Study on Torque Ripple Suppression of Axial Flux Permanent Magnet Stepper Motor with Multi-Layer Air Gap Torque Coupling

To address the issue of significant torque ripple in axial flux permanent magnet stepper motors with multi-air-gap coupling structures, a torque ripple suppression method based on the coordinated adjustment of rotor misalignment and structural parameters is proposed. Focusing on a dual-stator, triple-rotor, three-phase axial flux permanent magnet stepper motor, a three-dimensional finite-element model is established to analyze the phase superposition relationship of torque components in multiple working air gaps and their impact on the overall output torque ripple. First, the misalignment angle between adjacent rotors is utilized as the primary optimization variable to study the peak-shifting superposition effect of torque components under different misalignment angles. Subsequently, parameter scanning and stepwise optimization are conducted for the air gap distribution, the inner-to-outer diameter ratio of the stator core, the radial width ratio of the permanent magnet to the stator teeth, and the pole arc coefficient. The results demonstrate that by utilizing the phase offset effect of torque in multiple air gaps, combined with the modification of key structural parameters, the torque smoothness of the dual-stator, triple-rotor axial flux permanent magnet stepper motor can be significantly improved; the torque ripple rate is reduced from 62.67% to 19.32%. This study provides a reference for the low-vibration and smooth operation design of this type of motor.