Global control of vibration using a tunable vibration neutralizer

Tunable vibration neutralizers are currently used to control harmonic vibration of structures at the point at which they are attached, and the way in which the characteristics of the neutralizers influence their effectiveness in this role are reasonably well understood. However, the use of tunable vibration neutralizers to control global vibration of a structure has not been so well explored, and the aim of this paper is to investigate the parameters of the neutralizer that influence the control of the vibrational kinetic energy of a structure. It is shown that in general a de-tuned rather than a tuned vibration neutralizer is required at most frequencies, offering a stiffness-like or a mass-like impedance to the structure. However, because this control strategy requires a measure of the global vibration of the host structure, which can be difficult and/or costly in practice, it is preferable to use a tuned vibration neutralizer. For this to be effective it is demonstrated that the tuned neutralizer needs to be appropriately positioned on the structure. If this is the case then such a device can be almost as effective as a de-tuned neutralizer over quite a wide range of frequencies. An expression to determine the optimum ratio of the neutralizer mass to the modal mass of the structure is also derived. (C) 2000 Academic Press.