ARIES: Cylindrical Pendulum Actuated Explorer Sphere

Spherical rolling robots (SRR) have been a promising avenue for the exploration of unstructured environments with variable topologies. The advantages include the ability to move fast, robustness to collision, and a lower number of actuators. However, to finally be used in real missions and applications, they need to have a high maneuverability and have sufficient inner space to house a proper payload for the intended application, such as cave and tunnel exploration, without compromising on the performances. With barycentric spherical robot, adding mass with a payload may become challenging, as the location of the center-of-mass is critical for the locomotion. In this article, we propose a novel barycentric spherical robot with two degrees-of-freedom (DoF) named Autonomous Robotic Intelligent Explorer Spheres (ARIES). The motion of this SRR is generated by a cylindrical actuated joint acting like a 2-DoF pendulum. This design allows us to have a nearly empty upper hemisphere inside the spherical shell, which is dedicated to payloads adapted to the application. The full kinematics and dynamics are presented, and simulation results are included. The control scheme implemented is detailed. We conducted an experimental evaluation of the ARIES with different trajectories, as well as discussed practical considerations and future improvements.