Back-stepping approach for rolling motion control of an under-actuated two-wheel spherical robot

Spherical robots are the mobile robots with the locomoting by displacing its centre of gravity to generate torque and rotate itself. Therefore, the angle of the main body inside the robot determines the position and posture of the robot. There is only one contact point between the robot and the ground, and the inappropriate control strategy can generate the sizeable angular amplitude of the main body. As a result, the stable movement of the robot cannot be satisfied along with the appeared vibrations. This problem significantly impacts the tracking control quality and creates the clumsy gestures of the robot. In this research, an under-actuated dynamic model-based back-stepping control focusing on the rolling motion is developed and applied for a designed two-wheel spherical robot. With the provided closed-loop control law, both the precision and stability of the robot's movement are guaranteed. The entire work's efficiency is investigated by the experimental results.