Steering control of automatic lateral-pendulum unicycle by separate set-point controls of its longitudinal and lateral modes

Abstract

Automatic lateral-pendulum unicycle (ALP Cycle) is a unicycle robot with three main parts: wheel, chassis and pendulum. Its conceptual design is meant to mimic a human-ridden unicycle. It is an underactuated robot with only two actuators: wheel and pendulum motors, and five degrees of freedom. The wheel motor's function is to provide forward thrust while the pendulum motor provides steering torque. The combination of these forward thrust and steering torque results in gyroscopic effect which makes it possible for ALP Cycle to perform turning/yaw motion. In this paper, two separate linear quadratic integral controllers are designed for wheel and pendulum motors. The wheel-motor controller regulates the wheel's rotational speed based on the desired forward speed of ALP Cycle. The pendulum-motor controller regulates the lean angle of the ALP Cycle's wheel based on the desired turning speed of ALP Cycle. The performance of the controllers is shown by MATLAB simulation incorporating disturbance which represents wind.