Designing Decentralized controllers for distributed-air-jet MEMS-based micromanipulators by reinforcement learning.

International audienceDistributed-air-jet MEMS-based systems have been proposed to manipulate small parts with high velocities and without any friction problems. The control of such distributed systems is very challenging and usual approaches for contact arrayed system don't produce satisfactory results. In this paper, we investigate reinforcement learning control approaches in order to position and convey an object. Reinforcement learning is a popular approach to find controllers that are tailored exactly to the system without any prior model. We show how to apply reinforcement learning in a decentralized perspective and in order to address the global-local trade-off. The simulation results demonstrate that the reinforcement learning method is a promising way to design control laws for such distributed systems

Triggering, guiding and deviation of long air spark discharges with femtosecond laser filament

International audienceIn the perspective of the laser lightning rod, the ability of femtosecond filaments to trigger and to guide large scale discharges has been studied for several years. The present paper reports recent experimental results showing for the first time that filaments are able not only to trigger and guide but also to divert an electric discharge from its normal path. Laser filaments are also able to divert the spark without contact between laser and electrodes at large distance from the laser. A comparison between negative and positive discharge polarities also reveals important discrepancies in the guiding mechanism

Développement d'une méthodologie de conception matériel à base de modules génériques VHDL/VHDL-AMS en vue d'une intégration de systèmes de commande électriques

Malgré leur flexibilité et leur intérêt économique, les solutions numériques d'implantation de type logiciel ne s'imposent plus aujourd'hui comme les seuls choix de conception de commande de systèmes électriques. En effet, des solutions plus spécifiques de type matériel (PLD, ASIC) semblent mieux répondre aux contraintes technologiques actuelles ou à venir. Toutefois, malgré l'avènement d'outils et de langages CAO performants, ces solutions restent encore trop coûteuses et complexes à mettre en œuvre. L'objectif de cette thèse est d'offrir aux concepteurs de systèmes électriques une approche de description architecturale adaptée aux contraintes d'implantation sur cible matériel. C'est dans ce sens qu'une méthode basée sur les principes de la conception modulaire et d'Adéquation Algorithme Architecture (A3 ou AAA), et sur l'élaboration d'une bibliothèque de modules spécifiques, a pu être développée et appliquée à différents cas de commande. Ainsi, l'architecture de la commande directe du couple d'un moteur asynchrone a pu être établie en suivant cette méthode et son efficacité validée en comparant ses performances d'implantation à des approches plus classiques de conception. Par la suite, le cas d'une commande de vitesse " sans capteurs " d'un moteur à réluctance variable et celui d'un dispositif d'électronique de puissance ont également pu montrer l'efficacité de la méthode proposée. A partir de ce dernier cas de conception, une méthodologie globale du mode de conception modulaire a finalement pu être élaborée en développant une bibliothèque de modèles comportementaux de la commande et du système électrique associé. Ces modèles ont été décrits en langages VHDL et VHDL-AMS de manière à respecter la mixité (numérique et analogique) des éléments qui composent le système électrique. Cette approche permet aussi de prévenir le cas d'une intégration mixte du système, ouvrant par la même de larges perspectives de conception dans ce domaine d'application.Power electronic and electrical drive controllers are generally implemented by microprocessors or Digital Signal Processor (DSP) solutions. Recent progress in hardware solutions such as Very Large Scale Integration (VLSI) applications have improved implementation performances of controllers. However, the main problems of integrated circuit conception are their complexity and a long conception time. In this thesis, the author develops a new architectural approach for the integration of electrical controllers on ASIC and FPGA circuits. He proposes to apply a modular methodology that is based on specific Intellectual Properties (IPs) library. This methodology was confirmed by a large number of applications such as: a direct torque controller for an ac motor, a sensorless speed controller for a switched reluctance motor, and an active shunt filter. Results in terms of integration and control performances show that the adopted modular methodology matches perfectly the requirements of the integration of electrical controller. The same developed approach was used to model a global electrical systems. The obtained model is based on a mixed library of analogue and digital parts described in VHDL and VHDL-AMS language.STRASBOURG-Sc. et Techniques (674822102) / SudocSudocFranceF

