Study Of Stator Current Diagnosis Method For Planetary Gear Fault In Electromechanical Coupled System

In recent years,with the massive application of planetary gear transmission mechanism,engineers and researchers have higher and higher requirements on the stability and reliability of planetary gear operation.Due to the complex structure and harsh working environment of planetary gear,it is very easy to fail during operation,and because the disassembly and assembly process of planetary gear is tedious,so the state of planetary gear needs to be tested regularly.Among them,nondestructive fault diagnosis technology is a more cutting-edge field in the research of mechanical equipment fault diagnosis.The traditional non-destructive fault diagnosis technology is commonly used is vibration method,considering the high cost of this method and the accuracy is easily affected by the external environment,so this paper will use the motor current characteristic analysis method for the planetary gear transmission system fault diagnosis research.At the same time,combined with the past research results,it can be found that this method mostly reduces the relevant excitation of planetary gears to signals with fault characteristics,and does not use this method to study the failure mechanism of planetary gears in depth.To solve this problem,this paper will use the centralized parameter method to establish the electromechanical coupling model of planetary gear and three-phase induction motor,and analyze the dynamic characteristics of planetary gear and stator current change of three-phase induction motor when cracks and broken teeth occur respectively.The main contents of this study are as follows.1.Planetary gear stiffness excitation modeling.Combined with the theory of energy method to initially model the comprehensive time-varying meshing stiffness of planetary gears in normal state,based on which the comprehensive time-varying meshing stiffness model containing different fault types is derived based on the geometric relationship of gears,revealing the mechanism of planetary gear failure.2.The planetary gear dynamics model is established and the dynamics response is analyzed.The established kinetic model considers the influence of the meshing phase.Firstly,it is necessary to establish the corresponding meshing phase model according to the characteristics and geometric relationship of the planetary gear system,and then establish the planetary gear kinetic model based on the centralized parameter method.3.Three-phase asynchronous motor modeling and analysis.In order to reduce the difficulty of modeling and avoid the coupling effect between rotor winding and stator winding,it is necessary to transform the motor from three-phase stationary winding to two-phase stationary winding by using Clark transform,and finally obtain the mathematical model of three-phase asynchronous motor stator current.By coupling the electromagnetic torque as an intermediate quantity with the planetary gear dynamics model established in the previous chapter,a complete three-phase asynchronous motor-planetary gear electromechanical coupling model is finally obtained,revealing the mechanism of fault diagnosis using the motor stator current method.