Analysis Of Measured Signals Research Articles

Condition Monitoring of Power Electronic Systems Through Data Analysis of Measurement Signals and Control Output Variables

A major disadvantage of existing condition monitoring methods is the need for additional sensors and measuring equipment. In this work, this disadvantage is eliminated by completely avoiding additional hardware. Instead, software-based methods from the field of machine learning are used. Therefore, measurement signals and control output variables are utilized, which are acquired and processed in any power electronic system for the purpose of converter control. The publication focuses on two main converter components: power semiconductors and dc-link capacitor. For each component, the aging mechanisms that have been studied in the literature are explained. Based on the aging mechanisms, the degradation indicators are identified. Then, a converter model is built that allows the variation of degradation indicators in order to analyze their effects on the available dataset. These findings form the basis for mathematical models, which detects future failure mechanisms of this type during converter operation. The test setup must offer the possibility of generating reproducible failure cases in various components with the aid of additional failure equipment. Finally, failure mechanisms are intentionally introduced at the test bench in order to validate the methodology of the developed approach.

Interpretation of Stall Precursor Signatures

Abstract Unsteady aerodynamic phenomena appearing close to the stall boundary in axial fans and compressors have been the subject of extensive investigations. A particular phenomenon known as “rotating instabilities” typically occurs in the tip region at highly loaded conditions and is often linked to blade vibrations. During rig and engine testing, it is usually identified by the characteristic shape of its pressure spectra. In the 1990s, this shape has been explained as the result of a circumferentially propagating disturbance, which is unsteady in a frame of reference rotating with the disturbance. In this analysis, conclusions regarding its propagation speed and frequency have been made based on the analysis of spectral peaks, and this method is still often used to classify unsteady aerodynamic phenomena. However, in high subsonic and transonic machines, where aeroacoustic and aeroelastic phenomena interact with aerodynamic disturbances, the interpretation of measurements using spectra alone is challenging. The present article aims to demonstrate the difficulties and subtleties associated with the analysis of measurement signals, which need to be overcome to correctly interpret stall precursor signatures. At the example of a recent investigation on a composite fan, the consequences of sensor placement and postprocessing techniques are discussed with a focus on spectral averaging, isolation of non-synchronous phenomena, and multisensor cross correlation methods. It is seen that the interpretation of phenomena based solely on spectral peaks and their spacing can be misleading and that the characteristic features of a rotating instability spectrum do not require an unstable pulsating disturbance.

Testing of a Polarimetric Current Sensor in the Frequency Domain.

This paper proposes an original model of a polarimetric current sensor, in which the measuring coil was made of a single mode telecommunication optical fiber ITU-T G.652, G.653, G.655, and G.657. This sensor was subjected to the commercialization process, which was carried out by a company combining the functionality of a technology transfer center with the capabilities of the Startit Fund Sp. z o.o. The published results included the analysis of the implementation readiness, the analysis of the market potential, the valuation of the industrial property rights of the invention and indicated further directions of scientific research on the sensor, which include the frequency analysis of measurement signals. This prompted the conduct of relevant scientific research. In this paper, the idea of measurement of current using polarimetric current sensor with optical fiber coil has been briefly characterized. It shows the definition and basic properties of the Discrete Fourier Transform (DFT). It discusses the technique of determining the value of each harmonic of signal at the input and output of polarimetric current sensor. The value of measurement errors and total harmonic distortion (THD) have been calculated. The general conclusions for disturbances in the processing realized in polarimetric current sensor have been formulated. In addition, the impact of the molar concentration of the dopant GeO2 in the core of the single mode telecommunication optical fibers and the impact of the number of turns of the measuring coil on the distortion accompanying the process of processing have been determined. Therefore, it can be concluded that the key result obtained during the research is the confirmation of the fact that single mode telecommunication optical fibers can be used to build the measuring coil of a polarimetric sensor used for measuring alternating currents. This means that the considered sensor, when measuring this type of currents, does not introduce additional distortions and distortions of their waveforms.

Analysis of the possibilities in railways shape assessing using GNSS mobile measurements

In recent years, a dynamic development of satellite positioning techniques using both static and mobile GNSS coordinates register mode can be observed. In addition, still developing Real-time GNSS Networks, post-processing algorithms and another measurement signal analysis algorithms, make the satellite measurements increasingly used in railway industry sector. In the article the possibilities which follows from the mobile satellite measurements in railway engineering are briefly presented. In the years 2009-2015, the authors conducted a series of field investigations on operated railway lines. The obtained results of these measurements led to the development of a number of algorithms that increase the range of applicability of GNSS measurements. The analysis of obtained results also showed how the accuracy of the measurements have increased since 2009. The achieved accuracy has been increased due to a development of GNSS positioning systems as well as improvement of the measurement methodology, i.e. configurations of satellite receivers and layouts of their placement on a mobile measuring platform. It was also found that the development of data analysis algorithms contributed to the increase in the obtained accuracy in assessment of a railway track axis shape. The authors indicate the possibilities of applying GNSS techniques at various stages of construction and operation of railways. According to the authors, the most important advantage of both the presented measurement technique and computational methodology is the ability to effectively and relatively low-cost data acquisition regarding the existing state of the railway line. These data can be successfully used to design changes to the geometry of railway lines, and therefore satellite positioning has enormous application potential in the process of modernization of operated railway lines.

Determination of Aerosol Size Distribution from Angular Light-Scattering Signals by Using a SPSO-DE Hybrid Algorithm

The comparison of the angular light-scattering method (ALSM) and the spectral extinction method (SEM) in solving the inverse problem of aerosol size distribution (ASD) are studied. The inverse problem is solved by a SPSO-DE hybrid algorithm, which is based on the stochastic particle swarm optimization (SPSO) algorithm and differential evolution (DE) algorithm. To improve the retrieval accuracy, the sensitivity analysis of measurement signals to characteristic parameters in ASDs is studied; and the corresponding optimal measurement angle selection region for ALSM and optimal measurement wavelength selection region for SEM are proposed, respectively. Results show that more satisfactory convergence properties can be obtained by using the SPSO-DE hybrid algorithm. Moreover, short measurement wavelengths and forward measurement angles are beneficial to obtaining more accurate results. Then, common monomodal and bimodal ASDs are estimated under different random measurement errors by using ALSM and SEM, respectively. Numerical tests show that retrieval results by using ALSM show better convergence accuracy and robustness than those by using SEM, which is attributed to the distribution of the objective function value. As a whole, considering the convergence properties and the independence on prior optical information, the ALSM combined with SPSO-DE hybrid algorithm provides a more effective and reliable technique to obtain the ASDs.

An Analysis of Measurement Signals in Ventricle Assist Device in Terms of Their Diagnostic Usefulness

In this paper an analysis of the available measurement signals in external, pulsatile ventricular assist pump is carried out to evaluate their diagnostic usefulness, and to propose diagnostic system for such devices. Firstly, short description of device and used methodology is provided. Then a full set of diagnostic test is described. Next, diagnostic matrixes are defined. Paper ends with an analysis of the influence of measurements set on accuracy of diagnostic system.