Basic characteristics of the developed spherical stepping motor

The positioning accuracy, output torque, and the trajectory tracing property of the developed spherical stepping motor are tested. The motor is composed of two arc-shaped stepping submotors and a rotational stepping submotor. The rotational center of each submotor is identical. The following characteristics are derived from the experimental results. The positioning resolutions of the inner, middle, and outer submotors are 0.00781[deg], 0.00586[deg] and 0.00586[deg] respectively. The holding torques of the inner, middle, and outer submotors are 0.093[Nm], 0.38[Nm] and 2.06[Nm] respectively. It can trace along the circle and the radiation trajectory within 0.2[deg] error, and the star trajectory within 0.4[deg] error. In comparison with a spherical synchronous motor, the positioning resolution is better but the torque/diameter ratio is smaller