Research On Composite Fault Feature Extraction Method Of Gear Transmission System

Gear transmission system is an important part of mechanical equipment,and its operational health is very important.Not only will it be affected by defectivevparts,but it will also be affected by background noise during operation,which will cause the fault features in the signal to be submerged,and cause great trouble to the extraction and recognition of fault features.Therefore,how to effectively identify and extract the fault features in the composite fault signal is the key to ensure the normal operation of the gear transmission system.Firstly,the fault vibration analysis and experimental device of gear transmission system are introduced.The thesis introduces the fault type,cause and characteristic frequency of gear and bearing,and then introduces the vibration mechanism of gear and bearing,on the basis of which the vibration model of gear,bearing and composite fault is established.Finally,the experimental equipment is introduced.Secondly,a method to extract composite fault features of gear transmission system based on NMD is proposed.The EMD,EEMD and NMD methods are used to process the composite fault signal,and then the selected components are demodulated by symmetric difference energy operator.Simulation signal and gear pitting-wear composite fault signal verify the effectiveness of the proposed method.Then,a method for extracting composite fault features of gear transmission system based on improved CEEMDAN is proposed.The collected composite fault experiment signal contains a lot of noise,which causes great interference to the feature extraction of composite fault.Therefore,the CEEMDAN method is first used to decompose the composite fault signal,then appropriate components are selected according to the correlation coefficient method,and the selected components are denoised by wavelet threshold value,and finally the selected components are demodulated by symmetric difference energy operator.The effectiveness of the proposed method is verified by the simulation signal and the composite fault signal of gear wear bearing outer ring damage.Finally,a method for extracting composite fault features of gear transmission system based on improved ITD is proposed.Aiming at the modal aliasing phenomenon that appears in the signal processing process,and the fault characteristic information will be submerged in the noise.The MCKD is used as a pre-filter to filter the signal,and then ITD decomposes the filtered signal,and then demodulates the selected components using the symmetrical differential energy operator demodulation method.The effectiveness of the proposed method is verified by the simulation signal and the composite fault signal of gear broken tooth wear.