Abstract
We have developed an underactuated unicycle robot which consists of a body, a disk driven by a dc-motor to stabilize its posture, and a wheel driven by another dc-motor to move the body forward. The robot has only two motors and there is no direct force to change the yaw direction of the robot. The present paper proposes a control method for changing the yaw direction by using sinusoidal inputs, where the sinusoidal inputs for the roll and for the roll have the same angular velocity. At first, the yaw rate is shown to depend on the phase difference between these two sinusoidal inputs. And then a regulator is proposed, which changes the yaw direction to zero from any initial value by modifying the phase difference. Next, a tracking controller is proposed, which consists of the relation between the rate and the phase difference and the Kanayama's tracking control method for a car-like vehicle. The performance of the two controllers is confirmed by simulation results.
