New Simple High-Quality Torque Control for Permanent-Magnet Synchronous Motors

—Compensating for Torque Ripple Caused by Nonsinusoidal Back EMF—

Abstract

This paper proposes a new and simple torque-sensorless torque control method for permanent-magnet synchronous motors (PMSMs) with nonsinusoidal Back EMF. The method suppresses the sixth and/or 12th harmonic torque ripples caused by the back EMF in a feedforward manner even at high speeds; it consists of two subordinate methods for compensation command generation and command-tracking current control. The first subordinate method generates compensation current commands to cancel the torque ripples based on a mathematical model of PMSMs. The second controls the stator current to track a current command containing both fundamental and compensatory components. In conjunction with the current control, a dedicated disturbance observer that employs a digital speed-varying band-pass filter as a disturbance filter is also proposed. The effectiveness and usefulness of the proposed method were verified through extensive experiments.