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Flax fibre bundle: A remarkable multi-scale unidirectional composite material
No full textInternational audienceFlax fibre bundles possess a remarkable structure, mainly generated through intrusive growth, that can be likened to a unidirectional composite reinforced with discontinuous fibres, resulting in complex mechanical behaviour. The main objectives of the present work are to provide a detailed description of the microstructure and local mechanical properties of the bundle components to better explain their specific mechanical behaviour. Their tensile behaviour was examined using tensile testing and scanning electron microscopy, revealing disparities in the fracture phenomena. Micro-tomographic and multi-photon microscopy images revealed the presence of fibre ends (tips) with a high fraction of crystalline and oriented cellulose. Additional tests were conducted using atomic force microscopy to estimate the thickness and indentation modulus of the middle lamellae, the primary cell wall as well as the S1 and S2 layers. These observations elucidate the origin of the remarkable multi-scale structure of the flax bundles.</div
Feedback Equivalence and Time Minimal Geodesics for Controlled Euler Equation with a Single Actuator and Attitude Control
No full textIn this article we study the attitude transfer of a rigid spacecraft controlled by a single torque using time minimal control. The geodesics are parametrized by Pontryagin's maximum principle. We concentrate mainly our study to analyze the geodesics of the angular speed dynamics which are classified depending upon the position of the torque on the satellite. The important role in the study is related to the so-called abnormal geodesics which are branches of a ternary cubic which is analyzed in details in the frame of a real classification of cubic using symbolic and numerical computations. It is applied to describe attitude control techniques based on the construction of mechanical gates which in the future will be tested on low cost CubeSat. They can be interpreted as perturbations of the periodic or quasi-periodic solutions of the Euler-Poinsot (uncontrolled) dynamics in relation with KAM theory
Le changement climatique en Bretagne, Bulletin 2025 du HCBC: L’agriculture bretonne face au changement climatique
No full textBulletin du Haut Conseil Breton pour le Clima
ADAPTIVE SYNERGETIC AND LONG-RANGE COMMUNICATION LORA FOR QUADROTOR CONTROL AND INDOOR LOCALIZATION VIA INTERVAL ANALYSIS
No full textInternational audienceIn this article, a new approach based on the use of received signal strength indication (RSSI) combined with long-range (LoRa) communication technology has been developed to locate a drone. Additionally, an interval analysis was introduced to enhance localization accuracy and system reliability. This approach involves taking into account several RSSI measurements over defined time intervals. The quadrotor is controlled by an adaptive control system based on the passivity of the system’s ASC. By combining RSSI with LoRa technology, interval analysis, and passivity-based ASC control, our approach offers a robust and efficient solution for UAV control and localization. This methodology could be applied in a multitude of real-life scenarios, offering significant benefits in terms of safety, operational efficiency, and overall performance of UAV system
Revolutionizing Battery Safety: Real-Time Insights with Dynamic Electrochemical Impedance Spectroscopy
No full textInternational audienceIn-situ diagnosis represents an urgent need for long-term battery safety and optimized performance. Dynamic electrochemical impedance spectroscopy (DEIS) enables in situ frequency response analysis during battery operations, offering critical insights into evolving electrochemical behaviors and emerging failure mechanisms. DEIS links fundamental electrochemical science and dynamic battery performance by elucidating kinetic pathways across time scales. Furthermore, it enables the precise characterization of analytical dynamics and addresses real-world complexities such as nonequilibrium processes and coupled electrochemical-thermal interactions. Moreover, DEIS provides a deeper understanding of battery aging and failure mechanisms that drive advancements in material innovation and operational optimization. This perspective focuses on the potential of DEIS in battery research, offering real-time insights into the intricate interplay of electrochemical processes and enabling safer and high-performing battery systems
Deep Learning-Based Recognition and Classification of Soiled Photovoltaic Modules Using HALCON Software for Solar Cleaning Robots
No full textInternational audienceThe global installation capacity of solar photovoltaic (PV) systems is exponentially increasing. However, the accumulation of soil and debris on solar panels significantly reduces their efficiency, necessitating frequent cleaning to maintain optimal energy output. This study presents a deep learning-based approach for the recognition and classification of soiled PV images, aimed at enhancing the capabilities of solar cleaning robots through the HALCON software framework. Using EANN and CNN architecture along with advanced image processing techniques, the proposed system achieves precise detection and classification of soiling patterns. The HALCON framework facilitates image acquisition, preprocessing, segmentation, and deployment of trained models for robotic control. The trained models demonstrate exceptional accuracy, with the EANN and CNN achieving classification precision of 99.87% and 99.91%, respectively. Experimental results highlight the system’s potential to improve automation of cleaning strategies, reduce unnecessary cleaning cycles, and enhance the overall performance of solar panels. This research underscores the transformative role of intelligent visual analysis in optimizing maintenance practices for renewable energy applications
Exact solution for longitudinal vibration of elastically constrained biperiodic rod
No full textInternational audienceAbstract This article is focused on the exact determination of the eigenfrequencies of an elastically constrained biperiodic elastic rod. The rod is composed of biperiodic cells of stepped continuous rod elements. The axial displacement solution in each cell can be expressed from the resolution of a second‐order differential equation. After expressing the continuity conditions between each cell (displacement and normal force continuity), it is possible to relate the solution of each cell concerning its neighbors. The differential eigenvalue problem of the continuous biperiodic rod is converted into a linear difference eigenvalue problem associated with the coefficients of the expressed solution in each cell. A transcendental equation for the natural frequency of the elastically restrained continuous biperiodic rod is obtained from the resolution of the discrete linear difference eigenvalue problem. This transcendental equation is valid regardless of the number N of biperiodic cells, with N more prominent than 2. This general expression is validated by the natural frequency values obtained using a direct method for a few cells. This transcendental equation generalizes the results available in the literature for a free‐free biperiodic rod or a fixed‐fixed biperiodic rod. The eigenfrequencies of the biperiodic rod are compared to those of a homogenized rod, also in the presence of elastic restraints. The validity of the finite homogenized rod theory is confirmed when the number of cells is sufficient, even in the presence of elastic restraints
