Estimation of dq-axis Mutual Inductances for Vibration Reduction of Encoderless Control

This paper proposes an estimation method of dq-axis mutual inductances of Interior Permanent Magnet Synchronous Motors (IPMSM) for encoderless servo drive systems. These estimated values are utilized in the current control. Conventionally, the dq-axis mutual inductances are ignored in the current control. Since these values depend on the electrical angle and current of the motor, the measurement of these values is difficult. However, ignoring these values causes velocity and torque vibration from the position estimation error and the control model error. The estimation and the compensation of dq-axis mutual inductances improve the performance of encoderless control. The proposed estimation method is based on a high-frequency voltage injection position estimation method. The estimated parameters are implemented in decoupling control of current control. Experimental results show the validity of the proposed method.