CAROS-Q: Climbing Aerial RObot System Adopting Rotor Offset With a Quasi-Decoupling Controller

Unmanned Aerial Vehicles (UAVs) have continually proven their effectiveness in various fields. However, UAVs have not yet matured enough to be used for vertical surface maintenance tasks, such as building inspection or cleaning. To mitigate this issue, this letter proposes a novel design for a coaxial hexarotor (Y6) with a tilting mechanism that can morph midair while in a hover, changing the flight stage from a horizontal to a vertical orientation, and vice versa, thus allowing wall-perching and wall-climbing maneuvers. Furthermore, a rotor offset design has been adopted, in which the tilting rotors are offset from the tilting axle by a certain distance. In this configuration, the required distance between the wall and the platform is reduced, improving stability and increasing the opportunity to enhance power efficiency. However, owing to the rotor offset, the servo motor slows down and the tilting angle is one-way constrained. These conditions can cause a critical issue with the conventional control method. To tackle the problem, a novel control method called quasi-decoupling control is proposed. Our proposed method attains promising performance, overcoming the limitations of a servo motor's slow dynamics and angular constraint.