Cogging force compensation of a discontinuous permanent magnet track linear motor drive

Permanent magnet track linear motor drives are used in numerous industrial manufacturing processes covering a wide range of material handling and conveyor applications. A traditional solution is a permanent magnet linear motor (PMLM) in which the stationary part consists of permanent magnets and the moving part of the armature. To further reduce the initial costs of such a permanent magnet track linear motor drive system, the track elements can be assembled in a discontinuous fashion, that is, by forming a track that includes magnets for accelerating and decelarting the mover and areas where the mover is freewheeling. As a result, the mover has to face regions with and without magnets, resulting in disturbance forces during the edge crossings. In this paper, a disturbance force compensation method for a non-salient permanent magnet linear motor with a discontinuous magnet track is proposed. The disturbances forces, namely the cogging forces, are estimated by using a special PMLM test setup and used to built the compensation routine. Experimental results are provided to verify the estimation and the compensation routines.