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data_05_d_000.csv - Curve of the RMS values of voltage induced on piezoelectric electrodes for p = 0.183 and randomly selected initial conditions δ = 0.0, κ = 0.5. data_05_d_015.csv - Curve of the RMS values of voltage induced on piezoelectric electrodes for p = 0.183 and randomly selected initial conditions δ = 0.15, κ = 0.5. data_05_d_030.csv - Curve of the RMS values of voltage induced on piezoelectric electrodes for p = 0.183 and randomly selected initial conditions δ = 0.3, κ = 0.5. data_05_d_060.csv - Curve of the RMS values of voltage induced on piezoelectric electrodes for p = 0.183 and randomly selected initial conditions δ = 0.6, κ = 0.5. data_06r_o_19.csv - The orbits of the periodic solutions presented in Fig. 6(a) ω = 1.9, Poincaré points = 2. data_06b_o_19.csv - The orbits of the periodic solutions presented in Fig. 6(a) ω = 1.9, Poincaré points = 3. data_06r_o_21.csv - The orbits of the periodic solutions presented in Fig. 6(b) ω = 2.1, Poincaré points = 2. data_06g_o_21.csv - The orbits of the periodic solutions presented in Fig. 6(b) ω = 2.1, Poincaré points = 3. data_06b_o_21.csv - The orbits of the periodic solutions presented in Fig. 6(b) ω = 2.1, Poincaré points = 9. data_06r_o_26.csv - The orbits of the periodic solutions presented in Fig. 6(c) ω = 2.6, Poincaré points = 2. data_06b_o_26.csv - The orbits of the periodic solutions presented in Fig. 6(c) ω = 2.6, Poincaré points = 3. data_06g_o_26.csv - The orbits of the periodic solutions presented in Fig. 6(c) ω = 2.6, Poincaré points = 6. data_06r_o_38.csv - The orbits of the periodic solutions presented in Fig. 6(d) ω = 3.8, Poincaré points = 3. data_06b_o_38.csv - The orbits of the periodic solutions presented in Fig. 6(d) ω = 3.8, Poincaré points = 4. data_06g_o_38.csv - The orbits of the periodic solutions presented in Fig. 6(d) ω = 3.8, Poincaré points = 5. data_06lb_o_38.csv - The orbits of the periodic solutions presented in Fig. 6(d) ω = 3.8, Poincaré points = 7. data_06p_o_38.csv - The orbits of the periodic solutions presented in Fig. 6(d) ω = 3.8, Poincaré points = 9. data_07b_d_015.csv - Numerical results showing the influence of potential asymmetry on the probability of occurrence of particular solutions for δ = 0.15. data_07g_d_030.csv - Numerical results showing the influence of potential asymmetry on the probability of occurrence of particular solutions for δ = 0.30. data_07lb_d_06.csv - Numerical results showing the influence of potential asymmetry on the probability of occurrence of particular solutions for δ = 0.60. data_07r_d_000.csv - Numerical results showing the influence of potential asymmetry on the probability of occurrence of particular solutions for δ = 0.0. This repository contains the results of numerical simulations of a nonlinear bistable system for harvesting energy from ambient vibrating mechanical sources. Detailed model tests were carried out on an inertial energy harvesting system consisting of a piezoelectric beam with additional springs attached. The mathematical model was derived using the bond graph approach. Depending on the spring selection, the shape of the bistable potential wells was modified including the removal of wells’ degeneration. Consequently, the broken mirror symmetry between the potential wells led to additional solutions with corresponding voltage responses. The probability of occurrence for different high voltage/large orbit solutions with changes in potential symmetry was investigated. In particular, the periodicity of different solutions with respect to the harmonic excitation period were studied and compared in terms of the voltage output. The results showed that a large orbit period-6 subharmonic solution could be stabilized while some higher subharmonic solutions disappeared with the increasing asymmetry of potential wells. Changes in frequency ranges were also observed for chaotic solutions.

