Liste des publications
Particle swarm optimization based sliding mode control of variable speed wind energy conversion system
This paper proposes a particle swarm optimization based sliding mode control of squirrel cage induction generator of a variable speed wind energy conversion system. The key feature of sliding mode control is a wisely chosen sliding surface which allows the turbine to operate more or less close to the optimal regimes characteristic. Optimal control parameters which are the convergence speed to the sliding-mode, the slope of the surface and the switching component amplitude of SMC are determined using particle swarm optimization approach. The simulation results prove the viability of the proposed control structure. Voir les détails
Mots clés : Squirrel Cage Induction Generator (SCIG), Wind Energy Conversion System (WECS), Sliding Mode Control (SMC), Particle Swarm Optimization (PSO)
Microstructure and Mechanical Behavior in Dissimilar SAF2205/API X52 Welded Pipes
The welding of a duplex stainless steel SAF 2205 DSS (UNS 31803) and high strength low alloy steel API X52by shielded metal arc welding process was conducted using two different filler metals, the duplex E2209 and austeniticE309 grade. The microstructures of the dissimilar metal joints have been investigated by optical microscopy, scanningelectron microscopy, energy-dispersive spectroscopy (EDS) and X-ray diffraction. EDS analysis at the interface X52 weldmetal showed an evident gradient variation of Cr and Ni between boundaries of fusion and type II, where the highesthardness value was recorded. Tensile strength and toughness values of the weld metal produced by E309 electrode areslightly higher than those of the weld metal produced by E2209 electrode. Potentiodynamic polarization tests of differentregions of the welded joints evaluated in 3.5% NaCl solution exhibit a high corrosion resistance of both weld metals. Voir les détails
Mots clés : Dissimilar metals welding, 2205 Duplex stainless steel, API X52 HSLA steel, Heat affected zone, mechanical properties
Feedback linearization control based particle swarm optimization for maximum power point tracking of wind turbine equipped by PMSG connected to the grid
The main problem regarding wind power systems is the major discrepancy between the irregular character of the primary source (wind speed is a random, strongly non-stationary process) and the exigent demands regarding the electrical energy quality. This paper presents a feedback linearization controller based particle swarm optimization for maximum power point tracking of wind turbine equipped by PMSG connected to the grid, the proposed method which aims at maximizing the power captured by WECS. In order to drive the system to the optimal operating point using the selection of the controller parameters with particle swarm optimization. The obtained simulation results with a variable wind profile show an adequate dynamic of the conversion system using the proposed approach. Voir les détails
Mots clés : Wind turbine, Maximum Power Point Tracking, Feedback linearization control, Particle Swarm Optimization (PSO), Wind Energy Conversion System (WECS)
Numerical Simulation of Temperature Distribution and Material Flow During Friction Stir Welding 2017A Aluminum Alloys.
Abstract.This study describes the use of fluid dynamic code, FLUENT to model the flow of metal in the AA2017A case around the welding tool pin (FSW). A standard threaded tool profile is used for the analysis of phenomena during welding such as heat generation and flow of the material are included. The main objective is to gain a better understanding of the flow of material around a tool. The model showed a large number of phenomena similar to those of the real process. The model has also generated a sufficient amount of heat, which leads to a good estimate of the junction temperature. These results were obtained using a viscosity which is near the solidus softening. Voir les détails
Mots clés : Friction Stir Welding, 2017A aluminum alloy, Temperature distribution
Finite volume modeling of laser assisted friction stir welding of 2017A-T451 aluminum alloy for enhanced sustainability of welded joints.
This study focuses on a new welding modification friction stir welding, using a preheating during the welding phase. This method utilizes laser energy to pre-heat the workpiece to a localized area at the front of the FSW tool, thereby reducing the temperature gradient over a localized area in advance of the tool. The amount of heat generated during welding determines the quality of the weld. Therefore the understanding of the temperature distribution is required to determine the optimal method of welding parameters. In this study, a two-dimensional model of an aluminum alloy plate coupled to a circular laser source is developed, using FLUENT software that is based on the finite volume method, also the geometry of the pin of the FSW tool was modified in several configurations to highlight the effect of the geometry of the tool on the temperature distribution in the welded plate. The model developed can be used to better understand the process, predict process performance and to determine the optimal parameters of the process. Voir les détails
Mots clés : riction stir welding, 2017A-T451 aluminum alloy, Finite volume modeling
Residual stresses of a magnesium alloy (AZ31) welded by the friction stir welding processes.
