Pseudo-cyclostationarity of bearing IAS signals: cage resynchronisation & synchronous averaging
Résumé
This work explores the potential of using the cage referential for cyclicity to process IAS (instantaneous angular speed) signals. IAS signals are naturally expressed in the shaft angular referential on which the encoder is mounted. It is known that defective bearings produce cyclic variations of IAS. However, due to varying contact angle or slippage, a loss of cyclicity can occur with direct consequences on the efficiency of cyclicity-based signal processing techniques. This paper proposes a method to measure the deviation from the expected fault frequencies. The evolution of the cage speed with respect to the operating conditions is then observed. A method to restore the cyclicity of IAS signals is proposed. The restoration should allow easier diagnostic tasks, which is explored at the end of the paper. The developments are based on IAS signals from a 2MW wind turbine with a defective bearing.
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