應用布拉格光纖光柵感測器於風機基座螺栓鬆脫檢測評估

Abstract

本文利用布拉格光纖光柵感測器有高靈敏度、質量輕盈體積小、不受電磁波干擾、防水、抗腐蝕等優點，且可長時間監測多個觀測點的多點動態特性之特點，將多段光柵分別貼附於風力發電機基座主結構上，包含中央柱子與上方橫樑兩區域，並根據有限元素模擬軟體的3D振型結果，對結構的多個位置分別施予敲擊訊號，激發出整體結構的動態反應，再利用快速傅立葉轉換，獲得結構振動時產生的頻率反應，作為後續探討螺栓是否鬆脫的參考依據。在完成風機基座的自然頻率辨識後，於後續將用於結構鎖固的螺栓完全鬆脫，使用與前述相同的實驗方法測得各螺栓鬆脫組合對應的頻率反應，利用共振頻率、快速傅立葉頻譜強度與特徵等等多種條件，比較未鬆脫時的頻率與反應，建構可準確判斷各種組合下螺栓鬆脫的判斷方法，做為未來建立可程式化的結構健康監控系統之參考依據。

This study employs Fiber Bragg Grating (FBG) sensors, which offer advantages such as high sensitivity, lightweight and compact size, immunity to electromagnetic interference, water resistance, and corrosion resistance. Furthermore, FBG sensors are capable of long-term, multi-point dynamic monitoring. In this study, multiple FBG sensors were strategically affixed to the main structural components of a wind turbine foundation, specifically on the central column and upper beam. Based on the 3D mode shapes obtained from finite element simulations, impact excitation was applied at various locations of the structure to induce its dynamic response. The resulting vibration signals were analyzed using Fast Fourier Transform (FFT) to extract the corresponding frequency responses, which serve as a reference for subsequent investigation into the presence of bolt loosening. After identifying the natural frequencies of the wind turbine foundation, bolts used to secure the structure were deliberately loosened in controlled combinations. The same experimental procedures were repeated to obtain the frequency responses corresponding to each bolt-loosening condition. By comparing the resonance frequencies, FFT spectral magnitudes, and characteristic features between the intact and loosened cases, a set of diagnostic criteria was established to accurately identify the loosening condition for various bolt combinations. The findings of this research aim to support the future development of a programmable structural health monitoring system for wind turbine foundations.