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BARTOŠ, S. — DOLEŽEL, I. — NEČESANÝ, J. — ŠKRAMLÍK, J.
— VALOUCH, V.
Theoretical and Experimental Investigation of Parasitic Effects in Induction Motor Drives Supplied from Semiconductor Inverters [full paper]
The paper deals with the numerical modeling of a pulse-width modulated voltage inverter-fed induction motor drive for the common and differential current modes. The proposed model of the drive respects the influence of the feeding cable described by the lumped or distributed parameters. The theoretical analysis is supplemented by results of relevant simulations and experiments. Evaluated are also the frequency characteristics of selected parts of the system and their contributions to its resultant harmonic spectra.
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HÁJEK, P. — OLEJ, V.
Municipal Creditworthiness Modelling by Neural Networks [full paper]
The paper presents the design of municipal creditworthiness parameters. Further, the design of model for municipal creditworthiness classification is presented. The realized data pre-processing makes the suitable economic interpretation of results possible. Municipalities are assigned to clusters by unsupervised methods. The combination of Kohonen’s self-organizing feature maps and K-means algorithm is a suitable method for municipal creditworthiness modelling. The number of classes in this model is determined by indexes evaluating the quality of clustering. The model is composed of Kohonen’s self-organizing feature maps and fuzzy logic neural networks, where the output of Kohonen’s self-organizing feature maps represents the input of fuzzy logic neural networks. The suitability of the designed model is compared with other fuzzy logic based classifiers. The highest classification accuracy is achieved by the fuzzy logic neural network. The fuzzy logic neural network’s model is the best in terms of generalization ability due to this fact. By the designed model high classification accuracy, low average classification error and suitable interpretation of results are achieved.
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AZZOUZ, Z. E. — MIMOUNI, A. — GHEMRI, B. — CHERIFI,
A.:
Analysis of Radiated-Lightning Electromagnetic Fields above Imperfect Ground Using a Quasi-FDTD Hybrid Method [full paper]
In this paper, our purpose is to compute radiated lightning electromagnetic fields using the hybrid method principle. The proposed method called the quasi-FDTD method is a new version of the classical hybrid method which is based partially on the use of the finite difference method in time domain (FDTD) for the calculation of the electric field components after the evaluation of the magnetic flux density using the images theory. However, the particularity of the proposed method is to take into account the finite conductivity of the ground in the lightning electromagnetic field calculations. This is obtained by a modification brought to the formulation of the classical hybrid method presented by Sartori and al in [2]. Furthermore, in the proposed method, the representation of the lightning current distribution is achieved by the use of engineering models typically the MTLE and MTLD models since they have showed reasonable agreement with measurements. Finally the simulation results are compared with those obtained using numerical approximate methods taken from literature. This comparison has shown that the proposed hybrid approach, taking into account the finite ground conductivity, is completely valid since it reproduces similar wave shapes for the electric and the magnetic fields above the ground.
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BOHÁČIK, J. — JUHOLA, M. — LEVASHENKO, V.
Fuzzy IF-THEN Rule Induction with Cumulative Information Estimations Applied to Real-World Data [full paper]
Real-world data containing instances corresponding to patients with otoneurological diseases were explored with fuzzy IFTHEN rule induction. It was based on transformation of a fuzzy decision tree made with using cumulative information estimations as the locally optimal criterion at its nodes. This method uses linguistic variables that allow us to naturally model various situations appearing in this data. It also gives classification knowledge in a form of IF-THEN rules that are easily readable and understandable by an expert. Our study shows in comparison to multilayer perception neural networks that classification with the induced fuzzy IF-THEN rules is a useful technique for diagnostics of otoneurological diseases.
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TOUFOUTI, R. — MEZIANE, S. — BENALLA, H.
Techniques for Improvements of the Performances of Direct Torque Control Strategy for Induction Motor [full paper]
The basic concept of direct torque control of induction machines is investigated in order to emphasize the effects produced by a given voltage vector on stator flux and torque variations. The low number of voltage vectors which can be applied to the machine using the basic DTC scheme may cause undesired torque and current ripple. An improvement DTC schemes proposed in the research literature is presented and compared with the classical. In this paper, we propose two approach’s of improvement of Direct Torque Control (DTC) of Induction motor, first is Discrete Space Vector Modulation (DSVM_DTC) Where the Stator flux and torque are controlled using respectively by five-level hysteresis comparators, second is and The discrete time direct torque control (DTDTC) requires voltage and current measurements to calculate the back-EMF, and address the problem with torque ripple in the basic DTC system is introduced. Numerical simulations tests have been carried out to validate the proposed method.
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DŽURINA, J. — PLAVKA, J.:
O(n2) Algorithm for Computing Volume of Overlapping Spheres [full paper]
An exact analytical method for the calculation of volume of overlapping spheres is presented. In the considered procedure volume of overlapping spheres is expressed as surface integrals over closed regions. Using a natural continuous correspondence between the points of the sphere surface and the points of the plane the surface integrals are computed by the next transformation onto double integrals which are reduced onto curve integrals.
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DJAHBAR, A. — MAZARI, B.
A Novel Concept for Multimachine Drive System with Single Inverter Supply [full paper]
The interest in multiphase machines for high performance applications has been growing in recent years due to their potential advantages over three-phase machines.
One of the possibilities of taking advantage of the additional degrees of freedom that exist in multiphase machines is the series connection of several multiphase machines, with the supply coming from a single multiphase inverter.
This paper discusses the possibility of connecting in series the stator windings of a six-phase and three-phase induction machines in an appropriate manner. This enables full decoupling of the dynamics of the two machines by means of vector control. Mathematical derivations and simulation proof of independent vector control, achievable with this system, are provided for the series connection of six-phase induction machine and a three-phase induction machine. The existence of the independent control of the machines is fully verified both in torque and speed mode using indirect rotor-flux oriented control principles.
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ŠIMOŇÁK, S. — JAKUBČO, P.
Software Based CPU Emulation [full paper]
Software based emulation of a real hardware is an imitation of its internal design by the software application (model), which behavior is similar to the behavior of the hardware (keeps functionality). Emulators are used with advantage in development (where expensive or old hardware is partially or completely supplied by an emulator), testing and also as a support for machine non-compatible software. Considering a concept of Von-Neumann computer, the central processing unit (CPU) emulation is a core of the computer emulator. Within this paper, theoretical aspects of a CPU emulation are treated and a concrete software solution is also presented.
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GAMEC, J. — URDZÍK, D.:
Detection of Driving Space [full paper]
Road detection is one of the basic tasks for automatic guidance of vehicles in driver assistance system. In this paper an approach to detect road is proposed, which firstly transform RGB image into gray-scale image, then edge detection algorithm is applied and finally line extraction and highlighting is preformed. This algorithm has been tested on an images downloaded from the internet and on some photographs scanned by mobile phone equipped with camera.
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KURIMSKÝ, J. — KOLCUNOVÁ, I. — CIMBALA, R.:
Partial Discharge Analysis for Insulation Systems of Electric Rotating Machines with Various Voltage Stress [full paper]
High voltage insulation is loosing its quality during the operation of high voltage machines and generators. Degrading high voltage stator insulation is the main reason for sudden breakdown of stator windings. Partial discharge measurements can reveal a lot of defects in stator windings of high voltage rotating machines with operating voltage more than 3,3kV. Partial discharge monitoring provides reliable information necessary for basic maintenance of stator windings of motors and generators. Submitted paper deals with partial discharge measurements in stator windings during the increasing of applied voltage.
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