Design and Analysis of a Magnetic Field Screw Based on 3-D Magnetic Field Modulation Theory

This paper investigates the 3-D magnetic field modulation theory of the magnetic screw transmission. A magnetic field modulation screw (MFMS) is proposed to prove this theory. The MFMS consists of three parts, including the inner part and outer part carrying the helically permanent-magnet (PM) with different pole-pairs. The intermediate part has a set of helically ferromagnetic pole-pieces, which modulate the helical PM magnetic field. The innovation of this MFMS is that it can achieve fully helical magnetic coupled, which satisfies the 3-D modulation in the circumferential and axial direction, respectively. Moreover, the intermediate part can move in both rotation and linear motion without PMs. Therefore, it is very suitable for long-stroke, high force, and two-degree of freedom applications. Afterward, the prototype of a magnetic screw is built to verify the magnetic transmission capability. The effectiveness of the proposed approach is verified by both simulation and experiment.