Ando Noriyasu, Kono Tokuro, Ogihara Naomichi, Nakamura Sakiko, Yokota Hideo, Kanzaki Ryohei
Department of Life Engineering, Faculty of Engineering, Maebashi Institute of Technology, Maebashi, Japan.
Research Center for Advanced Science and Technology, The University of Tokyo, Tokyo, Japan.
Bioinspir Biomim. 2022 Oct 11;17(6). doi: 10.1088/1748-3190/ac8e40.
Indirect actuation of the wings via thoracic deformation is a unique mechanism widely observed in flying insect species. The physical properties of the thorax have been intensively studied in terms of their ability to efficiently generate wingbeats. The basic mechanism of indirect wing actuation is generally explained as a lever model on a cross-sectional plane, where the dorsoventral movement of the mesonotum (dorsal exoskeleton of the mesothorax) generated by contractions of indirect muscles actuates the wing. However, the model considers the mesonotum as an ideal flat plane, whereas the mesonotum is hemispherical and becomes locally deformed during flight. Furthermore, the conventional model is two-dimensional; therefore, three-dimensional wing kinematics by indirect muscles have not been studied to date. In this study, we develop structural models of the mesonotum and mesothorax of the hawkmoth, reconstructed from serial cross-sectional images. External forces are applied to the models to mimic muscle contraction, and mesonotum deformation and wing trajectories are analyzed using finite element analysis. We find that applying longitudinal strain to the mesonotum to mimic strain by depressor muscle contraction reproduces local deformation comparable to that of the thorax during flight. Furthermore, the phase difference of the forces applied to the depressor and elevator muscles changes the wing trajectory from a figure eight to a circle, which is qualitatively consistent with the tethered flight experiment. These results indicate that the local deformation of the mesonotum due to its morphology and the thoracic deformation via indirect power muscles can modulate three-dimensional wing trajectories.
通过胸部变形间接驱动翅膀是在飞行昆虫物种中广泛观察到的一种独特机制。胸部的物理特性已就其有效产生翅膀拍动的能力进行了深入研究。间接翅膀驱动的基本机制通常在横截面上被解释为杠杆模型，其中由间接肌肉收缩产生的中胸背板（中胸的背侧外骨骼）的背腹运动驱动翅膀。然而，该模型将中胸背板视为理想的平面，而中胸背板是半球形的，并且在飞行过程中会发生局部变形。此外，传统模型是二维的；因此，迄今为止尚未研究间接肌肉的三维翅膀运动学。在本研究中，我们从连续横截面图像重建了天蛾中胸背板和中胸的结构模型。将外力应用于模型以模拟肌肉收缩，并使用有限元分析来分析中胸背板变形和翅膀轨迹。我们发现，对中胸背板施加纵向应变以模拟降肌收缩产生的应变，会再现与飞行过程中胸部局部变形相当的局部变形。此外，施加在降肌和提肌上的力的相位差会使翅膀轨迹从数字“8”变为圆形，这在定性上与系留飞行实验一致。这些结果表明，由于其形态导致的中胸背板局部变形以及通过间接动力肌肉产生的胸部变形可以调节三维翅膀轨迹。