Modélisation VHDL/Spectre-HDL et simulation mixte sous Cadence : Conception d’un ASIC de commande de moteur asynchrone

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Impact of sputtered ZnO interfacial layer on the S-curve in conjugated polymer/fullerene based-inverted organic solar cells

The impact of crystalline structure changes of sputtered ZnO interfacial layer on performances of inverted organic solar cells (OSCs) has been investigated. We find that the structural modification of the ZnO cathode interfacial layer, obtained by thermal annealing, plays a crucial role in the origin and solving of the S-curve in conjugated polymer/fullerene photovoltaics. Our results show that the crystallization (i.e. crystallites size) of poly(3hexylthiophene) (P3HT) evolves as a function of that of ZnO according to the annealing temperature. This evolution can directly impact the interfacial orientation and organization of the chains of P3HT at the ZnO buried interface. Such an ordered profile favors the vertical phase segregation and raises the carrier mobility, which explains the disappearance of the S-shape observed in current density-voltage device characteristics for annealing temperatures above 200 degrees C. These results adequately address recent research and provide an important insight into the interfacial layers of inverted OSCs. (C) 2014 Elsevier B.V. All rights reserved

Room temperature ZnO growth by rf magnetron sputtering on top of photoactive P3HT: PCBM for organic solar cells:

In this work, we use rf magnetron sputtering to deposit at room temperature a ZnO thin film on top of a photoactive material based on P3HT:PCBM blend for organic photovoltaic devices. We investigate the influence of the sputtering conditions on the ZnO crystallinity, on the substrate layer nanoscale morphology and on the photovoltaic device performances. We show that, under appropriate sputtering conditions, the modification of the P3HT:PCBM film causes no functional damage of the photoactive layer, and leads to an improved performance of the photovoltaic devices

Annealing treatment for restoring and controlling the interface morphology of organic photovoltaic cells with interfacial sputtered ZnO films on P3HT: PCBM active layers:

In this paper, we report on the photovoltaic properties of conventional organic photovoltaic solar cells integrating a sputtered ZnO interfacial film deposited on the absorber P3HT:PCBM layer. An emphasis has been put on the influence of the annealing temperature and time for restoring and controlling the P3HT:PCBM/ZnO interface morphology, which can be damaged by the sputtering process. We show a significant improvement in the current-voltage (J-V) characteristics upon annealing up to 160 degrees C. This is evidenced by the reduction of the S-shape of these curves systematically observed for the cells integrating thick (100 nm) sputtered ZnO films. This approach was also highlighted on cells containing thinner (20 nm) ZnO films using a longer annealing process at 140 degrees C, which led to a significant improvement of the power conversion efficiency compared with the value recorded in as-prepared cells or in cells with no interfacial ZnO layer. These photovoltaic performances have been related to the change of the morphology of the absorber layer and to the vertical phase segregation of P3HT:PCBM at the interface with ZnO. Optical microscopy, scanning electron microscopy and atomic force microscopy have been performed in order to confirm this approach

Influence of flexible substrates on inverted organic solar cells using sputtered ZnO as cathode interfacial layer

Zinc oxide (ZnO) has recently shown to be of considerable interest for the development of interfacial buffer layers in inverted organic solar cells (OSCs). High quality ZnO thin films can indeed be prepared on large-area ITO-coated flexible substrates, using low temperature deposition techniques such as sputtering, a compatible technique with roll-to-roll process. However, further studies are still needed for a better understanding of the influence of the flexible substrate properties on the photovoltaic performances of those devices. In this work, ZnO films have been sputtered on ITO-coated flexible (PEN) substrates and annealed at different temperatures. The role of the surface morphology and the crystalline quality of ZnO films has been investigated. In the window of flexible compatible process, we found that moderate annealing temperatures of ZnO (<= 180 degrees C) lead to improved structural properties and performances. Interestingly, we achieve optimal performances for an annealing temperature of 160 degrees C, resulting in power conversion efficiency (PCE) equivalent to the highest performances usually achieved on rigid cells. (C) 2013 Elsevier B.V. All rights reserved