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1
Content available Comparison of sine-wave frequency estimation methods in respect of speed and accuracy for a few observed cycles distorted by noise and harmonics
Borkowski J., Kania D., Mroczka J.
Metrology and Measurement Systems
|
2018
|
Vol. 25, nr 2
283--302
EN
The paper deals with frequency estimation methods of sine-wave signals for a few signal cycles and consists of two parts. The first part contains a short overview where analytical error formulae for a signal distorted by noise and harmonics are presented. These formulae are compared with other accurate equations presented previously by the authors which are even more accurate below one cycle in the measurement window. The second part contains a comparison of eight estimation methods (ESPRIT, TLS, Prony LS, a newly developed IpDFT method and four other 3-point IpDFT methods) in respect of calculation time and accuracy for an ideal sine-wave signal, signal distorted by AWGN noise and a signal distorted by harmonics. The number of signal cycles is limited from 0.1 to 3 or 5. The results enable to select the most accurate/fastest estimation method in various measurement conditions. Parametric methods are more accurate but also much slower than IpDFT methods (up to 3000 times for the number of samples equal to 5000). The presented method is more accurate than other IpDFT methods and much faster than parametric methods, which makes it possible to use it as an alternative, especially in real-time applications.
2
Content available Prony’s method with reduced sampling - numerical aspects
Zygarlicki J., Mroczka J.
Metrology and Measurement Systems
|
2014
|
Vol. 21, nr 3
521--534
EN
This paper presents a new modification of the least-squares Prony’s method with reduced sampling, which allows for a significant reduction in the number of the analysed signal samples collected per unit time. The specific combination of non-uniform sampling with Prony’s method enables sampling of the analysed signals at virtually any average frequency, regardless of the Nyquist frequency, maintaining high accuracy in parameter estimation of sinusoidal signal components. This property allows using the method in measuring devices, such as for electric power quality testing equipped with low power signal processors, which in turn contributes to reducing complexity of these devices. This paper presents research on a method for selecting a sampling frequency and an analysis window length for the presented method, which provide maximum estimation accuracy for Prony’s model component parameters. This paper presents simulation tests performed in terms of the proposed method application for analysis of harmonics and interharmonics in electric power signals. Furthermore, the paper provides sensitivity analysis of the method, in terms of common interferences occurring in the actual measurement systems.
3
Content available Influence of A/D quantization in an interpolated DFT based system of power control with a small delay
Borkowski J., Kania D., Mroczka J.
Metrology and Measurement Systems
|
2014
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Vol. 21, nr 3
423--432
EN
Fast and accurate grid signal frequency estimation is a very important issue in the control of renewable energy systems. Important factors that influence the estimation accuracy include the A/D converter parameters in the inverter control system. This paper presents the influence of the number of A/D converter bits b, the phase shift of the grid signal relative to the time window, the width of the time window relative to the grid signal period (expressed as a cycle in range (CiR) parameter) and the number of N samples obtained in this window with the A/D converter on the developed estimation method results. An increase in the number b by 8 decreases the estimation error by approximately 256 times. The largest estimation error occurs when the signal module maximum is in the time window center (for small values of CiR) or when the signal value is zero in the time window center (for large values of CiR). In practical applications, the dominant component of the frequency estimation error is the error caused by the quantization noise, and its range is from approximately 8×10-10 to 6×10-4.
4
Content available A hybrid maximum power point search method using temperature measurements in partial shading conditions
Mroczka J., Ostrowski M.
Metrology and Measurement Systems
|
2014
|
Vol. 21, nr 4
733--740
EN
Photovoltaic panels have a non-linear current-voltage characteristics to produce the maximum power at only one point called the maximum power point. In the case of the uniform illumination a single solar panel shows only one maximum power, which is also the global maximum power point. In the case an irregularly illuminated photovoltaic panel many local maxima on the power-voltage curve can be observed and only one of them is the global maximum. The proposed algorithm detects whether a solar panel is in the uniform insolation conditions. Then an appropriate strategy of tracking the maximum power point is taken using a decision algorithm. The proposed method is simulated in the environment created by the authors, which allows to stimulate photovoltaic panels in real conditions of lighting, temperature and shading.
