A new type of double-stator permanent magnet spherical motor (DSSRPMSM) is proposed. Compared with most existing spherical motors, this motor uses a large number of stator iron cores, which can generate larger magnetic flux density and significantly improve torque capacity. The proposed DSSRPMSM can continuously rotate, swing and spiral, and can be used in the multi-degree-of-freedom motion fields of industrial robot joints, moment gyroscopes, panoramic photography tables and so on. Because the motor has the dual characteristics of rotary motor and arc linear motor, the comprehensive effects of stator slotting and stator iron core breaking should be considered. Cylindrical and trapezoidal PM poles are equivalent to dihedral PM poles, and stator coils are equivalent to PM pole models. Analytical models of PM pole magnetic field and stator magnetic field in a spherical coordinate system are established, and the air gap magnetic flux density under unequal magnetic potential boundary conditions is calculated by conformal transformation. The analytical calculation method proposed is consistent with the results of finite element method (FEM) simulation, and the experimental test further verifies the effectiveness and accuracy of this method.
K E Y W O R D Scogging effect, edge effect, magnetic field of PM poles, permanent magnet spherical motor, stator magnetic field
| INTRODUCTIONA spherical motor can realise multi-degree-of-freedom motion, which has the advantages of simple structure, light weight, fast control response speed, high precision etc. It improves the motion mode of motor and develops from simple onedimensional circular rotation to multi-degree-of-freedom motion, which meets the application requirements of industrial field [1-3]. Among them, the permanent magnet spherical motor has become a research hotspot because of its high power density and high efficiency [4,5].The existing permanent magnet spherical motor stator structure can be divided into four types: layered stator, nested stator, claw stator and double stator. The layered stator structure is shown in Figure 1a, and its typical feature is that the stator coil has two layers [6,7] or three layers of coils [8-10] along the axial direction, and each layer of coils is evenly distributed radially or horizontally, with a certain included angle between adjacent layers. By exciting all coils in the circumferential direction, the rotor can rotate around its axis. When the paired coils in the axial direction are excited, the rotor will tilt in two orthogonal directions. The nested stator structure, as shown in Figure 1b, has the most obvious feature that the stator coil group can be divided into large and small coils [11,12]. Large-area coils evenly distributed along the equator are used to complete the rotation motion. Large-area coils areThis is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is...