The 5th International Conference on Vibration and Energy Harvesting Applications (VEH 2024)

The electromagnetic vibration energy harvesting system is designed to extract energy from the vibrations, with its resonant frequency specifically tuned to match the primary vibration frequency of the energy source. However, the vibration frequency often deviates from resonant frequency under different operation/weather and installation circumstances. Such deviation can lead to a significant decrease in the collected output power. For example, a 1 Hz deviation in the vibration frequency results in a 51.3% decrease in induced voltage and a 76.3% decrease in output power. State-of-the-art wideband EVEH devices have either low output power or relatively large volume. Adopting a wideband EVEH is not a good choice. To address this issue, this paper proposes a new approach for fine-tuning the resonant frequency of EVEH by changing the structure of the spring. The details of the method is to add or remove bridge arms changing the rotation angle of the cantilever beams. The advantage of this method lies in the convenience of finely tuning the device's frequency while obtaining a larger output power. The results demonstrate that for the EVEH device designed at a resonant frequency of 60 Hz, the primary resonant frequency can vary from 58.5 to 59.5 Hz by nylon bridge arms. At resonant frequencies of 59 Hz and 0.5 g acceleration, the output voltage is increased by 77.1%. Output power reaches 15 mW, representing a 213.8% improvement.

The escalating threats of marine pollution and climate change underline the critical need for deploying water quality sensors in oceanic environments. Recent advancements in energy harvesting technologies have been pivotal in augmenting the life span and durability of these sensors. Notably, triboelectric nanogenerators (TENGs) emerge as a promising solution due to their ability to convert mechanical energy into electricity. However, the performance of TENGs in marine settings is hampered by inherent challenges: their high internal resistance and low current generation significantly limit power output. This limitation is further exacerbated by the ocean’s inherently chaotic energy landscape, characterized by low-frequency movements. Addressing these constraints is vital for optimizing TENGs’ utility in robust, long-term ocean monitoring applications. This work introduces the design and prototype of a rolling mode TENG (MO-TENG) for harnessing ocean wave energy, utilizing multi-tunnel grating electrodes and the opposite-charge-enhancement effect. The proposed MO-TENG exhibits impressive output performance and durability. The techniques and strategies detailed in this research have unveiled fresh possibilities for the development and utilization of TENGs in marine IoT applications.

Halbach array is a new type of permanent magnet array. Its special permanent magnet arrangement structure can not only increase the air gap magnetic flux but also weaken the magnetic flux density of the rotor yoke, thus increasing the energy density while reducing the size and cost of the motor. For the Halbach array, when the rotor volume is constant, the volume of the permanent magnet used by the cubic permanent magnet is smaller than that of the sector-shaped permanent magnet. Therefore, the impact of special-shaped permanent magnets on the energy capture efficiency of the Halbach array can be explored. This paper compares the magnetic field distribution of three common special-shaped permanent magnets, rectangular, trapezoidal, and sector-shaped, under the same rotor volume, using the same volume of special-shaped permanent magnets and using the same volume of the rotor under two different operating conditions and energy efficiency. Simulations and experiments show that the energy capture effect of the Halbach array composed of sector-shaped permanent magnets is the best whether using permanent magnets of the same volume or rotors of the same volume.

Rotational energy is abundant in numerous industrial applications, spanning from miniature devices like watches to massive installations such as offshore wind turbines. As wireless sensing technology continues to evolve, there is a growing interest in developing self-sustaining energy sources for wireless sensors used in rotating systems. This research aims to expand the operational bandwidth of energy harvesters by integrating a dual-beam structure and nonlinear magnetic interactions to enhance low-frequency, high-efficiency energy harvesting during rotary motion. Both theoretical and experimental approaches are employed to assess the influence of nonlinear magnetic forces on the performance of the harvester in rotary environments. The study begins with the design of a nonlinear energy harvester featuring parallel-aligned double beams in rotational motion. This configuration is shown to be highly efficient, capable of effectively capturing energy across a broad frequency spectrum from 15 to 35 rad/s. To further improve low-frequency energy harvesting, the research extends to the modeling and analysis of a vertically arranged nonlinear energy harvester in rotational motion. The findings reveal that this vertical arrangement significantly boosts the harvester's efficiency at low frequencies, particularly within the range of 10–37 rad/s. Experimental investigations are conducted to corroborate the theoretical predictions, confirming that the designed energy harvester exhibits desirable characteristics for low-frequency broadband energy harvesting. These results underscore the potential of the proposed harvester designs to meet the energy requirements of wireless sensors in various rotating machinery applications, thereby advancing the field of self-powered sensor technology.

