This paper elaborates upon a novel concept, the Delayed Resonator, a tunable active vibration absorber. This technique uses a control which has a time delayed feedback of the absorber mass displacement. The substance of this process is in that the absorber completely removes oscillations from the primary structure. Two very strong features that should be mentioned are: (a) the excitation frequency range can vary over a semi-infinite interval, and (b) the absorber can be tuned in real time. These are the unique characteristics of the technique distinguishing it from the others. Stability issues of the primary system combined with the Delayed Resonator are addressed following Nyquist and root locus methods. In particular, the absorption performance for cases with time varying excitation frequency is studied. The primary focus of this paper is on the analysis of transient absorption behavior of the Delayed Resonator during its tuning. An example case is provided which considers a step change in the excitation frequency. A well-pronounced manifestation of the tunability feature of the Delayed Resonator is observed. The superiority of the Delayed Resonator absorber over the conventional a priori tuned absorbers is also demonstrated.

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