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The recent rapid development of smart electronic devices, including wearable electronic devices, Internet of Things (IoT) devices, implantable medical devices and remote smart monitors, has raised great research interests on optimising battery power consumption in small-scaled and remotely operational electronic components. For the past ten years, there has been many research works in vibration-based energy harvesting, i.e., converting ambient vibration sources into electrical energy via different transduction methods. In dealing with environmental vibration sources, the most pressing issue for vibration-based energy harvesters (VEHs) from mechanical and structural perspectives is whether the device can efficiently output an optimised power level under realistic (i.e., non-stationary, time-dependent, distributed in frequency spectrum, etc.) excitation sources. Additionally, the performance of VEHs is also restricted in size, complexity of design, and power density issues. Under such design criteria, introducing nonlinearities into VEHs attracted wide attention. This research work aims to investigate the bandwidth performance of vibration-based energy harvesting by subjecting nonlinear phenomena/techniques with internal and externally induced dynamic behaviours into the systems, hence broadening the operational bandwidth and optimising the power level under a wide range of frequencies. The outcomes of this research work yield five peerreviewed journal papers and several international conference papers. The five journal papers are presented in five chapters (Chapter 3 to Chapter 7) as the main contributions of this thesis. Paper 1 presents a magnetic VEH using combined primary and parametric resonances. In order to merge the resonant regions of fundamental primary resonance and parametric resonance as one continuously operational bandwidth, the motion limiter is utilised to induce external hardening effects that aim to eliminate the off-resonance regime between the two resonances. Theoretical investigations, ...

In this work, theoretical, numerical, and experimental investigations for vibration based energy harvesters (VBEH) have been conducted. To improve the current limitations of VBEHs, a combination of parametric excitation, geometric nonlinearity arising from centreline extensibility (mid-plane stretching), geometric imperfection, mechanical stoppers and an array configuration have all been explored as suitable mechanisms for increasing the broadband behaviour of a VBEH. This work mainly focused on the increased broadband behaviour of a doubly-clamped beam resonator with a magnetic tip mass and electromagnetic induction as the transduction mechanism; however, cantilever beam setups were also used in some cases when combining this work with existing methods in the literature. A comparison of a transversely and parametrically system was conducted first to assess the benefits of parametric excitation; a model identification procedure was proposed and it was found, sustained oscillations could be achieved and this led to a greater nonlinear broadband behaviour. Using parametric excitation, the effects of electrical damping, load resistance, initial axial displacement, geometric imperfection have been investigated; it was found that by slightly adjusting geometry, the fundamental and parametric resonance were combined and using imperfections an initial softening followed by strong hardening behaviour was observed. Furthermore, the end of this thesis explores using parametric excitation and geometric nonlinearity with conventional methods in the literature, such as, mechanical stoppers and an array configuration; it was found that parametric resonance offered an increased bandwidth and power harvested for the VBEH devices fabricated. Parametric excitation, geometric nonlinearity and other nonlinear mechanisms have a significant effect on the qualitative and quantitative change in the frequency bandwidth of a VBEH device. This behaviour can be used to further enhance the bandwidth, power, efficiency, and performance of ...

There has been a significant increase in the research on vibration-based energy harvesting in recent years. Most research is focused on a particular technology, and it is often difficult to compare widely differing designs and approaches to vibration-based energy harvesting. The aim of this study is to provide a general theory that can be used to compare different approaches and designs for vibration-based generators. Estimates of maximum theoretical power density based on a range of commonly occurring vibrations, measured by the author, are presented. Estimates range from 0.5 to 100mW/cm 3for vibrations in the range of 1–10 m/s 2at 50–350 Hz. The theory indicates that, in addition to the parameters of the input vibrations, power output depends on the system coupling coefficient, the quality factor of the device, the mass density of the generator, and the degree to which the electrical load maximizes power transmission. An expression for effectiveness that incorporates all of these factors is developed. The general theory is applied to electromagnetic, piezoelectric, magnetostrictive, and electrostatic transducer technologies. Finally, predictions from the general theory are compared to experimental results from two piezoelectric vibration generator designs.

The fast-growing number of mobile and wearable applications has driven several innovations in small-scale electret-based energy harvesting due to the compatibility with standard microfabrication processes and the ability to generate electrical energy from ambient vibrations. However, the current modeling methods used to design these small scale transducers or microgenerators are applicable only for constant-speed rotations and small sinusoidal translations, while in practice, large amplitude sinusoidal vibrations can happen. Therefore, in this paper, we formulate an analytical model for electret-based microgenerators under general sinusoidal excitations. The proposed model is validated using finite element modeling combined with numerical simulation approaches presented in the literature. The new model demonstrates a good agreement in estimating both the output voltage and power of the microgenerator. This new model provides useful insights into the microgenerator operating mechanism and design trade-offs, and therefore, can be utilized in the design and performance optimization of these small structures.

Thesis (M.Phil.) (Research by Publication) -- University of Adelaide, School of Electrical and Electronic Engineering, 2017.

