Robust sensorless control of BLDC Motor using second derivative function of the sum of terminal voltages

This paper proposes a new sensorless control method for the speed and position control of a BLDC Motor. This sensorless drive technique calculates the commutations instants (duration of commutation) by deriving the sum of the terminal voltages of the motor (SigVi). Thus, it is possible to estimate the rotor position (and back EMF of the motor) by only using measurements of the stator line currents and voltages. The implantation of these detectors is easy and cheap. This method is quite robust across variations in stator resistance due to changes in temperature or frequency. With this method the motor can be started without needing the initial position of the rotor. This proposed method is validated through extensive simulations at different speeds, and a very satisfactory performance has been achieved

Aerosol vertical distribution, optical properties and dust transport in the Western Mediterranean basin (case study: Summer, 2012)

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Caractérisation d'un photomètre solaire conçu pour l'étude des propriétés optiques des aérosols atmosphériques

Colloque avec actes et comité de lecture. Internationale.International audienceLes aérosols atmosphériques sont des particules très fines présentant une large variété de taille et de composition chimique. L'impact de ces particules sur le climat est considéré, aujourd'hui, comme l'un des aspects les plus mal connus du changement climatique. L'implantation d'un photomètre solaire sur une région donnée, permet d'effectuer les mesures nécessaires pour la caractérisation des aérosols. Deux types de mesures peuvent être réalisées : une visée directe du soleil( mesure SUN ) permettant de mesurer l'épaisseur optique des aérosols ( ou abondance ) dans les différents canaux et un balayage de la voûte céleste ( mesure SKY )qui sert à déterminer la distribution en taille des particules ( ou granulométrie ). Dans le cadre d'un projet de recherche en collaboration avec le Laboratoire d'Optique Atmosphérique de Lille (France), un photomètre CIMEL a été installé en 2001 sur le site de Thala (Tunisie ). Les différentes données fournies durant la période de fonctionnement ont permis de tirer des résultats intéressant concernant la qualité environnementale de la région d'étude

Investigation on the Effects of Acoustic Liner Variation and Geometry Discontinuities on the Acoustic Performance of Lined Ducts

Noise reduction inside waveguide systems has gained momentum owing to a great interest in it. To attenuate the sound in a broad frequency range, this study aims to compare the effects of two acoustic liners, a perforated plate backed by an air cavity (PP-Air cavity), or by a porous material (PP-PM), on the acoustic behaviour of lined ducts using a numerical model to compute the multimodal scattering matrix. From this matrix, the reflection and the transmission coefficients are computed and therefore the acoustic power attenuation is deduced. Moreover, the effects of geometry of ducts with and without changes in the section are investigated. The numerical results are obtained for five configurations, including cases of narrowing and widening of a duct portion with sudden or progressive discontinuities. Accordingly, numerical coefficients of reflection and transmission as well as the acoustic power attenuation show the relative influence of acoustic liners in each type of configuration

Identification of Physical Parameters of a Porous Material Located in a Duct by Inverse Methods

Lined ducts with porous materials are found in many industrial applications. To understand and simulate the acoustic behaviour of these kinds of materials, their intrinsic physical parameters must be identified. Recent studies have shown the reliability of the inverse approach for the determination of these parameters. Therefore, in the present paper, two inverse techniques are proposed: the first is the multilevel identification method based on the simplex optimisation algorithm and the second one is based on the genetic algorithm. These methods are used of the physical parameters of a simulated case of a porous material located in a duct by the computation of its acoustic transfer, scattering, and power attenuation. The results obtained by these methods are compared and discussed to choose the more efficient one

Evaluation of the Acoustic Performance of Porous Materials Lined Ducts with Geometric Discontinuities

Duct silencers provide effective noise reduction for heating, ventilation and air conditioning systems. These silencers can achieve an excellent sound attenuation through the attributes of their design. The reactive silencer works on the principle of high reflection of sound waves at low frequencies. On the other hand, the dissipative silencer works on the principle of sound absorption, which is very effective at high-frequencies. Combining these two kinds of silencers allowed covering the whole frequency range. In this paper, the effect of liner characteristics composed of a perforated plate backed by a porous material and geometry discontinuities on the acoustic power attenuation of lined ducts is evaluated. This objective is achieved by using a numerical model to compute the multimodal scattering matrix, thus allowing deducing the acoustic power attenuation. The numerical results are obtained for six configurations, including cases of narrowing and widening of a radius duct with sudden or progressive discontinuities. Numerical acoustic power attenuation shows the relative influence of the variation in the values of each parameter of the liner, and of each type of radius discontinuities of ducts

Highly Luminescent and Photostable Core/Shell/Shell ZnSeS/Cu:ZnS/ZnS Quantum Dots Prepared via a Mild Aqueous Route

International audienceAn aqueous-phase synthesis of 3-mercaptopropionic acid (3-MPA)-capped core/shell/shell ZnSeS/Cu:ZnS/ZnS QDs was developed. The influence of the Cu-dopant location on the photoluminescence (PL) emission intensity was investigated, and the results show that the introduction of the Cu dopant in the first ZnS shell leads to QDs exhibiting the highest PL quantum yield (25%). The influence of the Cu-loading in the dots on the PL emission was also studied, and a shift from blue-green to green was observed with the increase of the Cu doping from 1.25 to 7.5%. ZnSeS/Cu:ZnS/ZnS QDs exhibit an average diameter of 2.1 ± 0.3 nm and are stable for weeks in aqueous solution. Moreover, the dots were found to be photostable under the continuous illumination of an Hg-Xe lamp and in the presence of oxygen, indicating their high potential for applications such as sensing or bio-imaging

Ligand Influence on Local Magnetic Moments in Fe-Based Metal–Organic Networks

Planar metal–organic networks are highly promising materials due to their modular nature and wide-ranging possible applications from spintronics up to biosensing. Spin state transitions connect local magnetic properties with structural modifications. In this paper, we report on ab initio calculations for two metal–organic planar networks, the Fe-phthalocyanine (Pc) polymer and its precursor material Fe-tetracyano­benzene (TCNB). The spin-polarized generalized gradient approximation to density functional theory with an explicit treatment of the Hubbard-<i>U</i> correction (SGGA+<i>U</i>) indicates a spin state transition between the well confirmed <i>S</i> = 1 state for Fe-Pc and a local, high-spin <i>S</i> = 2 state at the Fe site for Fe-TCNB. The high-spin state at the Fe site is confirmed by X-ray absorption spectroscopy (XAS) measurements of the Fe-TCNB network on the Au(111) substrate in connection with a multiplet analysis. We propose a possible spin state transition between Fe-TCNB and Fe-Pc by the on-surface synthesis of the latter compound. The ab initio results prove also a high chemical stability of the Fe-TCNB network, metallic and ferromagnetic behavior, as well as a partial screening of the Fe spin <i>S</i> = 2 by two antiparallel electrons on the ligand sites to a state with total spin of <i>S</i> = 1. All of this makes the Fe-TCNB network an interesting material for spintronics applications