Research On Fault Diagnosis Technology Of Gearbox Based On Time-Frequency Analysis

As a common rotating machinery,gearboxes are widely used in many fields such as machining,wind power generation,aerospace,etc.Because of their long-term operation in harsh working environments such as variable working conditions and strong impacts,the core components are prone to failure,affecting the operation of the entire equipment and even causing serious safety accidents.So it is of great significance to monitor and diagnose the condition of the gearbox during operation.This paper takes fixed-axis gearboxes and planetary gearboxes as the research object,and proposes a gearbox fault diagnosis method based on timefrequency analysis.A high-quality time-frequency analysis method is obtained by optimizing the window function of Gabor transform in the fractional domain,and uses it in the tacholess order tracking.The main contents of this paper are as follows:(1)Research the current domestic and foreign development status of gearbox fault diagnosis technology under variable working conditions,analyze the fault mechanism of gears,and propose different calculation failure characteristic frequency calculations for fixed-axis gearboxes and planetary gearboxes,and divide gear failures into distributed and localized types.The vibration simulation signal models of gear meshing points under different fault types are established.The principle of the traditional time-frequency transformation method is analyzed,and the advantages and disadvantages of various time-frequency transformation methods are compared by using the vibration simulation signal of the sun gear broken tooth.(2)Aiming at the problems of poor time-frequency aggregation and low resolution of traditional time-frequency analysis methods,a fractional domain optimal window function Gabor transform method is proposed,which introduces the rotation characteristics of the fractional Fourier transform into the time-frequency analysis method,optimizing the window function of the traditional Gabor transform in the fractional domain.Propose the principle of minimum time bandwidth product,and calculate the optimal window function under this principle.The validity and superiority of the proposed method are verified by the simulation signal of the sun gear broken tooth and the measured faulty gear signal.(3)Aiming at the problem of difficulty in obtaining speed signal with traditional order tracking method,a tacholess order tracking method based on instantaneous frequency estimation is proposed.Based on the study of traditional instantaneous frequency estimation methods,the proposed improved Gabor transform is applied to estimate instantaneous frequency,and the peak search method is used to extract the time-frequency ridges from the time-frequency image to obtain the frequency conversion information,and further carry out angular domain resampling to obtain angular domain signal that is not affected by speed fluctuations.The order spectrum obtained by Fourier transform can be used to extract the order of fault characteristics.The effectiveness and superiority of the proposed method are verified by the gear crack simulation signal and the measured faulty gear signal.(4)Build a gearbox condition monitoring and fault diagnosis system based on Lab VIEW,which can realize multiple functions such as data acquisition,signal processing,data storage,and data transmission.The optimized Gabor transform and the tacholess order tracking method are embedded in the diagnosis system to realize the condition monitoring and fault diagnosis of the gearbox under various working conditions.