Principle of Stable Running of an Unicycle Robot

In previous papers, we reported the world's first success in the driving of a human-riding-type unicycle with postural stability. However, the robotic unicycle was connected with a computer, motor drives, and a power source through electric cables. It was made clear by our experiments that the stability and dynamic behavior of the unicycle were largely affected by these extension cables, and the driving distance was also limited. This paper reports the development of an extension cable-less unicycle including the design of its control system and the principle of unicycle running. Firstly, an improved unicycle without extension cables is designed. Secondly, the principle of unicycle running is elucidated by simulations and experiments using the developed robot. Lastly, we propose a new control method including yaw-direction control. Experimental and simulation results show that the proposed method is effective for the developed unicycle robot to realize human-like stable motions.