Cogging Torque Reduction of a 3-Degree-of-Freedom Spherical Actuator Using an Auxiliary Pole

Abstract

　A 3-degree-of-freedom spherical actuator has a small size, light weight, and high positioning accuracy compared with conventional systems composed of several 1-degree-of-freedom motors. However, the torque of the spherical actuator is lower than that of the conventional systems, and there are some positions where the actuator cannot move due to a low torque. In order to increase the torque, iron core coils are used instead of air core coils. However, this increases the cogging torque and decrease the controllability. In this paper, for the purpose of reducing the cogging torque, a stator tooth structure with an auxiliary pole is proposed. In addition, the stator tooth arrangement is also optimized using a genetic algorithm.