Stability and Motion Control of a Unicycle (1st Report: Dynamics of a Human Riding Unicycle and Its Modeling by Link Mechanisms)

Abstract

In this paper, the dynamic characteristics of a human riding a unicycle are first analyzed by observation.: Based on observation and analysis, we discovered that the rider's body, thighs and shanks create two closed link loops; and this special mechanism plays an important role in the stability of the unicycle. We then developed a new model with two closed link mechanisms and one turntable to emulate a human riding a unicycle by a robot. Considering the nonholonomic constraint between the wheel and ground and applying recently developed general method to compute the multi-closed link mechanisms' dynamic motion, we obtained the dynamic equations of motion for this new model. Using these equations, simulation is conducted under the proposed control method. The simulation result indicates that both longitudinal and lateral stability of a human riding a unicycle can be satisfactorily emulated by the new model.