Research On The Compound Fault Of Gearbox On The Basis Of Wavelet Analysis

With the rapid development of the mechanical industry towards high precise and automation,the inner structure and the operation condition of the mechanical parts have become increasingly complex.As one of the most important gearing mechanical parts,the application value of the gear case has universality and the research value has a universal meaning.Since the gear case has complicated inner structure and severe working condition,the fault mode of the gear case turns from the simplification towards compound.In addition,the compound faults have mutual effect and mutual restriction between each other and the fault diagnosis cannot be conducted accurately,which leads to the increase of the damage of the gear case and the risk of the accidents.According to this background,this paper studied a diagnostic method of the compound fault of the gear case on the basis of the wavelet analysis.Firstly,after reviewing the previous studies on the failure mode of the gear case as well as the failure mechanism of the wheel gear and the antifriction bearing within the gear case,the characteristics of each failure mode of the wheel gear and the antifriction bearing are obtained.Secondly,on the basis of wavelet analysis and the compound fault features,this paper studied a unique allocation criterion of the compound fault band based on the wavelet decomposition.With the help of this criterion,two kinds of extraction algorithm of the compound fault features were proposed: at the state of the constant rotate speed,the limitation of the envelope in the application of compound fault was analyzed and an improved envelope demodulation algorithm,namely envelope energy ratio demodulation algorithm;at the state of variable rotate speed,the failure recognition capability of the angle-domain resampling order ratio spectrum within the non-stationary signal was adopted to realize the extraction of the compound feature extraction.Thirdly,the practical test data of the gear case testbed were combined to the extraction method of the compound fault proposed in this paper in order to realize the diagnosis of the compound fault of the gear case.Through the simulation and experiment,the following conclusions can be obtained: both the demodulation algorithm of the envelope energy ratio and the order ratio spectrum proposed by this paper can extract the compound fault features of the gear case accurately and achieve the goal of compound fault diagnosis.On the basis of comparison between these two algorithms,what can be concluded is that when the working mode of the antifriction bearing is the rotate of the inner ring with the axis of rotation and in the condition of constant rotate speed,the order ratio spectrum can reflect the bearing inner ring fault more easily compared with the demodulation algorithm of the envelope energy ratio.