The subject of the research contained in this repository is a new design solution for an energy harvesting system resulting from the combination of a quasi-zero-stiffness energy harvester and a two-stage flexible cantilever beam. Numerical tests were divided into two main parts-analysis of the dynamics of the system due to periodic, quasiperiodic, and chaotic solutions and the efficiency of energy generation. The results of numerical simulations were limited to zero initial conditions, as they are the natural position of the static equilibrium. The repository compares graphically the energy efficiency for the selected range of the dimensionless excitation frequency. For this purpose, three cases of piezoelectric mounting were presented on figures - only on the first stage of the beam, on the second and both stages. The analysis has been carried out with the use of diagrams showing difference of the effective values of the voltage induced on the piezoelectric electrodes. The results indicate that for effective energy harvesting, it is advisable to attach piezoelectric energy transducers to each step of the beam despite possible asynchronous vibrations.

Vibration control is a large branch in control research, because all moving systems may induce desired or undesired vibration. Due to the limitation of passive system's adaptability and changing excitation input, vibration control brings the solution to change system dynamic with desired behavior to fulfill control targets. According to preference, vibration control can be separated into two categories: vibration reduction and vibration amplification. Lots of research papers only examine one aspect in vibration control. The thesis investigates the control development for both control targets with two different control applications: vehicle suspension and ocean wave energy converter. It develops control methods for both systems with simplified modeling setup, then followed by the application of a novel mechanical motion rectifier (MMR) gearbox that uses mechanical one-way clutches in both systems. The flow is from the control for common system to the control design for a specifically designed system. In the thesis, active (model predictive control: MPC), semi-active (Skyhook, skyhook-power driven damper: SH-PDD, hybrid model predictive control: HMPC), and passive control (Latching Control) methods are developed for different applications or control performance comparison on single system. The thesis also studies about new type of system with switching mechanism, in which other papers do not talk too much and possible control research direction to deal with such complicated system in vibration control. The state-space modeling for both systems are provided in the thesis with detailed model of the MMR gearbox. From the simulation, it can be shown that in the vehicle suspension application, the controlled MMR gearbox can be effective in improving vehicle ride comfort by 29.2% compared to that of the traditional hydraulic suspension. In the ocean wave energy converter, the controlled MMR WEC with simple latching control can improve the power generation by 57% compared to the passive MMR WEC. Besides, the passive MMR WEC also shows its advantage on the passive direct drive WEC in power generation improvement. From the control development flow for the MMR system, the limitation of the MMR gearbox is also identified, which introduces the future work in developing active-MMR gearbox by using an electromagnetic clutch. Some possible control development directions on the active-MMR is also mentioned at the end of the thesis to provide reference for future works. Master of Science Vibration happens in our daily life in almost all cases. It is a regular or irregular back and forth motion of particles. For example, when we start a vehicle, the engine will do circular motion to drive the wheel, which causes vibration and we feel wave pulses on our body when we sit in the car. However, this kind of vibration is undesirable, since it makes us uncomfortable. The car manufacture designs cushion seats to absorb vibration. This is a way to use hardware to control vibration. However, this is not enough. When vehicle goes through bumps, we do have suspension to absorb vibration transferred from road to our body. The car still experiences a big shock that makes us feel dizzy. On the opposite direction, in some cases when vibration becomes the motion source for energy harvesting, we would like to enhance it. Hardware can be helpful, since by tuning some parameters of an energy harvesting device, it can match with the vibration source to maximize vibration. However, it is still not enough due to low adaptability of a fixed parameter system. To overcome the limitation of hardware, researches begin to think about the way to control vibration, which is the method to change system behavior by using real-time adjustable hardware. By introducing vibration control, the theory behind that started to be investigated. This thesis investigates the vibration control theory application in both cases: vibration reduction and vibration enhancement, which are mentioned above due to opposite application preferences. There are two major applications of vibration control: vehicle suspension control and ocean wave energy converter (WEC) control. The thesis starts from the control development for both fields with general modeling criteria, then followed by control development with specific hardware design-mechanical motion rectifier (MMR) gearbox-applied on both systems. The MMR gearbox is the researcher designed hardware that targets on vibration adjustment with hardware capability, which is similar as the cushion seats mentioned at the beginning of the abstract. However, the MMR cannot have capability to furtherly optimize system vibration, which introduces the necessity of control development based on the existing hardware. In the suspension control application, the control strategy introduced successfully improve the vehicle ride comfort by 29.2%, which means the vehicle body acceleration has been reduced furtherly to let passenger feel less vibration. In the WEC application, the power absorbed from wave has been improved by 57% by applying suitable control strategy. The performance of improvement on vibration control has proved the effect on further vibration optimization beyond hardware limitation.

