PVDF感測器應用於結構系統之動態量測能力探討

Abstract

感測器在彈性材料結構振動的量測實驗中扮演非常重要的角色，一般而言感測器必須能正確擷取振幅、能量、相位等等數據，方能對結構各種響應有一定程度掌握，並提供足夠資訊針對需求進一步控制該結構系統。 PVDF薄膜這類壓電傳感器，在極寬的頻帶中(可至 Hz)皆有穩定的機電效應，使用上有高度耐衝擊、耐紫外線、耐核能輻射、重量極為輕薄等特性，黏貼於結構物上不會增加質量，對待測物動態特性的影響也非常微小，因此被廣泛應用在各種場合，例如結構響應、振動抑制、非破壞性檢測、聲學顯微鏡、水下聽音器、機器人皮膚、生醫儀器等。 本文主要利用PVDF薄膜作為感測器，將其黏貼於懸臂梁、懸臂板與自由邊界厚板三種結構系統上，量測鋼珠落擊試件產生之動態響應，分別觀察不同面積之PVDF薄膜感測器量測表現、PVDF感測器量測訊號與有限元素法軟體暫態模擬分析之比較，以及在振動類型相異之結構上量測結果，根據這些主題探討PVDF感測器之動態量測能力，同時也從時域和頻域圖形上比較與應變規感測器異同之處，並對PVDF感測器的特性有更深一層的認識。

In this thesis, the dynamic sensing characteristics of PVDF film sensor are investigated in many perspectives. First, we compare the sensing results of different PVDF film sizes on a cantilever beam, which showing that the PVDF sensor with size of 5mm × 2.5mm has the best sensing performence. Second, we compare the experiment signals derived by PVDF sensor and the simulation signals of a cantilever plate, where the simulations are evaluated by finite element method software “Abaqus”. The comparing results indicate that the signals from experiments and simulations are highly consistent with each other. At last, we detect and analyze the dynamic responses of a thick plate with fully free boundary condition. The results show that PVDF film sensor has excellent performance in dynamic sensing. Not only can PVDF sensor distinguish the resonant frequencies of a great amount of vibration modes, it can also detect the mode energy correctly, which is proven by comparing the frequency spectrums and the mode shape plots. The strain gage is also applied as a sensing standard to understand the sensing properties of PVDF film sensor, in the reason that strain gage is one of the most convenient and wildly-used sensor to detect the dynamic responses of structures. Our research shows that PVDF film sensor has better dynamic sensing ability than strain gage.