Design and performance validation of an active spanwise-folding bionic flapping-wing aerial vehicles based on a single-degree-of-freedom linkage mechanism

Abstract Addressing the trade-off between flight efficiency and environmental adaptability in traditional fixed-wing micro-flapping aircraft, this paper draws inspiration from the dynamic wing deformation mechanisms of birds to design an active folding-wing bionic flapping aircraft based on a single-degree-of-freedom linkage mechanism. This design employs servo-driven tether lines to achieve wing folding. Combined with a lightweight skeleton, the total weight of the aircraft is controlled at 181 g, with power transmission efficiency improved by 18%. The maximum wing folding angle reaches 80°, reducing wing area by 60%. Bench and flight tests demonstrate stable operation at a 3.5 Hz flapping frequency and 120° amplitude. The aircraft can navigate through 70 cm narrow passages, achieving a 103.6% increase in landing speed compared to fixed-wing designs. Wing deployment relies on elastic joints for inertial reset. This single-degree-of-freedom design simplifies control logic, resolves structural redundancy issues in multi-degree-of-freedom mechanisms, enhances the aircraft’s maneuverability and adaptability to complex environments, and provides a new approach for the structural design of biomimetic flapping-wing aircraft. It also points to subsequent optimization directions such as lightweighting and intelligent control.