The Initial Phase Selection Of DDTFA And Its Application In Gear Fault Diagnosis

As a necessary key component of gear box of transmission mechanism,gear is complex,its state monitoring and fault diagnosis directly affect the safe and normal operation of complex transmission,and have great economic value and security value to the enterprise and even the society.The traditional gear fault diagnosis method for constant working conditions has been unable to meet the actual demand.It has become a hot topic for scholars at home and abroad to explore the gear fault diagnosis method based on non stationary signal in variable working condition.The core of the fault diagnosis based on the variable speed condition of vibration signal is to extract fault information from the vibration signal by using a suitable non stationary signal processing method.Sparse decomposition method is widely used in the decomposition of non-stationary signals in recent years because of its good adaptability and reflecting the essence of signals.Data-Driven Time-Frequency Analysis(DDTFA)Method is a newly proposed sparse decomposition method,This method realizes the sparse decomposition of the signal by solving the optimization problem,and obtains the time and frequency distribution of the signal.It has a definite mathematical theory basis,and can extract the non-stationary component of the signal accurately from the time-varying non stationary signal.The thesis is selected from the National Natural Science Foundation of China Youth Science Foundation "Research on mechanical fault diagnosis method based on nonlinear matching pursuit and data-driven time-frequency analysis"(51605151),based on the theoretical study of the DDTFA method,the selection of the initial phase function is studied,and the DDTFA method for selecting the initial phase functions by two different ways is put forward,and it is applied to the gear fault diagnosis of variable working conditions.The main research work of this paper is as follows:(1)The DDTFA method is studied theoretically,and analyzed from the aspects of decomposition accuracy,noise immunity and anti aliasing capability compared with the EMD method;the influence of initial phase function and bandwidth control parameters on DDTFA decomposition ability is studied,and the simulation shows that the trend of initial phase function is the key factor affecting DDTFA decomposition ability.(2)Based on the initial phase function trend directly affects the decomposition ability of DDTFA to non-stationary signals,while the trend of initial phase function can be converted to the instantaneous frequency of the signal in physical sense,the Multi-Scale Chirplet Sparse Decomposition(MSCSD)method,which can accurately estimate the instantaneous frequency of the signal,is used to estimate the initial phase function of DDTFA,and a MSCSD-DDTFA method is proposed.Firstly,the accuracy of MSCSD for non-stationary signal instantaneous frequency estimation is simulated and verified,which is superior to the Synchrosqueezing Transform(SST)method and General Parameterized Time-Frequency Transform(GPTFT)method.Then the simulation analysis verifies the accuracy of the MSCSD-DDTFA method for the non-stationary signal decomposition.Finally,the method is applied to the variable speed gear fault diagnosis of gear teeth,and the effectiveness of the method is verified.(3)Based on the poor timeliness of the MSCSD-DDTFA method,and the Variational Mode Decomposition(VMD)method can quickly and accurately decompose the central frequency of each component and the good noise resistance,VMD is used to select the initial phase of the DDTFA,and the VMD-DDTFA method is proposed.The simulation verifies the accuracy,anti noise and anti modal confusion of VMD-DDTFA for non-stationary signal decomposition.The method is applied to the fault diagnosis of gear crack in variable speed,and the effectiveness of the method is verified.(4)The validity of the method is verified by the comparison of two methods,MSCSD-DDTFA and VMD-DDTFA,from adaptability,timeliness,anti modal confusion and anti noise,and the influence of different bandwidth control parameters of MSCSD-DDTFA and VMD-DDTFA methods on the decomposition results of non-stationary simulation signals is also discussed.