FlyOrb: Spherical Terrestrial-Aerial Bimodal Vehicle

Unmanned aerial vehicles perform well in aerial tasks but still face limitations due to limited endurance. In this work, we present a novel spherical terrestrial–aerial bimodal vehicle, called FlyOrb, which is capable of both rolling and flying. The vehicle integrates inertial wheel actuation with a concise mechanism based on an unactuated hinge structure, enabling quadrotor- like flight and spherical robot– like rolling. Furthermore, the mass eccentricity design allows the vehicle to be self-stabilizing on the ground but makes it difficult to initiate rolling. We propose a resonance-driven rolling strategy for activating and efficient rolling. For both slope and step, the vehicle's traversal capabilities were analyzed theoretically and tested experimentally. Thrust experiments identify the more aerodynamically efficient structure, which retains 87.2% of the thrust compared to the configuration without arm. Futher, we analyze the impact of FlyOrb's design on its flight maneuverability. Finally, flight and rolling tests validate the vehicle's multimodal locomotion capabilities. In ground mode, the average speed is 0.3505 m/s, and the power saving efficiency reaches 96.8%.