5
Content available Performance analysis of regularization algorithms used for image reconstruction in computed tomography
Wysoczański D., Mroczka J., Polak A. G.
Bulletin of the Polish Academy of Sciences. Technical Sciences
|
2013
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Vol. 61, nr 2
467--474
EN
Computed tomography is one of the most significant diagnostic techniques in medicine. This work is focused on hard-field imaging, where signals take a form of straight rays and the reconstructed image can be presented as a matrix with unknown pixels. Algebraic methods for direct computation of the image have not been used in practice because of the scale of the problem and numerical errors appearing in the solution. The aim of this work was to analyse the performance of direct algebraic algorithms for tomographic image reconstruction including regularisation mechanism such as: generalised regularisation, Tikhonov regularisation, Twomey regularisation and ridge regression (RR), as well as comparing the results with the filtered backprojection (FBP) as the reference method. The performed analyses demonstrated that the regularised algebraic methods are more accurate than the commonly used FBP, and RR appeared the most precise among them. Additionally it was shown that the invariant system matrix (inverted during calculations) can be easily determined by solving the forward problem. Finally, potential directions of further research have been pointed out.
6
Content available remote Models of disturbances in power networks for testing frequency methods used in measurements of power quality
Szmajda M., Mroczka J.
Przegląd Elektrotechniczny
|
2012
|
R. 88, nr 4a
163-168
EN
This article presents the systematics of disturbances occurring in power networks, connected with low frequency conducted disturbances including disturbances related to the quality of electrical power. It also provides a proposal of test signals basis that may be useful in testing new, alternative frequency methods of signal processing, necessary for calculation of some parameters of power quality.
PL
W artykule przedstawiono systematykę zakłóceń, pojawiających się w sieci elektroenergetycznej związanych z niskoczęstotliwościowymi zaburzeniami przewodzonymi, do których należą zakłócenia związane z jakością energii elektrycznej. Zaprezentowano również propozycję bazy sygnałów testowych będących pomocnych w badaniach nowych, alternatywnych do DFT, metod częstotliwościowych przetwarzania sygnałów, koniecznych do obliczeń niektórych parametrów jakości energii elektrycznej.
7
Content available Variable-frequency Prony method in the analysis of electrical power quality
Zygarlicki J., Mroczka J.
Metrology and Measurement Systems
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2012
|
Vol. 19, nr 1
39-48
EN
The article presents a new modification of the the least squares Prony method. The so-called variable-frequency Prony method can be a useful tool for estimating parameters of sinusoidal components, which, in the analyzed signal, are characterized by time-dependent frequencies. The authors propose use of the presented method for testing the quality of electric energy. It allows observation of phenomena which, when using traditional methods, are averaged in the analysis window. The proposed modification of least squares Prony method is based on introduction and specific selection of a frequency matrix. This matrix represents frequencies of estimated components and their variability in time.
8
Content available Prony's method used for testing harmonics and interharmonros in electrical power systems
Zygarlicki J., Mroczka J.
Metrology and Measurement Systems
|
2012
|
Vol. 19, nr 4
659-672
EN
The article presents an application of Prony's method with some known components in the analysis of electric power quality. Modifications of the Prony algorithm broaden the scope of method application. Modification of the filter of known components enables more accurate analysis of the parameters of unknown components and components with known or assumed frequencies. This article presents a comparison of the results of analyses conducted with the proposed algorithm for simulated and real signals and the results obtained by means of a commercial electric power quality testing device, operating in class A and using the Fourier transform. The proposed method enables to estimate the levels of the harmonic components, the frequency of the fundamental signal and real parameters of the interharmonic components, which are grouped and averaged in the contemporary monitoring equipment. Knowledge of the individual parameters of the interharmonics has considerable diagnostic importance while removing causes of incorrect operation affecting sensitive equipment in some electric power systems. Additionally, the algorithm is capable of analyzing exponentially damped components and finds its application in analysis of disturbances, for example, transient oscillations.