Abstract. The objective of this study was to evaluate the residual stresses of FSW welding magnesium alloys (AZ31). The results show that the FSW processes lead to the formation of several distinct zones with differing mechanical properties. The residual stresses evolution have been explained by the heterogeneous modifications of the microstructure particularly a marked decrease in the grain size, a high modification of the crystallographic texture and the different anisotropic properties resulting from plasticity induced by the FSW process. Voir les détails
Mots clés : AZ31 magnesium alloy, Friction Stir Welding, residual stresses
Monitoring of Stator windings Faults in Induction Machine Using Fuzzy Logic
the monitoring and fault detection of theinduction machines drives becomes more and moreimportant. This made necessary the monitoringfunction condition of these machines for improved anexploitation of the industrial processessing. The aim ofthis task is the proposal of a monitoring strategy basedon the fuzzy logic inference system, that informs usabout the healthy function and stator fault condition,especially the open circuit and short-circuit inter-turnsof the stator windings. The principle adopted for thestrategy suggested is based on monitoring of theaverage root mean square value of stator current(RMS).Theoretical analysis, simulations results arepresentes to validate the effectiveness of the proposesdmethod. Voir les détails
Mots clés : Induction machine, Monitoring, diagnosis, Detection, Fuzzy logic, RMS
Asymmetric Generalized Gaussian Mixturesfor Radiographic Image Segmentation
In this paper, a parametric histogram-based image segmentation methodis used where the gray level histogram is considered as a finite mixture of asymmetricgeneralized Gaussian distribution (AGGD). The choice of AGGD is motivated byits flexibility to adapt the shape of the data including the asymmetry. Here, themethod of moment estimation combined to the expectation–maximization algorithm(MME/EM) is originally used to estimate the mixture parameters. The proposedimage segmentation approach is achieved in radiographic imaging where the imageoften presents an histogram with a complex shape. The experimental results providedin terms of histogram fitting error and region uniformity measure are comparableto those of the maximum likelihood method (MLE/EM) with the advantage thatMME/EM method reveals to be more robust to the EM initialization than MLE/EM. Voir les détails
Mots clés : AGGD, radiography, MLE/EM, MME/EM, image segmentation
Energetics of atomic hydrogen absorption in C15-Fe2Zr Laves phases with ternary additions: A DFT study
The pseudo-potential Density Functional Theory (DFT) method using the GeneralizedGradient Approximation (GGA) was applied to investigate hydrogen absorption trends inthe cubic C15-ZrFe2 Laves phase in the presence of several ternary additions. The effect ofthe ternary addition on the stability of the Laves phase was investigated. The relativestability of atomic hydrogen at various interstitial sites was determined taking into accountthe type of ternary addition for different H contents in the hydrides. The results wereanalyzed and particular attention was given to the formation and binding energies ofhydrogen. It was found that hydrogen prefers the 96g site in the clean C15-Fe2Zr, and itsabsorption leads to decrease the heat of formation of the formed hydrides with occurrenceof phase separation around 6H/fu. This effect was enhanced by the presence of ternaryadditions. Moreover, alloys with Be, V, Cr, Mn, Y and Tc elements at the Fe sites were foundto absorb hydrogen up to 6H/fu. More interestingly, the cohesion of hydrogen atoms wasfound to be very sensitive to the third element nature. The hydrides with V, Y, and moreparticularly Tc and Ru have exhibited interesting energetics which would be very attractivefor practical applications. Voir les détails
Mots clés : Laves Phases, Hydrogen absorption, Atomic defects, Relative stability, DFT
Optimal control based RST controller for maximum power point tracking of wind energy conversion system
This paper presents an LQ optimal control based RST controller for maximum power tracking in a wind energy conversion system (WECS) connected to the electrical grid through a back-to-back converter. Input-output discrete WECS model has been used to implement the input-output optimal control approach. The performance criterion has two terms: the first one is involved for maximum power tracking and the other one for the mechanical fatigue loading (control input) minimization. The obtained simulation results with the considered control and a variable wind profile show an adequate dynamic of the considered conversion system. Voir les détails
Mots clés : wind energy conversion system, Induction generator (IG), LQ optimal control, RST controller