Motion Analysis of a Sphere Driven by Rollers

Friction drive systems are adopted for many robots of spherical locomotion type. Such systems have problems, including traversing uneven surfaces, slipping of the roller, and dust between the sphere and the roller. Despite of the disadvantages, these systems attract attention because of the possibility of stepped climbing and omnidirectional locomotion. In the future, it is anticipated that the mechanism using the sphere are developed. When the kinematics with respect to multiple rotational axes in arbitrary contacted on the sphere is clarified, the mechanism may be widely used. In the paper, a general theorem for kinematics is discussed including the number of rollers driving the sphere, the type of roller (constraint or unconstraint), and the contact points of the rollers on the sphere and the roller axes direction. To verify the validity of the kinematics model a locomotion model of the ball dribbling mechanism with the two rollers is presented as a special example by carrying out the experimental demonstration using the device robot