9
Content available Method of testing and correcting signal amplifiers' transfer function using Prony analysis
Zygarlicki J., Mroczka J.
Metrology and Measurement Systems
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2012
|
Vol. 19, nr 3
489-498
EN
This article presents a way of analyzing the transfer function of electronic signal amplifiers. It also describes the possibility of using signal precorrection which improves the parasitic harmonics in the THD (Total Harmonic Distortion) of the amplified signal by correcting linearity of the tested amplifier?s transfer function. The proposed method of analyzing and presenting the transfer function allows to diagnose the causes of generating parasitic harmonics, what makes it a useful tool when designing low distortion amplifier systems, such as e.g. amplifiers in measurement systems. The presented THD correction can be used in e.g. amplifier systems that cooperate with arbitrary generators.
10
Content available Algorithms and methods for analysis of the optical structure factor of fractal aggregates
Mroczka J., Woźniak M., Onofri F. R. A.
Metrology and Measurement Systems
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2012
|
Vol. 19, nr 3
459-470
EN
We introduce numerical methods and algorithms to estimate the main parameters of fractal-like particle aggregates from their optical structure factor (i.e. light scattering diagrams). The first algorithm is based on a direct and simple method, but its applicability is limited to aggregates with large size parameter and intermediate fractal dimension. The second algorithm requires to build calibration curves based on accurate particle agglomeration and particle light scattering models. It allows analyzing the optical structure factor of much smaller aggregates, regardless of their fractal dimension and the size of the single particles. Therefore, this algorithm as well as the introduction of a criteria curve to detect the different scattering regimes, are thought to be powerful tools to perform reliable and reproducible analyses.
11
Content available remote Praktyczne zastosowanie zredukowanej metody Prony’ego - badanie napięciowych układów wejściowych urządzeń monitorujących jakość energii elektrycznej
Zygarlicki J., Mroczka J.
Przegląd Elektrotechniczny
|
2011
|
R. 87, nr 5
199-203
PL
W artykule przedstawiono przykład praktycznego zastosowania metody Prony'ego, w jej zredukowanej formie do badania charakterystyk napięciowych układów wejściowych, stosowanych w urządzeniach do badania jakości energii elektrycznej. Zaprezentowany przykład weryfikuje teoretyczne rozważania autorów publikowane we wcześniejszych artykułach dotyczące zredukowanej metody Prony'ego i pokazuje możliwości ich praktycznego zastosowania do rzeczywistych pomiarów.
EN
The article shows an example of the practical use of the reduced Prony's method. The presented method was used for the measurement of the voltage input devices that are usually used in power quality measurements systems. The presented example is some kind of verification of theoretical considerations that were shown in the earlier publications about the reduced Prony's method and shows the opportunity for its practical use in real life measurements.
12
Content available remote Mierzalność mechanicznych właściwości dróg oddechowych i tkanek płuc podczas krótkotrwałego przerwania przepływu powietrza przy ustach pacjenta
Jabłoński I., Mroczka J., Głomb G.
Przegląd Elektrotechniczny
|
2011
|
R. 87, nr 4
224-227
PL
Założenia wstępne formułujące ideę nieinwazyjnego algorytmu przerywanego przepływu powietrza, dedykowanego do pomiaru mechaniki oddychania, prowadzą do istotnych przeszacowań indeksu diagnostycznego (Rint) w bazowej wersji metody. Zasadniczym źródłem ograniczenia są prosta (jednoelementowa) fizyko-matematyczna reprezentacja systemu oraz stosowany algorytm (ekstrapolacji wstecznej) przetwarzania danych eksperymentalnych. W artykule, najpierw w sposób analityczny a następnie w drodze symulacji komputerowych, wykazano możliwość separacji składowych odpowiedzi z tkanek płuc i dróg oddechowych. Ponadto, w sposób ilościowy pokazano udział oporu klatki piersiowej w całkowitej odpowiedzi systemu na quasi-skokowe pobudzenie zaworem przerwaniowym. Uzyskane wyniki są elementem pośredniczącym w przejściu pomiędzy klasyczną i wzbogaconą wersją algorytmu okluzyjnego.
