主動式無線感測網路於結構健康監測與遠端局部損壞檢測系統

Abstract

近年來，結構健康監測已成為世界各國相繼投入的重點研究之ㄧ，結構健康 監測主要為利用智慧型感測器來監控結構物目前與長期的健康狀態，除可提供有 關何時需要維護與修繕工作的訊息外，亦可提早對可能發生的危害提出警訊。傳 統監測系統需要大量的建置成本與建置時間，而無線感測網路技術有著省電、價 格低廉、體積小安裝快速等優點，且其感測器本身具備微處理器可以先將所得到 的感測資料預先處理過後再傳回後端處理，進而提高了監測的效能與正確率。大 多數之無線感測網路都是被動式的，僅僅被動的接收外在環境的訊號與結構的狀 態。因此本研究之目的為發展一個以主動式無線感測單元所連結之無線感測網 路，應用於結構健康監測上，此主動式無線感測網路除了具有傳統無線感測網路 的優點，在平時可對於結構整體之健康監測與預警功能外，更可以無線的方式在 遠端主動檢測結構物局部破壞之位置與狀態。本研究所發展之主動式無線感測單 元包含多功能之感測介面、制動器介面、微處理器、記憶體、無線傳輸模組、電 力供應單位。在結構監測方面，感測介面可以接上如加速度計、位移計、壓力計、 壓電感測器等不同感測器來監測結構物之狀態，並藉由無線傳輸模組將資料傳回 監控中心。在結構局部破壞檢測方面，在監測端以無線傳送命令給無線感測單元 之微處理器，微處理器操作一主動式壓電致動器發射超音波於結構物上，再利用 感測介面上之壓電感測器接收反應訊號，藉由無線傳輸模組將資料傳回監測中 心。 本研究擬以三年的時間進行一系列主動式無線感測網路於結構健康監測與 遠端局部損壞檢測系統之相關研發工作。首先，將以熟悉無線感測網路相關技術 為主要工作，並針對相關元件作一系列之測試。計畫利用小型模擬地震震動台配 合所設計之小型鋼構架來驗證與測試相關元件之效能與其穩定性，並可與傳統感 測單元和光纖感測器相互比較。接著，將已測試完成之相關元件整合出本研究所 提出之主動式無線感測單元，並設計一系列之實驗，來驗證本主動式無線感測單 元之效能並改善其缺點。最後，以第二年所完成之主動式無線感測單元為感測節 點，建立一主動式無線感測網路。並於所設計之縮小尺寸之剪力屋結構模型建立 無線感測網路節點並進行動力與局部損壞評估試驗。

Owing to improved instrumentation and understanding of the dynamics of the complex structures, efforts to identify the location and extent of structural damage via structural health monitoring (SHM) system has received increasing attention recently. The aims of SHM are to monitor health condition of structure long term using smart sensor system, provide any information for maintaining or repairing the structure if need, and generate warning before it collapse unexpectedly. Conventional monitoring system needs amount of time and cost to set up. Wireless sensor system, however, has the advantages of low power, small size, low cost, and easy to set up as comparing with traditional sensors. Moreover, due to with microprocessor in it, the wireless sensors can process collected data before passed to post-processing unit. So far, most of wireless sensor network are passively; that is, the network can only receives the dynamic response data of the structure under external excitation. The goal of the research is to develop an active wireless sensor network in SHM system and remote local damage detection diagnosis system. The active wireless network system works not only as sensors for SHM system under external excitation (passively), but also an actuation capacities local damage detecting device under remotely control actively. The wireless sensor unit in the proposed system consists of sensor and actuator interfaces 、 microprocessor 、 main memory 、wireless communication module and power supply unit. For SHM, the sensor interface can connect to several different sensors, such as accelerometer 、strain gauge or piezoelectric device, to monitor the health condition of structure passively and the collected data then transfer to the hub of monitoring system via wireless communication module. In remote local damage detection sub-system, a piezoelectric device will be mounted on the wireless sensor unit via the actuator interface and be commanded by the wireless active sensing unit to excite and record the structure element. The detected information will be, then, transfer to the hub of monitoring system via wireless communication module too. The research will be scheduled in three years through a serial of experiments in lab. First, a prototype of wireless sensor will be developed and tested via a small-scale shaking table test. Then, a piezoelectric device will be mounted on the wireless sensor unit via the actuator interface and the utility and performance of the device will be verified. Finally, a wireless sensor network will be created and mounted on a 1/4 scale steel frame and tested via NCTU shaking table.