Beetle Allomyrina dichotoma is one of the largest insects that performs many remarkable modes of locomotion, particularly hovering flight capability. In order to stay airborne, its flexible hindwings are flapped so as to work as a thrust generator. However, the wing loading of the beetle is relatively large (38.94  ±  3.73 N m-2) compared to those of other insects and hummingbirds, indicating that it is challenging for it to achieve flight. Here, we measured the hindwing morphology and kinematics of the beetle in order to discover its flight performance. Unlike many other insects, the beetle flaps its hindwings with an extremely large sweep amplitude of about 191.33  ±  6.12 deg at high flapping frequencies ranging from 36 to 41 Hz (mean wing tip speed  ≈  13.45  ±  0.58 m s-1). These capabilities enable the beetle to produce enough lift force to stay airborne with its bulky body (4-10 g). In order to investigate how the sweep amplitude affects the beetle's flight efficiency, we utilized the unsteady blade element model to estimate the power requirements of the same vertical force production for various sweep amplitudes. The results indicate that the sweep amplitude as high as 190 deg is more beneficial for power requirements than the smaller amplitudes, which require higher frequencies resulting in higher inertial powers to produce the same vertical force. Thus, for this large beetle, high sweep amplitude may be a biological strategy for staying airborne. In addition, we thoroughly discussed the effects of input constraints on the outcome by investigating power loadings for variable sweep amplitudes at a constant vertical force, mean wing tip speed, and flapping frequency. Effect of wing surface area was also investigated and discussed to provide useful information for the development of an insect-inspired flapping-wing robot.

中文翻译：

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极高的后掠幅度使巨大的盘旋昆虫获得较高的机翼载荷。

甲虫Allomyrina dichotoma是最大的昆虫之一，其执行多种非凡的运动方式，尤其是具有悬停飞行能力。为了保持在空中，其柔软的后翼被拍打成推力发生器。然而，与其他昆虫和蜂鸟相比，甲虫的侧翼负荷相对较大（38.94±3.73 N m-2），这表明其实现飞行具有挑战性。在这里，我们测量了甲虫的后翅形态和运动学，以发现其飞行性能。与许多其他昆虫不同，甲虫在36到41 Hz（平均翼尖速度≈13.45±0.58 m s-1）的高拍打频率下以191.33±6.12 deg的极大扫掠幅度拍打其后翅。这些功能使甲虫能够产生足够的升力，以保持其庞大的身体（4-10 g）的空气传播能力。为了研究扫掠幅度如何影响甲虫的飞行效率，我们使用了非稳态叶片元素模型来估计不同扫掠幅度下相同垂直力产生的功率要求。结果表明，与较小的振幅相比，高达190度的扫描振幅对功率要求更有利，较小的振幅要求较高的频率，导致产生相同垂直力的惯性功率较高。因此，对于这种大甲虫，高扫幅可能是保持空中传播的生物学策略。此外，我们通过研究在恒定垂直力，平均翼尖速度和拍打频率下可变扫掠幅度的功率负载，彻底讨论了输入约束对结果的影响。还对机翼表面积的影响进行了研究和讨论，以为昆虫启发式扑翼机器人的开发提供有用的信息。