蜻蜓翅痣對振翅力與翅膀動態特性的效應

Abstract

本論文研究蜻蜓的翅痣對振翅力與翅膀動態特性的影響。振翅力方面，利用自行設計的三維測力計配合雷射位移計量測蜻蜓在固定姿態下三方向的平均力。在翅膀動態特性方面，依據基底振盪法以振盪器與雷射位移計量測蜻蜓翅膀上數個指定點的頻率響應函數，由曲線嵌合得到自然頻率與對應的振形。我們實際量測去除翅痣前後，在翅痣處增加質量後，蜻蜓的振翅力和翅膀的動態特性。另外利用頻率響應函數合成法推導蜻蜓翅膀基頻對不同位置處質量變化的靈敏度，藉此預測在翅膀不同位置處增減質量所導致的基頻的變化量，並和實驗結果相比對。我們詳細說明測力計的設計原理、量測蜻蜓振翅力的步驟、翅膀動態特性的量測方法，展示翅痣處增減質量前後的實驗結果並討論翅痣的效應。

The main object of this thesis is to study the effect of a dragonfly’s pterostigma on its lift force and the dynamical properties of its wings. To measure the lift force, we designed and made a three-dimensional load cell. The deformation of the load cell was measured by laser displacement sensors. To obtain the dynamical properties of a dragonfly’s wing, we used a shaker to excite the wing and a laser displacement sensor to measure the displacement at specified points according to the base excitation method. In this way, a complete set of frequency response functions of the wing were obtained. The natural frequencies and the associated mode shapes were then determined through a curve fitting process. We measured the lift force and wings’ dynamical properties before and after the removal of the pterostigma, and after the adding of some UV glue at the location of the pterostigma, respectively. Moreover, the frequency response function synthesis method was used to calculate the sensitive of the wing’s fundamental frequency to the change of mass at different locations. With the calculated sensitivity, the change of the fundamental frequency due to the removal of petrostigma was estimated and compared with the experimental results. We described in detail the design process of the load cell, experimental procedure to measure the dragonfly’s lift, and method to determine the dynamical properties of the wings; presented experimental results and discussed the effects of a dragonfly’s petrostigma.