Implementation of sensorless speed control for industrial material handling and processing applications based on short primary linear induction motor

Linear drives have been a feasible solution for industrial material handling and processing applications, due to its high dynamic response, high precision and robustness. This paper presents a short primary linear induction motor (LIM) on passive track, where the primary (moving windings) travels between the processing stations. Usually a linear scale is installed along the guidance profile; therefore in case of very long track applications, the costs can be reduced considerably by using a sensorless speed control method. The speed sensorless control should be activated when the vehicle travels outside the processing station, and it uses the classic MRAS (Model Reference Adaptive System) speed and flux estimators based on rotating induction machines. The control strategy during the transition between sensor based and sensorless regions of the track is experimentally verified and discussed.