Among active, semiactive, and passive vibration isolation methods, active control can provide the best isolation performances. However, high-energy consumption hinders its wide applications in civil engineering field. This paper proposes a novel vibration isolation technique based on a passive negative stiffness spring (NSS) and a semiactive device (SAD), aiming to achieve an active isolation performance by using a low-power semiactive technique. Due to its nature of negative potential energy, an NSS enables the semiactive isolation system to provide negative transient power flow that injects power into the structure and avoids the clipping phenomenon of semiactive control forces. Consequently, the combined NSS and SAD isolation system can perfectly generate the theoretical control forces calculated by an active control algorithm and achieve a considerably improved semiactive isolation performance. The prospects and performance advantages of the proposed NSS and SAD isolation system are validated through a series of numerical simulations of single-degree-of-freedom and multi-degree-of-freedom structures excited by various types of ground motions and a benchmark building model excited by seismic ground motions.

A multi-frequency sandwich type electromagnetic vibration energy harvester

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The low frequency horizontal vibration of engineering vehicles is a part of multidimensional vibration, which causes driver's occupational disease. Therefore, the design of low frequency horizontal vibration isolation is of great significance. The principle of rolling vibration isolation is applied to seat suspension for low frequency horizontal vibration isolation in this paper. The natural frequency characteristic model of horizontal suspension and the seat-human system dynamics model with horizontal suspension based on the Lagrangian equation are established. The dynamic characteristics of rolling horizontal suspension are studied on account of the established models. Results show that this horizontal suspension can achieve very low natural frequency so as to isolate the low frequency vibration in horizontal direction by the matching design of the rollers and concave dimensions. The vibration isolation characteristics of the front and back seat–human system are improved with the reduction of the rollers’ radius. The vibration isolation characteristic of the front and back seat - human system increases with the increase of the concave surfaces’ radius.