3-D Integrated Sub-Domain Model for On-Load Magnetic Field and Force Analysis of 6-DOF Screw-Motion Permanent Magnet Synchronous Motor

This article presents the 3-D integrated sub-domain model (3-D ISM) for the 6-degree-of-freedom (DOF) screw-motion permanent-magnet synchronous motors (Sm-PMSMs). For the actively controlled and decoupled 6-DOF motion, the novel pattern of PM-array is introduced, consisting of the checker-board PMs to drive the 2-DOF screw motion and the additional tilting PMs for the other 4-DOF magnetic bearings. The armature of the proposed Sm-PMSM design contains both the linear coil sets and the rotational coil sets, where the D-Q current excitation scheme with the peak current modulation method is utilized to generate the 6-DOF forces and torques in a decoupled manner. The 3-D ISM presented in this article accurately estimates the magnetic fields in the 3-D cylindrical space with an on-load condition, integrating the PM-induced fields from the magnetic scalar potential model and the current-induced fields from the hybrid vector potential model. The proposed 3-D ISM is validated by the equivalent 3-D finite element analysis (FEA) model, comparing the on-load magnetic fields, and the decoupled 6-DOF forces and torques. The fidelity of the proposed model is observed with an accuracy greater than 96%, while simultaneously improving the computational speed by two orders-of-magnitude as compared to the 3-D FEA.