Development of a Slot-less Motor for EPS with Small Torque Ripple

Abstract

　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 develops a slot-less permanent magnet (PM) synchronous motor for EPS motor, which has theoretically 0 cogging torque. Basic dimensions are determined by two-dimensional finite element (2-D FE) analysis. The characteristic of the designed motor is analyzed by the 3-D FE analysis. The use of soft magnetic composite is proposed. The proposed slot-less motor is fabricated. The characteristic of the motor driven by a sensor-less control is clarified. The torque ripple is smaller than that of the commercialized EPS motor.