Research On Torque Ripple Characteristics Of Permanent Magnet Synchronous Servo Motor For CNC Machine Tools

In this paper,using the finite element method of torque ripple characteristics of permanent magnet synchronous servo motor used for NC machine tool was studied,the main contents include the analysis of the permanent magnet motor magnetic field in the air gap,the analysis of stator structure,the analysis of permanent magnet structure and the corresponding transient electromagnetic field analysis and so on.The torque ripple of permanent magnet synchronous motor(PMSM)consists of cogging torque and ripple torque.The size of the tooth groove torque depends on the stator structure of the permanent magnet motor and the ripple torque mainly depends on the interaction between the stator and rotor magnetic field of the permanent magnet motor.Therefore,the dynamic electromagnetic field analysis of permanent magnet synchronous servo motor is carried out,and the analysis law of air-gap magnetic field in the motor with time and position is obtained,which lays a foundation for further weakening the torque ripple of the motor.In this paper,an8-pole 12-slot permanent magnet synchronous servo motor is taken as the research object.According to the theory of electromagnetism,the analytical method and the finite element method are adopted.The following studies were carried out:Firstly,the mechanism of the cogging torque of permanent magnet motor is theoretically analyzed,and the energy method is used to explain it further.From the theoretical analysis of the influence of the stator slot structure on the cogging torque of the permanent magnet motor,the structure of the spliced closed slot stator of the permanent magnet motor is obtained.The influence of stator closed slot structure on the cogging torque of permanent magnet motor is theoretically analyzed.The structure of spliced closed slot stator of permanent magnet motor is obtained.Considering the affected structure factors including the slot ratio and the two air gap at the splice place and so on.The structural parameters that affect the structure of the spliced closed groove are obtained.Secondly,the ideal state of the pole shape theory,comparing the traditional tile type magnetic pole and three pole arc magnetic pole,the reducing torque ripple of permanent magnet motor,the three arc pole is superior to the traditional tile type magnetic pole.At the same time,the structure parameters that affect the three arc magnetic poles are obtained,andthe influence degree of the structural parameters on the torque ripple of the motor is analyzed.The influence factors of permanent magnet motor's structural parameters on the cogging torque and torque ripple of permanent magnet motor are analyzed by finite element simulation.The flux density,magnetic line distribution and magnetic dense cloud diagram in the air gap of PMSM are obtained.The Maxwell stress tensor method is used to calculate the tangential electromagnetic force acting on the rotor side of the permanent magnet motor and the radial force acting on the inner surface of the stator.The influence of the torque ripple of the permanent magnet synchronous motor on the torque ripple of the permanent magnet synchronous motor(PMSM)is obtained by the different structural parameters.Finally,three kinds of multi-dimensional analysis methods are used to analyze the structural parameters of the motor,and the optimal combination scheme of the motor structural parameters is obtained.It provides a reference for the design of high performance and low torque pulsating PMSM.