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Page 907 of 939 Results 9061 - 9070 of 9382

Artur Przelaskowski, Anna Kukula
ESTIMATION OF DIAGNOSTIC ABILITY BY DIAGNOSTIC FEATURES ASSESSMENT TESTS

This paper presents a method of simplifying the diagnostic accuracy estimation for compressed mammograms. The proposed method consists of three main stages: a) the selection of abnormal structure features susceptible to wavelet compression method, b) subjective ratings of diagnostically important features and c) estimation of diagnostic pattern for processed mammograms. This pattern reflects diagnostic ability of radiologists using encoded images in clinical practice. Experimental pattern estimation confirmed even higher diagnostic quality of compressed to 1 bpp mammograms than their 12 bpp originals.

Valentyn V. Grabko, Volodymyr V. Grabko
MATHEMATICAL MODEL FOR THE DETERMINATION OF DISCHARGERS’ RESIDUAL WORKING RESOURCE AND THE DEVICE FOR ITS REALIZATION

The paper considers the mathematical model for dischargers diagnosing, considering the value and the duration of the current’s impulse at the moment of commutation and synthesized the device for its realization using the sequence’s mathematical tool.

Anton Scheibelmasser, Udo Traussnigg
USE OF MOBILE FLASH-CARD STORAGES IN MEASUREMENT DEVICES AND SMALL AUTOMATION SYSTEMS

Mobile Flash-Cards in different technologies and formats are well suited to act as an exchangeable non volatile mass storage for data or program code in measurement devices and small automation systems. Due to the use in the fields of digital photography and multimedia applications, flash cards have been introduced into the market and are available in a standardized and compact way. Because of their mobile characteristics, their solid-state design, security features and an easy handling, they are an appropriate storage medium in measurement data acquisition, but furthermore in the field of service and maintenance. This article is supposed to give an overview of the available storage media on the market as well as several ideas for the use in the field of measurement device instrumentation. In addition, the characteristics of the several flash cards are discussed, possible advantages and restrictions are compared.

Vittorio Belotti, Francesco Crenna, Rinaldo C. Michelini, Giovanni B. Rossi
WAVELET SIGNAL PROCESSING APPLIED TO RAILWAY WHEELFLAT DETECTION

Aim of this research is the development of a reliable automated procedure for the detection of wheelflat faults in railway diagnostics. This kind of fault occurs when the train wheel slides on the rail. The wheelflat produced by sliding is a relevant cause of acoustic pollution, passenger discomfort, damage to rails and boogies. A good wheelflat detection diagnostics is common interest, both, for railway and vehicles operators.
The diagnostic method presented in this paper is based on the wavelet analysis of accelerometric signals obtained by an experimental campaign on a test train. The application field for wavelet analysis is new, and the results hitherto obtained show a better and simpler issues than classical time-frequency based analysis.
From a statistical standpoint, the experimental data are exhaustive base to achieve relevant diagnostic estimates in the train speed range between 10 and 100 km/h. The wavelet analysis processing method allowed to distinguish a wheelflat defected wheel up to 94% of the considered cases. Moreover, the same accelerometer signal giving wheelflat diagnostic is used to measure the train speed by a proper processing method leading results within a 2% by respect to commonly used commercial sensor.

Norbert Nessler, Werner Reischer, Marcel Salchner
ELECTRONIC SKIN REPLACES VOLUNTEER EXPERIMENTS

Neutral electrodes (grounding plates used in electrosurgical operations) were tested with thermo cameras in volunteers experiments. These experiments are difficult to perform and expensive. A new test device swaroTEST with a measuring board "electronic skin" simulates the relevant electrical features of human skin to replace volunteer experiments. This device consists of a three dimensional resistor network representing the electric features of the skin and muscle tissue, and a temperature sensing array (one transistor for each cm²) to measure the resultant temperature increase after a standardized current load (700 mA hf current during 60 s, proposed in the relevant AAMI HF-18 standard). The comparison of test results with thermo camera images of volunteer experiments showed a sufficient coincidence, which proves the applicability of this test device to replace volunteer experiments.

