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

Abstract

The tuned vibration absorber (TVA) has been used for vibration control purposes in many sectors of civil/automotive/aerospace engineering for many decades since its inception by (Ormondroyd & Den Hartog, 1928). A tuned vibration absorber (TVA), in its most generic form, is an auxiliary system whose parameters can be tuned to suppress the vibration of a host structure. The auxiliary system is commonly a spring-mass-damper system (or equivalent) and the TVA suppresses the vibration at its point of attachment to the host structure through the application of an interface force. The tuned frequency a  of the TVA is defined as its undamped natural frequency with its base (point of attachment) blocked. The TVA can be used in two distinct ways, resulting in different optimal tuning criteria and design requirements (von Flotow et al., 1994): a. It can be tuned to suppress (dampen) the modal contribution from a specific troublesome natural frequency s  of the host structure over a wide band of excitation frequencies. b. It can be tuned to suppress (neutralise) the vibration at a specific troublesome excitation frequency  , in which case it acts like a notch filter. When used for application (a), the TVA referred to as a “tuned mass damper” (TMD). 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. Such devices are capable of retuning themselves in real time. Adaptive technology is especially important in the case of the TVN since the low damping requirement in the spring element can raise the host structure vibration to dangerous levels