Thrust characteristics improvement of a circular shaft motor for direct-drive applications

This paper presents a new circular shaft motor (CSM) model for development of haptic forceps system which has multi-degrees-of-freedom (MDOF). The prototype of CSM has issues; it is difficult to construct the stator as designed and the thrust characteristics is not enough high. The proposed CSM model includes trapezoidal magnets which are magnetized in axial direction. This structure can facilitate construction of the stator and decrease thrust ripple. In addition, by increasing the number of coil turns and shortening the magnetic gap between magnets and coils, the thrust characteristic can be improved. In this paper, the structure of proposed CSM is described. Then, the improvement of thrust characteristic is verified by magnetic field analysis. Finally, a prototype of the proposed model is developed, then thrust characteristic of the prototype of the proposed model is verified by primary experiment.