Nonlinear vibration energy harvesting represents a critical approach for achieving a bandwidth energy harvester. Difficulties in obtaining high-energy output for nonlinear energy harvesters become a huge obstacle in their practical applications. Recently reported strategies based on imparting external mechanical or electrical impacts have been verified to be promising for solutions. However, it is not demonstrated in experiment whether these strategies are suitable in the typical buckled-bridge nonlinear vibration energy harvesters. In this letter, we propose a buckled-bridge piezoelectric energy harvester to verify the feasibility of these strategies. The harvester is mainly consisted of a flexible piezoelectric buckled bridge. A bulked-bridge piezoelectric energy harvesting is analyzed in theory. Through modifying the theoretical model, the external impacts are introduced in theory. The fabricated harvester can reach the maximum output peak open-circuit voltage of 14.1 V (upward) or 9.6 V (downward) at the applied accelerations of 0.8 g. The obtained high-energy output has a big phase difference from the low-energy output. Meanwhile, the output voltage is not a perfect trigonometric function signal as the excited acceleration by the large inter-well oscillations.

Nonlinear piezoelectric energy harvesters (NPEHs) have attracted much attention in recent years due to their wide harvesting bandwidth and high harvesting efficiency. Due to the complexity of NPEHs, researchers usually use theoretical numerical and experiments to analyze. However, two problems prevent us from more accurate analysis and design. Firstly, the common magnetic model named magnetic dipole model (MDM) will usually cause an unacceptable error in NPEHs; secondly, the harmonic balance method (HBM) which usually only uses the first-order harmonic terms is accurate in the monostable configuration for low-amplitude vibrations, but for the bistable or multi-stable ones, this method has major differences compared to numerical methods such as sweep method (SM) or experiment. To solve the above two problems, we propose a more accurate magnetic model based on the MDM to reduce the error. Meanwhile, we use the swarm intelligent optimization algorithm (SIOA) to solve the high-dimensional nonlinear algebraic equations obtained by high order HBM, which is in agreement with the SM, and find out more nonlinear dynamical phenomena. What’s more, the high-energy orbital solutions which can be easily neglected in the SM and experiment but have significant advantages to energy harvesting have been found.

Friction-induced vibration (FIV), which leverages friction for excitation to achieve close to resonant frequency vibration, presents an efficient solution for vibration-based piezoelectric energy harvesting. Previous experimental dynamic responses exhibited variability due to uncertainties in the properties of frictional material. This study conducts uncertainty analysis of frictional parameters on energy output for a magnet-engaged nonlinear piezoelectric energy generator utilizing FIV. An electromechanical model depicts the dynamics, and the energy output is evaluated through transient charging simulation. Employing the root mean square (RMS) charging power $${P}_{\text{e}}^{\text{rms}}$$ P e rms as the performance function for uncertainty analysis, the Morris One-At-a-Time (MOAT) method, coupled with Latin hypercube sampling, evaluates the parametric influence induced by uncertainty on the system output. Notably, among the friction model parameters, sliding velocity $${v}_{0}$$ v 0 exhibits the predominant elementary effect on energy generation performance. Increased variation ratio $${v}_{\text{rt}}$$ v rt and decreased linear spring stiffness $${k}_{\text{l}}$$ k l increase the system's sensitivity to external parameter uncertainties. The observed trends in elementary effects for all the studied parameters reflect higher uncertainty sensitivity, when the initial state is near the stable region with reduced FIV. Future investigation could extend this research with a comprehensive uncertainty analysis of complicated energy generation systems under FIV for performance optimization.

This paper presents an approach to investigate the efficiency of a nonlinear anti-phase motion energy harvester (APMEH) when subjected to non-harmonic and harmonic excitations. Specifically, the paper aims to establish a trade-off between the device’s operational bandwidth, harvested voltage/power, and resonant operations under both harmonic and non-harmonic excitation. The repulsive force $$\left({F}_{rep}\right)$$ F rep in the magnets was identified to successfully create static preloads/offsets and a pseudo-hardening effect in the linear spring as the distances between them are varied. Consequently, the spring begins to show nonlinear characteristics with a slight manifestation of hardening while increasing resonant frequencies and bandwidths over different magnet spacings. The APMEH configurations were tested with three preload distances: 12.024, 15.748, and 25.522 mm, defined as configurations 1, 2, and 3, respectively. In the harmonic/resonant application of the design, APMEH harvested much larger power, reaching 65.08, 81.28, and 90.56 mW, respectively, for configurations 1, 2, and 3 at a harmonic acceleration of 0.40 g over an external load of 200.00 Ω. Linear performance of the APMEH shows that a lower static offset distance will enhance the operational bandwidth. For instance, the bandwidth of configuration 1 improved by 12.20% and 51.22% over configurations 2 and 3, respectively, at a compromised power output measured at configuration 1 relative to 2 and 3, which was compromised by 19.93 and 28.13%. The observed increase in resonance with a smaller offset was attributed to the inertia redistribution as a result of the magnitudes and directions of repulsive forces $$\left({F}_{rep}\right)$$ F rep initiating a hardening effect. In non-harmonic excitation, a larger $${F}_{rep}$$ F rep consequently improved the harvested voltage by 21.08 and 25.41% when the horizontal distance (x) is reduced by 23.65 and 52.89%, respectively, for the same reasons as mentioned above. Therefore, a trade-off on harvested power and bandwidth is possible with the APMEH through appropriate parametric tuning of static distances.

