Research On Dynamic Signal Analysis And Fault Diagnosis Of Planetary Gears

Planetary gearboxes are widely used in helicopters,automobiles,aircraft engines,heavy machinery and marine vehicles.Dynamic analysis' s necessary to the noise and vibration reduction.This work investigates some critical issues and advances the understanding of planetary gear dynamics.Because it often works in the critical condition that usually cause the failure of the tooth root.There are several vibrational sources as sun-planet gear pairs and a few ring planet gear pairs are meshing instantaneously.Furthermore due to the rotation of the carrier,distance varies between vibration sources and a transducer installed on gearbox housing.This thesis aims to simulate and understand the vibration signals of a planetary gear set,and then propose a signal processing method to detect gear tooth fault more effectively:In order to study the signal regularity of the gear and bearing failure of the planetary gearbox,the parts of the sun gear,planetary gear and planetary gear bearing(outer ring and inner ring)of the NGW11-8 planetary reducer were damaged in different degrees,and the fault simulation was carried out.The vibration letters at different speeds were used by the sensor and the signal acquisition instrument.The number is collected and analyzed to explore the law.Comparing the time-frequency spectrum of normal and fault signals of the planetary gearbox at the same speed extract the feature information and verify the existing conclusions.To compare the similarities and differences between the common vibration signal,the high frequency signal and the stress wave signal at the same speed,the same fault and the same position,which is more suitable for fault diagnosis and feature extraction.To study the influence of the transmission path on the collected signals,and find the best way of collecting and measuring points.The vibration signal of the gear was collected by empirical mode decomposition(EMD),and the fault feature information of gear box was extracted from normal,crack and broken teeth.The meshing and characteristic frequencies of the gears in different state at same speed were collected respectively.Finally,a signal decomposition method is proposed to detect a single tooth crack in a single planet gear and experimental validation is performed.The methods proposed in this thesis help us understand the vibration properties of planetary gearboxes and give insights into developing new signal processing methods for gear tooth fault detection.