In this dissertation, the application Wake-Induced Vibration (WIV) of a bluff body for harnessing the kinetic energy of a fluid flow is presented. WIV arises when a body undergoes vibrations in the wake of an upstream body. This project investigates the WIV of a bluff body (circular cylinder), constrained to vibrate in the transverse direction, operating in the wake produced by a stationary and upstream bluff body. The upstream body serves as an energy concentrator and increases the oscillations experienced by the downstream body. An efficient coupling of the spatially and temporally concentrated energy from the upstream body and the downstream and vibrating body will result in WIV being considered as a viable form of renewable energy. The application of induced vibration due to vortices in harnessing hydrokinetic energy of the fluid is relatively immature and this research work, which is written as a compilation of journal articles, attempts to address major scientific and technological gaps in this field. The wake behind a bluff body augments the hydro-kinetic energy in space as well as time, in the form of a vortex street. Firstly, the kinetic energy distribution of a bluff body (circular cylinder) wake is characterized using numerical modelling, in order to identify the form and density of the available energy. Secondly, the spatial and temporal energy in the wake from different bluff bodies is investigated experimentally to identify a flow energy concentrator that is more suitable for WIV than the circular cylinder. The semicircular, straight-edged triangular, convex-edged triangular and trapezoidal cylinders were chosen for this analysis where the semicircular and convex-edged triangular cylinders were found to augment more temporal energy compared to the circular cylinder. Thirdly, experiments were performed in the water channel to investigate the effects of Reynolds number and separation gaps for the different cross-sections of upstream cylinders. The results indicated that an upstream semicircular ...

We present experimental measurements of the vibrational relaxation of CO2 (1 20 1) by argon, at ambient temperature (295 ± 2 K). The CO2 molecules were directly excited to the (1 20 1, J = 14) ro-vibrational state by a tunable laser radiation at ∼2 μm. Time-resolved infrared fluorescence technique was used to study the collisional relaxation process. The bimolecular deactivation rate constant of CO2 (1 20 1) by argon was found to be (825 ± 43 Torr-1 s-1) while the self-deactivation by CO2 (0 00 0) was determined to be (3357 ± 135 Torr-1 s-1). The radiative life-time of the vibrational combination band (1 20 1), τ[CO2 (1 20 1)], was found to be (5.55 ± 0.27) μs. Modern angular momentum theory was used to explain values of the deactivation rate measured. It is concluded that the presence of the (0 80 0) state acts like an angular momentum sink leading to a fast deactivation rate of the CO2 (1 20 1) by argon. © 2009 Elsevier B.V. All rights reserved. ; Z.T. Alwahabi, J. Zetterberg, Z.S. Li, M. Aldén ; http://www.elsevier.com/wps/find/journaldescription.cws_home/505699/description#description

Vibration and impact protection have been a popular topic in research fields, which could directly affect the passengers’ and drivers’ comfort and safety, even cause spines fracture. Therefore, an increasing number of vehicle suspensions and aircraft landing gears are proposed and manufactured. Magnetorheological fluids (MRFs), as a smart material, are growly applied into the above device owing to its unique properties such as fast response, reversible properties, and broad controllable range, which could improve the vibration/impact mitigation performance. MRF was utilized to achieve adaptive parameters of the vehicle suspensions by controlling the magnetic field strength of the MRF working areas. Generally, the magnetic field is provided by a given current, subsequently, it would consume massive energy from a long-term perspective. Thus, a self-powered concept was applied as well. This thesis reports a compact stiffness controllable MR damper with a self-powered capacity. After the prototype of the MR damper, its property tests were conducted to verify the stiffness controllability and the energy generating ability using a hydraulic Instron test system. Then, a quarter-car test rig was built, and the semi-active MR suspension integrated with the self-powered MR damper was installed on a test rig. Two controllers, one based on short-time Fourier transform (STFT) and a classical skyhook controller was developed to control the stiffness. The evaluation results demonstrate that the proposed MR damper incorporated with STFT controller or skyhook controller could suppress the response displacements and accelerations obviously comparing with the conventional passive systems.

Transactions of the Tambov State Technical University is a four-language scientific-theoretical and applied multidisciplinary journal ; This paper describes a new experimental methodology for accurate measurements of the efficiency of energy conversion in PZ (piezoelectric) elements. These elements are often used to monitor on-line the progressive structural damage of engineering structures, such as bridges, aircrafts and pipelines. Harvesting energy from small amplitude mechanical vibrations of such structures can revolutionize these monitoring techniques by increasing their reliability, reducing the maintenance cost and making them fully autonomous. As the quantity of electrical energy that can be harvested from vibrations is rather low, it is important to ensure that the piezoelectric elements are operating at the best possible efficiency. ; http://vestnik.tstu.ru/eng/t_12/tom_N12_e.htm

Mechanical vibrations can be effectively converted into electrical energy using a liquid type of energy harvesting device comprised of a ferrofluid and a permanent magnet-inductor coil assembly. Compared to solid vibration energy harvesting devices, the liquid nature of the ferrofluid overcomes space conformity limitations which allow for the utilization of a wider range of previously inaccessible mechanical vibration energy sources for electricity generation and sensing. This report describes the design and the governing equations for the proposed liquid vibration energy harvesting device and demonstrates vibration energy harvesting at frequencies of up to 33 Hz while generating up to 1.1 mV. The proposed design can continuously convert mechanical into electrical energy for direct discharge or accumulation and storage of electrical energy.