Buffer-aware Worst Case Timing Analysis of Wormhole Network On Chip

A buffer-aware worst-case timing analysis of wormhole NoC is proposed in this paper to integrate the impact of buffer size on the different dependencies relationship between flows, i.e. direct and indirect blocking flows, and consequently the timing performance. First, more accurate definitions of direct and indirect blocking flows sets have been introduced to take into account the buffer size impact. Then, the modeling and worst-case timing analysis of wormhole NoC have been detailed, based on Network Calculus formalism and the newly defined blocking flows sets. This introduced approach has been illustrated in the case of a realistic NoC case study to show the trade off between latency and buffer size. The comparative analysis of our proposed Buffer-aware timing analysis with conventional approaches is conducted and noticeable enhancements in terms of maximum latency have been proved

Experimental and numerical study of laser-assisted machining of Ti6Al4V titanium alloy

Laser-assisted machining combines several experimental parameters such as cutting speed, feed rate, depth of cut, laser power and distance between tool rake face and the laser beam axis. The optimization of these parameters is necessary to ensure the efficiency of assistance and to increase productivity. This paper focuses on the understanding of the physical phenomena during laser-assisted machining, and on optimising this process. This contribution is based on an experimental and a numerical study. The experimentalpart highlights the effects of the laser power as well as the distance between the tool rake face and the axis of the laser beam. As for the numerical part, it was performed on the ABAQUS/Explicit software. The proposed model improves the understanding of the physical phenomena of chip formation and the cutting force reduction when machining with laser assistance. In addition, this model allows a better optimization of laser and cutting parameters.Numerical findings generally corroborate experimental results and can lead to some other information difficult to catch experimentally. The main contention in the paper is that the distance between the axis of the laser beam and the tool rake face is the most important parameter that controls the reduction of the cutting force. This cutting force reduction can exceed 50%

Analyse expérimentale et modélisation du transfert de matière et du mélange dans une couche cisaillée à bulles. Démarche pour l'optimisation des réacteurs diphasiques en traitement de l'eau

Ce travail vise l'amélioration des modèles eulériens à deux fluides pour l'hydrodynamique et le transfert de masse en écoulement turbulent à bulles. Nous étudions des zones de mélange oxygène-eau pour des taux de vide 2/infini/11%. Un gradient de taux de vide imposé en entrée génère des mouvements à grande échelle. La vitesse relative des bulles induit de profondes modifications de la turbulence aux petites échelles. On étudie donc des écoulements fortement contrôlés par la gravité. Nous avons fait des mesures locales caractérisant l'hydrodynamique et le champ d'oxygène dissous. Un travail de simulation numérique a consisté à améliorer les modèles d'échange interfacial de masse, de quantité de mouvement, et à prendre en compte la modulation de la turbulence qui modifie le transport turbulent. Les résultats obtenus avec le code Melodif montrent, qu'à condition de modéliser la modification des échelles par les interactions interfaciales, un bon accord avec les expériences est obtenu

