Conventional Vibration Energy Harvester Research Articles

Theoretical modelling and experimental investigation on a frequency up-converted nonlinear piezoelectric energy harvester

Ambient vibration energy harvesting has attracted the great attention of numerous researchers to replace the battery power supply strategy of electronic devices. However, the high natural frequency and narrow broadband operation are still significant shortcomings of the conventional vibration energy harvesters to be widely deployed. This paper presents a novel piezoelectric energy harvester (PEH) based on the traditional impact frequency up-converted PEH to achieve lower and broader operating frequency. Nonlinear magnetic force is adopted to regulate the working frequency of PEH. Distributed-parameter modelling and magnetic force simplified modelling are applied in analyzing the piecewise linear dynamic characteristics of the low-frequency driving beam, and the piezoelectric effect is employed for calculating the output voltage of the high-frequency generating beams. Theoretical results comparison between the traditional impact PEH and the proposed novel PEH shows that the introduced nonlinear magnetic force offers a lower initial frequency and broader operating bandwidth. The comparison experimental study achieves a close match to the theoretical results. Under excitation conditions of 3 m/s 2 excitation acceleration, 3 mm impact distance, and 19 mm magnet distance, the initial frequency decreases by about 9.5 Hz, and the operating bandwidth increases from 9 Hz to 16.5 Hz. The maximum power output value of the proposed PEH is 0.491 mW. The novel proposed PEH in this paper provides promising guidance and understanding for energy harvesting in low and broadband environmental vibration. • A novel frequency up-converted nonlinear piezoelectric energy harvester (PEH) is proposed for lower and wider bandwidth energy harvesting. • Developed the theoretical model and analyzed the performance of the device based on averaging method. • The comparison experimental results achieve a close match to the theoretical research that the novel PEH has lower and wider operating frequency than the conventional impact PEH.

A rotational vibration energy harvester for near-zero-energy applications in railway environment

The vibration in the railway environment contains a huge amount of available mechanical energy, which can be utilized as a practical power source for low-power independent distributed appliances. This paper proposed a rotational vibration energy harvester (RVEH) based on a linear cam mechanism for near-zero-energy applications in railway environment. The RVEH system mainly consists of a motion conversion mechanism (MCM) and electromagnetic generators. The motion conversion mechanism realizes the motion conversion from vibration to uni-directional rotation based on a linear cam and a one-way rectifier. The electromagnetic generators convert kinetic energy into electrical energy. The test shows that the electric outputs of the proposed RVEH is improved under vibration excitations compared with the conventional vibration energy harvester (VEH, the RVEH without a one-way rectifier). Also, the RVEH has a comparatively long duration of electric outputs after the vibration excitation, suitable for the intermittent vibration excitation input. And the RVEH can operate as a power supply, producing output characteristics of an average output power of 66 mW and a peak output power of 0.15 W, sufficient to power 155 LEDs in series or a thermometer. It is foreseeable that the RVEH is a promising self-powered solution for applications in railway environment.

Tunable, multi-modal, and multi-directional vibration energy harvester based on three-dimensional architected metastructures

Conventional vibration energy harvesters based on two-dimensional planar layouts have limited harvesting capacities due to narrow frequency bandwidth and because their vibratory motion is mainly restricted to one plane. Three-dimensional architected structures and advanced materials with multifunctional properties are being developed in a broad range of technological fields. Structural topologies exploiting compressive buckling deformation mechanisms however provide a versatile route to transform planar structures into sophisticated three-dimensional architectures and functional devices. Designed geometries and Kirigami cut patterns defined on planar precursors contribute to the controlled formation of diverse three-dimensional forms. In this work, we propose an energy harvesting system with tunable dynamic properties, where piezoelectric materials are integrated and strategically designed into three-dimensional compliant architected metastructures. This concept enables energy scavenging from vibrations not only in multiple directions but also across a broad frequency bandwidth, thus increasing the energy harvesting efficiency. The proposed system comprises a buckled ribbon with optional Kirigami cuts. This platform enables the induction of vibration modes across a wide range of resonance frequencies and in arbitrary directions, mechanically coupling with four cantilever piezoelectric beams to capture vibrations. The multi-modal and multi-directional harvesting performance of the proposed configurations has been demonstrated in comparison with planar systems. The results suggest this is a facile strategy for the realization of compliant and high-performance energy harvesting and advanced electronics systems based on mechanically assembled platforms.

