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We proposed a nonlinear multi-mode tri-leg compliant orthoplanar spring piezoelectric vibration-based energy harvester (COPS-PVEH), which provided the improved performance using a pure geometric nonlinearity, in terms of a wide bandwidth, and a high-voltage output in forward and reverse sweeps. This paper presents an application of magnetic force interaction to further enhance the performance of the COPS-PVEH. A repulsive magnetic force is added to the spring to change the harvester system’s stiffness. A lumped parameter model is derived and analytically solved for the designed harvester with a magnetic coupling. The experiments are carried out by adding a moving magnet at the center of the spring and a pair of fixed magnets at the top and bottom sides of the harvester. Both experimental data and simulation results show the benefits brought through the dynamics of a magnetic oscillator. In an experiment by adding magnetic force, a slight increase is observed in the operating bandwidth and a 10% increase in the magnitude of voltage output is achieved at the same excitation level. The magnetic interaction on the COPS-PVEH with an addition of multiple masses has also achieved an increase in voltage output and bandwidth. In addition, the gap between the three vibration modes has been reduced. [ABSTRACT FROM AUTHOR]

This paper presents the modeling and experimental parametric study of a nonlinear multi-frequency broad bandwidth piezoelectric vibration-based energy harvester. The proposed harvester consists of a tri-leg compliant orthoplanar spring (COPS) and multiple masses with piezoelectric plates attached at three different locations. The vibration modes, resonant frequencies, and strain distributions are studied using the finite element analysis. The prototype is manufactured and experimentally investigated to study the effect of single as well as multiple light-weight masses on the bandwidth. The dynamic behavior of the harvester with a mass at the center is modeled numerically and characterized experimentally. The simulation and experimental results are in good agreement. A wide bandwidth with three close nonlinear vibration modes is observed during the experiments when four masses are added to the proposed harvester. The current generator with four masses shows a significant performance improvement with multiple nonlinear peaks under both forward and reverse frequency sweeps. [ABSTRACT FROM AUTHOR]

Vibration energy harvesting has been a research subject of growing interest over the past few years, and is envisaged as a remedy to the unsatisfactory battery issue in low-power electronic devices. In this study, we propose a new magnetostrictive transducer to harvest energy from finger tapping. Galfenol is selected as the transducing material due to its high piezomagnetic coefficient and excellent machinability. To effectively harness energy in low-frequency conditions, we develop a frequency up-conversion mechanism that succeeds in converting vibration below 10 Hz from finger tapping up to the system's resonance of a few hundred Hz. Furthermore, multiple impacts are induced in each working cycle deliberately to boost the efficiency. A comprehensive model is built and solved to analyze the mechanical-magnetic-electrical coupling system. Based on the model, we elucidate the design criteria for high-performance magnetostrictive transducers. A prototype is fabricated with a Galfenol beam of 0.5 × 5 × 25 mm 3 and, under finger tapping, it generates 5.3 mW power and instantaneously lights up 10 commercial LEDs and a numeric LCD. [ABSTRACT FROM AUTHOR]

Piezoelectric energy harvesters have great potential for achieving inexhaustible power supply for small-scale electronic devices. However, the insufficient power-generation capability and the narrow working bandwidth of traditional energy harvesters have significantly hindered their adoption. To address these issues, we propose a nonlinear compressive-mode piezoelectric energy harvester. We embedded a multi-stage force amplification mechanism into the energy harvester, which greatly improved its power-generation capability. In this article, we describe how we first established an analytical model to study the force amplification effect. A lumped-parameter model was then built to simulate the strong nonlinear responses of the proposed energy harvester. A prototype was fabricated which demonstrated a superior power output of 30 mW under an excitation of 0.3g ( g = 9 . 8 m/s2). We discuss at the end the effect of geometric parameters that are influential to the performance. The proposed energy harvester is suitable to be used in low-frequency weak-excitation environments for powering wireless sensors. [ABSTRACT FROM AUTHOR]

Nonlinear vibration is capable of effectively extending the frequency bandwidth of energy harvesters. Either hardening or softening nonlinearity has been used in various designs to achieve broad-bandwidth energy harvesting. In this paper, we propose a new method to achieve reversible hysteretic responses, i.e., both hardening and softening nonlinear responses, mechanically without additional magnetic interactions. This tunable nonlinearity endows energy harvesters with a great adaptability to environment. The proposed energy harvester is composed of a flexural center and two mass blocks, supported by a pair of elastic rods that are fixed on a vibration base. Different nonlinear responses are invoked by tilting the fixed–fixed elastic rods at different angles. A lumped-parameter model is developed to simulate the nonlinear electromechanical coupling system, and that is analytically solved by virtue of the high-order perturbation technique. The dynamic responses under different frequencies and accelerations are analytically characterized and compared well with the experimental data measured from a fabricated prototype. Furthermore, a nonlinear conditioning circuit (self-powered series synchronized switch harvesting on inductor) is constructed and tested with the proposed nonlinear energy harvester, with which the performance is enhanced about 200% for both resistive loads and capacitive loads. [ABSTRACT FROM PUBLISHER]

We propose a new concept for harvesting vibration energy from multiple directions. Our approach effectively exploits the nonlinear vibration of a doubly clamped elastic rod, converting and amplifying excitations to compressive loads in piezoelectric materials. The proposed multidirectional compressive-mode piezoelectric energy harvester (MC-PEH) is capable of isotropically harnessing vibration energy from any angle in a plane. Meanwhile, the MC-PEH demonstrates a high-voltage output and a wide working bandwidth, along with the distinct softening nonlinear phenomena. Theoretical analysis and experimental testing are performed and exhibit good agreement over a range of excitation frequencies. This study enhances the practicability and adaptability of using energy harvesters in a complex environment. [ABSTRACT FROM PUBLISHER]

Harnessing ambient vibration energy using piezoelectric materials is a promising alternative solution to batteries to inexhaustibly power small-scale mobile devices. This paper presents an innovative energy harvester, named high-efficiency compressive-mode piezoelectric energy harvester (HC-PEH). It consists of a pair of elastic beams and a flex-compressive center where the piezoelectric element bears a dynamic compressive load. The compressive mode is preferred than the commonly-used bending mode and tensile mode due to the superior compressive strength of piezoceramics. To cater to the characteristic of piezoceramics: large ultimate stress, but extremely small ultimate strain, a multi-stage force amplification mechanism is developed in the design. The HC-PEH shows superior capability of high power output and favorable nonlinear phenomena at low frequency range. Under an acceleration of 0.5 g (g = 9.8 m/s 2 ), a maximum power of 19 mW is produced at 21 Hz, which is about one order of magnitude higher than the power output of energy harvesters previously reported. The capability of high power output of the HC-PEH demonstrates the practicability of using energy harvesters to power most of wireless sensors. [ABSTRACT FROM AUTHOR]