Eulerian Angle Non-singular Attitude Control of Quadrotor UAV at Large Pitch Angle

Large-angle flight can significantly enhance the maneuverability and adaptability of unmanned aerial vehicles (UAVs) in highly dynamic and complex environments, holding significant engineering and research value. To avoid singularities and achieve reliable large-angle UAV flight, this paper proposes a quaternion-based attitude model and control framework that employs a smooth global attitude representation. This study further introduces an Active Disturbance Rejection Control (ADRC) strategy tailored for the quaternion-based model to address the highly nonlinear and strongly coupled dynamic characteristics of quadcopter drones. A key feature of this study is the integration of unit quaternion modeling with ADRC, enabling more robust and precise attitude control, particularly under aggressive maneuvers or strong disturbances. To validate the effectiveness of the proposed method, four comprehensive experiments were conducted: model comparison experiments, large pitch angle attitude convergence experiments, continuous pitch angle tracking experiments, and visualization simulation experiments. The experimental results demonstrate that the ADRC controller designed in this paper exhibits superior performance.