A self-adjusting directional nonlinear energy sink

Abstract

Previous investigations on nonlinear energy sink (NES) have mainly concentrated on vibration energy absorption in given directions. It is a challenge to suppress direction-changing vibrations. To address this issue, an innovative self-adjusting directional nonlinear energy sink (SAD-NES) is designed to suppress unpredictable-direction vibrations. The mentioned NES can be passively tuned to the maximum vibration direction through its own inertia without additional assistance. To achieve this goal, the SAD-NES model is first designed. Then, the dynamic equations of the SAD-NES are derived according to the designed model. The effect of the SAD-NES on suppressing unpredictable-direction vibrations in the plane is theoretically predicted. The dynamic features influenced by parameters are revealed in the free and forced vibrations. Finally, an experimental platform of the SAD-NES has been established to validate theoretical predictions. The results illustrate that classic NES can significantly suppress vibrations for a given direction. For unpredictable-direction vibrations, the classical NES damping efficiency will decrease as the external excitation angle increases. This deficiency can be greatly improved by the mentioned NES. In free and forced vibrations, vibration in different directions is significantly suppressed by the mentioned NES. The vibration reduction effect of the SAD-NES can be improved by proper rotational damping. In a word, this paper provides a new design approach for NES and a highly feasible control strategy for unpredictable-direction vibrations in engineering practice. Moreover, the mentioned NES can enrich nonlinear dynamics theory.