Skywalker: A Compact and Agile Air-Ground Omnidirectional Vehicle

By taking the complementary advantage of multicopters and ground vehicles, air-ground vehicles have shown great potential in various fields due to their superior mobility and outstanding endurance. However, most of the previous works adopt complicated mechanisms, and fail to develop a controller with high precision for tracking challenging trajectories, which severely limits their application. In this work, we firstly propose the design of an air-ground vehicle, which we name as Skywalker, with a concise yet robust mechanism based on an off-the-shelf omnidirectional wheel. Furthermore, we deduce the vehicle's differential flatness considering support and friction forces, and propose a unified controller qualified for high-speed air-ground hybrid trajectory tracking and smooth mode switching. Meanwhile, comprehensive experiments and a benchmark comparison are carried out to validate the system's outstanding performance, where the system tracks trajectories under velocity up to
$\text{5.0}\,\text{m/s}$
and saves energy up to 75.2%.