Analysis of a 3-DOF Spherical Actuator Driven by 4-Phase Using Finite Element Method

Abstract

　A single 3-DOF spherical actuator can drive three degrees of freedom and is expected to be applied to robot eyes and positioning mechanisms. However, it is difficult to miniaturize the actuator because it has a complex structure with many coils and permanent magnets arranged three-dimensionally and is controlled by a large drive unit. We proposed a 4-phase 3-DOF spherical actuator that can be driven by only one 4-phase inverter. The actuator consists of four coils and four permanent magnets, and achieves 3-DOF rotation with a simple structure. This paper describes the change in torque characteristics when the coil shape is changed. The torque characteristics are investigated using a three-dimensional finite element analysis. In addition, the variation of inductance characteristics during rotation is investigated.