A 2-D Hybrid FE Model With Double Air Gap Elements for Eccentric Magnetic Harmonic Gears

Abstract

Eccentric magnetic harmonic gears with high gear ratios exhibit high torque densities. However, the revolution and rotation of the eccentric rotor increase the magnetic field analysis complexity. This paper presents a hybrid finite element approach of magnetic field analysis for magnetic harmonic gears. The eccentric air gap region has been divided into three parts: two uniform layers, adjoining the stator and the rotor respectively, are treated as air gap elements; one non-uniform middle layer, as a variable air gap permeance, is discretized by FE meshes similar to the stator and the rotor. Mesh reconstruction can be avoided because the annular cylindrical rings of the two air gap elements are introduced. The mixed eccentric motion of the rotor can be easily treated. In order to save the computational time an equivalent motion mode is introduced and the sliding surface technique is applied by which the coefficient calculation of the air gap elements only needs to be done once wherever the rotor moves. The torques are calculated from the flux densities of the air gap elements. A prototype test confirms the validity of the prediction, and the accuracy of the obtained results is evaluated with FEM.INDEX TERMS Hybrid finite element method, Double air-gap element, Eccentric magnetic harmonic gear This article has been accepted for publication in a future issue of this journal, but has not been fully edited. Content may change prior to final publication.

Investigation of transmission characteristic for harmonic magnetic gears considering dynamic eccentricity using magnetic equivalent circuit

“…The influence of both static and dynamic eccentricity (DE) on motor performance has been studied [24,25]. The performance of MGs with eccentricity has been studied in [26,27]. However, the case being considered is static eccentricity, where the distance between the rotor centre and stator centre is constant.…”