Delayed resonators as active dynamic absorbers

Vibrations in a structure having a large mass are damped by coupling thereto a damping member of smaller mass and continuously monitoring the frequency of excitation of the structure produced by applied load(s) and the displacement of the damping member. The monitored frequency of excitation and displacement of the damping member are processed together with data relative to the mass, stiffness and damping characteristic of the damping member. A signal is outputted to produce a force acting on the damping member proportional to the displacement of the damping member with a controlled time delay to produce a frequency of vibration in the damping member substantially equal to the monitored frequency of excitation of the structure, this produces resonance of the damping member substantially at the monitored frequency of excitation and is effective to damp substantially the vibrations of the structure at the monitored frequency of excitation. The output signal is variable to produce resonance of the damping member variable over a range of frequencies including the natural frequency of vibration of the structure.