Magnetic Field Analysis Of Permanent Magnet Spherical Motor For Attitude Control

The traditional satellite attitude control system is generally composed of multiple control moment gyroscopes or flywheels.The system structure is complicated and the components are redundantly repeated,which seriously affects the weight,volume,power consumption and cost of the attitude control system.Spherical motor is a new type of multi-degree-of-freedom electromagnetic device that has emerged in recent years.It can replace three-degree-of-freedom motion of the rotor instead of the complicated and complicated mechanical transmission structure.It has broad application prospect in aerospace field,but it is directly used as a momentum exchange device which is still in its infancy.In this paper,the permanent magnet spherical motor for satellite attitude control is taken as the research object,the spherical motor adopts the double polyhedron structure.The rotor poles are cylindrical permanent magnets,and the N and S poles are alternately arranged on the vertices connecting the virtual regular hexahedron and the ball.The stator coils are distributed at the vertices of the imaginary octahedron connected to the sphere,and the points the rays passing the center of the face and the midpoint of the edge and starting from the sphere center are projected on the spherical surface.Due to the surface-mount dihedral cone pole crossing the same longitude up and down and the same latitude left and right in the equatorial layer,the spatial magnetic field can be well resolved and expressed in the form of spherical harmonic function.While the advantages of ease of manufacture and the symmetry of the magnetic field in the space,the cylindrical pole is widely used in the design of the rotor pole of a spherical motor.Therefore,it is considered that the cylindrical pole in the virtual equatorial layer is approximately equivalent to the surface-mounted dihedral cone pole with the same thickness.The mathematical analysis model of the spatial magnetic field density is obtained by solving the Laplace equation based on the boundary conditions.The analytical model of other spherical distributed poles can be obtained through the rotation transformation.By linearly stacking them,the global magnetic field model of the surface-mounted dihedral cone magnetic pole rotor can be obtained.By comparing with the magnetic field data measured by finite element method and experimental data,it shows that this magnetic field modeling method is reasonable and effective.It has universal significance and popularization value,and lays the foundation for the following torque calculation,structure optimization and control system research of spherical motor.