addressed include torque vectoring, traction control system, sideslip angle control logic, and direct yaw control. Leveraging data-driven methods, mathematical modeling, and control systems techniques, this study designs robust, real-time adaptive control algorithms. While vehicle-to-vehicle and vehicle-to-infrastructure communication technologies are acknowledged, they fall outside the scope of this investigation. Simulation studies and real-world experiments validate the efficacy of developed algorithms, based on performance metrics such as control error, estimation error, maximum error, and root mean square error. The study contributes a new modular and scalable Smart Vehicle Motion Control architecture, a robust virtual sensing algorithm for vehicle sideslip angle reconstruction, and the concept of all-wheel speed balance control.Ce mémoire examine le développement de stratégies de commande avancées pour la conception d'un système de commande de châssis intelligent, qui sert de lien our encore d’interface entre le conducteur/les ADAS/le pilote automatique et les composants du châssis. Il vise à créer un cadre complet pour la conception et l'intégration de stratégies globales de commande du châssis, garantissant des performances optimales du véhicule dans divers scénarios de conduite. Un accent particulier est mis sur la génération et la distribution d'un signal de commande du moment de lacet global parmi un ensemble redondant d'actionneurs pour améliorer le suivi de la trajectoire, la stabilité et les performance guidage latéral. Les principaux aspects abordés sont la vectorisation du couple, le système de contrôle de la traction, la logique de contrôle de l'angle de dérive et le contrôle direct du lacet. En s'appuyant sur des méthodes basées sur les données, la modélisation mathématique et des techniques de commande des systèmes complexes, cette étude conçoit des algorithmes de commande adaptatifs robustes et en temps réel. Des études en simulation et des essais en conditions réelles valident l'efficacité des algorithmes développés, sur la base de mesures de performance telles que l'erreur de poursuite des consignes, l'erreur d'estimation, l'erreur maximale et l'erreur quadratique moyenne.L'étude contribue à une nouvelle architecture modulaire et évolutive de commande du mouvement des véhicules, un algorithme robuste d’estimation virtuelle pour la reconstruction de l'angle de dérive du véhicule, et le concept de contrôle de l’écart glissement inter-essieux ou des roues d’un même essieu
Inversion of Eddy-Current Signals Using a Level-Set Method and Block Krylov Solvers
No full textInternational audienceThe application motivating this work is related to the identification of deposits inside nuclear power plant steam generators using eddy-current probes. We consider a realistic experimental process that relies on the scan of a domain by sweeping along a tube axis a probe made out of coils, playing the role of the sources/receivers. Solving the inverse shape problem associated with these measurements using a least squares method requires solutions to the eddy-current and the adjoint problems for a large number of right-hand sides at each gradient-descent iteration. Additional cost in the forward solver comes from the use of a potential formulation of the problem that has the advantage of being independent from the topology of the conductive media (that may vary during iterations). We use a level-set approach to avoid remeshing and handle unknown topologies. The crucial ingredient in our algorithm is an optimized way of handling high numbers of right-hand sides for iterative solvers of large-scale problems. We first benchmark various block Krylov methods, block GMRES and block BGCRODR, to test their effectiveness compared to their standard counterpart, i.e., GMRES and GCRODR. Then, we propose for BGCRODR a new implementation for recycling information from previously generated Krylov bases that scales better than traditional approaches. This part is independent from the practical inverse problem at hand. The efficiency of the overall inversion procedure is finally demonstrated on realistic synthetic 3D examples
McKean SDEs with singular coefficients
No full textInternational audienceThe paper investigates existence and uniqueness for a stochastic differential equation (SDE) with distributional drift depending on the law density of the solution. Those equations are known as McKean SDEs. The McKean SDE is interpreted in the sense of a suitable singular martingale problem. A key tool used in the investigation is the study of the corresponding Fokker-Planck equation
A multi-scale experimental investigation for fatigue limit and fatigue crack initiation behavior of powder bed fusion-laser beam 316L stainless steel
No full textInternational audienc
Experimental and numerical investigations of a soft projectile impact three-point bending (SPITPB) test for adhesion assessment under dynamic loading
No full textInternational audienceThe increasing use of digital twins for design in aerospace industry requires the development of validation tests at an intermediate scale prior to full-scale testing. In this paper, a new experimental set-up called Soft Projectile Impact Three-Point Bending (SPITPB) has been investigated by numerical and experimental methods. SPITPB corresponds to an intermediate-scale test representative of a bird strike test, dedicated to the study of the strength of adhesively bonded assemblies. The experimental set-up is detailed in terms of projectile, specimen and boundaries conditions. Three impact velocities leading to three different levels of damage of the adhesive joint are investigated, from intact to highly damaged specimens. A numerical simulation of the SPITPB is achieved with the commercial code LS-DYNA®. A Smooth Particle Hydrodynamics model is used to describe the projectile, while the specimen is modelled with a finite element approach. The focus is on the structural response of the specimen and the damage of the adhesive joint. Numerical simulation results demonstrate a good correlation with the experimental data in terms of structural displacement, local strain and post-mortem crack length observations. The dynamic behaviour of the adhesive and the failure model are finally validated as a result of this correlation
