Development of a ball drive unit using partially sliding rollers — An alternative mechanism for semi-omnidirectional motion —

There are several works on mobile robots that employed a single ball as their wheel. Each of them used a kind of inverted pendulum control and a specific ball drive mechanism. The requirement for the mechanism is to roll the ball in two orthogonal directions for maintaining robot attitude and traveling on a two dimensional surface. In addition to these rolling motions, rotation around a vertical axis is useful for turning the robot body. The author developed robots that used wheels for omnidirectional motion of the ball in previous works. However, the wheel was complex to produce in large quantities and expensive. The purpose of the work described in this paper is to develop a new simpler mechanism with drivability almost comparable to previous driving mechanism but lower in cost. The idea of a roller with semi-passive features and a ball drive mechanism are described as well as experimental results using a robot with the proposed mechanism.