EN
Preliminary assumptions postulated for the idea of the airflow interrupter technique, dedicated for respiratory mechanics measurement, lead to significant overestimation of the diagnostic index (Rjnt) in a basal version of the method. Essential sources of that limitation are simple (one-element) physical-mathematical representation of the system and the back-extrapolative algorithm used for experimental data processing. Analytic considerations have been firstly provided in the paper and next the possibility to separate airway and tissue component in the pressure-flow outpul has been shown during airflow interruption using computer simulation. Moreover, quantitative assessment of thoracic loading in the resistive response of the system on quasi-step excitation by valve closing has been documented. Results can be perceived as a linkage between the classical and enhanced version of the occlusional algorithm.
13
Content available Zaawansowane metody analiz w pomiarach jakości energii elektrycznej
Górecki K., Szmajda M., Zygarlicki J., Zygarlicka M., Mroczka J.
Pomiary Automatyka Kontrola
|
2011
|
R. 57, nr 3
284-286
PL
W artykule przedstawiono problematykę pomiarów jakości energii elektrycznej oraz zaprezentowano najważniejsze metody analizy zakłóceń występujących w sieciach elektroenergetycznych, jakie rozwijane są w zespole zajmującym się jakością energii elektrycznej w Instytucie Automatyki i Informatyki Politechniki Opolskiej. Przedstawiono systematykę metod analiz sygnałów oraz określono metody wykorzystywane obecnie w pomiarach sygnałów elektrycznych. Ponadto zaprezentowano metody alternatywne do transformacji Fouriera umożliwiające precyzyjną analizę częstotliwościową (analiza Prony'ego) oraz lokalizację zakłóceń za pomocą metod czasowo-częstotliwościowych (transformacja Falkowa, dyskretna transformacja Falkowa, dystrybucja Wignera-Ville'a i jej odmiany, transformacja Gabora-Wignera).
EN
The issue of measuring power quality parameters and the most important analyses of disturbances occurring in the power network are presented in the paper. These subjects are developed by a power quality and signal analysis group, working at the Faculty of Electrical Engineering, Automatic Control and Informatics. The basic classification of signal analysis methods is given in the paper (Fig. 1). Moreover, the methods currently used in power quality measurement systems are described. In most cases the analyses are based on Fourier Transformation [2-4]. The methods, due to 10-cycles measurement period, cause significant computational errors in case of existence of short duration harmonics in a signal. Moreover, very precise synchronization of the sampling frequency and real power wave-form frequency is needed. Therefore other kinds of analyses in power quality measurement systems are currently investigated. The alternative to Fourier Transformation methods allowing precise estimation of the signal spectrum is Prony analysis [5]. The analysis enables extracting frequency components on the basis of a much shorter measurement window than FFT [6-10]. For localizing the power disturbances, linear (Short-Time Fourier analysis STFT, Gabor Transform GT [12, 13], Wavelet Transform [14, 15, 16]) and bilinear (Wigner-Ville WVD, Pseudo-WVD [17,18]) time-frequency analyses are performed. The combination of both groups of methods (Gabor-Wigner Transform GWT [19,20]) is also presented in the paper. Application of image processing algorithms [21, 22] is also considered in the paper.
14
Content available Short time algorithm of power waveforms fundamental harmonic estimation with use of prony's methods
Zygarlicki J., Mroczka J.
Metrology and Measurement Systems
|
2011
|
Vol. 18, nr 3
371-378
EN
This paper presents an example of practical use of Prony's method for monitoring of power waveform fundamental harmonic fluctuations, which is required for the analysis of window synchronizations in frequency analyses in power monitoring systems. The example presented offers verification of the authors' theoretical considerations published earlier in articles about Prony's method and its opportunities for practical use for real life signals. The investigations shown are based on the least squares Prony's method, which, in connection with digital filtrations, enables estimations of fundamental frequency at the rate of even tens of times per one fundamental harmonic period.
