Multiple Delayed Resonator vibration absorbers for multi-degree-of-freedom mechanical structures

This study is on the use of multiple Delayed Resonators (DR) in suppressing tonal vibration of multi-degree-of-freedom mechanical structures. The DR is a recently introduced, actively tunable vibration absorber which converts a conventional passive absorber into a marginally stable resonator. This structure absorbs all the vibratory energy at its point of attachment. Control forces in the form of proportional acceleration feedback with variable gains and time delays are considered here. Attractive features of DR have already been demonstrated for single DR absorber cases. When excitation has multiple harmonics, multiple DRs can be used, each DR suppressing one of the harmonics. The stability assessment, however, becomes very complex in this case, due to the presence of unrelated time delays in the system. Therefore, a simpler situation is considered here; single harmonic excitation and multiple identical DRs acting on the system. A strategy called "Stability charts" is used not only to resolve the stability question but also to find out the tuning speed of the absorption. An example case of two identical DRs on a 3-DOF system is presented. The results demonstrate the feasibility of using multiple DR absorbers. (C) 1999 Academic Press.