This paper presents a novel micro VEH based on 1:2 internal resonance with electromagnetic effect. The system having a volume of 2.31 cm3 is made of copper, including outer circular mass, inner circular mass, base support, and spiral beams connecting them. The outer mass introduces nonlinear magnetic force into the system to achieve 1:2 internal resonance with a circular magnetic plate opposed to another on the base support, which achieves the coupling of the first two resonant modes. The inner mass is equipped with a permanent magnet to convert energy based on electromagnetic effect. This structure is combined with multi-modal mechanism nonlinearity. Energy method is used to describe dynamic behavior, and two modes’ coordinates and corresponding natural frequencies are calculated by matrix calculation. Then the equations are simplified to the standard form using the orthogonality of the modes, which are solved with the multi-scale method. Theoretical and numerical simulation results demonstrate the proposed system is capable of improving energy harvesting efficiency by frequency up-conversion, as well as broadening the 3 dB frequency bandwidth by an order of magnitude via the split resonance peak. This VEH with a new mechanism could be an alternative source of wearable electronics devices and other applications.

In this study, we report a piezoelectric energy harvester adopting a fishtail bluff body (FTEH) to scavenge ambient wind energy. The biomimetic nature of the FTEH contributes to enhancing the harvester's performance. This enhancement stems from the geometric variations of the fishtail bluff body, which undergoes undulation during fluid–structure interactions, thereby affecting the dynamic behavior of the harvester. An electromechanical coupling model has been developed to explain this phenomenon. Experiments were conducted to evaluate the energy-harnessing performance of harvesters equipped with three distinct bluff bodies. The results demonstrate that the FTEH exhibits outstanding performance compared to traditional energy harvesters utilizing cuboid bluff bodies after the threshold wind speed. Specifically, under the excitation of airflow at a speed of 23 m/s, the RMS voltage for the fishtail structure, about 3.24 V, surpasses the corresponding voltage for the cuboid-L bluff body (0.73 V) to approximately 440% and that for the cuboid-S bluff body (0.40 V) to approximately 810%. Moreover, the charging capability, for a 100 μF capacitor, of the FTEH is around 60 and 110 times greater than that for those cuboid bluff bodies, respectively. This study holds significant implications for the development of self-powered systems in windy environments.

To harness the abundant water flow energy for powering remote sensors or small microelectronic systems in the ocean is of great significance. Piezoelectric energy harvesting from flow induced motion can be an approach. In this paper, a piezoelectric energy harvester was embedded in a cylinder to form an inertial energy harvester. The cylinder together with springs forms a two-degree-of-freedom vortex induced motion structure in the flowing water. Two downstream columns were placed near the cylinder in the in-line direction, which can produce collisions between the column and the cylinder and offer a frequency up-conversion mechanism for the inside piezoelectric energy harvester. The system is analyzed theoretically based on the fluid mechanics and a prototype is fabricated for verification. Experiments were conducted in a low-speed circulating water channel. The trajectory of the cylinder was experimentally investigated. It is demonstrated that the output performance of the energy harvester is related to the flow speed and the gap distance between the columns and cylinder. The results show that when the flow speed is 0.371 m/s and the gap distance is 17 cm, the maximum output of the energy harvester is 861.39 μW for one piezoelectric element with a 150 kΩ external resistor.

Nowadays, the worldwide scarcity of lithium-ion batteries is mainly due to the increased demand for electric vehicles, energy storage systems, and consumer electronics that rely on these batteries. While many experts in the industry anticipate a resolution to this shortfall shortly, it appears that the battery dilemma remains an ongoing obstacle for electrical systems, likely to reoccur. A novel system has been proposed for harnessing natural environmental kinetic energy, which can be utilized alongside all mechanical amplifiers employed as vibration-based energy harvesters. This mechanical system operates as both a rectifier and converter, capable of producing unidirectional rotary motion that can be stored as potential energy. A magnetic transducer will be employed to convert the stored potential energy into electrical energy. The system presented herein serves as a mechanical rectifier, energy converter, and energy reservoir, proficient not only in harvesting vibration-based energy but also in storing it.