A broadband energy harvester using leaf springs and stoppers with response stabilization control

This paper presents the design, fabrication and experimental verification of a broadband vibration energy harvester having a nonlinear oscillator using leaf springs and stoppers. In the conventional vibration energy harvester having a linear oscillator, there is a trade-off relationship between the magnitude of the resonance peak and the resonance band. Since the resonance band is expanded by using the nonlinear oscillator, the harvester can more efficiently generate electric energy in a wider frequency band. In this study, we designed and fabricated a nonlinear vibration energy harvester with leaf springs and stoppers, and verified the frequency response characteristics and the power generation performance of the proposed harvester by sinusoidal sweep tests with the input acceleration amplitude of 0.2 Grms. The overall resonance bandwidth was approximately 33 Hz, which was over 75 % of the linear natural frequency of 42 Hz. The response stabilization control successfully destabilized the coexisting low-energy solution, and activated only the high-energy response in the resonance band.

Piezoelectric Cylindrical Design for Harvesting Energy in Multi-Directional Vibration Source

Vibration Energy Harvester (VEH) has attracted a great attention recently both in academia and industry. One of the most challenging issues in VEH is the possibility to harvest vibration energy in multiple directions. In fact, Conventional VEH (CVEH) using cantilever beam’s structure may possibly become inefficient for the application under multi-directional vibration sources. To overcome this shortcoming of CVEH, this paper proposes a novel design of piezoelectric cylindrical energy harvester (PCEH) which is using patches of piezoelectric material attached to the surface of a cylindrical structure. The Finite Element Method (FEM) analysis using COMSOL Multiphysics software package showed that PCEH has a great potential for the applicability of VEH in the multi-directional vibrating applications such as wearable devices and biomedical devices.

Nonlinear analysis of a two-degree-of-freedom vibration energy harvester using high order spectral analysis techniques

Conventional vibration energy harvesters are generally based on linear mass-spring oscillator models. Major limitations with common designs are their narrow bandwidths and the increase of resonant frequency as the device is scaled down. To overcome these problems, a two-degree-of-freedom nonlinear velocity-amplified energy harvester has been developed. The device comprises two masses, oscillating one inside the other, between four sets of nonlinear magnetic springs. Impacts between the masses allow momentum transfer from the heavier mass to the lighter, providing velocity amplification. This paper studies the nonlinear effects introduced by the presence of magnetic springs, using high order spectral analysis techniques on experimental and simulated data obtained for a range of excitation levels and magnetic spring configurations, which enabled the effective spring constant to be varied. Standard power spectrum analysis only provide limited information on the response of nonlinear systems. Instead, bispectral analysis is used here to provide deeper insight of the complex dynamics of the nonlinear velocity-amplified energy harvester. The analysis allows identification of period-doubling and couplings between modes that could be used to choose geometrical parameters to enhance the bandwidth of the device.

A self-adaptive energy harvesting system

This paper reports on a self-adaptive energy harvesting system, which is able to adapt its eigenfrequency to the operating conditions of power units. The power required for frequency tuning is delivered by the energy harvester itself. The tuning mechanism is based on a magnetic concept and incorporates a circular tuning magnet and a coupling magnet. In this manner, both coupling modes (attractive and repulsive) can be utilized for tuning the eigenfrequency of the energy harvester. The tuning range and its center frequency can be tailored to the application by careful design of the spring stiffness and the gap between tuning magnet and coupling magnet. Experimental results demonstrate that, in contrast to a conventional non-tunable vibration energy harvester, the net power can be significantly increased if a self-adaptive system is utilized, although additional power is required for regular adjustments of the eigenfrequency. The outcome confirms that active tuning is a real and practical option to extend the operational frequency range and to increase the net power of a conventional vibration energy harvester.

