Proposal of a Slot-less Motor for Electric Power Steering with Small Torque Ripple

As the quality characteristics of electric power steering (EPS) motors, the high average torque, small torque ripple, and small cogging torque are required. This paper proposes a slot-less permanent magnet (PM) synchronous motor for EPS motor, which has theoretically 0 cogging torque. Magnet volume and coil volume are determined by 2-D finite element (FE) analysis. The 3-D FE analysis shows that it has the average torque of 2.667Nm and the torque ripple of 0.053Nm. Therefore, it is verified that the proposed motor has a great decrease of torque ripple.