Permanent Magnet Motor Fault Diagnosis Based On Interval Observer And Dual-tree Complex Wavelet Transform

In modern industry,servo feed system is one of the core components of computer numerical control machine tools.It can ensure the machine to keep high speed,high precision and high reliability in the process of operation.The working conditions in the servo feed system include variable speed and load,which will make the servo motor more prone to failure.Once this happens,the accuracy of the feed system will be reduced and the work-piece will be damaged.Therefore,there is important theoretical significance and research value in the research on the fault diagnosis of the servo motor.The servo motor is considered as a nonlinear model in this paper.The fault diagnosis problem of permanent magnet motor affected by uncertain factors such as parameter variation and interference is studied.Firstly,based on the theoretical formula of motor and ball screw,the electromechanical coupling model of servo feed system is established.A three-phase asymmetric fault model is established,and the fault characteristics and influence are analyzed by simulationSecondly,according to the motor model,an interval observer is designed.In the observer,the phase current with rotor position information is regarded as the observed state quantity to reduce the influence of external interference.Then the model after linear transformation is obtained,and the residual calculation method is designed to detect faults.The calculated residual is robust to interference and sensitive to faults.After all,the simulation results verify the validity of the fault detection method.Thirdly,aiming at the three-phase unbalanced faults of permanent magnet motor,the current signal of the motor is decomposed and reconstructed by dual-tree complex wavelet transform.The simulation results show that the dual-tree complex wavelet transform has good anti-aliasing and shift invariance.The fault features in current can be extracted effectively.Finally,the experimental platform of servo feed system is built.Design the fault diagnosis method of permanent magnet motor.The faults of permanent magnet motors under normal and fault conditions are diagnosed respectively.This method is proved to be feasible and can effectively avoid the misdiagnosis caused by the external interference of the motor.