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

Harmonic magnetic gears (HMGs) have the advantage of lubrication-free, high speed ratio and high torque density, which make it an attractive solution for safety critical applications. Due to eccentricity caused by machining and assembly, HMG suffers from dynamic eccentricity (DE) in operation, however, its effect on HMG performance is still unknown. Transmission characteristic of HMG under DE is studied. First, a magnetic equivalent circuit (MEC) model of HMG is proposed to build the magnetic coupling torque analytically, and the geometry of air gap is analysed parametrically to derive its equivalent reluctances. Flux density and coupling torque can be acquired by solving MEC equations. The accuracy of the MEC model is verified by finite element method. To study the transmission characteristic, an electromechanical coupling simulation framework for HMG is constructed, motion trajectories of rotors are investigated in case of DE, the output torque in locked-rotor condition and speed response in continuous operation can be derived by simulation. It is found that torque ripples that have the same frequency with input rotor are induced by DE; the results are then verified in the experiment. This paper provides a theoretical guidance for the design and condition monitoring of HMG. The transmission characteristic of harmonic magnetic gear needs to be studied under the electromechanical coupling framework. The electromechanical coupling simulation framework is built based on the magnetic equivalent circuit model and mechanical dynamic model.image

Automated summary

This study investigates the effect of dynamic eccentricity on the transmission characteristics of harmonic magnetic gears (HMGs). By proposing a magnetic equivalent circuit model and constructing an electromechanical coupling simulation framework, the output torque and speed response under dynamic eccentricity are obtained. The torque ripples induced by dynamic eccentricity are verified through experiments. This paper provides theoretical guidance for the design and condition monitoring of HMGs.