peer-reviewed Vibration energy harvesters (VEHs) scavenge ambient vibrational energy, offering an alternative to batteries for the autonomous operation of low power electronics. VEHs are typically spring-mass-dampers that extract mechanical energy from a vibrating source, converting it into useful electrical energy. A number of transduction mechanisms can be utilised, with electromagnetic induction of interest herein. Velocity amplification, a technique used to increase velocity through impacts, is employed in this thesis to improve the power output and operational bandwidth of multiple-degree-of-freedom (multi-DoF) piecewise linear (PWL) VEHs, compared to linear resonators. Such a harvester is referred to as a velocity ampli ed electromagnetic generator (VAEG), with a gain in power achieved by increasing the relative velocity between the magnet and coil in the transducer. In this thesis, VAEGs were investigated numerically and experimentally under sinusoidal excitation, for a range of parameters. An analysis of the in uence of mass con guration on multi-DoF VAEGs was undertaken. It was determined that under forced excitation, contrary to velocity ampli cation theory, 2-DoF con gurations achieve higher RMS velocities and, hence, voltages than systems with greater numbers of DoFs. With increasing mass ratio, despite the RMS velocity increasing, the RMS voltage actually decreases, as the increase in velocity does not compensate for the reduction in transducer size. A 2-DoF VAEG with a mass ratio of R = 3 was selected for in-depth investigation. The harvester was characterised with frequency sweeps for a range of base acceleration levels and gap lengths|a key geometric parameter. A shift in peak output power towards lower frequencies is observed with increasing gap, due to the decreasing e ective sti ness, while RMS velocity also increases. The acceleration level required to achieve large amplitude oscillations increases with gap, however. An optimisation of the 2-DoF VAEG is presented, resulting in the prediction of a relatively high volume gure of merit (FoMV = 2:83%) at high accelerations (10 m=s2) and low frequencies (16.4 Hz). It is demonstrated that the hysteresis behaviour and dependence of RMS response on initial conditions associated with non-linear VEHs is not present in the VAEGs herein. Consequently, the frequency responses presented are independent of initial conditions, which is signi cant for the applicability of VAEGs. To determine the in uence of scale on the harvester response, the 2-DoF VAEG was fabricated at three length scales (s = V olume1=3), with the electrical and mechanical systems considered separately|a number of deviations from linear scaling methodologies were required to achieve this. It was determined that the gap does not scale, while the load power is predicted to scale as PL x s5:51, suggesting that achieving high power densities in a VAEG at low device volumes is extremely challenging. VAEG con gurations with 2-DoFs and low mass ratios demonstrate the highest power densities, while the optimal gap is dependent on the excitation conditions and increases with increasing acceleration amplitude, at the optimal frequency. VAEGs are found to be most suitable for applications with high acceleration levels and low frequencies, where high power densities can be achieved.

Molecular reorientation of the four isomeric butanols are investigated with molecular dynamics simulations. The purpose of this study is to probe how alcohol reorientational and hydrogen-bond (H-bond) dynamics is influenced by the arrangement of the steric bulk of the isomeric butanols in their liquid state. The OH reorientation times are explained with the extended jump model in which the OH reorientation is broken down into contributions due to ``jumps'' between H-bond partners and ``frame'' reorientation of the intact H-bonded pair. In the case of the isomeric butanols, the model provides a quantitative description of the OH reorientation times. Our results show that reorientation is fastest in iso-butanol and slowest in tert-butanol, while sec- and n-butanol have similar reorientation times. Similar reorientation times for sec- and n-butanol is due to the unpredictable cancellation between the jump and frame reorientation in the two alcohols. Entropic, enthalpic and dynamical factors that include transition state recrossing effects are seen to contribute to the jump reorientation times. Finally, a model that is based on the liquid structure is offered to evaluate the enthalpic and entropic contributions to the jump time. This study represents the foundation for a model that predicts OH reorientation times in alcohols even though further work is needed for a better prediction of frame reorientation times and the transition state recrossing effects. An estimation of the activation energy of chemical reactions like jump reorientation of OH groups in alcohols from molecular dynamics simulations has always required numerous simulations at several temperatures. In this work, several methods for calculating the activation energies at a single temperature have been explored. The applications explored include classical and quantum systems and the activation energy is evaluated using the same time correlation functions that are used to evaluate rate constants from molecular or quantum dynamics trajectories. The use of ...

