Structure Design of Multi-DOF Motor with Stator Permanent Magnet based on Flux Switching

Abstract

This paper aims at the problems of no core in the stator coil of a compact multi-degree-of-freedom (M-DOF) motor, i.e., small output torque and low power density. In order to increase the output torque, a stator permanent magnet spherical motor based on flux switching is proposed. Firstly, the principle of flux switching is introduced. The basic structure of the new motor is preliminarily designed, and the motion mechanism is analysed for spin motion and tilt motion respectively. Then the minimum model of a novel motor is established in ANSYS by using the virtual displacement method. The key parameters such as the ratio of stator pole tooth to permanent magnet size, different stator pole tooth end structures, different pole tooth surface shapes, different pole sizes, permanent magnet thickness, different magnetisation methods and different ampere-turn numbers are optimised within a reasonable parameter range. The simulation results are analysed and discussed, and the optimal results for each key parameter are thus given. Finally, considering the arrangement of the stator and rotor poles, the rationality of the three-DOF motion was verified by means of two energising strategies, spin motion and tilt motion, verified the reasonableness of the above optimal parameters and thus determined the structural parameters of the new spherical motor to accomplish the three-DOF motion and the maximum torque range. The simulation results show that the electromagnetic torque varies approximately linearly over a range of ampere-turns for the same position of the rotor pole teeth. It provides an opportunity for the M-DOF motor design of a high torque output and power density.