Examination of intermediate spheres arrangement for miniaturization of spherical speed reducer capable of uniform deceleration in all directions

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. A spherical speed reducer is necessary to change the output torque and motion speed of a multiple-degrees-of -freedom system. We have developed a spherical speed reducer capable of uniformly decelerating in all directions and demonstrated its applicability by speed reducing experiments using a prototype speed reducer. However, when the reduction ratio becomes large, the entire mechanism of the speed reducer will become large. Therefore, in this study, we investigated the optimization of the sphere arrangement so that the entire mechanism can be made as small as possible. This paper shows the objective function and constraint expression set from geometrical considerations. This paper also shows the analysis results of the change of the value of objective function by changing the arrangement of intermediate spheres placed between the rotor of a spherical motor and output sphere.