| With the continuous improvement of the locomotive’s traction weight and speed in recent years,a higher requirement for the stability and safety of locomotive operations has been proposed.Due to the long-term influence of complex wheel-rail excitation,locomotive transmission gears are prone to failure in the early stage.However,under the influence of complex wheel-rail noise,the gear vibration response caused by the failure is very weak generally,which requires a higher performance of the signal processing algorithm and brings great difficulties to the fault diagnosis.On the basis,considering the interaction of the traction motor and gear transmission system,an electromechanical coupling model of locomotive’s traction motor-gearbox has been established.And considering the influence of track irregularity excitation on the dynamic characteristics of the electromechanical coupling system,the time-varying mesh stiffness under different health conditions of the gears is used as the internal excitation of the system,and the dynamic characteristics of the electromechanical coupling model under steady-state conditions and track irregularity disturbance conditions has been studied.Meanwhile,the response characteristics of gear fault characteristics in electrical signals were analyzed,and the locomotive gear fault diagnosis method based on electrical signals was studied.The main research contents and conclusions of this article include:1.An electromechanical coupling model of locomotive traction motor-gearbox is established.The motor model is a mathematical model of a three-phase asynchronous motor in static coordinate;the gear transmission system model is established by a lumped parameter method,and the flexibility of the bearing,motor shaft and wheelset shaft is considered in the model.2.The simulation and analysis of the vibration characteristics of the transmission gear under different load conditions are performed.The effects of different fault types and fault degrees on gear vibration response characteristics were studied,and the gear vibration characteristics under track irregularity excitation conditions were investigated.3.The simulation and analysis of the response characteristics of the electrical signal of the electromechanical coupling model under different load conditions are performed.The law of the responses of gear fault characteristics in electrical signals has been explored,the manifestation of track irregularity disturbance in the electrical signal time-frequency domain response is studied,and the sensitivity of electrical signals to the changes in gear failure levels is simulated and analyzed.4.The gear fault diagnosis method based on electrical signal dual-tree complex wavelet is studied,which effectively solves the amplitude modulation phenomenon caused by the current fundamental frequency and time-varying load in the electrical signal.The results show that there is no amplitude modulation in the electromagnetic torque signal under steady-state conditions.Among the dual-tree complex wavelet decomposition results of the electrical signals under other load conditions,the amplitude of the gear fault characteristic frequency in the first high-frequency component signal’s spectrum is the most obvious,which can effectively accomplish the fault diagnosis of gears.5.The application of time-frequency domain characteristics of motor electrical signals in gear fault diagnosis is explored.Using tooth root crack faults with different degrees of deterioration as internal excitations,the time-frequency domain characteristics of electrical signals under different load conditions were simulated,and the evaluation indices are set to evaluate the stability of each characteristic in the characterization of gear failure levels.The results show that the accuracy of the non-dimensional characteristics of the electrical signal to characterize the degree of gear failure is minimally affected by external disturbances and signal types,and has better stability than the dimensional characteristics. |
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