Control of Wheeled Pendulum

Wheeled pendulum is a mobile robot composed basically of an inverted pendulum which is provided with two wheels at the bottom. This allows the robot to describe translation displacements on a plane. Variables describing robot movements are 6: two coordinates on the plane, pendulum tilt angle, robot orientation on the plane, right wheel angular position, and left wheel angular position. However, only two actuators (DC motors) are used at the wheels to provide torque to the whole robot. Thus, we say that wheeled robot is an underactuated mechanical system. This feature and the fact that an inverted pendulum is unstable render this mechanical system very interesting for control design.