Better quantifying inter-annotator variability: A step towards citizen science in underwater passive acoustics
No full textInternational audienc
TrustSoC : Architecture SoC hétérogène légère et efficace sécurisée par conception
No full textInternational audienceAu cours des dernières années, les SoC (System-on-a-Chip) hétérogènes embarquant des processeurs à plusieurs coeurs et de la logique programmable ont progressé en terme de complexité et hétérogénéité. D'un point de vue sécurité, cela entraîne une augmentation de la surface d'attaque exploitable par un attaquant pour prendre le contrôle du système et/ou avoir accès à des données sensibles. Pour adresser ce problème, dans cet article, nous proposons les bases d'une architecture de SoC hétérogène de confiance sécurisée par conception appelée TrustSoC. Nous montrons que la sécurité ne doit pas être ajoutée après design, mais plutôt pensée depuis la phase de conception. Nous démontrons aussi que cette sécurité doit considérer tous les composants du SoC : matériels et logiciels. Nous basons notre proposition sur l'extension de la technologie ARM Trust-Zone, des contrôleurs de communication, des règles de fonctionnement et une isolation entre les composants logiciels et matériels et les partitions mémoires
Grounding Large Language Models in Interactive Environments with Online Reinforcement Learning
No full textInternational audienceRecent works successfully leveraged Large Language Models' (LLM) abilities to capture abstract knowledge about world's physics to solve decision-making problems. Yet, the alignment between LLMs' knowledge and the environment can be wrong and limit functional competence due to lack of grounding. In this paper, we study an approach (named GLAM) to achieve this alignment through functional grounding: we consider an agent using an LLM as a policy that is progressively updated as the agent interacts with the environment, leveraging online Reinforcement Learning to improve its performance to solve goals. Using an interactive textual environment designed to study higher-level forms of functional grounding, and a set of spatial and navigation tasks, we study several scientific questions: 1) Can LLMs boost sample efficiency for online learning of various RL tasks? 2) How can it boost different forms of generalization? 3) What is the impact of online learning? We study these questions by functionally grounding several variants (size, architecture) of FLAN-T5
Fatigue of short carbon fiber reinforced PEEK under compression: Influence of the load ratio and predictions from heat buildup measurements
No full textInternational audienceFew works investigate the fatigue of short fiber reinforced thermoplastics under cyclic compression. Furthermore, the heat buildup approach to quickly predict the fatigue lifetime of these materials has not yet been investigated for compression–compression loadings. This paper first describes an experimental protocol to perform well-controlled cyclic compression tests without anti-buckling device that may induced bias. The uniaxiality of the global loading is checked during the test based on kinematic and thermoelastic coupling field measurements. Then, the paper compares the results from fatigue and heat buildup tests performed on polyetheretherketone reinforced with 30 wt% of short carbon fibers for several load ratios. It is shown that the fatigue lifetime is higher in compression than in tension and depends on the compression load ratio. The heat buildup approach appears to be relevant to quickly predict the fatigue lifetime of the material for the different loading ratios studied, including compression–compression
Background, advancement, and applications of in situ structural health monitoring based on different modes of failure detection in composites
No full textInternational audienceVast investigation had been going on for the past few years to overcome the gap that still hinders real-time failure detection of composites in applications such as wind turbines and their components. However, real-time monitoring has been made more applicable with the advancement of smart materials and nanotechnology thus emerging as a possible solution for better in situ monitoring of these materials in their specific application. In addition, there is another important aspect on which structural health monitoring (SHM) can be classified which includes the selection of in situ SHM techniques for specific loading conditions such as vibration loads, compression, bending, etc., and failure behaviors such delamination, reinforcement failure, matrix cracking, etc., that has limited information in the literature. This chapter provides a summary of how the introduction of nanomaterials and the development of nonmaterial approaches have revolutionized real-time SHM technology. Then, an extensive literature review on the specific applications of these advanced in situ SHM techniques to detect and monitor damage in composites under different static/quasi-static/dynamic loading parameters. This is the main objective of this article and will benefit the researchers in the selection of in-situ SHM techniques best suitable for specific damage detection in composite structures. This study is important for better durability, safety, and sustainability of operational structures such as wind turbines