This paper gives an overview of the use of inverse methods in damage detection and location, using measured vibration data. Inverse problems require the use of a model and the identification of uncertain parameters of this model. Damage is often local in nature and although the effect of the loss of stiffness may require only a small number of parameters, the lack of knowledge of the location means that a large number of candidate parameters must be included. This paper discusses a number of problems that exist with this approach to health monitoring, including modelling error, environmental effects, damage localization and regularization.

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Damage identification using inverse methods

Prognostics and health management (PHM) is a framework that offers comprehensive yet individualized solutions for managing system health. In recent years, PHM has emerged as an essential approach for achieving competitive advantages in the global market by improving reliability, maintainability, safety, and affordability. Concepts and components in PHM have been developed separately in many areas such as mechanical engineering, electrical engineering, and statistical science, under varied names. In this paper, we provide a concise review of mainstream methods in major aspects of the PHM framework, including the updated research from both statistical science and engineering, with a focus on data-driven approaches. Real world examples have been provided to illustrate the implementation of PHM in practice.

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Prognostics and Health Management: A Review on Data Driven Approaches

There are a number of approaches to the modeling of cracks in beam structures reported in the literature, that fall into three main categories; local stiffness reduction, discrete spring models, an...

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Crack Modeling for Structural Health Monitoring

Cyclostationarity: New trends and applications

List of Figures. Foreword M. Vetterli. Preface. 1. Signal Models and Analysis-Synthesis. 2. Sinusoidal Modeling. 3. Multiresolution Sinusoidal Modeling. 4. Residual Modeling. 5. Pitch-Synchronous Models. 6. Matching Pursuit and Atomic Models. 7. Conclusions. Appendix A: Two-Channel Filter Banks. Appendix B: Fourier Series Representations. References. References for Poetry Excerpts. Index.

Adaptive Signal Models: Theory, Algorithms, and Audio Applications

Free-vibration behaviour of a cracked cantilever beam and crack detection

In the present method and apparatus for processing a vibro-acoustic signal (1) emitted by a high-voltage switching system, the vibro-acoustic signal (1) is converted into a digital signal (3). The digital signal (3) is rectified and the resulting rectified signal (5) is applied to a convolutional filter with a spectral window (6) to produce a smoothed signal (7). The smoothed signal (7) is decimated to produce a decimated signal (9) representing an envelope of the vibro-acoustic signal (1). A time realignment of the decimated signal (9) is carried out with respect to a reference signature (13A) to produce a realigned signal (11). Time deviation values generate an alarm if they exceed a limit threshold. The realigned signal (11) is added as a factor of means providing a reference signature (13A) and an actualized signature (13B). Variances (15A, 15B) of the realigned signal (11) are calculated with respect to the reference and actualized signatures (13A, 13B). The realigned signal (11) is compared with the actualized and reference signatures (13A, 13B) to detect a gradual behavior change or a sudden defect, taking the variances (15A, 15B) into consideration.

Vibro-acoustic signature treatment process in high-voltage electromechanical switching system

In order to detect, localize and interpret a partial discharge occurring in a partial discharge site along an electrical equipment, two measurement probes and a synchronization probe are installed along the electrical equipment. The measurement probes detect pulses travelling in the electrical equipment while the synchronization probe detects a phase angle in the electrical equipment and is usable for calibration purposes. A control unit receives the signals sensed by the probes and conditions them. Digital processings applied on the conditioned signals, involving their correlation, a time-frequency distribution and a form factor estimation, allows establishing a diagnosis indicating a detection of a partial discharge and its localization along the electrical equipment.

Detection, localization and interpretation of partial discharge

Phase spectrogram and frequency spectrogram as new diagnostic tools

According to the invention, the time synchronization of the phase between measurement devices that do not share a single clock for the respective sampling of the signals thereof is carried out by the time tagging of signal samples in time blocks followed by an adjustment of the phase values of components of interest of the signals in the grouped time blocks, such that said values refer to time references which are common between the measuring devices. The tagging is carried out using a synchronization signal that is available for the measuring devices, and that is completed by means of counting values provided by a counter operated by a reference clock for each measurement device.

François Léonard

Papers

Free-vibration behaviour of a cracked cantilever beam and crack detection

Vibro-acoustic signature treatment process in high-voltage electromechanical switching system

Detection, localization and interpretation of partial discharge

Phase spectrogram and frequency spectrogram as new diagnostic tools

Method and system for time synchronization of phase of signals from respective measurement devices