Finite-time posture control of a unicycle robot

This paper deals with the problem of posture control for a unicycle (single-wheel) robot by designing and analyzing a finite-time posture control strategy. The unicycle robot consists of a lower rotating wheel, an upper rotating disk, and a robot body. The rotating wheel enables the unicycle robot to move forward and backward to obtain pitch (longitudinal) balance. The rotating disk is used for obtaining roll (lateral) balance. Therefore, the unicycle robot can be viewed as a mobile inverted pendulum for the pitch axis and a reaction-wheel pendulum for the roll axis. The dynamics models for unicycle robots at roll and pitch axes are derived using the Lagrange equation. According to the dynamics models, two finite-time controller are designed, which includes the finite-time roll controller and the finite-time pitch controller. Moreover, the stability on the unicycle robot with the proposed finite-time posture control strategy is also analyzed. Finally, simulations are worked out to illustrate the effectiveness of the finite-time posture control strategy for the unicycle robot at roll and pitch axes.