Liste des publications
Contribution to the Fault Diagnosis of a Doubly Fed Induction Generator for a Closed-loop Controlled Wind Turbine System Associated with a Two-level Energy Storage System
In this article, a contribution to the fault diagnosis of adoubly fed induction generator for a closed-loop controlled wind turbinesystem associated with a two-level energy storage system usingan on-line fault diagnostic technique is proposed. This technique isproposed to detect the rotor fault in the doubly fed induction generatorunder non-stationary conditions based on the spectral analysis of statorcurrents of the doubly fed induction generator by an adaptive fastFourier transform algorithm. Furthermore, to prevent system deterioration,a fractional-order controller with a simple design method isused for the control of the whole wind turbine system. The fractionalordercontroller ensures that the system is stable in both healthy andfaulty conditions. Additionally, to improve the production capacityunder wind speed fluctuations and grid demand changes, a two-levelenergy storage system consisting of a supercapacitor bank and leadacidbatteries is proposed. The obtained simulation results show thatthe objectives of the fault diagnosis procedure and control strategyare reached. Voir les détails
Mots clés : Wind energy conversion systems, adaptive Fast Fourier transform, doubly fed induction generator, fault detection and diagnosis, fractional-order control, two-level energy storage system
Effects of sol concentration on structural, morphological and optical waveguiding properties of sol-gel ZnO nanostructured thin films
Nanostructured ZnO thin films with different precursor concentrations (0.5-0.8 M) have been deposited on glass substrates by sol-gel dip coating technique. X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), UV-visible spectrophotometer, and m-lines spectroscopy have been employed to investigate the effect of solution concentration on structural, morphological, optical and waveguiding properties of ZnO thin films. XRD spectra have shown that all the films are polycristalline and exhibit the wartzite hexagonal structire. SEM micrographs and AFM images have revealed that morphology and surface routhness of the thin films deprnd on sol concentration. The UV-visible transmittanceresults show a high transparency in the visible range and a shift of the maximum transmittance to the higher wavelength with increasing sol concentration. Waveguiding properties such as refractive index, number of propagating modes and attenuation coefficient measered at 632.8 nm wavelength by m-lines spectroscopy indicate that our ZnO slab waveguides are single mode and demonstrate optical losses estimated around 1.5 decibel per cm (dB/cm) for the thin film prepared with a sol concentration of 0.7 M. Voir les détails
Mots clés : ZnO, sol-gel, thin film
Modeling and Control of the Wind Energy Conversion Systems Based on DFIG Under Sub- and Super-Synchronous Operation Modes
In this work, the modeling and control of the Wind Energy Conversion Systems (WECS) based on doubly fed induction generator (DFIG) are presented. Firstly, we developed the models of the different elements of the conversion chain. After, we consider the vector control strategy of the active and reactive powers in order to ensure an optimum operation. Finally, the dynamic model of a DFIG and wind turbine grid connected system is determined in the dq-synchronous reference frame. The numerical simulation results obtained with Matlab/Simulink software present the behaviors of the sub-synchronous and super-synchronous operation modes. Voir les détails
Mots clés : wind power generation, doubly fed induction generator, renewable energy, modeling, control.
