In recent years, tail-sitter unmanned aerial vehicles (UAVs), capable of vertical take-off and landing (VTOL) and long-range flight, have garnered extensive attention. However, the challenge of yaw control, particularly for large-scale UAVs, has become a significant obstacle. It is challenging to generate sufficient yaw moments by motor differential thrust without compromising control authority in other channels or increasing mechanical complexity. Therefore, this paper proposes the concept of blown yaw, which utilizes the high-velocity airflow over rudders, induced by the propellers slipstream, to enhance the yaw control torque actively. An over-actuated, hundred-kilogram-class, tail-sitter UAV is designed to validate the effectiveness of the proposed method. To address the control allocation problem introduced by the implementation of blown yaw, an optimization-based control allocation module is developed, capable of precisely mapping the required forces and torques to all actuators. The proposed method, combined with computational fluid dynamics (CFD) simulations, accounts for the propeller model and the significant differences in actuator effectiveness across various flight conditions. Simulation results demonstrate that the proposed blown-yaw method significantly enhances the yaw control performance, achieving an overall energy savings of approximately 8.0% and a 60% reduction in the mean-squared error. Furthermore, the method exhibits robust performance against variations in control parameters and external disturbances.

Compared to tilt-rotor or dual-system electrical vertical takeoff and landings (eVTOLs), tail-sitter eVTOLs eliminate tilting mechanisms and redundant propellers, offering a structurally simpler solution. However, large-scale tail-sitter aircraft remains rare due to several challenges. During the transition between vertical flight and level flight, actuators must generate sufficient pitch moment during the entire 90° aircraft rotation. Additionally, propulsive fans must deliver high thrust in vertical flight while maintaining efficiency in forward flight. Oblique freestream flows to the propeller disk during transition also induce blade vibration. To support the development of a future series of large-scale tail-sitter eVTOLs, Eagle of Taihu 100 (ET100) with a maximum take-off weight (MTOW) of 120 kg was designed as a technology demonstrator. An empirical-based parametric design workflow is introduced for initial phase development. Next, the aerodynamic design of the ET100 is discussed, which features a canard configuration and custom propellers. Computational fluid dynamics is employed for performance assessment. The numerical simulations for the propeller are validated through experiments conducted using in-house test rigs and good agreement can be observed between the two. A model is developed for the propeller thrust with oblique freestreams. Next, transition envelopes of the ET100 are analyzed, in which an optimal transition path is highlighted to guide flight control strategy. Finally, preliminary flight tests are reported, and directions for future work are discussed.

As the size of tail-sitter electric vertical take-off and landing (eVTOL) aircraft increases, significant challenges have arisen due to a lower thrust-to-weight ratio, more nonlinear aerodynamics during transition, and slower control response. To support the design and implementation of the flight control system for the large-scale tail-sitter eVTOL Eagle of Taihu 100 (ET100), a one-third-scale, 13 kg subscale technology demonstrator, ET10, was developed. This paper presents the control framework tailored for ET series. In this framework, a refined state-error-based model predictive control (MPC) scheme is proposed. By reformulating the translational dynamics, the coupling between translation and rotation is explicitly captured. Aerodynamic feedforward and efficiency-aware control allocation are integrated to mitigate model uncertainties. A PX4 software-in-the-loop (SITL) platform was constructed by integrating data from computational fluid dynamics (CFD) simulations and experiments to ensure a high-fidelity aerodynamic modeling. Flight simulations were first conducted to evaluate the improved algorithm in terms of tracking performance across various tasks. Next, flight tests of the ET10 were conducted, demonstrating the reliability and robustness of the scheme across the full flight envelope.

Trajectory planning for large tail-sitter electric vertical take-off and landing (eVTOL) aircraft during level flight is particularly challenging.Such vehicles typically feature highly nonlinear aerodynamics, a low thrust-to-weight ratio, and sluggish dynamics in both control surfaces and propulsion systems. These characteristics impose stringent feasibility and safety constraints on trajectory planning.To address this challenge, the paper proposes a trajectory planning algorithm leveraging the differential flatness property of tail-sitter aircraft.%The algorithm is designed to ensure flight safety, feasibility, %stability, and efficiency. The approach incorporates aerodynamics of the tail-sitter and maneuvering constraints into the optimization process, generating envelopes on critical physical states to enhance reliability throughout the entire level flight regime. The proposed algorithm is evaluated through a three-tier validation framework. First, numerical simulations assess its computational efficiency and success rate in generating feasible trajectories.Second, software-in-the-loop (SITL) tests are conducted using the PX4 autopilot to enable high-fidelity, low-cost verification.Finally, real-world flight experiments are performed on the Eagle of Taihu 10 (ET10), a 13 kg subscale technology demonstrator of the 120 kg Eagle of Taihu 100 (ET100), to demonstrate practical feasibility, robustness, and real-time performance.Owing to the generality of the planning formulation, only minor modifications are required to adapt the algorithm to trajectory planning for other fixed-wing aircraft.