Study On Vibration Characteristics And Fault Diagnosis Method Of Two-stage Planetary Transmission System Under Variable Operating Conditions

Planetary transmission systems are widely used in aerospace,wind power generation,coal mine equipment and many other fields because of their large transmission ratio,compact structure and high transmission efficiency.Because of its complex working environment,it is often under variable speed and variable load conditions,which causes planetary gear failures to occur from time to time,which seriously affects production efficiency.Therefore,by establishing a dynamic model of the two-stage planetary transmission system,the vibration characteristics of the planetary transmission system in normal and fault states under different working conditions are revealed,and then the fault diagnosis method is proposed.It has a good reference significance for the accurate diagnosis of the fault of the two-stage planetary transmission system.According to the characteristics of the two-stage planetary transmission system,a two-stage planetary transmission system model under different cracks and broken teeth of the two-stage sun gear is established by using SOLIDWORKS.The first-stage planet carrier and the second-stage sun gear,which affect the vibration response characteristics of the system,have been flexibly processed.The correctness of the rigid-flexible coupling model is verified by the rotation speed in the simulation results and the characteristic frequencies in the time and frequency domain diagrams.Through dynamic simulation analysis,the time and frequency domain amplitude and characteristic frequency change law of different cracks and broken tooth fault vibration signals,as well as the change law of sidebands are revealed.The influence of different loads on the vibration characteristics of crack faults is summarized,and the influence of variable speed operating conditions on the vibration characteristics of different crack faults is studied,and the above-mentioned vibration characteristics change law is verified by experiment.Through dynamic simulation analysis and experimental verification,it reveals the time and frequency domain index value change law of different crack and broken tooth fault vibration signals under constant working conditions,and the time and frequency domain index value change law of vibration signals under variable load conditions.The change rule of time domain index value of crack fault vibration signal under variable speed conditions,the results show that under constant working conditions and variable load conditions,the waveform indicators and margin indicators in the time and frequency domain of the vibration signal can be used for fault diagnosis;under variable speed conditions,there is frequency aliasing,which makes the spectrum analysis impossible Realize fault diagnosis.Aiming at the problem of fault diagnosis of planetary transmission system under variable speed working conditions,the order analysis technique is combined with envelope spectrum,and a fault diagnosis method based on envelope order spectrum analysis is proposed.This method first performs Hilbert envelope analysis on the vibrational non-stationary time-domain signal of the planetary gear transmission system,then converts the non-stationary time-domain envelope signal into an equal-angle angle-domain signal,and finally performs Fourier transform on the equal-angle angle-domain signal Get the envelope order spectrum of the signal.In order to verify the effectiveness of the method proposed,it was verified by simulation analysis and power transmission fault diagnosis integrated test bench(DDS).The results show that the envelope order spectrum analysis method can effectively extract the characteristic order of the modulation signal under variable speed conditions,and can achieve accurate diagnosis of planetary gear system faults under variable speed conditions.