Grzegorz Wiczynski

Analysis of Voltage Fluctuations in Power Networks

Voltage fluctuations analysis is one of the basic elements of power quality assessment in the power network. Presently, two voltage fluctuations measures are used-voltage fluctuations indexes and short-term Pst and long-term Plt flicker severity indicators. The voltage fluctuations indexes describe the variability of the root-mean-square (rms) value by means of the amplitude and the frequency. Pst and Plt indicators are used for the assessment of flicker obnoxiousness. This paper includes the comparison of both measures showing, beside definition differences, various diagnostic possibilities.

Distance Estimation With a Long-Range Ultrasonic Sensor System

This paper presents the results of tests conducted with an ultrasonic proximity measurement system (composed of Polaroid 600 sensors and a Sonar Ranging Module SN28827), which is used in sensory subsystems in many mobile robots. The tests took into account distances ranging from 0.4 to 11 m. The analysis of the obtained measuring results created the basis for selecting a distance estimator that would guarantee the smallest measuring errors in the whole measuring range of the system. The research described was carried out in a closed room at constant environmental conditions so as to eliminate the influence of external factors on the measurement result. Each measuring series was composed of 100 measurements. For the best estimator chosen in such environment, the value of absolute measuring error never exceeded plusmn 0.03 m. Histograms that present the scatter of measurement results are also included. The minimal number of measurements necessary to achieve a reliable measurement with the selected distance estimator was determined. It is shown that in order to achieve a relative measuring error smaller than 1% with 0.99 probability there is a need to perform at least seven measurements. A proposition of the distance measuring procedure with the chosen estimator is presented. The analysis described in this paper helps to evaluate the reliability of measurements performed with ultrasonic sensors.

A Model of the Flickermeter for Frequency Modulation of the Input Voltage

Flickermeter is a term used for a system that measures the obnoxiousness of flicker caused by voltage fluctuations. The processing performed by a signal chain of this system is very complicated. Thus, it is not easy to obtain the output values only by analytical mean. The aim of this paper is to obtain a simple model of a flickermeter for a case of frequency modulation (FM) of the input signal. There is still a lack of a International Electrotechnical Commission flickermeter standard specification for that case. In this paper, a proposal was made to determine such a model at FM with slowly varying signals and signals in a frequency range from 1 Hz to 155 Hz. The quality of characteristic approximation evaluated was based on numerical simulations with sinusoidal as well as rectangular waveforms as input signals. The presented model makes it possible to clearly understand the flickermeter signal chain operation and helps to verify the functioning of a real measuring device in the considered frequency range.

Sectional Approximation of the Flickermeter Transformation Characteristic for a Sinusoidal Modulating Signal

The short-term flicker severity indicator Pst is the output signal of a so-called flickermeter system that makes it possible to estimate the obnoxiousness of flicker caused by voltage fluctuations. The processing characteristic of the flickermeter is based on a limited set of standard points. In this paper, the results of the analysis of a simplified model of this system are presented. The model consists of a set of three equations that interpolate and extrapolate the transformation characteristic for modulation with a sinusoidal modulating signal. The proposed deterministic model makes it easier to understand the processing being performed in the examined signal chain.

Basic characteristics of IEC flickermeter processing

Flickermeter is a common name for a systemthatmeasures the obnoxiousness of flicker caused by voltage fluctuations. The output of flickermeter is a value of short-term flicker severity indicator, Pst. This paper presents the results of the numerical simulations that reconstruct the processing of flickermeter in frequency domain. With the use of standard test signals, the characteristics of flickermeter were determined for the case of amplitude modulation of input signal, frequency modulation of input signal, and for input signal with interharmonic component. For the needs of simulative research, elements of standard IEC flickermeter signal chain as well as test signal source and tools for acquisition, archiving, and presentation of the obtained results were modeled. The results were presented with a set of charts, and the specific fragments of the charts were pointed out and commented on. Some examples of the influence of input signals bandwidth limitation on the flickermeter measurement result were presented for the case of AM and FM modulation. In addition, the diagrams that enable the evaluation of flickermeters linearity were also presented.

Optical scanner for mobile robots

In this paper, an optical scanner which can be used to investigate a 3D space, has been presented. Some main applications of that device, have been described. The diagram scheme of the scanner as well as a principle of operation and design of particular functional parts are shown. Major tasks of the software which is built in a controller and cooperates with the scanner, are presented. The methods on how create a geometrical model of environment to be useful for navigation of mobile robot, have been discussed. Some results of experiments are given.

Voltage-Fluctuation-Based Identification of Noxious Loads in Power Network

Very often, voltage fluctuations can cause a decrease in power quality. It is possible to improve this quality by changing the characteristics of the fluctuation source and/or the supply circuit. To do so, it is necessary to find the source of a given fluctuation and determine its properties. The problem-causing loads are most often identified through the analysis of fluctuation amplitude variations. Less popular is a method that compares the variations of the current with the variations of the voltage fluctuation indices. In this paper, both methods are described, and their properties are compared.

Standard measurement of interharmonics in a power supply system while evaluating obnoxiousness of a flicker

Flicker is caused by the fluctuation of voltage that supplies the source of light. Such a fluctuations are accompanied by the existence of interharmonics. This paper summarizes the measurement of interharmonics accordant to IEC 61000-4-7 standard. Also included are the results of analysis of flickermeter signal chain for the input signal composed of two interharmonics. The relation between the Pst indicator value and amplitudes and phases of the two interharmonics is determined. Condition for taking into consideration the phase relations while evaluating the Pst indicator value is also given. It is concluded that the evaluation of Pst indicator value is not possible only on the basis of IEC 61000-4-7 standard measurements for harmonics.

Role of optical techniques in combined use of selected methods of medical imaging

The subject matter of this paper concerns advanced techniques of imaging used in diagnosis and minimally invasive procedures applied in non-operable cases of the digestive tract tumour therapy. The role of optical techniques in current medical imaging is significant. Optical properties of transilluminated or illuminated tissues and organs depend on strong light absorption and scattering. Numerous issues related to the result interpretation still remain unsolved. Effectiveness and precision can be especially improved when some combined methods of imaging are used. Videoendoscopy imaging, X-ray imaging, and endoscopic ultrasound imaging are three complementary methods applied during the interventions described in this work. All interventions have concerned with the upper part of the digestive tract. Especially, interdisciplinary issues of combined medical imaging are presented using some examples of a modern approach to imaging of esophagus and biliary stenting. The selected examples of effects obtained during interventions assisted by combined imaging of the operation site are presented. The operator can have great control over the appearance of desirable effects as well as undesirable complications in order to work comfortably and safe.

Examples of Transillumination Techniques Used in Medical Measurements and Imaging

Transillumination is understood as the phenomenon of transmitting optical radiation with defined parameters by an object, which becomes the carrier of information on the characteristic size of the object [1]–[7]. In case of biological objects the optical properties of systemic liquids and other tissues are utilized. Transillumination as a method of examination by passage of light through tissues or a body cavity is a diagnostic technique in the course of intensive development at the moment.