仿生型水下載具側線感測元件設計

Abstract

物競天擇使得生物在演化的過程中，為了能夠延續生命而發產出最佳效率的移動方式以及靈敏的感測系統，魚類身體的兩側佈滿了由神經元所組成的側線系統，能感測流場的變化以及外界壓力的分佈，提供自身充分且足夠的環境資訊，藉此達到躲避天敵以及閃躲障礙物等功能。在本研究中，利用聚偏氟乙烯(PVDF)的壓電特性，量測水下的壓力並轉換為電壓訊號，製作出可使用在仿生型自主式水下載具(BAUV)上的感測元件，並且增強仿生型自主式水下載具對於環境資訊擷取的能力。同時藉由模擬與實驗探討聚偏氟乙烯在不同頻率的外部刺激之下，壓電敏感度的測試結果，找出實驗量測與模擬值誤差最小的特定頻率。提供將來可實際運用在仿生型自主式水下載具上，相應於外部刺激之下設計最佳聚偏氟乙烯尺寸的方法。使仿生型自主式水下載具在聲納與視覺回授系統無法運作時，仍可利用聚偏氟乙烯感測週遭壓力變化、辨識環境特徵，並增加仿生型自主式水下載具前進時的穩定性。

A sensing element composed by a piezoelectric material PVDF with an appropriate electric circuit are presented and its feasibility is shown through a experiment. It was presented how the oscillation pattern of a fish tail beat is similar to the oscillation pattern of an acoustic underwater dipole. Such an artificial acoustic dipole can be simulated experimentally by using a small and rigid vibrating sphere. The behavior of the PVDF film under the presence of a dipole was studied in order to simulate the tail beat of a fish and its effect on a PVDF film for a pressure sensing purpose. In order to do this, the theory of a small oscillating rigid body of arbitrary shape was studied to understand the theory of a vibrating sphere. The latter was also carried out in an experiment. The vibrating sphere was used as the external exciter for a sensitivity test experiment with the PVDF film under different stimulus frequencies to establish a way to choose a PVDF film as a pressure sensor. Finally, selection method for the size of the PVDF film corresponding to the external exciter frequency was presented.