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In this work, singular spectrum analysis is employed to process vibration signals resulting from rolling bearings. A monitoring indicator is defined from the fact that the structure of a signal recorded from a bearing becomes more complex when the bearing becomes defective. This can be explained by the nonstationarity and the nonlinearity induced by the defect. The effects of operating parameters such as load and speed on the indicator are studied. Results demonstrate that the indicator defined in this paper is less sensitive to these parameters than the rms value, a traditional vibratory indicator.

This paper proposes to highlight two aspects of denoising in vibration analysis. The first aspect aims to reveal the singularities, and the second eliminates the noise in order to keep the useful signal. These two aspects are the cause of the surjection of denoising, especially due to the choice of the performance criteria. This paper highlights the use of denoising through these aspects, and then proposes a performance criterion suitable for vibration analysis as part of a noise suppression, to apply a processing method. This paper provides a reflection on the use of discrete wavelet transform through the various parameters which are used during processing.

Within the framework of monitoring rotating machines, vibration analysis remains an effective tool for fault detection. This analysis generally consists of measuring acceleration signals from critical and judiciously chosen points of a machine with the help of piezoelectric sensors. However, relevant information concerning the machine health can be masked by disturbances such as noise. The detection reliability will then be conditioned directly by the quality of the collected signal. Signal preprocessing methods, in particular denoising methods, can significantly improve the detection quality in terms of reliability. In this paper we aim to compare two methods of denoising based on signal spectral content analysis: discrete wavelet transform and empirical mode decomposition. A first study is carried out in order to optimize specific parameters related to each of the two methods, starting from experimental data obtained on degraded bearings. In fact for each parameter, one has to define conditions which allow the best detection of periodic pulses in vibration signals thanks to indicators such as kurtosis and crest factor. The second study consists of assessing the effectiveness of each denoising method on a vibration signal measured on a failed bearing. This signal is then disturbed by various noises simulated with variable levels. This study aims to show the effectiveness of each of these two methods on the early detection of impulse defects.

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This study evaluated the possibility of infrared thermography to measure accurately the temperature of elements of a rotating device, within the scope of condition monitoring. The tested machine was a blower coupled to a 500 kW electric motor, that operated in multiples regimes. The thermograms were acquired by a fixed thermographic camera and were processed and recorded every 15 minutes. Because the normal temperature variations could easily mask a drift caused by a failure, a corrected temperature was computed using autorecursive models. It was shown that an efficient temperature correction should compensate for the variations of the process, and for the ambient temperatures variations, either daily or seasonal. The standard deviation of the corrected temperature was of a few tenth of degree, making possible the detection of a drift of less than one degree and the prediction of potential failure.

Cetteétude explore l'utilisation des techniques de Machine Learning pour la classification de l'état d'outils en usinage. Une analyse spectrale singulière (ASS) pseudo-locale des signaux vibratoires relevés sur le porte-outil, coupléeà un filtrage passe-bande a permis la définition et la mise enévidence d'indicateurs très sensiblesà l'évolution de l'état de l'outil. Ces indicateurs sont définisà partir des sommes des raies spectrales des signaux reconstruits par ASS et de leurs résidus, dans des gammes de fréquence judicieusement choisies. Les taux de reconnaissance de l'usure sont très bons et dépassent les 80 %. Cetté etude met enévidence deux aspects importants : la forte richesse en information des composantes hautes fréquences des signaux vibratoires et la possibilité de s'affranchir du bruit inutile par la combinaison de l'ASS et d'un filtrage passe-bande.