Basic characteristics of the small spherical stepping motor

A small spherical stepping motor with two degrees of freedom is developed. The motor is composed of two sub stepping motors. Each submotor is the two-phase permanent-magnet bipolar linear stepping type and the shape is semi-circle. The rotational axes of two submotors cross at the same point, and this structure enables the developed motor to move in any direction. The size of the motor is 75x75x68 [mm]. The positioning resolutions of the inner and the outer submotors are 0.01[deg] and 0.03[deg] respectively and the holding torques of the inner and outer submotors are 0.2[Nm] and 0.03[Nm] respectively. The feature of the small torque and the high positioning resolution of the motor are suitable to apply it to the robotics eyes with small CCD camera.