Sensorless position control of surface permanent magnet linear synchronous motors

In this paper, a novel sensorless position control for a surface permanent magnet linear synchronous motor (SPMLSM) is presented. The position and speed of the SPMLSM drive is obtained through a closed loop observer by only measuring phase voltages and currents. Estimation of speed is done using difference between estimates of the current derivatives in the dq frame, which calculated two different ways: first using a high-gain observer, and then using the motor model. Estimation of the mover position is done through integrating the estimation of speed. The proposed scheme works in a closed loop fashion. It enhances the allowable initial position error; can be used without any physical modification; does not rely on motor saliency and requires no knowledge of the load. Results from numerical simulations and practical implementation are presented to validate the proposed schemes.