A chaotic vibration energy harvester using magnetic material

Abstract

Abstract. This paper presents a new wideband electromagnetic vibration energy harvester (VEH) composed of a magnetic core embedded into the coil axis. The magnetic core generates a nonlinear magnetic force, which gives rise to the nonlinearity in the behavior of the VEH. Moreover, the magnetic core increases the flux linkage with the coil. These features improve the operational bandwidth and output power of the VEH. Numerical analysis and experimental measurements reveal that the operational bandwidth of the proposed VEH is over 30Hz in which the output power is kept about 0.1mW. Moreover, the proposed VEH operates by complicated oscillation due to nonlinear forces acting on the oscillator. Evaluation of the Lyapunov exponent for the measured oscillation suggests that the proposed VEH produces chaotic oscillation. IntroductionEnergy harvesting has been receiving much attention as a voltage source for low-power electronic devices. So-called harvesting devices make it possible to create self-powered systems. In particular, the harvesting devices can be effectively used in wireless sensor networks for monitoring of structures such as bridges and tunnels [1][2][3]. Wireless sensor nodes with the harvesting devices can work for a long time without having to replace their batteries. Hence, the energy harvesting can realize wireless sensor systems with a large number of sensor nodes, which are suitable for monitoring the "health" of structures. The electromagnetic vibration energy harvester (VEH) [e.g. 4, 5] transforms vibration energy into electrical energy through magnetic induction. The VEHs basically consist of permanent magnets and pick-up coils. The magnets, which are oscillated by ambient vibrations, are placed on a cantilever. As a result, the magnetic flux across the coil temporally changes, and an electromotive force is induced.Conventional VEHs produce the electrical energy through linear spring-damper oscillations. The maximum output power is thus generated when the ambient vibration matches the natural frequencies of a VEH. Linear VEHs are designed to have a high Q-factor in order to increase the output power at resonance. However, the ambient vibration in real constructions usually has very complicated vibration modes with a wide frequency spectrum [6]. It is clear that linear VEHs can absorb very little energy from such vibrations. To make effective energy harvesting from real-world vibrations, VEHs should have a wide frequency response.

Magnetic circuit modeling of chaotic vibration energy harvester

“…Moreover, it suddenly goes down at 38 Hz and 66 Hz. Figure 9 and figure 10 show that the time variations of and trajectories on phase plane( ,), respectively, when the input acceleration is 1.5 G. This suggests that the chaotic, interwell and intrawell vibrations are induced at 10 Hz, 30Hz, and 70 Hz, which are also observed in the measurement [3]. That is, the oscillator makes transition between two equilibrium positions of the potential energy when frequency is smaller than 66 Hz, whereas it traps to one of the wells of the potential energy when frequency is higher than 67 Hz.…”

“…A conventional VEH works only at around the resonance frequencies, whereas the actual vibration can have wide frequency spectra. To overcome this difficulty, we have proposed the chaotic VEH (CVEH) which works in wider frequency ranges [3,4]. In CVEH, the potential energy whose derivative corresponds to the magnetic force between the permanent magnets and the silicon steel plates embedded in the coil has a double-well structure.…”

Properties of chaotic vibration energy harvester: comparison of numerical results with experiments

“…However, these bistable VEHs would not have limited efficiencies because the interlinkage magnetic flux in the coils is not sufficiently strong due to open magnetic circuits. To overcome this difficulty, Sato et al have developed a chaotic VEH in which the magnetic circuit is closed and the interlinkage fluxes through the coils are increased by inserting ferromagnetic material into the coil bobbin axis …”

“…To overcome this difficulty, Sato et al have developed a chaotic VEH in which the magnetic circuit is closed and the interlinkage fluxes through the coils are increased by inserting ferromagnetic material into the coil bobbin axis. 11 In this work, on the basis of the above-mentioned chaotic VEH, we have developed a chaotic VEH that is equipped with a pair of coils to improve the power-generation efficiency. In this paper, we will discuss the essential properties of this VEH on the basis of numerical analysis and experiments.…”

Nonlinear analysis of an electrodynamic broadband energy harvester

“…On the other hand, Sato et al [18] investigated a novel electromagnetic wideband generator. The system consists on the use of magnetic core placed in the coil axis which is fixed and surrounded by moving magnets attached to the end of an cantilever.…”