A magnetically coupled two-degrees-of-freedom piezoelectric energy harvester using torsional spring

Abstract

Two-degrees-of-freedom magnetically coupled energy harvesters have been presented by several researches to achieve a broader response bandwidth. However, most two-degrees-of-freedom systems are composed of two piezoelectric beams, while in the low frequency operating environment with limited space, the dimension of the piezoelectric beam is limited which leads to high stiffness of the generated beam. Therefore, the output of dual-beam system is relatively low under low frequency and amplitude vibrations. This paper presents a magnetically coupled two-degrees-of-freedom energy harvester by using torsional spring. The proposed harvester consists of a piezoelectric beam with a tip magnet and an interacting magnet mounted on a rotatable bar with a torsional spring. The shape of the potential well changes with the rotation of the bar, facilitating the occurrence of the snap-through motion under low amplitude and wideband vibration excitation. What’s more, the stiffness of the torsional spring can be easily adjusted to make the designed harvester suitable for low frequency vibrations. Compared with the conventional bi-stable harvester, the presented harvester could easily overcome the potential barrier and generate larger power under low excitation intensity. Analytical, simulation, and experimental results demonstrate that the proposed energy harvester is capable of harvesting low frequency wideband vibration energy.

A nonlinear magnetic and torsional spring coupling piezoelectric energy harvester with internal resonance

“…Compared to single-degree-offreedom systems, multi-degree-of-freedom systems generate multiple response bands through the interaction between magnets thus expand the operating bandwidth [25]. Wang et al [26] proposed a torsion spring coupling piezoelectric energy harvester to construct a two-degree-of-freedom system. Besides, magnetic coupled dual-beam system, a more common structure, can produce two frequency bands when the intrinsic frequencies of the two beams are set differently.…”

A novel two degree of freedom single magnet bistable energy harvester based on internal resonance

“…Song et al [27] proposed a bistable energy harvester which can realize four different bistable states by adjusting the position of the beam, the special structure can capture energy in different frequency bandwidths, widening the frequency bandwidth. Wang et al [28] designed a magnetically coupled bistable energy harvester, which consists of a magnet, a torsional spring and two cantilever beams. By introducing the torsional spring structure the potential energy well can be changed which allows the harvester to break through the potential barrier more easily with low excitation and produce more power.…”