The SpHelico: A coaxial drone inside a gimbal system. Modeling, design, and control

Abstract This paper presents the SpHelico , a novel aerial platform composed of a coaxial rotor with dual control vanes, enclosed within a freely actuated spherical gimbal. This mechanical design ensures protection against collisions while maintaining full maneuverability. A bounded attitude tracking controller is developed on the Special Orthogonal Group , accounting for actuator saturation and external disturbances. To achieve full six‐degree‐of‐freedom control, a hierarchical control scheme is proposed that incorporates a geometric position controller on , generating the desired orientations and thrust vectors required for translational tracking. Theoretical guarantees of exponential convergence are provided for both attitude and position tracking errors. Extensive simulations validate the proposed strategy under realistic conditions, including perturbations and actuator limitations, and benchmark its performance against a sliding mode controller. Additionally, the paper details the complete mechanical design and provides a video demonstration using a real prototype to illustrate the practical feasibility of the approach.