This paper presents the robust optimization of a galloping-based piezoelectric wind energy harvester (GPWEH) using Taguchi method. A mathematical model of the GPWEH is established for calculating the voltage output of the harvester. The Taguchi design method is used to formulate the experimental designs for the harvester with the parameters variations. The signal-to-noise ratio (S/N) of the voltage output is derived from the larger-the-better characteristic value of each experimental condition. The maximum S/N obtained from the effect analysis of the S/N of the voltage output is used to determine the optimal factorial combination of the parameter level. The results show that with the optimal design combination, the average voltage output of the harvester is 114.9 V at an excitation wind speed of 6 m/s, which is 12.4% higher than that from the original design combination. The study provides a guideline for the robust optimization of the GPWEH based on the Taguchi method.

Wave energy is a promising renewable energy source with vast reserves, but it is challenging to harvest because of its low frequency and random nature. Triboelectric nanogenerators are an emerging technology that efficiently generates energy from different forms of mechanical excitation, including wave excitation. In this work, an accelerator-based triboelectric nanogenerator (A-TENG) is proposed for wave energy harvesting. A-TENG is based on the contact-separation principle and comprises two layers: a copper electrode and fluorinated ethylene propylene film in the bottom and a flexible copper electrode in the upper layer. The bendable upper layer is inspired by the accelerator structure, whereby it fully contacts the bottom layer upon applying a force to the upper layer. A detailed summary of A-TENG and its potential applications for energy harvesting are discussed. A-TENG is a simple, low-cost solution that can yield higher output with an array network. The A-TENG is proposed to be mounted to shoreline structures like seawalls for energy generation from surface waves. Moreover, water-resistant A-TENGs can be installed on the seabed to generate energy from underwater pressure variations. This unique solution shows promise for efficiently harvesting wave energy, e.g. for powering electronics.

Aquafarms, often located in remote areas, face challenges accessing reliable power sources. Existing renewable solutions, such as wind and solar, are heavily limited by unpredictable weather conditions and can only be used in some scenarios. However, a more predictable energy resource exists in ocean wave energy. Addressing this, our research aimed to design a wave energy converter meeting specific criteria: producing at least 100 W on average, storing electricity, integrating with existing infrastructure, and being effective in calm wave conditions. A point absorber wave energy converter (WEC) emerged as the optimal solution through ideation and simulations, focusing on capturing heave and surge motion for power generation. The chosen concept, a buoy equipped with a helix design moving along a rail, was initially prototyped for wave flume testing at a small scale. While successful, improvements were identified-increasing the height-to-width ratio and minimizing friction in the mechanism. Iteratively, a larger prototype incorporating a gearbox for enhanced speed was developed and tested, demonstrating proof of concept. Producing up to 3 watts per kg of moving mass in laboratory testing, our innovative approach shows promise in providing sustainable and reliable power solutions for remote aquafarms.

Ocean wave energy is a widely anticipated new type of renewable energy. However, due to the ultra-low-frequency and random motion characteristics of ocean waves, effectively harnessing it presents a significant challenge. This paper proposes a Mag-Boost mechanism based on the phenomenon that the magnetic torque undergoes a sudden change when the magnetic poles of two magnets are orthogonal. This innovative mechanism, requiring just a trigger below 1 Hz, can stimulate a power-magnet to generate high-frequency oscillation without direct contact. Utilizing this mechanism, a high-power wave energy harvester (WEH) with ultra-low-frequency response capabilities has been developed. Tested on a six-degree-of-freedom platform, the WEH demonstrated a high-output power of 1.44W and a power density of 1.2 kW/m3 at a frequency of 1 Hz and an inclination angle of 30°. The peak open-circuit voltage of the WEH reached 5 V, ensuring a completely independent and stable power supply for wireless temperature and humidity sensors. Furthermore, the Mag-Boost mechanism also shows considerable potential for harvesting other forms of low-frequency environmental energy, including wind, vibration, and human kinetic energy.

The research examines the conversion of kinetic energy to electricity via a liquid piston powered by a thermoacoustic Stirling engine. Bypassing the complexities of solid pistons, this engine harnesses sound wave oscillations in a water-filled vertical U-tube, functioning as the acoustic load. Connected to a looped tube engine through a T-junction, the system incorporates three differentially heated regenerators and the branch U-shaped liquid column. Innovatively, a permanent magnet nested within a floating device inside the liquid column interacts with a solenoid coil, inducing electromotive force by cutting through magnetic flux lines. Utilizing the working fluids of water and air, the apparatus presents a cost-effective and reliable method for generating electricity on a small scale. Thermoacoustic engines, which typically employ resonance tubes and regenerators, depend on substantial axial temperature gradients to convert heat to mechanical work. Our approach advances this design by integrating a liquid column, for promoting a float-type linear alternator. This proceedings paper demonstrates the viability of this technology for sustainable energy generation.

