Design, Kinematic Modeling and Aerodynamic Performance Evaluation of a Beetle-Inspired Folding Wing with High Folding Ratio

Foldable wings significantly improve the portability of flapping-wing micro air vehicles. This study presents a novel multi-stage bio-inspired wing design, inspired by the venation pattern and folding mechanism of the hindwing of Xylotrupes dichotomus, achieving a folding ratio of up to 3.44 while ensuring reliable folding operation. A flapping-wing structure integrating linkages and a membrane is designed with a high-stiffness strategy. A systematic theoretical kinematic analysis is conducted to investigate the motion relationships among the linkages during the folding process, and a kinematic model is established to ensure stable folding operation. A one-way fluid-structure interaction analysis is subsequently performed to verify the high-stiffness assumption and to establish an aerodynamic baseline for the specific corrugation pattern induced by the folding mechanism. Results indicate that the maximum elastic deformation is approximately 5.7% of the wingspan, validating the quasi-rigid treatment. Comparative analysis with a flat-plate model further demonstrates that the corrugation has a negligible effect on aerodynamic performance. The validated high-stiffness configuration thus provides a well-characterized rigid-wing reference for future stiffness-modulated investigations.