Investigation of Magnetic Isolation in a Double-Side Asynchronous Rotor-AFPM Machine Based on Harmonic Analysis

Abstract

Electric machines are important components in the actuators of robot dogs, but these actuators usually need several freedoms. To get two free mechanical ports, the double-side asynchronous rotor axial-flux permanent magnet (DSAR-AFPM) machine is proposed. The DSAR-AFPM machine has two different configurations on two sides, which are 20-pole-24-slot (20P24S) and 42-pole-36-slot (42P36S) configurations. The two asynchronous rotors can output torques independently at any speed. This article performs an investigation for the magnetic isolation of the DSAR-AFPM machine. The working harmonics and interference harmonics are all calculated when different pole-slot combinations are applied. It is verified that there is magnetic isolation between the two sides. Then, a 3-D finite element analysis is conducted to verify the effect of harmonics on the performances of the DSAR-AFPM machine. It is compared with the 20P24S and 42P36S single-side AFPM machines. The results are consistent with the investigation of magnetic isolation. The back electromotive forces (EMFs) and torques on two sides are unrelated. Finally, an experiment is conducted to validate the independence of two asynchronous rotors.