Research On Planetary Gearbox Fault Diagnosis Method Based On Time-Frequence Demodulation Analysis

Planetary gear trains system is a key part of the mechanical transmission system. It is widely used in aerospace, shipbuilding, wind energy equipment, engineering machinery and other fields. Once a component fails in operation, it will lead to an impact on the entire equipment. For this reason, new methods and new technologies of fault diagnosis based on the time-frequency demodulation analysis are studied in this thesis for the purpose of the planetary gearbox condition monitoring and fault diagnosis. The main contents of this thesis are as following several aspects:(1) According to the problem that there is a deviation between the theoretical calculation frequency and actual failure frequency in the traditional planetary gearbox fault vibration spectrum characteristics analysis method, a new fault spectrum analysis method that regards planetary gear structure of the system as the equivalent structure of bearing is proposed and accurately characterizes the fault characteristic frequency of the planetary gearbox components. It provides a theoretical basis for the subsequent signal fault feature extraction.(2) Based on the non-stationary characteristics of planetary gearbox vibration signals, the combination of wavelet packet transform and Hilbert envelope demodulation technology is used in the planetary gearbox fault diagnosis and effectively extracts the high frequency shock component of planetary gearbox fault.(3) Focusing on the problem of early weak fault feature extraction for planetary gearbox, the method that combines lifting wavelet package transform with maximum kurtosis index is proposed for planetary gearbox fault diagnosis and ideally extracts the high frequency shock characteristic information on planetary gearbox early weak fault.(4) To extract fault feature of planetary gearbox under strong noise background, ensemble empirical mode decomposition(EEMD) that is a noise-assisted analysis method to overcome the modal aliasing of the classical empirical mode decomposition(EMD) method, is utilized in the fault diagnosis of the planetary gearbox and displays the obvious advantages of the EEMD method in the high frequency part characteristics extraction of the planetary gearbox under strong noise background.(5) The monitoring and diagnosis system software is developed based on time-frequency demodulation analysis. Introduce structure and function of this software. This software achieves calling data for the condition monitoring and fault diagnosis of planetary gearbox in MATLAB environment.