Application of a dynamic vibration absorber with negative stiffness for control of a marine shafting system

A dynamic vibration absorber (DVA) with negative stiffness is proposed to suppress the longitudinal vibration transmission along a marine shafting system. Stiffness models of the DVA with negative stiffness, which is composed of a rubber pad and a Belleville spring, are established. An analytical model of the shafting system with and without the proposed DVA is set up by employing the equivalent model of a propeller and employed to perform vibration control in the low frequency range. A stability analysis is carried out and optimal parameters of the DVA with negative stiffness are obtained. A parametric study is also carried out to investigate the influence of the parameters of the DVA and negative stiffness on the vibration suppression for a specific shaft. A design scheme to obtain the static and dynamic stiffness of Belleville springs under different operation conditions is given, which takes into consideration variation in oil stiffness of the thrust bearing and propeller static thrust. Compared with a traditional DVA, the proposed DVA with negative stiffness achieves enhanced vibration transmission suppression performance for a much broader absorber frequency range around resonance and with a much smaller size of mass, which is very favorable for a marine shafting system.