Novel dual-pitch linear pulse motor and its operating characteristics

The linear pulse motor (LPM) has the advantage of simple structure and easy drive characteristics. However, there is the relation of trade-off between high-velocity operation and high-resolution positioning. In order to improve the trade-off characteristic, a novel structure that the authors call the dual-pitch LPM (Dual-LPM) is presented in this paper. The Dual-LPM has both large-pitch-width structure for high-velocity operation (large-pitch armature) and small-pitch-width structure for high-resolution positioning (small-pitch armature). To operate the Dual-LPM, it is necessary to switch the armature to which the excitation current flows. Furthermore, in order to prevent a sudden change of velocity during switching, the magnetic-teeth position to which the armature current is going to flow should be sensed. On the proposed control method, back EMF voltage on the corresponding armature winding is utilized. Hence, switching over the excitation of the armature from small-pitch to large-pitch, or vice-versa, is performed stably without a position sensor. This paper also discusses the dynamic thrust characteristics. The operation characteristics are verified experimentally by the prototype Dual-LPM set up