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 75×75×68 mm. The positioning resolutions of the inner and the outer submotors are 0.01deg and 0.03deg respectively and the holding torques of the inner and outer submotors are 0.2Nm and 0.03Nm 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.