Lanto Rasolofondraibe

Improvement of the sensitivity of the scalar indicators (crest factor, kurtosis) using a de-noising method by spectral subtraction: application to the detection of defects in ball bearings

The aim of this article is to show the interest of spectral subtraction for the improvement of the sensitivity of scalar indicators (crest factor, kurtosis) within the application of conditional maintenance by vibratory analysis on ball bearings. The case of a bearing in good conditions of use is considered; the distribution of amplitudes in the signal is of Gaussian kind. When the bearing is damaged, the appearance of spallings comes to disturb this signal, thus modifying this distribution. This modification is due to the presence of periodical impulses produced each time a rolling element meets a discontinuity on its way. Nevertheless, the presence of background noise induced by random impulse excitations can have an influence on the values of these temporal indicators. The de-noising of these signals by spectral subtraction in different frequency bands allows to improve the sensitivity of these indicators and to increase the reliability of the diagnosis.

Advanced detection of rolling bearing spalling from de-noising vibratory signals

The aim of this article is to show the interest of spectral subtraction for the improvement of the sensitivity of scalar indicators (crest factor, kurtosis) within the application of conditional maintenance by vibratory analysis on ball bearings. The case of a bearing in good conditions of use is considered; the distribution of amplitudes in the signal is of Gaussian kind. When the bearing is damaged, the appearance of spallings comes to disturb this signal, modifying this distribution. This modification is due to the presence of periodical impulses produced each time a rolling element meets a discontinuity on its way. Nevertheless, the presence of background noise induced by random impulse excitations can have an influence on the values of these temporal indicators. The de-noising of these signals by spectral subtraction in different frequency bands allows to improve the sensitivity of these indicators and to increase the reliability of the diagnosis.

Performance of wavelet denoising in vibration analysis: highlighting

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.

Method of De-Noising By Spectral Subtraction Applied to the Detection of Rolling Bearings Defects

In this paper we aim to show the significance of spectral subtraction for the improvement of the sensitivity of scalar indicators (crest factor, kurtosis) within the application of conditional maintenance by vibratory analysis on ball bearings. If we consider the case of a bearing in good condition of use, the distribution of the amplitudes in the signal is Gaussian. When the bearing is damaged, the appearance of spallings disturbs this signal, modifying this distribution. This modification goes through the presence of periodical impulses produced each time a rolling element meets a discontinuity on its way. Nevertheless, the presence of background noise induced by random impulse excitations can have an influence on the values of these temporal indicators. The de-noising of these signals by spectral subtraction in different frequency bands allows us to improve the sensitivity of these indicators and to increase the reliability of the diagnosis.

Early Detection of Rolling Bearing Defect by Demodulation of Vibration Signal Using Adapted Wavelet

Vibratory analysis allows us to interpret the fundamental conditions of rotating machines. This interpretation is useful in the diagnosis of defects. Many studies implement advanced processing tools for mechanical detection of defects in individual components. Among these processes, wavelet demodulation is a powerful tool for signal processing. This technique requires the use of a traditional wavelet, such as a Morlet wavelet, which is defined by two parameters: Decrease and frequency. However, this determination is hard to do. Moreover, the processing required is very expensive in computing time, which prevents instantaneous follow-up. This paper suggests a new form of wavelet, which is adapted to shock response, and a methodology for its use in which the parameters are determined automatically.

High-resolution methods in vibratory analysis : application to ball bearing monitoring and production machine

Abstract This paper is concerned with the implementation of parametric spectrum analysis using a high-resolution technique for setting up a conditional maintenance program via vibration analysis on a forming press. To achieve this, the resolving power of signal-processing-based parametric techniques is illustrated using spectrum assessment computation. Processing of the experimental results enabled (i) various autoregressive (AR) spectrum analysis methods and especially Burg’s algorithm to be tested and (ii) conventional spectrum analysis techniques such as the correlogram to be compared with parametric methods in terms of detection level as well as for mechanical component fault monitoring, especially ball bearing defects. Among various possible models, the AR model was retained along with Burg’s algorithm and the Akaike information criterion. A detection and location methodology for faults likely to occur on rotating machinery was developed on the basis of the results that were obtained. The methodology, supplementing other analysis techniques, relies on the understanding of component spectrum behavior and various constraints, such as component access, spectral resolution of the industrial measuring device, and statistical properties of the power spectral density measurements of a random signal. The results show that parametric methods are particularly worthwhile in the early detection of component defects, especially when two characteristic frequencies are close to one another. However, the complexity of these techniques necessitates many precautions when they are implemented; consequently, they should not replace conventional methods, but supplement them.

A Novel Capacitive Safety Device for Target Localization and Identification

A novel capacitive device dedicated to the safety of people working on automated production sites has been developed. It can be implemented on an articulated mechanical system (robot, press) to estimate the distance between sensors that are fixed on such a system and a mobile target. An interdigital sensor has been fabricated to identify the target nature among them (human beings or objects). The variable geometry of the system is taken into account as well as its motion relatively towards the ground by means of an ingenious sensitive element design. Furthermore, the sensors are made of conducting paint, thus providing low weight and negligible space hindrance devices. Results show this novel low-cost sensing setup has a great potential to estimate the distance and to discriminate targets.

Capacitive Sensor Device for Measuring Loads on Bearings

This paper aims to present an experimental device, which measures the displacement of an outer ring of a roller bearing subjected to two loads: a stationary load and a rotational load. This displacement is measured with a very high degree of accuracy, by means of a capacitive probe. The probe and its associated electronics convert the displacement into a proportional voltage. The relation displacement/load is proportional since linear elasticity domain of the material is not exceeded. The empirical mode decomposition applied to the measured signal allows discriminating the stationary and rotational loads and thus gives an easy access to the value of the load. Both the numerical simulations and prototype testing confirm the relevance of the device. The applications are numerous: 1) located on the wheels of motor vehicles, potential optimization of the information received by the integrated safety devices; 2) opportunity to measure the load on lifting equipments; and 3) possibility to monitor the defects of machines through vibratory analysis.

Static Stress Measurement Based on Capacitive Probes Integrated Inside Rolling Rings

An experimental setup has been conceived to measure the deformation of a rolling ring subjected by stress. This deformation is measured by means of a capacitive sensor. Such a sensor behaves like a displacement sensor that translates the displacement into an electrical signal. Mechanical and electrical operating points determine the sensitivity of the probe and its measurement range. Numerical simulations and tests performed on a prototype confirm the relevance of the device. Applications are numerous: i) mounted on the wheels of motorized vehicles, such sensors allow one to improve the quality information transmitted to integrated safety devices and ii) placed on devices of lift, they measure the load.

Numerical determination of the mechanical stiffness of a force measurement device based on capacitive probes: Application to roller bearings

Abstract Bearings allow external loadings to be transferred from one raceway to the other through rolling elements, which induces strains in the bearing constituents. In order to measure the radial component of these forces, the fixed ring is inserted within a housing equipped with capacitive probes able to measure displacements with very high sensitivity. This work mainly focuses on determining the optimal housing shape using FE simulations and their influence on the global stress state undergone by the structure. Finally, an averaged global stiffness is computed, allowing proper calculation of the contact forces involved in the bearing.