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Blind Enhancement of Harmonically Related Signals by Maximizing Skewness
Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering. Rubico Vibration Analysis AB.
2014 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Rolling element bearings are used in rotating machinery in various industry branches. Their health status must be monitored continuously in order to establish proper operational conditions in a production process. Numerous approaches, which can be investigated under the subject of ``Condition Based Maintenance", have been studied within mechanical engineering and signal processing to be able to detect and classify possible faults on rolling bearings.Periodic impulsive signals can emerge from defected bearings within rotating machinery. As the signal is distorted by an unknown transfer function, noise and severe interference, the challenge becomes to reduce these effects as much as possible to extract valuable and reliable information about the rolling bearings' health status. Without any observation of the source signal, a scale-invariant higher order moment, skewness, can be used as a tool to characterize statistical properties to enhance the desired signal. It is the impulsiveness, thus asymmetry of the signal that will be promoted. To assess the performance of skewness, a signal model that consists of harmonically related sinusoids representing an impulsive source is built. Depending on such a model, surface characteristics of skewness are investigated. In relation to harmonic content, the ability of skewness in discovering such harmonic relation is studied. It has been observed that the optimization process converges to a setting where all harmonics are preserved, while any component that does not possess such a harmonic relation is suppressed. In the case of multiple mutually inharmonic source signals with harmonic support, it is shown that skewness maximization results in a setting where only the harmonic set with highest skewness remains. Finally, experimental examples are provided to support theoretical findings.

Place, publisher, year, edition, pages
Luleå tekniska universitet, 2014.
Licentiate thesis / Luleå University of Technology, ISSN 1402-1757
Research subject
Signal Processing
URN: urn:nbn:se:ltu:diva-26461Local ID: e5906010-90eb-433e-a39f-7f3d5e682f7dISBN: 978-91-7439-917-2ISBN: 978-91-7439-918-9 (PDF)OAI: diva2:999623
Godkänd; 2014; 20140214 (kubova); Nedanstående person kommer att hålla licentiatseminarium för avläggande av teknologie licentiatexamen. Namn: Aziz Kubilay Ovacikli Ämne: Signalbehandling/Signal Processing Uppsats: Blind Enhancement of Harmonically Related Signals by Maximizing Skewness Examinator: Professor Johan Carlson, Institutionen för system- och rymdteknik, Luleå tekniska universitet Diskutant: Tekn. Dr. Magnus Sandell, Toshiba Research Labs, Bristol, UK Tid: Onsdag den 4 juni 2014 kl 10.15 Plats: A1545, Luleå tekniska universitetAvailable from: 2016-09-30 Created: 2016-09-30Bibliographically approved

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