Research On Structural Design And Excitation Method Of New Permanent Magnet Spherical Motor

Conventional single-degree-of-freedom motors only provide single-axis rotation,while typical motion control systems such as series robots and parallel manipulators need to have multiple single-axis rotating machines.The resulting bloated structure and complicated control limits their application and development.The permanent magnet spherical motor can realize three-degree-of-freedom motion and has a good prospect in future industrial applications.The image of the spherical harmonic function on the spherical surface of the threedimensional space has a high degree of symmetry,by comparing it with the distribution of the rotor permanent magnets,the basic laws of the rotor permanent magnets distribution can be obtained.When the distribution of rotor permanent magnets is determined,the main-order harmonic harmonics of the excited magnetic field are the same as the spherical harmonic order in the structural reference design;the derivation method like rotation and spatial symmetry are used to derive the stator coils distribution laws;then the equivalent concept of the cylinder and the cone is utilized,the magnetic field analytical expressions of the double stator coil and the double rotor permanent magnet are derived,and the overall coil and permanent magnet magnetic field are obtained by coordinate transformation and magnetic field superposition.After determining the basic structure of the new permanent magnet spherical motor,the control method needs to be simple and feasible.This paper proposes a corresponding excitation method to provide reference for its further control.Firstly,the main order harmonic coefficients of the stator magnetic field and the rotor magnetic field are analyzed.Then the equations are listed according to the idea that the rotor main order harmonic coefficients are proportional at any time,and the coil current equations of each group are obtained and analyzed by solving the coil current of each group.Finally,taking a permanent magnet type spherical motor as an example,determining the basic position information and other dimensional information of the motor,using the finite element method to analyze the stator and rotor magnetic fields,and comparing the main harmonic coefficients of the stator and rotor magnetic fields under the above coil energization method.It is shown that the stator coil excites the same rotating magnetic field as the rotor magnetic field;the magnetic field data excited by the stator coil under the given current excitation is experimentally measured,and the magnetic field data is compared with the simulation results to verify the feasibility of the proposed excitation method.This paper has important reference significance for the size of other types of permanent magnet spherical motors or new coil and magnetic pole structure design,magnetic field,torque analysis and further control.