Combined operation of short-primary permanent magnet linear synchronous motor and linear induction motor in material handling applications

In material handling applications where high precision, very long tracks and closed paths are required, short primary linear drives are proposed. The short primary type uses an active vehicle (moving winding) on a passive track (stationary magnets or induction rail). To implement this topology, this paper presents a combined operation of a short permanent magnet linear synchronous motor (PMLSM) and a linear induction motor (LIM). The costs can be reduced considerably by using a simple induction rail, instead of permanent magnets on the track. The control unit and converters are mounted on board of the active vehicle. A contactless energy transmission provides the average power and an ultracapacitor bank provides the peak power demanded by the active vehicle via a bidirectional DC-DC converter. The field oriented control, the drive control, the machine model and the control structure are based on field oriented control (FOC) using the rotating AB-reference frame. The transition control strategy is described and experimental results demonstrate the transition between sections with permanent magnets and induction rail.