In this paper, we propose a novel swashplateless-elevon actuation (SEA) for dual-rotor tail-sitter vertical takeoff and landing (VTOL) unmanned aerial vehicles (UAVs). In contrast to the conventional elevon actuation (CEA) which controls both pitch and yaw using elevons, the SEA adopts swashplateless mechanisms to generate an extra moment through motor speed modulation to control pitch and uses elevons solely for controlling yaw, without requiring additional actuators. This decoupled control strategy mitigates the saturation of elevons' deflection needed for large pitch and yaw control actions, thus improving the UAV's control performance on trajectory tracking and disturbance rejection performance in the presence of large external disturbances. Furthermore, the SEA overcomes the actuation degradation issues experienced by the CEA when the UAV is in close proximity to the ground, leading to a smoother and more stable take-off process. We validate and compare the performances of the SEA and the CEA in various real-world flight conditions, including take-off, trajectory tracking, and hover flight and position steps under external disturbance. Experimental results demonstrate that the SEA has better performances than the CEA. Moreover, we verify the SEA's feasibility in the attitude transition process and fixed-wing-mode flight of the VTOL UAV. The results indicate that the SEA can accurately control pitch in the presence of high-speed incoming airflow and maintain a stable attitude during fixed-wing mode flight. Video of all experiments can be found in youtube.com/watch?v=Sx9Rk4Zf7sQ

翻译：本文提出一种用于双旋翼尾座式垂直起降（VTOL）无人机（UAV）的新型无斜盘升降副翼驱动（SEA）。与通过升降副翼同时控制俯仰和偏航的传统升降副翼驱动（CEA）不同，SEA采用无斜盘机制，通过电机转速调制产生额外力矩来控制俯仰，并仅依靠升降副翼控制偏航，无需额外执行器。这种解耦控制策略减轻了在大幅俯仰和偏航控制动作下所需的升降副翼偏转饱和问题，从而提升了无人机在大幅外部扰动下的轨迹跟踪与抗干扰控制性能。此外，SEA克服了CEA在无人机贴近地面时执行器性能退化的问题，实现了更平滑、更稳定的起飞过程。我们在多种真实飞行条件下验证并比较了SEA与CEA的性能，包括起飞、轨迹跟踪、悬停飞行以及外部扰动下的位置阶跃响应。实验结果表明，SEA的性能优于CEA。同时，我们进一步验证了SEA在VTOL无人机姿态过渡过程及固定翼模式飞行中的可行性。结果表明，SEA能在高速来流条件下精确控制俯仰，并在固定翼模式飞行中保持稳定姿态。所有实验视频见youtube.com/watch?v=Sx9Rk4Zf7sQ。