励振周波数を追従する板ばねの水平方向移動要因の推定

Vibration energy harvester has gained attention in accordance with the growth of the demand of wireless sensors used for vibration condition monitoring of machinery. Most conventional vibration energy harvesters consist of a linear oscillator. These devices are designed so as to resonate with the mechanical vibration for the purpose of getting large electricity. However, once the frequency of the input vibration changes, the linear oscillator cannot maintain resonance. As the result, the amount of electricity obtained by the vibration energy harvester decreases considerably. In our laboratory, we devised a test equipment of the vibration system in which resonance automatically follows the fluctuated excitation frequency. This equipment is comprised of sector-like shaped bases and a long and narrow plate spring. Under the excitation, the test equipment automatically tunes its natural frequency in such a way as to match the excitation frequency without any controllers. By applying this automatic tuning mechanism of the test equipment to a vibration energy harvester, it will be able to keep high generating efficiency even when the excitation frequency of the mechanical vibration changes. However, the detailed mechanism that the test equipment automatically tunes its natural frequency into excitation frequency has not been explained. In this paper, we conduct excitation experiments on the proposed equipment and detailed observation of the behavior of the plate spring in the automatic tuning phenomenon. As the result, a part of the mechanism of the automatic tuning phenomenon can be experimentally deduced.

Flexible piezoelectric vibration energy harvester using a trunk-shaped beam structure inspired by an electric fish fin

This paper presents a bio-inspired structure that can enhance the efficiency of piezoelectric power generation in vibration-type energy harvester. Inspired by an electric fish, Gnathonemus petersii, a trunk structure for high-performance vibration energy harvester is explored. The proposed vibration energy harvester consists of a flexible PVDF film and thin glass fiber plate shaped with auxiliary delta wings to mimic the trunk structure of the electric fish. An experimental study of the prototype energy harvester shows that the proposed piezoelectric vibration energy harvester featuring the new bio-inspired structure produces 45% more power output than the conventional vibration energy harvester due to its electret-like material behavior.

Compliant bistable mechanism for low frequency vibration energy harvester inspired by auditory hair bundle structures

This paper presents a bio-inspired mechanism for the performance enhancement of piezoelectric power generation in vibration energy harvesting. A compliant bistable mechanism for vibration energy harvesting was explored based on the negative stiffness inspired by the auditory hair bundle structures. The proposed mechanism consists of a compliant, four-bar linkage system to mimic the hair bundle structure inside an inner ear. Our initial prototype energy harvester demonstrates that the compliant bistable mechanism featuring negative stiffness outperforms the conventional vibration energy harvester in the infra-low frequency range (1–10 Hz).

A multiple-degree-of-freedom piezoelectric energy harvesting model

Conventional vibration energy harvesters have been usually studied as single-degree-of-freedom models. The fact that such harvesters are only efficient near sole resonance limits their applicability in frequency-variant or random vibration scenarios. In this article, a novel multiple-degree-of-freedom piezoelectric energy harvesting model is presented. First, a two-degree-of-freedom model is analyzed, and its two configurations are characterized. In the first configuration, the piezoelectric element is placed between one mass and the base, and in the second configuration, it is placed between the two masses. It is shown that the former is advantageous over the latter since with a slight increase of overall weight to the single-degree-of-freedom model, we can achieve two close and effective peaks in power response or one effective peak with significantly enhanced magnitude. The first configuration is then generalized to an n-degree-of-freedom model, and its analytical solution is derived. This solution provides a convenient tool for parametric study and design of a multiple-degree-of-freedom piezoelectric energy harvesting model. Finally, the equivalent circuit model of the proposed n-degree-of-freedom piezoelectric energy harvesting model is developed via the analogy between the mechanical and electric domains. With the equivalent circuit model, system-level electric simulation can be performed to evaluate the system performance when sophisticated interface circuits are attached.

Enhancing output power of a piezoelectric cantilever energy harvester using an oscillator

The piezoelectric cantilever with a tip mass (Mass-PC), as a conventional vibration energy harvester, usually works at its fundamental frequency matching ambient excitation. By attaching an oscillator to a piezoelectric cantilever (Osc-PC), a double-mode energy harvester is developed to harvest more power from two matched ambient driving frequencies. Meanwhile, it allows the first operating frequency of the Osc-PC to be adjusted to be very low with only a limited mass attached. A distributed-parameter model of this harvester and the explicit expressions of its operating frequencies are derived to analyze and design the Osc-PC. Numerical investigations reveal that a heaver oscillator placed near the clamped end of the piezoelectric cantilever has better performance at the given exciting frequencies. Following the specified design criteria, an Osc-PC whose operating frequencies match two given exciting frequencies was constructed for the purpose of experimental testing. The results show that, compared to that of a corresponding Mass-PC whose operating frequency matches the lower exciting frequency, the energy harvesting efficiency of the Osc-PC increases by almost four times at the first operating frequency, while the output power at the second operating frequency of the Osc-PC accounts for 68% of that of the Mass-PC.