摘要 :
Energy harvesting is a process through which energy can be extracted from different sources and conserved or stored for useful purposes. Nowadays, harvesting energy from vibration is one of the most promising technologies. However...
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Energy harvesting is a process through which energy can be extracted from different sources and conserved or stored for useful purposes. Nowadays, harvesting energy from vibration is one of the most promising technologies. However, the majority of current researches obtain 10 mW to 100 mW powers, which has only limited applications in self-powered wireless sensors and low-power electronics. With the global concern on energy and environmental issues, energy harvesting from large-scale vibrations is more attractive and becomes a research front line. The Subtopics include energy assessment from large vibrations, piezoelectric materials and electromagnetic transducers, motion transmission and magnification mechanisms, power electronics, and vibration control. In this paper, vibration energy harvesting from Wind Turbine and Diesel Generator are analyzed. In wind turbine and diesel Generator, energy is harvested with the help of vibration energy harvester. This energy can be stored in battery and may be used further for MEMS and other assisting sensors. The relevant applications discussed in this paper include vibration energy harvesting from human motion, vehicles, transportations, and civil structures. The unique challenges and future research directions of large-scale vibration energy harvesting are also discussed.
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We have carried out a detailed investigation of the acceptor tunneling in the water dimer. This motion is responsible for the largest splitting of vibrational states in the dimer, the so-called acceptor splitting. Our results conf...
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We have carried out a detailed investigation of the acceptor tunneling in the water dimer. This motion is responsible for the largest splitting of vibrational states in the dimer, the so-called acceptor splitting. Our results confirm that this splitting is due to a coupled 2-fold motion: The internal rotation of the donor with respect to the O-O axis, and the wagging of the acceptor. The minimum potential energy path along the corresponding coordinate was computed using the coupled-cluster ab initio with single, double, and perturbative triple excitations (CCSD(T)) method and the augmented correlation consistent polarized valence quadruple basis set (aug-cc-pVQZ). The pure acceptor tunneling energy levels were obtained by the variational method with a free rotor basis. The acceptor splittings associated with the O-H stretching overtone states of the water dimer were calculated with a simple model which employs adiabatic separation between the tunneling motion and high-frequency vibrations.
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The localization of shaking forces acting on an operating machine is an important step to identify vibration and noise sources. The forced vibration response of a linearly vibrating structure is assumed to be linear. However, the ...
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The localization of shaking forces acting on an operating machine is an important step to identify vibration and noise sources. The forced vibration response of a linearly vibrating structure is assumed to be linear. However, the energy distribution of a linearly vibrating structure contains “coupled terms” in the modal decomposition of the vibration energy density function. These coupled energy terms represent the cross-modal energy density associated with the exciting force of a dynamic structure under forced vibration. In this research, it is proved analytically that the high-order cross-modal energy densities of a linear dynamic structure are highly correlated to the location of the external exciting force. Using this finding, a new force localization index based on the high-order cross-modal energy densities of a dynamic structure is proposed and tested. Numerical tests on uniform and step beam structures under force excitation with different frequencies and locations have been carried out to test the effectiveness of the proposed force localization method. It is found that the proposed force localization method works well on vibrating beam structures. Experiments are carried out to verify the proposed force localization method.
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A micro-power-generator is developed with piezoelectric ceramics, which can convert the structural vibration energy generated by wind power into electricity to provide energy for micro-devices such as wireless sensor nodes. The vi...
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A micro-power-generator is developed with piezoelectric ceramics, which can convert the structural vibration energy generated by wind power into electricity to provide energy for micro-devices such as wireless sensor nodes. The vibration modes of the device are analyzed. The standard interface circuit for piezoelectric energy recovery and LTC3588-1 voltage stabilization circuit are selected, and the hardware circuit of the device is designed. The output voltage and power characteristics of micropower-generator were analyzed under different loads, frequencies and amplitudes. The experimental results show that under the same wind speed, When the blunt body is a cuboid, the power generation effect of this device is the best under the optimal load, with the maximum output power of 350.7 mu W. Under the same load with the same shape and structure, the load voltage and output power increase with the increase of wind speed.
