Measurement of rotation of output ball in a spherical speed reducer using one small ball

Abstract

　In order to construct a system with multi-degree of freedom by only using the motors with one degree of freedom, the same number of motors as the degree of freedom is required. On the other hand, in a spherical motor with three degrees of freedom, it is possible to realize a system with three degrees of freedom by only one spherical motor, and it is possible to reduce the size of the system. However, in many spherical motors driven by electromagnets, a spherical speed reducer is required as a device to extract and transmit the output torque. The spherical speed reducer considered in this study is composed of an output ball and an intermediate small ball to transmit the torque from the rotor. In the mechanism of the spherical speed reducer, a model of the rotation transmission to control suitably the rotor is required for a desirable rotation of the output ball. The purpose of this study is to measure angular velocities of the small ball and the output ball in order to derive a rotation transmission model. The angular velocity of each ball is measured using two optical mouse sensors. From the measurement results, a valid rotation transmission model is derived.