Online tuning method for current measurement offsets and gain deviations for SPMSM

AC servo motors are operated by current sensors. However, these current sensors often exhibit offsets caused by age-related deterioration and thermal variation. Gain deviation also causes current measurement errors. These errors lead to torque ripples and dq-axis current ripples. This paper proposes a new method of estimating and compensating for gain deviation in current measurement using a current simulator. The method uses dq-axis current ripples arising from sensed current and estimated current. Thus, it can be applied in conjunction with a proposed offset estimation method. In this paper, the methods are tested on a surface-mounted permanent magnet synchronous motor, in which the current sensors are arranged in u-phase and w-phase. Simulation and experimental results confirm that the proposed methods suppress current and torque ripples caused by offset and gain deviation in current sensors.