Mechanism and Control of a Reconfigurable Footprint Omni-Directional Vehicle.

Abstract

A newly designed four wheeled omni-directional vehicle which can vary its footprint is presented. Each wheel (made with a normal rubber tire) is attached with an offset to the tip of a link through a rotary joint and the another tip of the link is installed to the robot body with a rotary joint. The former joint is called “elbow” and the later one is “shoulder.”Individual joint has a DC servo motor and an electro-magnetic brake to control its angle. Thus, this mechanism consists of 12 motors and 8 brakes. First the concept of the proposed mechanism is described, and its kinematic behavior is analyzed. The principal part of the analysis is to derive a continuity condition of the elbow angle to design the trajectories for non-side-slip motions. The analysis is verified by some experimental results using a prototype one. Finally, the effectiveness of the proposed mechanism to gain the running stability based on controlling the zero moment point (ZMP) is also discussed.