Fast Initial Pole-Position Estimation for Non-Salient PM-LSM Based on Agreement of Two Reference Frames

This paper proposes a new initial pole-position estimation method for non-salient permanent magnet linear synchronous motor (PM-LSM) without any pole sensors, which is based on the agreement of two reference frames in the command and the actual axes. The estimation method consists of the specific force command pattern, the measurement of mechanical mover position, the estimation of the angle error in the two reference frames, and the adjustment of the error. Since the angle error estimation is directly estimated using two measured mover positions, set electrically ±45 degree apart from the initial pole-position command, the error is rapidly compensated. Furthermore, the force command correction considering the minimization of disturbance such as friction and cogging, stabilizes the estimation. As a result, the fast initial pole-position estimation is realized almost at standstill. The experimental results show the effectiveness of the proposed estimation method with a non-salient PM-LSM for which the saliency or saturation based pole estimation method does not work.