周波数応答関数の位相データを用いた1自由度法の実験モード解析手法

（第2報，近接モードが同定精度に及ぼす影響評価）

抄録

Modal parameters such as natural frequencies, damping ratios and natural modes of mechanical structures can be experimentally identified by applying experimental modal analysis methods to frequency response functions (FRF) obtained from vibration testing. As a variant of the linear fit method (LFM), a single-degree-of-freedom method using phase data of the frequency response function was proposed in our previous study. The proposed method (PM) was able to identify the modal parameters with the same level of accuracy as the LFM when there were no modes close to the mode being analyzed. However, the identification accuracy when identifying the mode being analyzed with the existence of a close mode has not been evaluated. In this study, the identification accuracy of the mode parameters identified by the PM, LFM, and circle fit method (CFM) are compared for high and low modal damping ratios using FRF with a close mode. In instances where the modal damping ratio is high, the errors in identified natural frequencies and modal damping ratio applying the PM and LFM are approximately 0.1 % and 1.5-3 %, respectively. Conversely, in instances where the modal damping ratio is low, the errors in identified 2 modal parameters applying the PM and LFM are approximately 1×10-4 % and 0.1 %, respectively. According to these results, the PM can identify the natural frequencies and mode damping ratios with the same level of accuracy as the LFM when there are modes close to the mode being analyzed.