Research On Fault Detection Method Of Motor-Planetary Gear Coupling System Based On Current Signal

Planetary gearbox is widely used in large and complex mechanical equipment and is the key part of the transmission system of equipment.Gears in the gearbox are subjected to complex dynamic loads,and the harsh working environment can lead to gear failure.If the fault cannot be found in time,the gear fault may turn into the fault of the transmission system,or even the whole mechanical equipment will be shut down,which leads to serious accidents and huge economic losses.Therefore,the state detection of planetary gear system is very important to ensure the safety,efficient and stable operation of mechanical equipment.The planetary gear system fault detection based on vibration signals is a widely studied technology,and it is also the most important method of planetary gearbox state detection at present.However,this method also has some drawbacks,such as additional sensor installation and susceptibility to environmental noise.At the same time,it is difficult to collect vibration signals for special mechanical equipment.Motor Current Signature Analysis(MCSA)uses the current signal of the motor to obtain fault information,which can effectively avoid the installation of sensors and reduce the cost of detection and maintenance.Therefore,it is of more practical significance to apply the MCSA method to the fault detection of planetary gear systems.In order to further study the specific characteristics of the current signal directly related to the planetary gear system fault,this paper takes the motor-driven planetary gearbox as the research object,and establishes the motor-planetary gear system dynamics model.The proposed model can also consider the motor rotor eccentricity and Gear failure.The model integrates various internal excitations,including gear timevarying meshing stiffness,motor magnetic saturation effects,nonlinear air gap permeance,and component failures.The main research contents of the thesis are as follows:1.Based on the Magnetic Equivalent Circuit(MEC),an electrical model of the three-phase asynchronous induction motor model Y100L2-4 was established.The expression of air gap permeance when the rotor is eccentric is established,so that the model can simulate the electrical characteristics when the rotor is eccentric.According to the energy of the air gap field,the expressions of electromagnetic torque and unbalanced magnetic tension are derived.The corresponding motor model was established in the finite element software to verify the correctness of the electrical model of the motor.2.By improving the existing planetary gear system dynamic model,a gearbox dynamic model suitable for coupling to the electric motor is proposed,and the meshing stiffness of the five tooth root crack lengths is calculated using the energy method.Considering the torsional stiffness and damping of the shaft,the gear dynamics model is combined with the eccentric motor rotor dynamics model to establish a mechanical system dynamics model.The dynamic model of the mechanical system and the electrical model of the motor are coupled through the electromagnetic torque and unbalanced magnetic tension,and the electromechanical coupling dynamics model of the motor-planetary gear system is established.3.An iterative numerical integration method is proposed to solve the electromechanical coupling dynamic model,and the dynamic interaction of the electromechanical coupling system is analyzed.Based on the established model simulation,the current time-domain signal is obtained,the influence of rotor eccentricity and different tooth root crack lengths on the current signal is studied,the sensitivity of different time-domain statistical indicators to gear faults is explored,and the analysis and summary can be detected in the current signal Time-domain statistical indicators of gear failures.4.In order to further understand the information in the current,the frequency spectrum structure of the current is analyzed.The characteristic frequency of the fault associated with the planetary gearbox system in the current is determined.In a planetary gearbox system test bench driven by a three-phase asynchronous induction motor,the motor current signal was obtained.The rationality of the spectrum structure of the simulated current signal is verified by comparison.The sensitivity of different current fault characteristic frequencies and frequency domain statistical indicators to gear faults is studied,and the current characteristic frequencies and frequency domain statistical indicators that can better detect gear faults in the current frequency domain are given.