A Model of an Underactuated Unicycle Robot and a Control Method for Changing its Yaw Direction

A. Shiigai, S. Majima, and T. Kasai (Japan)


Non-Linear Control, Cruise Control, Underactuated Robot, Modeling


An underactuated unicycle robot has been picked up in the field of a non-linear control system. The robot 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. Since the robot has only two motors and there is no direct force to change the yaw direction of the robot, conventional controllers cannot change the yaw direction. In the present paper, two types of controller for changing the yaw direction are proposed. The first controller is a regulator, which changes the yaw direction from an initial value to zero by using sinusoidal inputs. The robot moves back and forth and gradually changes its direction toward zero. The second controller is for a cruise control. The controller changes the yaw direction of a moving unicycle robot. By using the controller, the robot can follow a circular trajectory or can control the traveling direction so as to change lanes. The performance of these controllers is confirmed by computer simulations.

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