Design and Implementation of a Closed-Chain Flapping Wing Mechanism for Bionic Compound Motion with Active Torsion

Inspired by the structural features, kinematic differences, and functional distinctions between the arm wings and hand wings of birds, we propose a design method for a two-loop closed-chain flapping wing mechanism. The primary bionic motion is achieved through two single-loop mechanisms, while functional integration is facilitated by the double-loop coupling. A double-loop closed-chain spatial six-bar flapping wing mechanism with a single degree of freedom (DoF) is ultimately designed. The proposed mechanism can realize the coupled movements of flapping, folding, and twisting with a single motor, making the motion morphology closer to that of real birds. The flapping wing mechanism, based on bionic design, was verified through kinematic and aerodynamic analyses to resemble biological movement and exhibit aerodynamic characteristics. The flight maneuverability of this single DoF spatial mechanism is further validated through prototype fabrication and experimental testing. Our study explores the coupled motions of bird wing flapping, folding, and twisting, contributing to a novel single DoF spatial flapping wing mechanism.