Research On The Vibration Characteristics And Diagnosis Technology Of Gearbox Composite Fault

As one of the most important transmission parts of mechanical equipment,the working condition of gearbox will directly affect the operation of the whole equipment.In addition,the signal contains background noise,which makes the weak fault feature often submerged and difficult to identify.Therefore,how to use the effective signal processing method to separate and extract the fault features of the composite fault signal with noise is the key to the research of the composite fault diagnosis technology of gearbox.Firstly,the fault vibration characteristics of the gear and the test equipment are analyzed.This paper mainly analyzes the type and vibration mechanism of gear fault,establishes the mathematical model of gear fault vibration signal,and on this basis,analyzes the vibration characteristics of gear tooth breaking,pitting,wear and composite fault in time and frequency domain,and briefly introduces the gearbox test platform in this paper.Secondly,a composite fault diagnosis method for gearbox based on EMD and improved variational mode decomposition is proposed.Due to the improper value of the number of modal components k and penalty factor ?,or the influence of noise,there will be aliasing,frequency crossing and noise components phenomenon in the decomposition results of VMD.While the essence of EMD method is equivalent to a wiener filter,which has complete adaptability when processing signals.Therefore,EMD is used to denoise the fault signal and obtain the combined modal function(CIMF);then,the waveform method and envelope entropy are used to improve the VMD method to determine the combination of parameters k and ?,and the improved VMD decomposition of CIMF is carried out according to the obtained parameter values to achieve the purpose of fault feature separation;finally,the envelope demodulation spectrum analysis is carried out for the decomposed finite bandwidth modal components to extract the fault features barrier characteristic frequency.The effectiveness of the proposed method is verified by the simulation signal and the pitting-wear composite fault test signal of the gearbox.Then,a composite fault diagnosis method for gearbox based on improved local mean decomposition is proposed.When the LMD method decomposes the complex fault signal with background noise,it is easy to have mode aliasing phenomenon,and the weak fault feature is easily submerged by noise.However,MCKD has a good effect in improving SNR and enhancing weak fault characteristics.Therefore,MCKD is used as the prefilter of LMD method to improve it,and the fault signal is denoised by MCKD;then the denoised signal is decomposed by LMD;finally,the strong correlation PF component is selected for Hilbert envelope demodulation spectrum analysis to extract the fault characteristic frequency.The effectiveness and superiority of this improved method is verified by comparing simulation signal and the composite fault test signal of gearbox broken-wear.Finally,a composite fault diagnosis system of gearbox based on VB is designed by combining VB and MATLAB.Through the analysis of the functions needed by the system,this paper introduces the overall interface design of the system,including login interface,information acquisition module,amplitude value domain analysis module,improved LMD analysis module,EMD and improved VMD analysis module.Through the operation of each module interface,it shows its specific functions.