Proximate In-Phase Current Estimator to Reduce Torque Ripple in Permanent-Magnet Stepping Motor

This paper proposes microstepping via a proximate in-phase current estimator (PIpCE) to improve position control performance with reduced torque ripples in permanent-magnet (PM) stepping motors. In conventional microstepping control, low-pass filters (LPFs) are used to filter out measurement noise resulting from the implemented current feedback loops. However, the phase lag caused by LPFs can degrade position control performance. In this paper, we propose a current tracking controller with PIpCE. The globally uniformly ultimately bounded current tracking error is proved via the Lyapunov theory. The proposed PIpCE also enhances current tracking performance over that of the conventional method. The proposed controller not only reduces the torque ripple caused by the phase lag but also increases the operational range of microstepping by pushing the electromechanical resonance frequency to a high-frequency region. We experimentally validated the effectiveness of the proposed method and observed that this method provides uniform position tracking performance without step-out or speed reversal, even in high-speed operation.