Global Control of Vibration Using a Tunable Vibration Neutraliser

Abstract

Tunable vibration neutralisers 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 neutralisers influence their effectiveness in this role are reasonably well understood. However, the use of tunable vibration neutralisers to control global vibration of a structure has not been so well explored, and in this article the neutraliser parameters that influence the vibrational kinetic energy of a host structure are highlighted. It is shown that in general a de-tuned rather than a tuned vibration neutraliser 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 neutraliser. For this to be effective it is demonstrated that the tuned neutraliser 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 neutraliser over quite a wide range of frequencies.

Adaptive Tuned Vibration Absorbers: Design Principles, Concepts and Physical Implementation

“…(Brennan, 1997) defines the attenuation D provided by a TVN for harmonic excitation as the ratio of the vibration amplitude at A without the TVN to the amplitude there with the TVN attached and optimally tuned:…”

“…Also, for given absorber damping, the TVA's attenuating capability degrades as , ae ff m is reduced. In fact, for a host structure that is a rigid machine of mass M mounted on soft isolators, (Brennan , 1997) showed that…”

“…a  is optimally tuned to a value slightly lower than that of the targeted mode s  and an optimal level of damping needs to be designed into the absorber. When used for application (b), the TVA is referred to as a "tuned vibration neutraliser" (TVN) (Brennan, 1997, Kidner & Brennan, 1999 or "undamped TVA". The optimal tuning condition is in this case is a    and the TVN suppresses the vibration over a very narrow bandwidth centred at the tuned frequency.…”

“…Total suppression of the vibration at this frequency is achieved when there is no damping in the TVN. Deviation from the tuned condition (mistuning) degrades the performance of either variant of the TVA (von Flotow et al, 1994) and it can be shown that a mistuned vibration neutraliser could actually increase the vibration of its host structure (Brennan, 1997). To avoid mistuning, smart or adaptive tunable vibration absorbers (ATVAs) have been developed.…”

“…The device must also be cheap and easy to manufacture. To maximise vibration attenuation, the retuning mechanism should add as little as possible to the redundant mass of the device and, in the case of the neutraliser, have a low structural damping (Brennan, 1997). The technical challenge is to design an adaptive device with such attributes.…”