15
Content available remote Wpływ temperatury na dokładność pomiarów pulsoksymetrycznych
Nowocień S., Mroczka J.
Przegląd Elektrotechniczny
|
2010
|
R. 86, nr 10
289-292
PL
W pracy dokonano analizy wpływu temperatury na dokładność oznaczania poziomu saturacji tlenowej krwi. Przeprowadzono badania symulacyjne wpływu zmian temperatury na charakterystykę widmową typowych emiterów LED wykorzystywanych w pomiarach pulsoksymetrycznych oraz wpływu tych zmian na końcowy wynik pomiaru. Z przeprowadzonej analizy wynika, że wzrost temperatury emitera powoduje nieznaczne zawyżanie końcowego wyniku pomiaru SaO2. Przy czym błąd pomiaru zależy dodatkowo od poziomu badanego wysycenia. Możliwa jest minimalizacja tego błędu przez dobór odpowiednich długości fal pomiarowych oraz wprowadzenie współczynnika korekcyjnego uwzględniającego błąd „termicznego przesunięcia widma”.
EN
This study has investigated the effect of temperature impact on accuracy of pulse oximetry measurement. Changes in ambient temperature has negligible influence on accuracy of this measurement. Using a basic oximetry law and theoretical LED model proposed by F.Reifegerste, the effect of lambda peak shifts was examined. The analysis shows that the increase in ambient temperature causes a slight increase of the final result of the measurement of SaO2 –usually several percentage. Minimization of this error is possible by selection of proper length of measuring wave and introduction of corrective ratio taking into consideration error thermal slip spectrum.
16
Content available remote System do pomiaru mechaniki płuc podczas sztucznej wentylacji z wykorzystaniem techniki przerwaniowej
Jakuszkin K., Mroczka J.
Przegląd Elektrotechniczny
|
2010
|
R. 86, nr 9
59-62
PL
Autorzy określili możliwość adaptacji techniki przerwaniowej do wykorzystania podczas cyklu wentylacyjnego, z ujęciem trybu wentylacji oraz miejsc występowania okluzji. Określono problemy sprzętowe związane z taką adaptacją oraz przeprowadzono testy na obiekcie rzeczywistym (sztucznym płucu). Uzyskane wyniki pomiarów wskazują na potencjalne możliwości wykorzystania sztucznie wprowadzonego przerwania do kontrolowania stanu pacjenta lub sterowania pracą respiratora. W referacie wskazano problemy występujące podczas pracy rzeczywistego układu wentylator-płuco oraz nakreślono kierunek prac prowadzących do ulepszenia systemu.
EN
Authors described possibilities of adaptation Interrupter Technique in artificial ventilation cycle concentrating on type of support and occlusion points. Hardware issues were indicated and test on real object were carried out. Results indicate on potential usefulness of additionally inserted occlusion in patient condition monitoring or respirator control. Paper shows essential problems occurring during lung-ventilator set-up work. Possible ways of system improvement were pictured.
17
Content available Analiza wydajności obliczeniowej systemu pomiarowego jakości energii elektrycznej opartego na urządzeniu embedded BeagleBoard z systemem operacyjnym Linux
Zygarlicki J., Mroczka J.
Pomiary Automatyka Robotyka
|
2010
|
R. 14, nr 12
50-52
PL
W artykule przedstawiono możliwości zastosowania niskobudżetowego modułu embedded BeagleBoard na bazie procesora OMAP firmy Texas Instruments, działającego pod kontrolą systemu Linux, do budowy zaawansowanego urządzenia pomiarowego parametrów jakości energii elektrycznej. W artykule przeanalizowano czasy obliczeń złożonych algorytmów przetwarzania sygnałów na przykładzie metody Prony'ego, mogących mieć zastosowanie przy wyznaczaniu parametrów jakości energii elektrycznej. Czasy te będą porównane z czasami obliczeń dla typowych urządzeń klasy PC o architekturze 8086. Dodatkowo zostaną pokazane możliwości dołączenia do systemu urządzeń peryferyjnych oraz sond pomiarowych.