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The vibration of rod structures is investigated. The energy-loss coefficients in channel bars and I beams are established experimentally. Regression equations are derived for determination of the vibration spectrum of structures a...
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The vibration of rod structures is investigated. The energy-loss coefficients in channel bars and I beams are established experimentally. Regression equations are derived for determination of the vibration spectrum of structures at the design stage.
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This work develops a comparative study using theoretical models and experimental evaluation of the dynamic behavior of a magnetic spring based vibration energy harvester that can be switched from a mono-stable to a bi-stable confi...
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This work develops a comparative study using theoretical models and experimental evaluation of the dynamic behavior of a magnetic spring based vibration energy harvester that can be switched from a mono-stable to a bi-stable configuration. The design uses coupled magnetic interactions to achieve bi-stability. A mono-stable configuration consists of an oscillating magnet that is levitated between two stationary top and bottom magnets. A cluster of peripheral solid magnets is fixed around the harvester casing and results in a bi-stable configuration. Traditionally, magnetic forces in magnetic spring based harvesters are represented using empirical polynomial fits that are integrated into the equation of motion. In this work, first principle physics based analytical models describing the interaction between magnets are developed and integrated into the equation of motion. Results suggest that, for the bi-stable configuration, introduced analytical model provides more accurate results compared to those obtained using polynomial functions. Results show that a variety of load-deflection characteristics can be obtained by changing geometric ratios of the peripheral magnets in the bi-stable configuration. During dynamic operation, the bistable configuration exhibits interwell, chaotic, and intrawell motion at different acceleration levels. Thinner peripheral magnets are favorable for the bi-stable design, especially at lower acceleration levels. Thinner peripheral magnets yield lower energy barriers, improved frequency responses, and exhibit approximately zero stiffness near equilibrium position. Furthermore, the use of thinner peripheral magnets causes the harvester to move towards monostability.
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A power take-off based on the inerter pendulum vibration absorber (called IPVA-PTO) is
integrated with a spar-floater system to study its hydrodynamic response suppression and
wave energy conversion capabilities in regular waves...
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A power take-off based on the inerter pendulum vibration absorber (called IPVA-PTO) is
integrated with a spar-floater system to study its hydrodynamic response suppression and
wave energy conversion capabilities in regular waves. The hydrodynamics of the spar-floater
system is computed using the boundary element method with linear wave theory. With the
wave height and wave frequency as the bifurcation parameters, it is found that the system
can undergo two bifurcations: period-doubling bifurcation around the first resonance frequency
(spar mode) and secondary Hopf bifurcation around the second resonance frequency (floater
mode). The period-doubling bifurcation results in an energy transfer between the spar-floater
system and the IPVA-PTO for small electrical damping values. As a result, the IPVA-PTO
system simultaneously reduces the maximum response amplitude operator (RAO) of the spar
and increases the normalized capture width in comparison with the optimal linear benchmark.
Experiments performed on a ‘‘dry’’ single-degree-of-freedom system integrated with the IPVAPTO
where the base excitation is substituted for the wave excitation verify the simultaneous
performance enhancement due to the period-doubling bifurcation. The system performance
beyond the period-doubling bifurcation is also experimentally investigated. On the other hand,
as the wave height approaches and passes the secondary Hopf bifurcation, the pendulum
responses transition from primary harmonic responses to quasi-periodic responses to rotations.
When the rotations occur, the IPVA-PTO system increases the maximum normalized capture
width threefold to fivefold compared with the optimal linear benchmark, yet slightly increases
the RAO around the second resonance frequency. Nevertheless, the RAO remains smaller than
the global maximum RAO of the optimal linear benchmark. Finally, parametric studies are
performed to study the effects of parameters on the bifurcations. It is observed that by varying
the electrical damping, the wave height required for achieving the period-doubling bifurcation
can be changed significantly, which can be exploited to stabilize the spar.
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Continuum modeling of finite temperature mechanical behavior of atomic systems requires refined description of atomic motions. In this paper, we identify additional kinematical quantities that are relevant for a more accurate cont...
