Aerodynamic layout and control strategy design and flight verification of a wing-foldable variant VTOL aircraft

Vertical Takeoff and Landing (VTOL) aircraft combine the performance advantages of fixed-wing aircraft, such as long flight range and high speed, with the maneuverability and vertical takeoff and landing capabilities of rotorcraft. In recent years, VTOL aircraft have become a hot topic in the field of aircraft research. Tail-sitter VTOL aircraft, in particular, have garnered significant attention due to their simple structure and high weight efficiency. This article proposes a general layout scheme for a variable-wing tail-sitter VTOL aircraft, and designs a wing variant actuation mechanism with the self-locking function. Wind tunnel force measurements are conducted to study the aerodynamics of the aircraft in the fixed-wing cruise mode and quadcopter hover mode, and during the transition between these modes. The results offer valuable insights into the aircraft’s trimming capabilities and its flight performance in the fixed-wing cruise mode, as well as the aerodynamic characteristics during the forward transition phase. An elevon-rotor coordinated yaw enhancement control strategy is introduced to improve the yaw control effectiveness during the hover mode. By studying the aerodynamic forces acting on the aircraft during the transition process, a transition control strategy based on the airspeed and pitch attitude angle is developed. Flight tests are conducted to validate the aircraft’s performance, demonstrating good maneuverability and wind resistance of the aircraft in the quadcopter hover and fixed-wing cruise modes. The successful and smooth mode transitions without altitude loss validate the effectiveness of the control strategies.