In this paper, we describe a measurement procedure to fully characterise a novel vibration energy harvester operating in the ultra-low-frequency range. The procedure, which is more thorough than those usually found in the literature, comprises three main stages: modelling, experimental characterisation and parameter identification. Modelling is accomplished in two alternative ways, a physical model (white box) and a mixed one (black box), which model the magnetic interaction via Fourier series. The experimental measurements include not only the input (acceleration)–output (energy) response but also the (internal) dynamic behaviour of the system, making use of a synchronised image processing and signal acquisition system. The identification procedure, based on maximum likelihood, estimates all the relevant parameters to characterise the system to simulate its behaviour and helps to optimise its performance. While the method is custom-designed for a particular harvester, the comprehensive approach and most of its procedures can be applied to similar harvesters.

BRL-1122 ; Dept. of the Army Project no. 5B03-04-002, Ordnance management structure code no. 5010.11.815. ; Includes bibliographical references (p. 45). ; Mode of access: Internet.

This is the supplementary document to the paper titled, ‘Twenty-Eight Orders of Parametric Resonance in a Microelectromechanical Device for Multi-band Vibration Energy Harvesting’. EPSRC [EP/L010917/1]

The resilience of power infrastructure against environmental challenges, particularly wind-induced vibrations, is crucial for ensuring the reliability and longevity of overhead power lines. This dissertation extends the development of the Mobile Damping Robot (MDR) as a novel solution for mitigating wind-induced vibrations through adaptive repositioning and energy harvesting capabilities. Through comprehensive experimental and numerical analyses, the research delineates the design, optimization, and application of the MDR, encompassing its dynamic adaptability and energy harvesting potential in response to varying wind conditions. The study begins with the development and validation of a linearized model for the MDR, transitioning to advanced nonlinear models that more accurately depict the complex interactions between the robot, cable system, and environmental forces. A global stability analysis provides crucial insights into the operational limits and safety parameters of the system. Further, the research explores a multi-degree-of-freedom system model to evaluate the MDR's efficacy in real-world scenarios, emphasizing its energy harvesting efficiency and potential for sustainable operation. Findings from this research show the clear promise for the development of the MDR with the consideration of the nonlinear dynamics in play between the robot, the cable, and the wind. This work lays a foundational framework for future innovations in infrastructure maintenance, paving the way for the practical implementation of mobile damping technologies in energy systems. Doctor of Philosophy Across the United States, over 160,000 miles of power lines crisscross the landscape, powering everything from small homes to large industrial complexes. These critical infrastructures, however, are constantly battered by the elements, particularly by strong winds capable of inducing Aeolian vibrations. Such vibrations lead to oscillations in the power lines due to wind forces, potentially causing severe structural damage, compromising public safety, and incurring considerable economic costs. In response to these challenges, various mitigation strategies have been employed. Traditional methods include regular inspections carried out by foot patrols, helicopters, or sophisticated inspection robots, though these approaches are notably resource-intensive and costly. Additionally, mechanical devices like Stockbridge dampers are utilized to dampen the vibrations, but they suffer from efficiency issues when misaligned with the vibration nodes. This dissertation extends the study to an innovative solution to overcome these limitations: a mobile damping robot designed to navigate along power lines and autonomously position itself at the points of highest vibration amplitude, thereby optimizing vibration dampening. This study delves into the feasibility and effectiveness of such a solution, supported by thorough numerical simulations. The aim is to demonstrate how this advanced approach could redefine maintenance strategies for power lines, enhancing their resilience against wind-induced vibrations and reducing the reliance on laborious inspection methods and static damping devices with limited efficiency.