Development of a Spherical Speed Reducer that Uniformly Change Rotation Speed in All Direction

Abstract

　In order to construct a multiple-degrees-of-freedom system by using the motors with one degree of freedom, the same number of motors as the degree of freedom is required. On the other hand, a spherical motor has three degrees of freedom. It is possible to realize a system with three degrees of freedom by one spherical motor and, therefore, it can reduce the size of the system. In order to transmit the output torque by a spherical motor, a spherical speed reducer that can also change the rotation speed and output torque is required. This study develops a new mechanism for spherical speed reducer using intermediate small balls that their rotations are restricted in two rotation axes. This paper describes the mechanism of the proposed spherical speed reducer, theoretical rotation transmission model between the rotor of a spherical motor and the output sphere of the spherical speed reducer. The theoretical transmission model is confirmed by the results of the spherical speed reduction experiments using a prototype spherical speed reducer.