A method of cutting permanent magnets with circular arcs of offset center was proposed on the basis of the principle of similarity under the condition of slip drive to obtain a permanent magnet transmission scheme for low permanent magnet torque fluctuations. The magnetic flux distribution of each region in the magnetic circuit was altered by changing the shape of the permanent magnet. Different magnetic torque curves were obtained by selecting silicon steel sheet with different thicknesses. The relationship between the magnetic flux distribution and the relative rotation angle in the silicon steel sheet was further analyzed, and the direct cause of the influence of the thickness of the silicon steel sheet on the magnetic torque was obtained. The parameters of different eccentric arcs were selected for simulation calculation, and a smooth magnetic torque curve was obtained after fixing the thickness of the silicon steel sheet. On the basis of the results of the former two, the parameters of the eccentric arc were obtained by the magnetic torque value volatility using an approximation method, and the magnetic torque value was measured by making the physical object. According to the results of the simulation and experiment, the permanent magnets with eccentric arcs can be used to obtain the smooth magnetic torque in the range of a 0◦–۹۰◦ relative rotation angle, which has a certain application value.

Introduction

The magnetic transmission concepts dated back to the early 20th century [1]. Recently, many studies on permanent magnet transmission have emerged. The axial-flux modulated superconducting magnetic gear has currently been specifically studied using a superconducting bulk magnet replacing conventional permanent magnet [2]. The coaxial magnetic gear with an eccentric pole of the inner rotor and Halbach arrays of the outer rotor was proposed and studied to improve the torque density of a coaxial magnetic gear (CMG) [3]. Substantial studies on the CMG were performed in [4]–[۶]. Magnetic gears that were well suited to execute high-torque direct-drive operations for oceanic wave energy harvesting applications were designed [7]. The shape of the flux modulators of the concentric magnetic gear affects the torque capability and ripples [8]. A new geometry was proposed for the magnetic gear to reduce the eddy-current loss of permanent magnets and improve the torque transfer efficiency [9]. The permanent magnet shape is one of the main factors affecting the performance of permanent magnet transmission. The CMG has a great advantage when a large radius and a small axial length are permissible. Hence, the CMG is suitable for the drivetrain of vehicles [10]. A novel topology of a planetary magnetic gear having only two rotating parts demonstrated a torque density of 187 kN · m/m3 [11]. The air-gap magnetic fields and eddy-current densities of a non-rotary mechanical flux adjuster (MFA) were investigated under the different shifting distances of a MFA, which reveals the fairly good torque regulation effects [12].