Like many nonlinear dynamical systems, thermoacoustic engines (TAEs) exhibit hysteresis in the amplitude of self-excited acoustic oscillations when the temperature gradient implemented across the porous material is first increased and then decreased. This research numerically studies the hysteresis features of a quarter-wavelength standing-wave TAE. Computational Fluid Dynamics (CFD) is employed to investigate the effects of the stack parameters on the hysteresis characteristics. It is found that the lower critical temperature, the upper critical temperature, the difference between upper and lower temperatures, and the maximum pressure amplitude in the hysteresis loop are all dependent on the gap between stack plates and the stack position. This study deepens the understanding of the hysteresis phenomena reported in previous studies, providing useful guidance for reducing the lowest temperature gradient for the initiation of acoustic oscillations in TAEs.

In an effort to mitigate thermoacoustic oscillations in cryogenic distribution systems, the coupled oscillators are established and a phase-tuned tube has been introduced between the system’s distribution branches. The findings indicate that this phase-tuned tube effectively modulates the pressure oscillation state within the distribution pipe. A detailed examination of the phase-tuned tube’s operational mechanism reveals that almost no phase alteration occurs at symmetrical positions proximate to the midpoint, and pressure oscillations remain in a chaotic state, with trajectories exhibiting near-perfect consistency. However, when deviations from the midpoint position increase, the phase disparity between pressure oscillation sequences at symmetrical positions becomes more pronounced. Consequently, the oscillation state transitions into a multi-periodic pattern, although the trajectory remains inconsistent.

As attention increasingly focuses on green energy, thermal energy emerges as a widely available energy source. Therefore, harvesting this energy has been the subject of extensive studies. Thermoacoustic-piezoelectric energy harvesters are championed as innovative devices for transferring renewable thermal energy green energy to green energy applications. The onset frequency, a crucial parameter in thermoacoustic engine design and operation, has typically been determined through targeting method or numerical iteration, involving a cumbersome process. This paper introduces an analytical method tailored for one-dimensional standing-wave type thermoacoustic-piezoelectric energy harvesters. The method facilitates the determination of the harvester’s onset frequency under arbitrary boundary conditions. The original thermoacoustic equation is reconstructed by refining the Fourier series, and subsequently yields the eigenvalue equation for the onset frequency through the Galerkin method. Building upon this foundation, the paper explores the impact of factors such as engine length and fluidd type, plate stack length and position, general impedance boundary conditions, and temperature on the onset frequency.

This paper introduces a novel thermoacoustic musical instrument, bamboo flute. The system harnesses waste heat to produce sound through thermoacoustic principles, controlling the frequency by opening and closing multiple perforations and achieving the playing effect of a traditional Chinese bamboo flute. Initially, a model of the thermoacoustic flute is developed. Subsequently, an analysis is conducted to assess the impact of the position and number of perforations on thermoacoustic system. The results reveal that the perforation closest to the thermoacoustic core determines the frequency and the distribution of acoustic power. Through manipulation of the perforation boundaries, the system achieves frequency modulation within the range of 277–523 Hz, fulfilling the essential criteria for a G key bamboo flute.

In this paper, a symmetric single-sided vibro-impact nonlinear energy sink (SSSVI NES) is introduced to the shock response suppression of a cantilever beam. The equations of motion of the system are derived. The modal test of the cantilever beam is carried out to verify the correctness of the assumption of the Euler–Bernoulli beam. The SSSVI NES is designed based on the modal test results. An experimental study is performed to validate the response suppression performance of the SSSVI NES on the beam under shock excitation. The time history of the acceleration response, wavelet spectrum, and peak response in the frequency domain are all examined. Both simulation and experimental results show that SSSVI NES can effectively suppress the shock response of a cantilever beam.

Compared to traditional linear vibration absorber (LVA), nonlinear vibration absorber (NVA) has been proved to be more effective in terms of frequency range and/or magnitude of vibration suppression. Nonlinear energy sink (NES) is one representative NVA. Recently, parallel NESs have been investigated by many researchers. However, there is still a lack of study on parallel NESs featuring multistability. To address this gap, this study investigates the vibration suppression capabilities of parallel NESs with tristability introduced by three repulsive magnets (P-3RMNESs) under strong impulse excitation. The dynamic model of the whole system is formulated considering beam rotation and bending, and dipole–dipole model of magnetic force. For a fair comparison, the critical parameters of both the single 3RMNES and P-3RMNESs are optimized using the genetic algorithm. Simulation results reveal that with the same mass, the optimized P-3RMNESs with tristability has better performance compared to the optimized single 3RMNES with tristability. This work provides an approach for designing effective parallel NESs for strong impulse response mitigation.

