- 會議論文
應用旋轉角加速度計於自由樑之實驗模態分析
Application of Rotational Accelerometer to Experimental Modal Analysis for Free-Free Beam
摘要
傳統上實驗模態分析（Experimental Modal Analysis, EMA）多採用加速度計為感測器，搭配衝擊鎚為驅動器，以量測結構之頻率響應函數（Frequency Response Function, FRF），本文擬用旋轉角加速度計評估取代加度計之可行性及探討其在實驗模態分析之影響與限制。首先由理論分析推導自由樑點力及旋轉角加速度計之FRF，並探討EMA執行方式對擷取模態參數之影響。同時建立有限元素分析（Finite element analysis）模型分別進行模態分析及簡諧分析，以分別求得理論模態參數及FRF。EMA則採旋轉角加速度計及加速度計為感測器，以衝擊鎚為驅動器，分別以移動感測器或移動加速度計進行EMA共四組實驗，分別探討EMA得到之模態參數差異及物理意義，結果顯示此實驗方法能適用於其他結構。
並列摘要
Conventional experimental modal analysis (EMA) adopts the accelerometer as the sensor and the hammer as the actuator to measure the structural frequency response functions (FRFs). This work evaluates the feasibility and effects of the rotational accelerometer, instead of accelerometer, in performing EMA on a free-free beam structure. First, the FRF between the actuator input and sensor output is derived. The effect of testing procedures, either roving the sensor with the fixed actuator or roving the actuator with the fixed sensor, is then be discussed. Finite element analysis (FEA) by using commercial code is also carried out to obtain structural modal parameters and FRFs for comparison. In experiments, both the rotational accelerometer and accelerometer sensors are used, respectively, while the impact hammer is used as the actuator. Four pairs of experiments for different testing procedures are conducted to extract experimental modal parameters. The discrepancy and physical meaning of mode shapes among experiments are well interpreted. The test method can then be adopted for other structures as well.