EN
The article show the possibilities of use of the low cost BeagleBoard embedded system based on Texas Instruments OMAP processor with Linux operating system used for advanced power quality monitoring system. The authors show analysis results of the required time computation for presented advanced signal analysis methods like Prony's method, which can be used for power quality parameters estimation. The results were compared with computations made for PC standard computers, with x86 architecture. Additional, the article show possibility of peripheral devices connections to the presented system.
18
Content available remote Telemedical system "pulmotel-2010" for monitoring patients with chronic pulmonary diseases
Polak A. G., Głomb G., Guszkowski T., Jabłoński I., Kasprzak B., Pękala J., Stępień A. F., Świerczyński Z., Mroczka J.
Metrology and Measurement Systems
|
2010
|
Vol. 17, nr 4
537-547
EN
Telemedicine is one of the most innovative and promising applications of technology in contemporary medicine. Telemedical systems, a sort of distributed measurement systems, are used for continuous or periodic monitoring of human vital signals in the environment of living. This approach has several advantages in comparison to traditional medical care: e.g. patients experience fewer hospitalizations, emergency room visits, lost time from work, the costs of treatment are reduced, and the quality of life is improved. Currently, chronic respiratory diseases comprise one of the most serious public health problems. Simultaneously patients suffering from these diseases are well suitable for home monitoring. This paper describes the design and technical realization of a telemedical system that has been developed as a platform suitable for monitoring patients with chronic pulmonary diseases and fitted to Polish conditions. The paper focuses on the system's architecture, included medical tests, adopted hardware and software, and preliminary internal evaluation. The performed tests demonstrated good overall performance of the system. At present further work goes on to put it into practice.
19
Content available remote Gabor Transform, SPWVD, Gabor-Wigner Transform and Wavelet Transform - Tools for Power Quality monitoring
Szmajda M., Górecki K., Mroczka J.
Metrology and Measurement Systems
|
2010
|
Vol. 17, nr 3
383-396
EN
The one-dimension frequency analysis based on DFT (Discrete FT) is sufficient in many cases in detecting power disturbances and evaluating power quality (PQ). To illustrate in a more comprehensive manner the character of the signal, time-frequency analyses are performed. The most common known time-frequency representations (TFR) are spectrogram (SPEC) and Gabor Transform (GT). However, the method has a relatively low time-frequency resolution. The other TFR: Discreet Dyadic Wavelet Transform (DDWT), Smoothed Pseudo Wigner-Ville Distribution (SPWVD) and new Gabor-Wigner Transform (GWT) are described in the paper. The main features of the transforms, on the basis of testing signals, are presented.
20
Content available remote Systemy pomiarowe jakości energii elektrycznej
Szmajda M., Zygarlicki J., Mroczka J.
Przegląd Elektrotechniczny
|
2009
|
R. 85, nr 2
1-6
PL
W artykule przedstawiono systematykę urządzeń do badania jakości energii elektrycznej biorąc pod uwagę różne aspekty konfiguracji hardwarowej oraz softwarowej. Dokonano krótkiej charakterystyki systemów pod kątem mocy obliczeniowych zastosowanych mikroprocesorów oraz oprogramowania. Przedstawiono najnowocześniejsze trendy w dziedzinie aplikacji procesorów sygnałowych w pomiarach jakości energii elektrycznej oraz pokazano sposób zastosowania dedykowanego systemu czasu rzeczywistego DSP/BIOS.
EN
The systematics of power quality measurement systems considering different aspects of software and hardware configuration was presented in the article The short characteristic of the systems considering computational power of processors and software (firmware) was performed. The modern trends of DSP processors application in power quality measurement systems was also presented. Moreover, utilization of real time operational system DSP/BIOS was shown.
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