Low frequency multimode vibration suppression of floating raft system based on NES cells

The vibration reduction for the low frequency band has always been a challenge for floating raft vibration isolation systems. This paper presents, for the first time, the application of the limited nonlinear energy sinks (L-NESs) and cells to achieve vibration suppression of floating raft isolation systems. In comparison to a traditional NES, L-NES increases the constraint on the NES vibrator by introducing piecewise stiffness. In addition, L-NES cells can not only effectively suppress the vibration of the floating raft system, but also display high practicability and flexible versatility by changing the number of cells. In this paper, a mechanical model of the floating raft isolation system with four degrees of freedom is established. The installation mode of the floating raft system is analyzed. Analysis of the parameters of the damping system with the NESs and L-NESs is carried out respectively. Hyperbolic tangent function is used to fit non-smooth models. Then the harmonic balance method (HBM) is applied as an analytical method to obtain the approximate solution of the system, and the accuracy is verified. The damping effects of the vibration reduction systems coupled with the traditional NESs and L-NESs are compared. Meanwhile, a vibration reduction model of the floating raft system with the L-NES cells is established. The influence of the number of the L-NES cells on the vibration suppression efficiency of the system for the first three modes is analyzed. The results show that the vibration suppression effective of the floating raft can be extremely improved and the problem of achieving damping for the low frequency band can be solved by the proposed L-NESs and cells. In a word, the research in this paper provides a novel and effective idea for the vibration control of floating raft systems.