Analyse et optimisation des réseaux avioniques hétérogènes

La complexité des architectures de communication avioniques ne cesse de croître avec l’augmentation du nombre des terminaux interconnectés et l’expansion de la quantité des données échangées. Afin de répondre aux besoins émergents en terme de bande passante, latence et modularité, l’architecture de communication avionique actuelle consiste à utiliser le réseau AFDX (Avionics Full DupleX Switched Ethernet) pour connecter les calculateurs et utiliser des bus d’entrée/sortie (par exemple le bus CAN (Controller Area Network)) pour connecter les capteurs et les actionneurs. Les réseaux ainsi formés sont connectés en utilisant des équipements d’interconnexion spécifiques, appelés RDC (Remote Data Concentrators) et standardisé sous la norme ARINC655. Les RDCs sont des passerelles de communication modulaires qui sont reparties dans l’avion afin de gérer l’hétérogénéité entre le réseau cœur AFDX et les bus d’entrée/sortie. Certes, les RDCs permettent d’améliorer la modularité du système avionique et de réduire le coût de sa maintenance; mais, ces équipements sont devenus un des défis majeurs durant la conception de l’architecture avionique afin de garantir les performances requises du système. Les implémentations existantes du RDC effectuent souvent une translation direct des trames et n’implémentent aucun mécanisme de gestion de ressources. Or, une utilisation efficace des ressources est un besoin important dans le contexte avionique afin de faciliter l’évolution du système et l’ajout de nouvelles fonctions. Ainsi, l’objectif de cette thèse est la conception et la validation d’un RDC optimisé implémentant des mécanismes de gestion des ressources afin d’améliorer les performances de l’architecture de communication avionique tout en respectant les contraintes temporelles du système. Afin d’atteindre cet objectif, un RDC pour les architectures réseaux de type CAN-AFDX est conçu, intégrant les fonctions suivantes: (i) groupement des trames appliqué aux flux montants, i.e., flux générés par les capteurs et destinés à l’AFDX, pour minimiser le coût des communication sur l’AFDX; (ii) la régulation des flux descendants, i.e., flux générés par des terminaux AFDX et destinés aux actionneurs, pour réduire les contentions sur le bus CAN. Par ailleurs, notre RDC permet de connecter plusieurs bus CAN à la fois tout en garantissant une isolation entre les flux. Par la suite, afin d’analyser l’impact de ce nouveau RDC sur les performances du système avionique, nous procédons à la modélisation de l’architecture CAN-AFDX, et particulièrement le RDC et ses nouvelles fonctions. Ensuite, nous introduisons une méthode d’analyse temporelle pour calculer des bornes maximales sur les délais de bout en bout et vérifier le respect des contraintes temps-réel. Plusieurs configurations du RDC peuvent répondre aux exigences du système avionique tout en offrant des économies de ressources. Nous procédons donc au paramétrage du RDC afin de minimiser la consommation de bande passante sur l’AFDX tout en respectant les contraintes temporelles. Ce problème d’optimisation est considéré comme NP-complet, et l’introduction des heuristiques adéquates s’est avérée nécessaire afin de trouver la meilleure configuration possible du RDC. Enfin, les performances de ce nouveau RDC sont validées à travers une architecture CAN-AFDX réaliste, avec plusieurs bus CAN et des centaines de flux échangés. Différents niveaux d’utilisation des bus CAN ont été considérés et les résultats obtenus ont montré l’efficacité de notre RDC à améliorer la gestion des ressources du système avionique tout en respectant les contraintes temporelles de communication. En particulier, notre RDC offre une réduction de la bande passante AFDX allant jusqu’à 40% en comparaison avec le RDC actuellement utilisé. ABSTRACT : The aim of my thesis is to provide a resources-efficient gateway to connect Input/Output (I/O) CAN buses to a backbone network based on AFDX technology, in modern avionics communication architectures. Currently, the Remote Data Concentrator (RDC) is the main standard for gateways in avionics; and the existing implementations do not integrate any resource management mechanism. To handle these limitations, we design an enhanced CAN-AFDX RDC integrating new functions: (i) Frame Packing (FP) allowing to reduce communication overheads with reference to the currently used "1 to 1" frame conversion strategy; (ii) Hierarchical Traffic Shaping (HTS) to reduce contention on the CAN bus. Furthermore, our proposed RDC allows the connection of multiple I/O CAN buses to AFDX while guaranteeing isolation between different criticality levels, using a software partitioning mechanism. To analyze the performance guarantees offered by our proposed RDC, we considered two metrics: the end-to-end latency and the induced AFDX bandwidth consumption. Furthermore, an optimization process was proposed to achieve an optimal configuration of our proposed RDC, i.e., minimizing the bandwidth utilization while meeting the real-time constraints of communication. Finally, the capacity of our proposed RDC to meet the emerging avionics requirements has been validated through a realistic avionics case study

Gateway optimization for an heterogeneous avionics network AFDX-CAN

The gateway impact on the end to end system performances is a major challenge in the design process of heterogeneous embedded systems. In this paper, this problem is tackled for a specific avionics network AFDX with CAN to identify the main interconnection issues. The results herein show the possible enhancements of the system performances thanks to an optimized gateway based on a frames pooling strategy, compared to a basic gateway

Interconnection optimization for multi-cluster avionics networks

National audienceThe increasing complexity and heterogeneity of avionics networks make resource optimization a challenging task. In contrast to many previous approaches pursuing the optimization of traffic-source mapping and backbone network analysis, our work presented herein mainly focuses on the optimization of interconnection devices for multi-cluster avionics networks. In this paper, we introduce an optimized interconnection device, integrating novel frame packing strategies and schedulability analysis to enhance the communications between an AFDX-like backbone network and various peripheral sensor/actuator networks in terms of resource savings. The performance analysis conducted on a representative avionics communication architecture highlights the efficiency of our proposal to save resources particularly consumed bandwidth. These latter is considered as an important feature for avionics applications to guarantee easy incremental design during the long lifetime of an aircraft

