光纖變形監測系統改進與研發

Abstract

光纖光柵感測器系統具有不受電磁波干擾、不受雷擊影響、可以做多點分佈式監測、訊號遠距離傳輸後之衰減非常低與體積小耐久性佳等優點。在土木與防災監測領域中，光纖光柵感測器更能顯現出其優勢。本研究主要目的在於研發與改良先前所研發之自動化光纖感測系統，主要訴求有三個方面，包括光纖光柵節理式偏斜儀（FBG-SD）之改良、光纖光柵測傾儀(FBG-IP)與光纖光柵加速度計研發。FBG-SD量測相鄰兩個硬管節理間相對偏斜角度之變化。FBG-SD可以任何角度做串接來監測其標的結構之變形分佈，但FBG-SD偏斜角度有量測誤差累積之缺失。在現場安裝時將FBG-SD單元連結在一起同時安置於監測標的結構，此一程序耗時同時容易損傷FBG-SD單元。本研究首先將FBG-SD做微型化，並使其可在試驗室做FBG-SD單元之串接。如此可以使得預先連接完成之FBG-SD串列易於搬運及做現地安裝。FBG-IP量測硬管節理相對於重力方向傾斜角度之變化。FBG-IP可以延垂直(重力)方向做串接來監測其標的結構延監測線之變形分佈，FBG-IP之系統設計與微型化FBG-SD類似，也可在室內預作串接，但沒有如FBG-SD量測誤差累積之缺失。光纖光柵加速度計主要是為一震動圓錐貫入儀(seismic cone penetrometer)而設計，符合震動圓錐貫入儀之機構設計與試驗需求。本論文敘述這些光纖光柵感測器之改良/研發，與部分之現地運用測試。

Optic fiber Bragg grating sensors typically have the advantages that include: immune to electromagnetic interference or lightning, capable of cascading multiple sensors on a single optic fiber, and the optical signal can be transmitted over long distances. In civil engineering and disaster monitoring, these advantages are especially oimportant. The objective of this research has three facets that include: improve the fiber Bragg grating segmented deflector (FBG-SD), development of an FBG inclinometer probe (FBG-IP) and an FBG accelerometer. The FBG-SD measures the relative deflection angle between two neighboring tubular rigid segments. A string of multiple FBG-SD units may be connected together in any direction to monitor the deflection distribution of a target structure. The errors in relative angle measurements accumulate through the connected FBG-SD’s. The individual FBG-SD units are connected in the field as they are attached or installed in the target structure. This process is time consuming and tends to damage the FBG-SD. The first task in this research is to minimize the FBG-SD units, and allow them to be pre-assembled into an array in the laboratory. The arrangement makes shipping and field installation of the FBG-SD array significantly more efficient. The FBG-IP measures change of its inclination in reference to gravity. Multiple FBG-IP’s can be connected into a string and monitor the deformation distribution along the line (gravity or vertical direction) of measurement. The system design of FBG-IP is similar to the minimized FBG-SD, allowing an array of FBG-IP’s be pre-assembled in the laboratory, but the errors in inclination angle measurements do not accumulate as the FBG-SD. The FBG accelerometer is designed mainly to be used in a seismic cone penetrometer. The design fits the mechanical design of the cone and characteristics needed for seismic cone penetration tests. The thesis describes the details of these FBG sensors improvement/development, and part of their field applications.