Sensorless positioning of a non-salient permanent magnet linear motor by combining open-loop current angle rotation method and back-EMF estimator

A sensorless positioning method for a non-salient permanent magnet linear synchronous motor is presented in this paper. The control method combines an open-loop current angle rotation method to the back-EMF estimator method. The open-loop current angle rotation method is used at low velocities and the back-EMF method at higher velocities. The position accuracy is defined by the open-loop current angle rotation method and improved with current angle compensation. The position accuracy of the sensorless method is verified with position measurements in experimental tests.