二自由度系に対する二自由度フラムダンパの振動抑制の特性

Frahm damper is the dynamic absorber without damping. This damper suppresses vibration in some range of excitation frequency using anti-resonance point of frequency response function. In this study, two DOF Frahm damper attached to two DOF system is investigated. Two combinations of the stiffnesses of two DOF Frahm damper for desired natural frequencies are obtained. The frequency response functions of the dampers alone show that these dampers have same resonance frequency and different anti-resonance frequency. In the point of vibration suppression, these dampers have same ability near the 1st natural frequency, but different characteristic near the 2nd natural frequency is observed. The damper with better performance suppresses vibration as well as two traditional Frahm dampers. To investigate the difference in the performance of the dampers, mode vectors are illustrated. In the mode vectors of the dampers alone, mode localization is observed in only one of the damper, which is effective in vibration suppression near the 2nd natural frequency. In the mode vectors of whole system, the components corresponding to the main system have almost same values. But the components corresponding to the damper has same characteristics of mode vectors of damper alone. The mode localization is observed in the two traditional Frahm dampers.