Sensorless position-control method based on magnetic saliencies for a Long-Stator Linear Synchronous-Motor

A sensorless method based on evaluating magnetic saliencies by HF signal injection is investigated for long-stator linear synchronous-motors. For long carriageways, the stator is divided into several independently fed segments, in order to reduce the reactive power and to allow more than one vehicle to move on the same carriageway. This kind of linear motors present difficulties, not found in rotative ones, in order to implement the sensorless methods. For instance, due to the end-effect of the stator, stationary saliencies arise which interfere with the position detection. In addition, the position dependent inductance of each segment is non-periodic. Therefore the position information from one segment must be synchronized with the adjacent one when the mover passes over a segment transition. In this paper, a sensorless position-control method providing means to overcome the stationary saliencies and the segment transition is proposed. It was tested in an experimental setup and performance results are shown