Vibration control combining nonlinear isolation and nonlinear absorption

Quasi-zero stiffness system has been widely used to isolate structural vibrations. However, its small dynamic stiffness may result in drastic low-frequency vibration. This is a curse of employing quasi-zero stiffness systems in engineering. In this paper, a nonlinear energy sink (NES) is used to overcome this difficulty. In order to reduce the additional weight of the NES, the mass of the NES is replaced by an inerter. By superposing the quasi-zero stiffness system and the inertial NES together, a combined vibration control technique is proposed. The equations of the motion of the primary structure and the combined control system are established. The steady-state response of the system is solved by the harmonic balance method and verified numerically. The suppression performance is evaluated based on the resonance suppression efficiency and the effective vibration isolation bandwidth. In addition, the parameters of the inertial NES are optimized. The results show that the combined control system has a better vibration control effect than the quasi-zero stiffness isolator. Specifically, the combined control system provides a smaller resonance amplitude and a wider vibration isolation band. In summary, the combined control scheme has both effects of the nonlinear isolation and the nonlinear absorption. Therefore, this paper proposes a vibration control technique that can achieve a wide band of vibration isolation and small vibration amplitude with a very little additional mass.