Proposal of Spherical Speed Reducer that Constraints Rotation Axis of Intermediate Balls and Construction of Theoretical Rotation Transmission Model for the Reducer

Abstract

　Common multiple-degrees-of-freedom system consist of some uniaxial motors. In contrast, a spherical motor that has a spherical rotor realizes the motion of three degrees of freedom by the motor itself. So, a system by a spherical motor can reduce its size and has advantages such as shorter control time than the system combining uniaxial motors. Most of spherical motors driven by electromagnetic forces have a problem that it is difficult to generate high output torque. So, the development of a spherical speed reducer is required to increase the output. In the development of a spherical speed reducer, it is necessary to construct a rotation transfer model to generate required rotation of the output sphere. This study proposes a spherical speed reducer that the rotation axis of the small spheres, that are intermediate spheres, is constrained not to rotate around an axis in a fixed three-dimensional orthogonal coordinates system. A rotation transmission model from the rotor to the output sphere is constructed using the fact that the rotation of a small sphere is simplified by constraining the rotation around one axis. From the experimental results, the applicability of the rotation transmission model is confirmed.