Nonlinear structures with specially designed nonlinearities, including quasi-zero stiffness, multi-stability, and frequency-up conversions, are of significant interest for energy harvesting and vibration isolation. This paper experimentally evaluates a 3-DOF (3-degrees-of-freedom) X-shaped structure coupled with a piezoelectric harvesting mechanism to enable multidirectional low-frequency energy harvesting and vibration isolation. The X-structure enables performance tunability and facilitates energy harvesting and vibration isolation in multiple directions. In multidirectional vibration experiments, the test results demonstrate the effectiveness of the 3-D X-mechanism, which exhibits robust band-pass-like harvesting spectra, enabling broadband energy harvesting at low frequencies and in multiple directions. The results indicated the capability of the 3-D X-structure, as a passive structure, to effectively achieve multidirectional vibration isolation. The X-structure demonstrated peak power outputs of 3, 0.05, and 0.065 mW under low-frequencies in the vertical, horizontal, and in-plane rotation directions, respectively. Due to the beneficial high static and low dynamic nonlinear stiffness, our X-structure achieved effective low-frequency vibration isolation (<4 Hz) more effectively in vertical and horizontal directions.

Vibration energy harvesting and vibration isolation and are conflict in most existing works. As for suspension systems, vibration isolation is always considered as the main goal. In this case, the efficiency of vibration energy harvesting is sacrificed to achieve a trade-off optimization, so it is urgent to reveal the relationship between vibration energy harvesting and vibration isolation. In this paper, a one-degree-of-freedom (1-DOF) simultaneous vibration isolation and energy harvesting (SVIEH) system is investigated by using quasi-zero stiffness (QZS) and its electromechanical coupling equation is derived. The output power and the force transmissibility are selected to evaluate the performances vibration energy harvesting and vibration isolation, respectively. Then the coupling mechanism between the two performance indices is clarified by numerical analysis and the key parameters for possible de-coupling are revealed, including damping ratio, electromagnetic coupling coefficient, load resistance and external excitation.

Piezoelectric metasurfaces have been investigated as means of introducing remarkable methods of vibration mitigation and control; including energy harvesting, mode localization, vibration absorption, and elastic waveguiding. The full-scale realization of such devices remains a considerable challenge, however, due to the high precision required in the synthesis and calibration of the electrical shunts in the presence of parametric and practical uncertainties. This paper establishes a systematic methodology for assessing the susceptibility of resonant piezoelectric waveguides to variations in local properties. An analytical procedure based on the transfer matrix approach and phase gradient design is applied to calibrate the metasurface for anomalous elastic-wave refraction at a specified target angle. Numerical simulations demonstrate good agreement with the initial design, and subsequently enable local LC-resonances, parasitic resistances, and piezoelectric coupling to be individually perturbed. An experimentally based uncertainty quantification is applied to determine reasonable bounds of uncertainty in these parameters, which is applied to a Sobol sensitivity analysis leveraging the finite element model. This approach is used to rank and compare the cumulative impact of spatially distributed uncertainty on the realized refraction angle. The findings identify local resonance and piezoelectric coupling as the most influential parameters, facilitating a practical understanding of piezoelectric waveguide performance while forming the basis for subsequent advancement in uncertainty assessment and testbed implementation.

In order to obtain the optimal PVDF piezoelectric fiber film to enhance its piezoelectric properties, PVDF was used as solute, N–N dimethylformamide (DMF) and acetone were used as solvents, and the electrospinning process parameters and electrode corona were optimized. Based on the control variable method, the effects of solvent ratio (volume ratio of DMF to acetone), solution concentration, spinning voltage, solution injection speed and receiving drum speed on the performance of PVDF piezoelectric fiber membrane were studied and analyzed. The characterization results of the viscosity of PVDF solution, the microstructure of PVDF piezoelectric fiber membrane, the content of crystal phase, the piezoelectric constant, the tensile strength and the dielectric constant after silver electrode were measured. The optimal preparation process parameters of PVDF piezoelectric membrane were obtained: solvent ratio 6:4, solution concentration 15%, spinning voltage 21.5 kV, solution injection speed 0.04 mm/min and receiving drum speed 1800 rpm.

This study explores the design of an intelligent bearing and its capacity for self-powered operation. Leveraging the dual functionalities of piezoelectric transducers for both monitoring the health of the bearing and harnessing energy from bearing internal strain, this study focuses on utilizing the dynamic strain energy from the bearing and evaluating the potential for energy generation. The ball bearing is nested in a piezoelectric transducer ring with different electrode sections to form a smart structure. The underlying hypothesis posits that, as the bearing ball passes through the designated cut section of the piezoelectric transducer, it can harness the dynamic strain energy from the rotation of the bearing and utilize the energy to charge a capacitor. Three configurations of piezoelectric transducers with different cutting section areas have been tested in the experimental studies under different conditions of rotating speed and transverse load. Remarkably, the outcomes manifest as a peak DC output of 0.8 V, coupled with a root mean square (RMS) power of 43.979 μW within a 128-s operation. Beyond the implication for self-powering in the present study, this intelligent structure signifies the potential to achieve concurrent self-powering and condition monitoring by employing distinct cutting sections of the piezoelectric ring and machine learning algorithm.

