Analysis Of The Spherical Motor Magnetic Resistance Torque Based On Spherical Harmonic Function

With the continuous development of modern industrial,medical,aerospace and other fields,multi-degree of freedom of the mechanical structure has a broader application.PM(permanent magnet)spherical motor is a novel motor.It can achieve rotation along any space axis in a joint structure.It can replace the traditional multi-degree of freedom machine that is composed of several single degree of freedom electrical motor.With the development of permanent magnetic materials technology,PM spherical motor has Compact,fast response,high energy density and other characteristics,and becoming the hotpot of multi-degree of freedom motor.Firstly,the magnetic field of a novel permanent magnetic spherical motor calculated by analytical method.The radial component of the air-gap magnetic flux density was derived by Laplace equation and the boundary conditions,and expanded into spherical harmonic series.Harmonic distribution of the field was analyzed.The radial component of the air-gap magnetic flux density distribution was calculated with finite element method.Compared with the two methods,the results verify the accuracy of magnetic analytical model.On the basis of magnetic analytical model,the relationship between magnetic field and parameter of permanent magnet was researched,and it provides the basis for optimal motor structure.Based on the theory of fractional-slot concentrated winding and spherical harmonics,the stator magnetic field of permanent magnet spherical motor poles and gear selection for analysis and research.The reference current equations of spherical motor rotation and tilt were derived,when the phase number is arbitrary value.Using the finite element simulation and least squares fitting method,the spherical harmonics as the base function,get the distribution of the stator magnetic field and coefficient of each harmonic.Since the stator fundamental magnetic field and rotor fundamental magnetic field are the same,proof that reference current law can produce synchronized magnetic field with the rotor,and harmonic analysis in latitude lines can reflect the distribution of the stator magnetic field harmonic.Analysis the different combinations of poles tooth,obtain the relationships of harmonic order and greatest common divisor and phase numbers.Finally,the cogging torque was analyzed by finite element method.Increase the stator coil core is an effective means of increasing the with load capacity of permanent magnet spherical motor,but the core cause the motor to generate cogging torque,lead to the electromagnetic torque fluctuations,and affect the accuracy and performance of the motor control.Using the finite element method to discuss the cogging torque generated by the stator core,and analyze changes regulation of cogging torque in the different positions,this facilitates optimization of permanent magnet spherical motor.