Investigation on Pole-pair Number Combinations of a Two Degree-of-Freedom Rotary-Linear Machine with Hybrid Permanent Magnets

The two degree-of-freedom rotary-linear electric machine with hybrid permanent magnets array is suitable for micro-scale applications due to its high dynamic performance and compact design. To achieve optimal performances, the pole-pair number combinations for both rotary and linear parts are investigated in this paper. By analyzing the pole ratio and winding factor, the potential pole-pair number candidates are selected. Furthermore, with the results from no-load and on-load studies, the relationship between the pole-pair numbers and output performances is revealed. Along with the evaluation of magnetic field coupling effect between two motions and the cost function method, the optimal pole-pair number combinations of both motions are obtained. In addition, the same investigation procedures are applied to the RL machine with radial magnetized PMs array and spoke-type PMs array. Consequently, a performance comparison is held under various mover thicknesses which demonstrates the benefits of the hybrid PMs array.