RoboBall: An All-Terrain Spherical Robot with a Pressurized Shell

Spherical robots are a different type of mobility platform. A spherical robot is self-contained within its shell rather than relying on a chassis with wheels to navigate. In this shell, it is completely shielded from dust and the environment. This benefit of geometric simplicity has led to the spherical robot becoming an advantageous option for all-terrain exploration and surveying. This paper focuses on a novel iteration of such a robot with a pressurized pneumatic shell design. A soft robot of this type brings benefits of a passive, compliant contact surface that can affect its performance. However, the added softness of its shell adds new unmodeled dynamics into the system that impair commonly used control schemes. This paper outlines the design and manufacture of a soft, inflatable, spherical shell designed for a robot driven by an internal 2-DOF pendulum. In addition, it presents models for controlling the pendulum and understanding the shell dynamics. The paper concludes with experimental validations of these models and field tests of the system on slopes, gravel, rough grass, and on water.