This paper presents the design, implementation, and validation of balance control and point-to-point motion control of a single-wheeled (unicycle) robot. The robot consists of a wheel, a body, a reaction wheel, and a turntable. The wheel is used to move the robot forward and backward to obtain longitudinal stability. The reaction wheel is used for obtaining lateral stability. The turntable provides steering torque about the vertical axis of the robot. The dynamic model of the system is derived using Euler-Lagrange formulation. By retaining the predominant nonlinear terms and neglecting the high-order coupling terms, the system model is simplified to three decoupled systems. Sliding mode control is then used to design the balance and steering controllers for the simplified model. By combining the obtained balance control and steering control, a point-to-point motion control strategy is proposed. The experimental results are presented to verify the effectiveness of the designed control schemes.

This paper seeks to improve the zero-state performance of a standard model reference adaptive control scheme for rigid robots by augmenting the usual model reference control law with an auxiliary component synthesized from the tracking error. A condition involving a certain design parameter is given which can be used to decide a priori whether the modified scheme can potentially outperform its unmodified counterpart. If the joint accelerations are available for measurement, then it is shown that this condition can always be satisfied and the zero-state performance of the modified scheme can in fact be arbitrarily improved.