The Study On Incipient Bearing Fault Diagnosis Of Wind Turbine Gearbox Under Gear Signal Interference

Gearbox is an important part of wind turbine transmission system,under the irregular alternating load and poor operating conditions,the probability of bearing failure in gearbox member is the highest,and the downtime is the longest.Therefore,the bearing failure initiation mastered in order to advance the diagnosis to the early stages of abnormal symptoms associated with failure and degradation information,can effectively avoid the economic loss caused by fault or the occurrence of major accidents.However,in the early stage of bearing failure,transient impact characteristic information is weak.The early weak feature extraction method represented by high frequency demodulation technique is widely used in industry because of its simple principle.But the technology is susceptible to other interference signals.The gear signal is widely used in the vibration signal as the interference component,which increases the difficulty of removing the gear signal.In the time domain,the vibration signal generated by gear meshing will cover the bearing impact characteristics,and there will be more interference peaks in the spectrum.It is necessary to remove the weak characteristic of the bearing.At the same time,the high frequency demodulation technology based on the spectral kurtosis is susceptible to the random impact signal,and the demodulation bandwidth cannot be selected precisely.For this purpose,this paper studies the separation of gear signal interference and the accurate selection of frequency band in high frequency demodulation.Firstly,the structure and failure modes of gearbox are analyzed,meanwhile the influence of special operation condition and complex structure on vibration signal is analyzed.The characteristic frequency can be conveniently located to the specific fault type to realize the precision fault identification.Therefore,the common failure types and vibration mechanism of bearing are analyzed.And the validity of fault diagnosis of early weak signal of fault bearing is verified by using envelope demodulation method,which provides the theoretical basis for the fault diagnosis.Secondly,in view of the gear mesh amplitude has an impact on covering up early weak characteristic information of fault bearing and selecting precisely the high frequency resonance center band caused by fault bearing,the generalized demodulation algorithm can change time-varying signal into stationary signal with frequency constant,rolling bearing fault diagnosis method of gear signal separation based on iterative generalized demodulation is proposed.The separation of the harmonic signal and the order resampling technique of non-bonding phase are solved mainly to realize the early weak feature information extraction and fault type discrimination of gear box bearing.Finally,in order to solve the problem of the influence of stochastic impact on the optimal high frequency resonance demodulation band with the use of resonance demodulation to extract the weak characteristic information of the bearing.According to characteristics of fault bearing transient impact characteristics represented by Multievaluation index from different angles and uncertainty measurement represented by entropy weight method,the bearing optimal demodulation center disturbed by random shocks and bandwidth selected precisely are solved mainly.The effectiveness of the technique is verified by simulation and experiment.