Properties of Co-doped ZnO thin films grown by pulsed laser deposition on glass substrates
Undoped and cobalt-doped zinc oxide (CZO) polycrystalline piezoelectric thin films (Co: 3,5 at.%) using a series of high quality ceramic targets have been deposited at 4501C ontoglass substrates using a pulsed laser deposition method. The used source was a KrFexcimer laser (248 nm, 25 ns, 2 J∕cm2). X-ray diffraction patterns showed that the Codoped ZnO films crystallize in a hexagonal wurtzite type structure with a strong (002) orientation, and the grain sizes calculated from these patterns decrease from 37 to 31 nmby increasing Co doping. The optical waveguiding properties of the films were characterized by using a prism-coupling method. The distinct M-lines of the guided transversemagnetic (TM) and transverse electric (TE) modes of the ZnO films waveguide have beenobserved. With the aim of study the optical properties of the ZnO films, an accuraterefractive index and thickness measurement apparatus was set up, which is called M-linesdevice. An evaluation of experimental uncertainty and calculation of the precision of therefractive index and thickness were developed on ZnO films. The optical transmittancespectra showed a good transparency in the visible region. Calculated optical band gapvarying from 3.23 to 3.37 eV when the content of Co doping increases from 0 to 5 at.%. Voir les détails
Mots clés : Thin films, ZnO, pulsed laser deposition, Piezoelectric, Waveguiding properties, Optical transmittance
First principles calculations of structural, electronic and opticalproperties of Zn1-xBexSeyTe1-y quaternary alloys
The structural, electronic and optical properties of Zn1-xBexSeyTe1-y quaternary alloys are investigatedusing the full potential-linearized augmented plane wave (FP-LAPW) method within density functionaltheory (DFT). We used both the Wu–Cohen and the Engel–Vosko generalized gradient approximationsof the exchange-correlation energy that are based on the optimization of the total energy and the corre-sponding potential, respectively. Some basic physical properties, such as lattice constant, bulk modulus,electronic band structures, and optical properties (dielectric constant and refractive index) are calculated,nonlinear dependence on the compositions x and y are found. In addition, the energy band gap of zinc-blende Zn1-xBexSeyTe1-y quaternary alloys lattice matched to GaAs substrate is investigated. To ourknowledge this is the first quantitative theoretical investigation on Zn1-xBexSeyTe1-y quaternary alloysand still awaits experimental confirmations Voir les détails
Mots clés : alloys, Ab initio calculations, Electronic structure, optical properties
First-principles prediction of the structural, elastic, thermodynamic, electronic and optical properties of Li4Sr3Ge2N6 quaternary nitride
Structural parameters, elastic constants, thermodynamic properties, electronic structure and optical properties of the monoclinic Li4Sr3Ge2N6 quaternary nitride are investigated theoretically for the first time using the pseudopotential plane-wave based first-principles calculations. The calculated structural parameters are in excellent agreement with the experimental data. This serves as a proof of reliability of the used theoretical method and gives confidence in the predicted results on aforementioned properties of Li4Sr3Ge2N6. The predicted elastic constants Cij reveal that Li4Sr3Ge2N6 is mechanically stable but anisotropic. The elastic anisotropy is further illustrated by the direction-dependent of the linear compressibility and Young’s modulus. Macroscopic elastic parameters, including the bulk and shear moduli, the Young’s modulus, the Poisson ratio, the velocities of elastic waves and the Debye temperature are numerically estimated. The pressure and temperature dependence of the unit cell volume, isothermal bulk modulus, volume expansion coefficient, specific heat and Debye temperature are investigated through the quasiharmonic Debye model. The band structure and the density of states of Li4Sr3Ge2N6 are analyzed, which reveals the semiconducting character of Li4Sr3Ge2N6. The complex dielectric function, refractive index, extinction coefficient, absorption coefficient, reflectivity and electron energy-loss function are calculation for incident radiation polarized along the crystallographic directions and for energy up to 40 eV. Voir les détails
Mots clés : Quaternary nitride, First-Principles calculations, Elastic constants, Electronic structure, optical properties, Thermal Properties
Structural, elastic, electronic, chemical bonding and optical properties of Cu-based oxides ACuO (A = Li, Na, K and Rb): An ab initio study
