ATHMOS: Experimental Validation and Hybrid Mobility Control of a Spherical Aerial-Ground Robot

This paper presents the experimental validation of ATHMOS a spherical hybrid aerial–ground robot designed for confined, contact-rich environments that combines energy-efficient terrestrial rolling with agile aerial locomotion. A mode-dependent model-based con-trol and state estimation architecture is implemented to manage flight, rolling, mode transi-tion phases and contact interactions, dominated by nonlinear phenomena. We experimentally validated the current prototype through repeatable outdoor tests covering rolling and flying segments, take-off, landing, and transition maneuvers. Reported metrics include tracking per-formance, state estimation accuracy, transition response times, contact-detection reliability, and energy per distance in rolling versus low-speed flight. The results confirm the feasibility of using rolling as the primary energy-efficient locomotion mode and flight as a complemen-tary mode for obstacles, discontinuities, and three-dimensional maneuvers, overcoming the trade-off between agility, contact robustness, and energy efficiency. The contribution offers a reproducible methodology, hybrid control logic, and experimental protocols, for early-stage evaluation of spherical aerial–ground robots operating under nonlinear dynamics and inter-mittent environment interaction.