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1. Monitoring policies
1.1 Periodic monitoring
Periodic (or continuous) machine monitoring, generally part of a conditional maintenance policy, triggers a programmed alarm. Depending on the type of fault(s) feared and the complexity of its (or their) detection, this is determined by choosing an indicator representative of the degradation and by determining a threshold amplitude deemed critical, over a defined frequency range.
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The chosen indicator can represent :
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a physical quantity (displacement, speed or acceleration of vibratory motion) :
• displacement for defects whose vibratory effects will be felt at very low frequencies, or when...
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Monitoring policies
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Standardization
Association française de normalisation AFNOR
NFE 90 300 May 1978 Mechanical vibration of machines with a rotation frequency between 10 and 200 per second. Basis for the development of assessment standards.
International Organization for Standardization ISO
Notion of cepstrum
1. Definition
There are generally two definitions of cepstrum.
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The first, particularly appropriate for vibratory signals, defines it as the inverse Fourier transform of the decimal logarithm of its direct Fourier transform (complex spectrum):
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