Three Dimensional Posture Control of Mono-wheel Robot with Roll Rotatable Torso

This paper presents three dimensional stabilization of a mono wheel robot that has a roll axis joint at the waist part of the robot and a wheel. The robot is under actuated system. The robot in sagittal plane approximates a pendulum on a cart. The robot in lateral plane approximates a double pendulum whose first axis is under actuated. This robot has only two actuators and is supposed to be the minimum structure of the mobile robot. In this paper, the motion equation of the system is derived. Then, stabilizing controllers for sagittal and lateral motion are presented. Through the three dimensional simulation where whole three dimensional dynamics is considered, the validity of the controller is verified. Moreover, in combination of sagittal and lateral controller, turning motion around yaw axis is realized in spite of lack of a yaw axis actuator.