Hierarchical Sliding Mode Control for a 3D Ballbot that is a Class of Second-order Under-actuated System

This paper proposes a hierarchical sliding mode controller for a three-dimensional ballbot in an extremely complicated operation of three omni-directional wheels, a ball, and body. Three ball motors simultaneously drive four outputs comprising ball motion and two tilt angles of the body. Simulation tests are performed to investigate the controller qualities. The proposed controller asymptotically stabilizes and consistently maintains system response.