Yetkin Tatar

Time–frequency analysis of phonocardiogram signals using wavelet transform: a comparative study

Analysis of phonocardiogram (PCG) signals provides a non-invasive means to determine the abnormalities caused by cardiovascular system pathology. In general, time–frequency representation (TFR) methods are used to study the PCG signal because it is one of the non-stationary bio-signals. The continuous wavelet transform (CWT) is especially suitable for the analysis of non-stationary signals and to obtain the TFR, due to its high resolution, both in time and in frequency and has recently become a favourite tool. It decomposes a signal in terms of elementary contributions called wavelets, which are shifted and dilated copies of a fixed mother wavelet function, and yields a joint TFR. Although the basic characteristics of the wavelets are similar, each type of the wavelets produces a different TFR. In this study, eight real types of the most known wavelets are examined on typical PCG signals indicating heart abnormalities in order to determine the best wavelet to obtain a reliable TFR. For this purpose, the wavelet energy and frequency spectrum estimations based on the CWT and the spectra of the chosen wavelets were compared with the energy distribution and the autoregressive frequency spectra in order to determine the most suitable wavelet. The results show that Morlet wavelet is the most reliable wavelet for the time–frequency analysis of PCG signals.

The analysis of heart sounds based on linear and high order statistical methods

This paper investigates the applicability of high order statistical autoregressive (AR-HOS) modeling method in analyzing biomedical signals. The autoregressive (AR) method using linear prediction and AR-HOS method using cumulants; are applied on normal and pathological heart sound signals. It is found that the AR-HOS modeling a signal produce a more accurate and higher resolution spectrum than AR modeling.

Design and implementation of an integrated environment for real‐time control of power electronic systems

In this article, an integrated lab environment for the electrical engineering education is presented which includes hardware and software for the modeling, simulation and control of multilevel inverters. A five‐level cascade inverter is designed and implemented which is an educational platform for the students to test different pulse width modulation (PWM) techniques and verify simulation results. The integrated environment is based on Matlab together with dSPACE. Sinusoidal PWM (SPWM) and Selected Harmonic Elimination PWM (SHEPWM) blocks are constructed in Matlab/Simulink and converted to C code using Matlab/Real‐Time Workshop. C codes are sent to dSPACEs DS1103 digital signal processor (DSP) via dSPACE/Real‐Time Interface software. Voltages with variable frequency and amplitude obtained from SPWM and SHEPWM techniques are applied to an induction motor. Simulation and experimental results are visualized on the designed graphical user interface (GUI). The GUI is developed using dSPACEs ControlDesk software.

An application of SHEPWM technique in a cascade multilevel inverter

Purpose – In this paper, a new application of the Selected Harmonic Elimination Pulse Width Modulation (SHEPWM) technique used in the cascade multilevel inverter topology which is formed by series connections of one‐phase bridge type inverters (H‐bridge) is introduced. The advantage of the SHEPWM technique is its ability to operate in low switching frequency that makes it suitable for high power applications.Design/methodology/approach – First, the switching angles are calculated using constrained optimization technique. By using these switching angles, the fundamental harmonic can be controlled and the selected harmonics can be eliminated. Then, using these calculated switching angles, a set of equation is formed which calculate the switching angles with respect to the modulation index. The switching angles at any modulation index can be easily obtained by solving the equation set. In this study, this equation set has been solved online using dSPACE DS1103 controller board. Using this technique, three‐ph...

Effects of input filter on stability of matrix converter using venturini modulation algorithm

In this paper; simulation, design, and implementation of three-phase to three-phase matrix converter using Venturini modulation algorithm have been presented. Furthermore, effects of input filter on stability of matrix converter have been examined. A Simulink model has been developed in such a way that it supports real time work with the use of DSP control card supported by Simulink. Simulation and experimental results for the input and output waveforms of the matrix converter using R-L load are given at various operating conditions. Good agreement was obtained between the simulation results and the results obtained from the prototype.

Detection DoS Attack on FPGA Using Fuzzy Association Rules

This paper proposes a programmable embedded system based on data mining and fuzzy logic to determine Denial of Service (DoS) attacks in real time. The proposed system detects the DoS attacks to a web service. The system consists of two phases. At the first phase, the number of terminated connection and the number of connection request statistics and so on have been extracted from packet. These obtained features constitute training data. Each record in training data was obtained with 2 sec intervals from network traffic. Then Fuzzy classification rules have been obtained from training data by data mining and fuzzy logic. At the second phase, DoS attacks have been detected using these rules in real time for testing purpose. The proposed system has been tested on Alter a Cyclone III EPC3C40F484C7 in the FPGA environment.

Fuzzy-based Closed-loop Speed Control of Induction Motor Fed from Matrix Converter

Abstract In this study; closed-loop speed control of an induction motor that was achieved by a fuzzy-based slip regulation technique has been performed. As a power source for the motor, a three-phase matrix converter has been used, and the space-vector modulation was adapted for the generation of the switching control signals. Real-time control signals for the matrix converter were generated through MATLAB/Simulink (The MathWorks, Natick, Massachusetts, USA) supported digital signal processor control card. The space-vector modulation technique used in this work is simpler than other control algorithms, both in terms of implementation and the input power factor control. Furthermore, the proposed space-vector modulation technique for the matrix converter reduced “turn-on” number of the switching devices in a switching period, and therefore, fewer switching losses have occurred. Simulation and corresponding experimental results were given for various operating conditions.

FPGA based programmable embedded intrusion detection system

In this article, the design of a Field Programmable Gate Array (FPGA) based real time Intrusion Detection System (IDS) is presented. The embedded system first summarizes and normalizes the packets and then determines whether there is an attack or not using this summary according to the naive bayesian algorithm. The packet summaries which play an important role in the accurate classification of the packets include data such as the IP numbers of the packets, port numbers, protocol types and packet length. Real time Intrusion Detection System (IDS) was designed in the Altera Cyclone III based FPGA development environment and tested. As a result of the tests performed, appropriate results were obtained.

Implementation of DSP-based matrix converter using space vector modulation algorithm

In this paper; simulation, design, and implementation of space vector controlled three-phase to three- phase matrix converter have been presented. A Simulink model has been developed in such a way that it supports real time work with the use of DSP control card supported by Simulink. Space vector control algorithm has been preferred to the other control algorithms since it is easy to implement and to control the input power factor with reduced switching loses. Simulation and experimental results of the input and output waveforms of the matrix converter for R-L load are given at various operating conditions. Good agreement was obtained between simulation and laboratory experiments.

Characterization of phonocardiogram signals using bispectral estimation

The application of the bispectrum as a high-order spectrum (HOS) method in analyzing normal and pathological heart sound signal is investigated in this paper. The bispectrum of phonocardiogram (PCG) signals is used to characterize the abnormalities while detecting non-linearity or non-Gaussianity in order to improve the diagnostic performance. In the comparison of the diagonal slice of the bispectrum and the power spectrum of PCG signal, the results have shown that the HOS reveal the differences in heart sound analysis indicating non-Gaussianity or non-linearity. It is concluded that the diagonal slice and the peaks of bispectrum are efficiently determine the cardiac dysfunctions effecting on heart sounds.