Ab initio total energy calculations were performed to study in details the structural, elastic, electronic, chemical bonding and optical properties of Cu-based ternary oxides ACuO (A = Li, Na, K and Rb). Optimized atomic coordinates and lattice constants agree well with the existing experimental and theoretical data. Numerical estimations of the six independent elastic constants Cij and their related properties for monocrystalline ACuO were obtained. A set of elastic moduli for polycrystalline ACuO, namely bulk modulus B, shear modulus G, Young’s modulus E, Poisson’s ratio r, Lamé coefficients k and Debye temperature hD were evaluated. Band structure, total and site-projected l-decomposed densities of states, charge-carrier effective masses, charge transfers and charge density distribution maps were obtained; analyzed and compared with the available theoretical data. Complex dielectric function, refractive index, extinction coefficient, reflectivity and loss function spectra were calculated with an incident radiation polarized parallel to both [100] and [001] crystalline directions. Voir les détails
Mots clés : Cu-based oxides Ab initio calculations Elastic constants Electronic properties Chemical bonding
Image-based Control for Cable-based Robots
Some human robot interactive applications involved in tele-robotics, remote supervisory andunmanned systems require specific capabilities. This demand has promoted various interactive modesand high-level control techniques such as tele-manipulation, speech, vision, gesture, etc. Among theseinteractive modes, the image based control which is often named point and click control has proven tobe the most appropriate one that offers multiple advantages. This mode consists of only and simplypointing in an appearing object of an image received from a remote site, to convert this click into a robotcommand towards the corresponding location in the real world space. This mode is suitable for remoteapplications, frees the human operator from being involved into the loop enabling him/her to usecommands in the sense of click and forget. This paper presents, firstly, the design and the realization ofan experimental planar cable-based robot constituted of four cables. Secondly, it presents the designand the implementation of a high-level image-based control. Some typical experiments which havebeen performed prove the simplicity and the effectiveness of the image-based control. Moreover, itopens perspectives for new applications with cable-based robots, particularity for rehabilitation applications. Voir les détails
Mots clés : Cable-based robot, human-robot interaction, image-based control, point and click, robot control.
Etude expérimentale et analyse probabiliste du comportement à la rupture en traction de composites verre-perlon-acrylique à usage orthopédique
Les effets de la nature des séquences de la stratification ainsi que les influences significatives du sens de découpe des échantillons par rapport au sens du flux de moulage sur le comportement mécanique en traction d’une série de matériaux composites stratifiés sont mises en évidence à partir d’une analyse de leurs propriétés mécaniques. Ces stratifiés à usage orthopédique et à base de résine acrylique renforcée de couches de fibres de verre et de perlon sont disposées selon trois différentes architectures. Une importante dispersion est observée sur les résultats de mesure du module de Young et des contraintes à la rupture. Ces dernières montrent des valeurs supérieures dans le sens perpendiculaire à celui du flux de moulage. La mesure de la fragilité, la caractérisation du comportement à la rupture de ces stratifiés ainsi que l’aspect probabiliste de cette dernière sont décrits quantitativement à partir de l’application du modèle probabiliste à deux paramètres de Weibull. Le caractère fragile de la rupture de ces stratifiés est ainsi traduit par les faibles valeurs mesurées des modules de Weibull. Un constat des principaux mécanismes responsables de la rupture est dressé à partir des observations microscopiques des faciès de rupture des éprouvettes rompues. Voir les détails
Mots clés : stratification, Fibre De Verre, Perlon, Dispersion, Module De Weibull
Numerical simulation for cracks detection using the finite elements method
The means of detection must ensure controls either during initial construction, or at the time of exploitation of all parts. The Non destructive testing (NDT) gathers the most widespread methods for detecting defects of a part or review the integrity of a structure. In the areas of advanced industry (aeronautics, aerospace, nuclear …), assessing the damage of materials is a key point to control durability and reliability of parts and materials in service. In this context, it is necessary to quantify the damage and identify thedifferent mechanisms responsible for the progress of this damage. It is therefore essential to characterize materials and identify the most sensitive indicators attached to damage to prevent their destruction and use them optimally.In this work, simulation by finite elements method is realized with aim to calculate the electromagnetic energy of interaction: probe and piece (with/without defect).From calculated energy; we deduce the real and imaginary components of the impedance which enables to determine the characteristic parameters of a crack in various metallic parts. Voir les détails
Mots clés : Eddy Current, Non-destructive testing (NDT), Cracks, Finite Element Method