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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.

Tihomir Mihalic, Tomislav Stašic, Nastia Degiuli
UPGRADING OF A BELL PROVER

Bell provers have a wide usage for calibrating various types of flow meters by timing the bell ascendance. They are often used as a working standard. Known area of the bell along with measured displacement of the bell produce, with some measurement uncertainty, volume generated by the bell. This volume with measured time gives the flow generated by the bell.
The temperature and the pressure of the gas in the bell are not constant. Further more the temperature and the pressure at the flow meter are not equal to those in the bell due to losses in pipes. Because of that it is imperative to measure all of them. When those measurands are stored in database entire measurement can be analyzed at referent conditions.
In order to automate measurements with the bell prover, to improve the measurement uncertainty of the results, and to obtain some additional quantities like velocity and acceleration of the bell, computerized measurement equipment has been installed on the bell prover.

Nastia Degiuli, Andreja Werner, Zdravko Doliner
EXPERIMENTAL DETERMINATION OF WAVE PATTERN RESISTANCE OF A TRIMARAN

The experimental determination of wave spectra and wave resistance from measurements of the wave pattern behind a ship model while being towed in a tank received considerable attention in the sixties and seventies. The Landweber, Hogben and Baba methods of experimental determination of wave pattern resistance based on wave height measurements in several longitudinal measurement cuts have been introduced in this paper. The programme of experimental determination of wave pattern resistance has been carried out in DINMA-Trieste for a trimaran whose individual hulls are Wigley parabolic models, for the Froude number range 0.254-0.420, with a total of 12 runs. The above mentioned methods are based on identical hydrodynamic model, and a starting basis are identical analytic expressions. By experimental determination of wave pattern resistance, a comparison of the calculation results (amplitude spectrum, wave resistance, reconstructed waveforms) is given. It has been shown that all three methods are equal and that they give the same results if the criteria based on frequency content determination and resolution in frequency are respected.

Andrej Predin, Ignacijo Biluš
SECONDARY FLOW MEASURING AT THE RADIAL FAN ENTRANCE

Analyze is given of different measuring methods relating to the prerotation flow in the entrance pipe of the radial pump. The appearance of the prerotation flow is a result of complicated fluid flow model, which appears as a consequence of the pump operating out of design point and reduce the pump efficiency. The goal of this contribution is in estimating the adequate measuring method, taking into account the inconvenience of conventional Laser – Doppler anemometry. Therefore, two measuring methods – multiblade (ASB) and single blade anemometer (ASSB) are introduced, analyzed and compared with well known 2 channel hot wire anemometry (HWA). The advantages of the introduced measuring system - ASB are in its simple construction and simple use and its low price. Direction and the swirl flow intensity in the entrance pipe of radial pumps and fans, using this method, could be measured.

Mihail Radu Patrascoiu
PROPOSED METHOD FOR GAUGE CALIBRATION BY A SERIES EXPANSION SYSTEM AT NML–CSIR, SOUTH AFRICA

There are various types of series expansion systems around the world, offering high accuracy for calibration of standards. The method investigated in this paper considers a much simpler system with a higher degree of certainty in measurements. The novelty of the method does not offer a new calculation, but rather a muchsimplified design Instead of using a high number of vessels, where the gas expands into, the system is limited to only two. The uncertainties will relate only to the pressure reduction factors or volume ratios and other known external factors.

Milan Adámek, Miroslav Matýsek, Petr Neumann
SMALL GAS FLOW MEASUREMENTA MICROCOMPUTER APPLICATION

This paper presents a flowmeter design applicable for measurement of low gas flow amounts. The designed flowmeter with a time–of–flight sensor represents a microcomputer application with a control and evaluation procedure. The mathematical model of energy and temperature balance is simulated in the FEMLAB environment. The designed measurement device was used for research of a reaction kinetics of biodegradation reactions successfuly.

Florian Maier, Bernhard G. Zagar
EXPERIMENTAL ULTRASONIC FLOW MEASUREMENT IN SMALL CAPILLARIES

In this paper we present preliminary results of an ultrasonic flow measurement set-up designed to accurately measure the flow velocity profile of blood mimicking fluid pumped through a capillary flow phantom even under the deteriorating effects of clutter and noise always seen in medical ultrasound applications. The measurement system is set up in a way to acquire and display 3-dimensional velocity and/or topological data.

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