PURPOSE:To efficiently attenuate the vibration of a structure by using an electrodynamic actuator as a structure vibration absorber and controlling a counter electromotive force produced by vibrations by means of structure vibration signals. CONSTITUTION:A main system 1 has a mass (m) and spring constant (k) and an electrodynamic actuator 3 has a mass m4 and, at the same time, is provided with a magnet 4 coupled with the main system 1 with a spring having a spring constant k4 and an armature 5 fixed to the main system side. A variable resistance element VR is connected between the terminals of the armature 5. When an external force is applied to the main system 1, vibration signals produced by the displacement of the system 1 are detected by a sensor and supplied to a personal computer 8 which controls the resistance value of the resistance element RV after the signals are amplified by an amplifier of K in amplification degree. The vibration signals are subjected to calculation at the computer 8. During the period which requires damper action by means of the actuator 3, the resistance element VR is controlled to a limited value and, during the period which does not require the damper action, to infinity. Therefore, vibrations of a structure can be attenuated efficiently.
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