Control system for a spherical robot

Abstract

Spherical robots utilize an original locomotion system by displacing its center of gravity in order to generate torque and rotate itself. They are believed to have several benefits. First, the only contact point with the ground allows locomotion with minimal friction, leading to low-energy motion. Second, the spherical structure allows the motion in tightly constrained spaces. Third, the spherical body protects the inner structure against external shocks or dust. Finally, it cannot lose mobility simply by overturning thanks to its spherical shape. Spherical robots, however, can generate only a small amount of torque for rotation. This makes its locomotion ability for up-hill climbing and obstacle overrunning greatly limited. Therefore, this study focuses on spherical robots operating on smooth flat floors. It describes the basic dynamics and control methods, which can still be applied for indoor use. This is an important step for further investigation of more complex dynamics and control methods. First, the dynamics of a spherical robot is investigated for two motions: driving and steering. Second, this paper describes the newly developed prototype robot, including its wireless communication system. The wireless system is one of the critical components of the prototype, since rotation does not allow physical wiring. Third, in order to avoid clumsy and unstable motion coming from the spherical shape, several control methods for smooth locomotion have been developed using the prototype.