Analysis Of The Time-frequency Feature Of Coupling Faults In Rotor System

Rotating machinery is widely used in industrial production,and fault diagnosis of rotor system,which is the key component of rotating machinery,is of great significance in reducing economic losses and ensuring personal safety.The fault signal of rotor system often shows the characteristic of nonlinearity and nonstationarity,and the time-frequency analysis method has been widely used in the field of rotor fault diagnosis because of its good ability to analyze nonlinear and non-stationary signals.This paper has carried out related work on the analysis of time-frequency feature of rotor system faults,especially coupling faults.The main work is as follows:In order to select a better time-frequency analysis method,the time-frequency analysis methods are compared at first.The signal decomposition effects of empirical mode decomposition(EMD)and variational mode decomposition(VMD)are compared and analyzed by simulation.At the same time,the experiments of rubbing,oil film instability,crack and corresponding coupling faults of the rotor system are carried out by using Bently RK4 rotor test bench,and the analysis effect of time-frequency analysis method based on two signal decomposition methods on each single fault data is compared.The results show that compared with the EMD algorithm,the VMD algorithm has better anti-modal aliasing characteristic,and the time-frequency analysis method based on VMD can more clearly show the time-frequency feature of single fault in rotor system.In view of the good analysis effect on single fault in rotor system,the time-frequency analysis method based on VMD is further applied to extract and analyze time-frequency feature of oil film instability-rubbing and crack-rubbing coupling faults in rotor system.The results show that the time-frequency feature of coupling faults can not be clearly expressed,furthermore the single fault and corresponding coupling faults are difficult to distinguish by the time-frequency analysis method based on VMD.Aiming at the problem that the time-frequency analysis method based on VMD can not effectively extract the time-frequency feature of coupling faults,the full-time-frequency analysis method based on complex VMD(CVMD)algorithm is introduced into the analysis of coupling faults in rotor system,the results show that the full-time-frequency analysis method can effectively extract the full-time-frequency feature and better reflect the coupling characteristics of coupling faults.The time-negative frequency diagrams of different faults provide distinct time-frequency feature,combined with the precession of the rotor system represented by the full Hilbert three-dimensional diagrams can provide a basis for identifying the coupling faults and single faults.