Large-Pitch Hovering Control of Tilt Trirotor UAVs Using Symmetric Control Formulation

Large-pitch hovering can substantially extend the maneuvering envelope of tilt trirotor uncrewed aerial vehicles (TTR) UAVs, yet it introduces severe orientation-dependent coupling that limits the efficacy of conventional multirotor control methods. To address this, this article presents a task-oriented modeling and control framework tailored for the large-pitch hovering of TTR UAVs around nonzero pitch equilibria. We introduce an auxiliary coordinate frame that embeds the hovering equilibrium, reformulating the strongly coupled translational dynamics into a symmetric force-moment representation. This structural transformation preserves compatibility with standard hierarchical control architectures and conventional control allocation schemes. As a result, a unified position and attitude controller can effectively govern a wide range of pitch angles without the need for gain scheduling or controller switching. Comparative simulation studies establish a fair baseline against a conventional roll-only coupling approach under matched horizontal responses. Furthermore, real-world flight experiments validate the framework, demonstrating sustained large-pitch hovering with highly stable position regulation and smooth actuator dynamics under a constant controller structure. Ultimately, these findings confirm the practical feasibility and robustness of the proposed symmetric control formulation for physical TTR UAV platforms.