This paper studies the dynamics of a transient-motion piezoelectric energy harvester (TM-PEH) with a piezoelectric beam and two magnets. We first established the governing equations based on dynamic theories and the dipole–dipole model. Subsequently, an equivalent circuit model (ECM) of the TM-PEH is built based on electromechanical analogies to analyze the effects of various system parameters on the performance of this TM-PEH. Particularly, a decoupling phenomenon is observed when the mover’s speed exceeds a threshold, referred to as the decoupling velocity. Once the speed rises over it, the efficiency of the TM-PEH will decrease. Moreover, we utilized a self-powered synchronous electric charge extraction (SP-SECE) circuit to further improve the efficiency of the TM-PEH. Our analysis revealed that with the increase of the mover speed, using the SP-SECE can help harness more energy during the plucking motion. However, if the mover speed is below a threshold, the SP-SECE circuit will deteriorate the performance of the TM-PEH. The above results indicate that any TM-PEH design has an optimal applicable speed range. Following the analysis procedures presented in this paper, one can accurately identify and optimize the optimal speed range of a given TM-PEH design.

This paper presents a piezoelectric energy harvesting interface circuit that utilizes a Synchronous Switch Harvesting on Inductor Capacitor (SSHIC) circuit as the buck-boost module, based on one inductor and four capacitors, and replaces the traditional interface circuit's Fixed-Bias Rectifier (FBR) with a preceding switch array. The size of the inductor used is reduced from the traditional circuit’s 100–5 μH, and the total capacitance is reduced to equal the parasitic capacitance of the PEH (CP). This paper analyzes the advantages of the SSHIC buck-boost structure over the SSHI and SSHC in terms of flipping efficiency and proposes an SSHIC buck-boost circuit that divides the flipping phase into the currently highest nine phases, achieving up to 93.5% flipping efficiency and an output power of 35.12 μW. It presents an efficient solution when large inductors cannot be used.

This study presents a pioneering design of a single-layer graphene nano-resonance band. A high-frequency nano-electromechanical resonator is nonlinearly modeled, facilitating precise tuning of the resonant frequency comb within the nano-resonant band by adjusting the back-gate voltage—a novel approach. Graphene nano-resonators are characterized by etching a strip cavity on a silicon substrate, transferring a single layer of graphene to create a double-ended fixed beam structure, and achieving coordinated driving through back-gate electrodes. The resonator's dynamic equation, based on Euler-Bernoulli beam theory, adjusts the resonant frequency by manipulating membrane tension through electrostatic forces generated by a back-gate. Utilizing alternating current, high-frequency vibration is achieved, enabling the realization of 1:2 modal frequency matching. The study calculates the back-gate voltage threshold and frequency range of the frequency comb using Floquet theory, providing clarity on structural design requirements and external excitation conditions for the frequency comb. This research significantly advances our understanding of nano-resonant bands and contributes to broader applications, shaping the landscape of scientific exploration and technological innovation.

In this paper, a multiple traces sensing scheme with a single output channel via a weakly coupled cantilever array is proposed. An analytical model of the resonator using the Euler-Bernoulli beam theory has been developed and the dynamic behavior has been further explored using the Galerkin method. We have discovered numerically that, in the weakly coupled cantilever array, the Amplitude-frequency (A–f) curve of any cantilever physically reflects the vibration features of other cantilevers. Hence, by measuring the output signal of a single cantilever, multiple traces applied on each cantilever respectively can be identified and detected synchronously. A single output channel via a weakly coupled resonator array is constructed and validated through simulations and experiments. Equivalent experiments have been further conducted for verification. Experimental results indicated that the five analytes applied on each cantilever can be detected synchronously and independently by measuring the frequency shifts of the five resonant peaks of the center cantilever. Multiple traces sensing with a single output channel is thus realized. By enhancing the driving voltage, the mass resolution can also be improved via nonlinear vibration. This work reveals a new coupled vibration phenomenon and provides a new avenue for multiple analytes detection.

