Research On Air Gap Magnetic Field And Cogging Torque Of Permanent Magnet Toroidal Motor

Permanent magnet toroidal motor is a new type of generalized composite permanent magnet motor developed based on planetary worm drive and introducing electromagnetic elements.It realizes the direct drive integrated with the reducer and effectively combines the permanent magnet motor and mechanical transmission.It has a wide application prospect in the field of electric drag.In this paper,the permanent magnet toroidal motor is studied from the following aspects:Firstly,the structure and operation principle of the permanent magnet toroidal motor are introduced,and the space spiral closed magnetic circuit of the motor is analyzed.Based on the analysis of the electromagnetic meshing of the motor,the equivalent current method is adopted to apply the Biot-Savart law to the tile-like structure of the permanent magnet teeth on the planetary gear and the spiral variable cross-section structure of the permanent magnet beam of the outer stator.The expression of the double air-gap magnetic field inside and outside the motor is obtained by segmented integral derivation.The distribution law of the double air gap magnetic field of the motor are analyzed,and the influence of design parameters such as the spiral wrap angle and air gap value on the air gap magnetic field distribution of the motor are analyzed,so as to obtain structural parameters that can improve the magnetic field distribution of the electric gap.Secondly,According to the structural characteristics of the space spiral of the stator winding slot in the permanent magnet toroidal motor,the cogging torque of the motor is divided into two directions: rotation and revolution.In order to solve the problem of variable cross-section of the slot caused by the spiral structure of the winding slot,the spiral angle of the structural parameter is introduced into the open slot coefficient.In the process of calculating the air gap magnetic energy of the motor,the Fourier series is used to expand the magnetic induction intensity and air gap magnetic conductivity,and the cogging torque expression of the motor is derived by calculating the magnetic energy deviation.In addition,the virtual displacement method is used to calculate the electromagnetic force of the single tooth engagement of the planet gear.According to the relationship between rotation and revolution,the output torque expression of the motor is obtained by the superposition of multiple teeth;The influence of structural design parameters,such as pole arc coefficient,open slot coefficient,inner stator spiral angle and air gap value on cogging torque and output torque of the motor is analyzed.Finally,perform finite element simulation on a four-pole twelve-slot permanent magnet toroidal motor.Through the comparative analysis of simulation results and analytical calculation results,the validity of the mathematical model of air gap magnetic field,cogging torque and output torque established in this paper is verified,and the feasibility of the analysis results of the influence of structural parameters on cogging torque and output torque of this motor is illustrated,which provides theoretical basis for the subsequent experimental test of this motor.