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Continuum modeling of finite temperature mechanical behavior of atomic systems requires refined description of atomic motions. In this paper, we identify additional kinematical quantities that are relevant for a more accurate continuum description as the system is subjected to step-wise loading. The presented formalism avoids the necessity for atomic trajectory mapping with deformation, provides the definitions of the kinematic variables and their conjugates in real space, and simplifies local work conjugacy. The total work done on an atom under deformation is decomposed into the work corresponding to changing its equilibrium position and work corresponding to changing its second moment about equilibrium position. Correspondingly, we define two kinematic variables: a deformation gradient tensor and a vibration tensor, and derive their stress conjugates, termed here as static and vibration stresses, respectively. The proposed approach is validated using MD simulation in NVT ensembles for fcc aluminum subjected to uniaxial extension. The observed evolution of second moments in the MD simulation with macroscopic deformation is not directly related to the transformation of atomic trajectories through the deformation gradient using generator functions. However, it is noteworthy that deformation leads to a change in the second moment of the trajectories. Correspondingly, the vibration part of the Piola stress becomes particularly significant at high temperature and high tensile strain as the crystal approaches the softening limit. In contrast to the eigenvectors of the deformation gradient, the eigenvectors of the vibration tensor show strong spatial heterogeneity in the vicinity of softening. More importantly, the elliptic distribution of local atomic density transitions to a dumbbell shape, before significant non-affinity in equilibrium positions has occurred.
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This paper describes a vibration energy harvester based on an origami mechanism through piezoelectric energy conversion. The device is capable of broadband energy harvesting from low frequency ambient vibrations. This design utili...
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This paper describes a vibration energy harvester based on an origami mechanism through piezoelectric energy conversion. The device is capable of broadband energy harvesting from low frequency ambient vibrations. This design utilizes bistability inherent in the waterbomb base origami structure to increase the bandwidth of its frequency response. The folding along the crease pattern of the origami mechanism can facilitate large bending deformations of piezoelectric films to generate high electric power output. The compact size and light weight of the origami mechanism render it convenient for integration into various hosts subjected to vibrations. Performance of the origami mechanism is investigated under external excitations with various vibration magnitudes and acceleration levels. This work demonstrates a scheme of broadband vibration energy harvesting by integration of an origami structure with piezoelectric materials. A high fractional bandwidth of 40% is attained under a sinusoidal excitation with a peak acceleration of 0.1 g.
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This paper presents a theoretical study on the scaling laws of electromagnetic and piezoelectric seismic vibration energy harvesters, which are assembled from discrete components. The scaling laws are therefore derived for the so ...
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This paper presents a theoretical study on the scaling laws of electromagnetic and piezoelectric seismic vibration energy harvesters, which are assembled from discrete components. The scaling laws are therefore derived for the so called meso-scale range, which is typical of devices built from distinct elements. Isotropic scaling is considered for both harvesters such that the shape of the components and of the whole transducers do not change with scaling. The scaling analyses are restricted to the case of linearly elastic seismic transducers subject to tonal ambient vibrations at their fundamental natural frequency, where the energy harvesting is particularly effective. Both resistive-reactive and resistive optimal electric harvesting loads are considered. The study is based on equivalent formulations for the response and power harvesting of the two transducers, which employ the so called electromagnetic and piezoelectric power transduction factors, Pi(2)(cm) and Pi(2)(pe). The scaling laws of the transduction coefficients and electrical and mechanical parameters for the two transducers are first provided. A comprehensive comparative scaling analysis is then presented for the harvested power, for the power harvesting efficiency and for the stroke of the two harvesters. Particular attention is dedicated to the scaling laws for the dissipative effects in the two harvesters, that is the Couette air losses and eddy currents losses that develop in the electromagnetic harvester and the material, air and dielectric losses that arise in the piezoelectric harvester. The scaling laws emerged from the study, are thoroughly examined and interpreted with respect to equivalent mechanical effects produced by the harvesting loads. (C) 2020 The Authors. Published by Elsevier Ltd.
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