Leon Swedrowski
DIAGNOSTIC MEASUREMENTS OF CURRENT SUPPLYING AN ELECTRIC MOTOR

The object of the investigation presented in the paper are measurements related to diagnostics of induction motors. The described system is based on the measurement and spectral analysis of current feeding an electric motor. Diagnostic methods of motor windings making use of the current analysis are already known. The author proposes involving in this method also examination of mechanical defects, in particular, damages caused to bearings. In order to obtain positive results it is necessary to theoretically obtain information referring to the type of components that accompany the current spectrum in certain sorts of faults. This can be accomplished by tests on a motor model. The model tests should be followed by creating an appropriate measuring system sensitive to the spectral components responsible for some specific damages . Due to the fact that the amplitude of the network voltage basic harmonic in the current spectrum is high, there has been proposed a preliminary elimination of this component from the analog current signal. The proposed filter and its characteristics are shown in the paper. Further processing of the signal is carried out numerically. The paper presents also the measuring system and provides results of the investigations carried out on real objects, i.e. faultless motors, and those encumbered with specially prepared defect.

Czeslaw Cempel
MULTI FAULT CONDITION MONITORING OF MECHANICAL SYSTEMS IN OPERATION

The paper presents the introductory results in application to multi fault condition monitoring of mechanical systems in operation, in particular internal combustion engines. This generalization to multi dimensionality and multi fault condition monitoring is possible by utilizing transformed symptom observation matrix, and by successive application of singular value decomposition (SVD). On this basis one can make full extraction of fault related information from symptom observation matrix created by traditional monitoring technology. Moreover, by SVD we can create several independent fault measures and indices, and some combined measures of overall system condition. In another words, full utilization of SVD enable us to pass from multi dimensional - non orthogonal symptom space, to orthogonal generalized fault space, of much reduced dimension. This seems to be important, as it can increase the scope and the reliability of condition monitoring of critical system in operation. It enables also to maximize the amount of condition related information, and/or to minimize redundancy in the primary symptom observation matrix, and the same, to redesign the traditional condition monitoring system.

Artur Robotycki, Romuald Zielonko
HOMOTOPIC METHOD OF FAULT DIAGNOSIS OF PIECEWISE LINEAR CIRCUITS BASED ON SENSITIVITY MODEL

In the paper a new homotopic method of fault diagnosis of analogue piecewise linear (PWL) circuits based on a large-deviation sensitivity model is presented. Homotopy maps one function f(x) into another g(x) by changing the homotopy parameter t∈[0,1]. The idea of the method relies on using the function f(x) to the description of the circuit under test (CUT) in the non-faulty state and the function g(x) to the description of the faulty CUT. For verification of assumed fault hypotheses node homotopic paths are used.
The method enables localisation and identification of parametric (soft) faults in nonlinear circuits of PWL type. It is simpler in interpretation and calculation and more robust to the influence of CUT element tolerances and voltage errors in comparison with the homotopic method previously proposed by authors. The method is illustrated by the example of single-fault diagnosis of a one-stage transistor amplifier.

A.Fort, C.Michelassi, M.Mugnaini, M.Catelani
SOFT FAULT DIAGNOSIS IN ANALOG LINEAR CIRCUIT BY ARX MODELLING

In this paper a soft fault diagnosis technique of analog linear circuits is presented. A Simulation-Before- Test (SBT) approach is used, where the fault dictionary is designed by circuit signatures obtained using ARX model identification.

Karel Chmelnik, Vaclav Cech
DIAGNOSTIC OF BEARINGS OF ELECTRIC MACHINES

Recently many articles discussing about shaft voltage and bearing currents and about their influence on operating life and reliability of sliding and anti-friction bearings appeared. Negative influence of electric current passing through bearings is known from beginning of the last century but new problems were occured with assotiation of electric machines feeding from static frequency converters. And just this problem is described in the article. We want to show our results of laboratory experiments and mathematical analysis of bearings damage in this paper.

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