Analysis and optimiozation of heterogeneous avionics networks

The aim of my thesis is to provide a resources-efficient gateway to connect Input/Output (I/O) CAN buses to a backbone network based on AFDX technology, in modern avionics communication architectures. Currently, the Remote Data Concentrator (RDC) is the main standard for gateways in avionics; and the existing implementations do not integrate any resource management mechanism. To handle these limitations, we design an enhanced CAN-AFDX RDC integrating new functions: (i) Frame Packing (FP) allowing to reduce communication overheads with reference to the currently used "1 to 1" frame conversion strategy; (ii) Hierarchical Traffic Shaping (HTS) to reduce contention on the CAN bus. Furthermore, our proposed RDC allows the connection of multiple I/O CAN buses to AFDX while guaranteeing isolation between different criticality levels, using a software partitioning mechanism. To analyze the performance guarantees offered by our proposed RDC, we considered two metrics: the end-to-end latency and the induced AFDX bandwidth consumption. Furthermore, an optimization process was proposed to achieve an optimal configuration of our proposed RDC, i.e., minimizing the bandwidth utilization while meeting the real-time constraints of communication. Finally, the capacity of our proposed RDC to meet the emerging avionics requirements has been validated through a realistic avionics case study

Hierarchical Traffic Shaping and Frame Packing to Reduce Bandwidth Utilization in the AFDX

The increasing complexity and heterogeneity of avionic networks make resource savings a challenging task to guarantee easy incremental design during the long lifetime of an aircraft. In this paper, we focus on the optimization of interconnection devices for multi-cluster avionic networks, called Remote Data Concentrators (RDC), and especially for the CAN-AFDX network. The design of this optimized RDC device consists in implementing frame packing strategies to manage upstream (sensors) flows to improve bandwidth utilization in the AFDX; and Hierarchical Traffic Shaping (HTS) algorithm to control downstream (actuators) flows to guarantee bandwidth isolation on CAN. Schedulability analysis integrating the effects of these new mechanisms is detailed and validated. Furthermore, a heuristic approach to tune the Hierarchical Traffic Shaping parameters within the RDC device is proposed to reduce as much as possible bandwidth utilization in the AFDX, while ensuring flows schedulability. The performance analysis conducted on a realistic avionic case study proves the efficiency of the optimized RDC device to reduce bandwidth utilization in the AFDX, compared to the basic device currently implemented in avionics

Comparative Study of Different Active Control Systems of High Rise Buildings under Seismic Excitation

Large number of active vibration control systems existing in the literature has brought lot of confusion for engineers and junior researchers. This study deals with the comparison of different active control systems of a 20-storey building under seismic excitation for three control devices: Active Mass Damper (AMD), Active Bracing System (ABS) and Connected Building Control (CBC). Two different control configurations are considered to add active damping to the building. The first one employs force actuator and displacement sensor and is examined with first and second order Positive Position Feedback, Lead compensators and Direct Velocity Feedback. The second configuration employs a displacement actuator collocated with a force sensor and an Integral Force Feedback control law. A total number of 15 control cases are compared from the point of view of stability, robustness, performance and control effort

MHD natural convection nanofluid flow in a heat exchanger: effects of brownian motion and thermophoresis for nanoparticles distribution

The free convection of Cu-water nanofluid is simulated and investigated inside a square heat exchanger chamber in the presence of MHD magnetic field. The Buongiorno model with the effects of Brownian and thermophoresis motion is considered to nanoparticles distribution inside the chamber. The geometry consists of a square chamber with two cylinders on the right and left sides as heater and cooler in order to create the buoyancy force, respectively. These cylinders represent hot and cold pipes, and the walls of the chamber are heat and mass insulation. the FVM with SIMPLE algorithm are used for velocity and pressure coupling. In current two-phase simulation, the effects of Rayleigh number, Hartmann number, inclination angle of chamber and volume fraction on streamline contours, isothermal lines, Lorentz force lines, nanoparticle distribution and Nusselt number are investigated. By modeling the motion of nanoparticles and evaluating it, a nanoparticle transport zone was observed. The diffusion effects of thermophoresis were significant in this zone. The nanoparticles were thrown from the hot cylinder to the cold cylinder. The application of a magnetic field enlarged the nanoparticle transport zone. However, increasing the Rayleigh number and decreasing the inclination angle of the enclosure caused the nanoparticles to disperse evenly