Fine self-tuning method of both current sensor offset and electrical parameter variations for SPM motor

The servo system of a permanent magnet (PM) motor is always required to maintain fine torque and speed response. The current-control system is designed by using the electric parameters of the PM motor. However, motor parameters vary and the current sensors have offset values. When each U-phase and V-phase current sensor has an offset value, the PM motor servo system has the torque ripple and cannot accurately identify the motor parameters. In this paper, we propose a new online-estimation method for both current-sensor offsets and electrical parameters for PM motors by using a current simulator. The experimental results confirm that the proposed method accurately estimates both the U-phase and V-phase current sensor offsets, the motor resistance R_a, the motor inductance L_a, and carries out the fine self-tuning for the current controller of PM motor servo system.