In this paper, we present a novel gas sensing mechanism leveraging mode localization and adsorption expansion to achieve high-sensitivity detection of low-concentration gases. Unlike traditional resonant structures, our approach amplifies the frequency shift through the combined effects of changes in the sensing beam's mass and stiffness. Furthermore, by utilizing mode localization, the frequency shift is converted into modal amplitude variation, providing a second stage of sensitivity amplification. We derive the dynamics of the coupled resonator mode and perform MATLAB simulations to validate our approach. Theoretical results indicate that a higher absorption-expansion coefficient of the functional film leads to greater sensitivity amplification. These findings are corroborated by equivalent experimental results. Experimental analysis proves a striking sensitivity amplification, with the amplitude ratio sensitivity exhibiting a 20-fold increase over the relative frequency change sensitivity. Subsequent to the sensitivity enhancement in preliminary, our ongoing research endeavors are poised to focus on the design and production of tangible microelectromechanical system (MEMS) sensors, with an intensified emphasis on the refinement of absorption-expansion sensing technology. These sensors are anticipated to hold immense potential for diverse industrial applications necessitating precise and discerning detection capabilities.

Human-machine interaction is an important aspect of exchanging information between the virtual reality world and the physical world. Haptic information interaction enables users to have immersive and efficient interactions, enhancing the overall experience. With the increasing number of tactile sensors and actuators in human-machine interaction systems, there are new requirements for multifunctional integration, lightweight energy consumption, and portability of devices. This paper proposes a human-machine interaction interface based on multi-modal haptic sensing and feedback fusion devices. This human-machine interaction interface has the following functions: touch-slip sensation sensing based on triboelectric-piezoelectric hybrid effect, vibration feedback, and pneumatic pressure feedback. We apply this human-machine interaction interface to robot digital twin interaction control, providing users with a more realistic control experience through the integration of haptic sensing and feedback.

This paper presents the development of a water flow energy harvester (WFEH) designed to power smart water meters within residential piping systems. Utilizing the kinetic energy of flowing water, the device harnesses this energy and converts it into electricity via electromagnetic principles. The impeller's shape, quantity, and guide vane height at the inlet were simulated using computational fluid dynamics (CFD) software, comparing impeller rotational speeds under various simulation parameters to select the appropriate impeller configuration. Experimental data indicate that with an inlet water pressure of 0.12 MPa and an outlet pressure of 0.06 MPa, a single coil in the device generates a peak voltage of 3.6 V, with a peak power of 54.2 mW and a head loss of 6 m. The maximum head loss permitted in residential water pipes is 10 m. The energy generation module of the WFEH has been designed with a six-coil array, significantly enhancing its performance output. Theoretically, the output power of the WFEH is sufficient to meet the energy needs of smart water meters. Therefore, the WFEH holds potential for integration into urban water management systems, providing a stable energy supply for data collection and transmission, and contributing to the development of self-powered smart meters.

Bearing is a critical machine element whose fault-free health status is crucial to the reliable operation of the machine. In recent times, machine learning-based approaches of training models on huge amount of measured data are adopted to monitor the bearing health status. However, collecting a large number of complete fault samples in an industrial set-up is very expensive thereby fostering the need to introduce methods that have excellent classification and clustering performance without depending on an extensive amount of training data. To address this, a dynamic time warping (DTW)-based signal similarity measuring approach is proposed. In this paper, a reference signal corresponding to a particular bearing health class is generated, which is then warped by DTW on any test bearing signals to reveal the inherent similarity by calculating their cumulative distances. The distance measure is used to classify the bearing health. It is observed that DTW alone cannot obtain acceptable results when employed to handle complex bearing signals because of the presence of measurement noise and unwanted interfering components. An enhancement is proposed by integrating DTW-based similarity search with spectral kurtosis (SK)-based demodulation for enhanced classification. The proposed method is validated using the Case Western Reserve University (CWRU) bearing dataset.

In multilayered cement-based structures, the characteristics of ultrasonic waves are influenced by the laminar and meso-scale properties of the materials, leading to frequency dispersion effect. This phenomenon enables the utilization of surface wave dispersion energy (SWDE) to identify the damages in these structures. However, interpreting complex composite damages using SWDE in such structures is challenging. To address this, the potential of convolutional variational autoencoder (CVAE) in detecting complex composite damage in multilayered cement-based structures through SWDE is investigated in this work. Specifically, the finite difference method is employed to establish the model for the ultrasonic wave field in multilayered cement-based structures, incorporating the mesoscopic material properties. Subsequently, ultrasonic wave signals, indicative of different types of complex composite damages, are extracted and transformed into SWDE. Finally, the CVAE model, trained with these SWDE datasets, is employed for the identification of various damages. The results demonstrate that the proposed method is capable of effectively extracting and interpreting structural characteristics in the time, frequency, and spatial domains from SWDE, and is sensitive to changes in structural features due to invisible complex composite damages in multilayered cement-based structures. The effectiveness of the proposed method is validated by compared to other deep learning methods.