The spherical motor with gear structure to realize two degrees of freedom with crossed revolute axes has been developed. This spherical motor is called “spherical omnidirectional driving gear” because its structure is based on the theory of the omnidirectional driving gear with two gear structures that are perpendicular to each other developed by the authors in previous research. The gear structure with involute curve is deployed on the outer surface of the inner core gear and the inner surface of the outer shell gear. These gear structures are perpendicular to each other to realize rotational motions around two axes. Spur gears with conical teeth transmits power to the inner core gear and the outer shell gear. In this paper, we introduce two possible mechanisms of the spherical omnidirectional driving gear and explain their principles. The experiments to compare the power transmission efficiencies of the spherical omnidirectional driving gear and the ordinary spur gear were conducted.
