Research progress on the flight mechanism of butterfly and butterfly-inspired flapping wing air vehicle

Bionic flapping wing air vehicle presents notable advantages, including high maneuverability, concealment, and efficiency. It holds promising applications in military reconnaissance and exploration search and rescue, rooted in a comprehensive exploration of biological flight mechanisms. Advanced motion observation and experimental techniques have facilitated more convenient and precise recording and analysis of insect flight behavior. Research indicates that common insects exhibit a high flapping frequency, ranging from 25 to 400Hz, while butterflies, characterized by a lower flapping frequency of approximately 10Hz, stand out. Despite the unique attributes of butterfly flight, there remains a scarcity of aerodynamic research compared to other flying organisms, resulting in an insufficient understanding of their intricate flying skills. Butterflies, distinguished by large forewings and hindwings that flap nearly synchronously on the same side of the body, spanning a substantial range of up to 180o, display significant pitch swing during flight, with highly coupled wing and body movements. Remarkably, despite these complexities, butterflies demonstrate agile flight capabilities, enabling them to embark on long-distance migrations spanning thousands of kilometers. This exceptional characteristic renders them exemplary subjects for bionics research, capturing the attention of scholars globally. In contrast to other insects, the flight mechanism of butterflies is uniquely intricate, adding complexity to the development of butterfly-inspired flapping wing air vehicles. Current endeavors in this field often simplify the mechanism of butterfly wing-body coupling, with only a few achieving controlled and stable flight. Consequently, this paper synthesizes the distinctive flight behavior and mechanisms observed in living butterflies, elucidating key technologies pivotal for the development of butterfly-inspired flapping wing air vehicles. It also delineates the future trajectory for advancing this aircraft category.