Order Tracking Based Methods For Planetary Gearbox Fault Detection And Diagnostics Under Variable Operational Conditions

Planetary gearbox is composed of some key components,such as ring gear,sun gear,planetary carrier,planet gear and so on.These components are assembled in a compact gearbox.Thanks to its unique mechanical structure,planetary gearbox has a large transmission ratio and withstands heavy loads.For this reason,it is widely used in many machineries as an important part of transmission systems.However,in practical engineering,the variable operational conditions will cause overloaded and time-varying loads and they will lead to serious damages to planetary gearbox.Those severe failures occurred in planetary gearbox may cause unexpected economic loss.Condition monitoring of planetary gearboxes under non-stationary operational conditions therefore becomes a key method to ensure the reliability of the whole system.To use the measured vibration signals for planetary gear fault diagnostics,the degree of complexity and the non-stationary nature of the measured vibrations become two main obstacles for the effectiveness of condition monitoring.Therefore,how to reduce the complexity of signal and ensure diagnostic capabilities of a planetary gearbox system under variable operational conditions become a more and more important issue.Considering that,this thesis proposed some methods based on order tracking techniques and statistical techniques to realize enhanced diagnostics to a planetary gearbox under non-stationary operational conditions.The main contributions of this thesis are as follows:(1)In order to select a suitable bandwidth for Vold-Kalman filter to ensure a consistent monitoring procedure,computed order tracking technique and statistical indicator are chosen to aid the selection of bandwidth for Vold-Kalman filter.An order spectrum based selection method to Vold-Kalman filter bandwidth for ordering tracking analysis is proposed in this thesis.(2)For the purpose of reducing the complexity of vibrations of planetary gearbox under variable operational conditions,computed order tracking technique and VoldKalman filtering are employed subsequently to simply the vibrations of planetary gearbox.Finally,a diagnostic signal selection scheme for planetary gearbox vibration monitoring is proposed in this thesis.(3)With regard to remove the influences caused by variable operational conditions and further simplify the complexity of the measured vibrations,phase information is taken into consideration seriously.Besides,with the help of order tracking techniques and statistical techniques,a phase angle based diagnostic scheme to planetary gear faults diagnostics under variable operational conditions is rendered in this thesis.At last,the proposed methods are explained and demonstrated in both signal simulation model and experimental studies and the methods prove to be effective for planetary gearbox fault diagnosis.