Electrical Resonance Frequency Research Articles

Bandgap Calculation and Experimental Analysis of Piezoelectric Phononic Crystals Based on Partial Differential Equations.

Focusing on the bending wave characteristic of plate-shell structures, this paper derives the complex band curve of piezoelectric phononic crystal based on the equilibrium differential equation in the plane stress state using COMSOL PDE 6.2. To ascertain the computational model's accuracy, the computed complex band curve is then cross-validated against real band curves obtained through coupling simulations. Utilizing this model, this paper investigates the impact of structural and electrical parameters on the bandgap range and the attenuation coefficient in the bandgap. Results indicate that the larger surface areas of the piezoelectric sheet correspond to lower center bands in the bandgap, while increased thickness widens the attenuation coefficient range with increased peak values. Furthermore, the influence of inductance on the bandgap conforms to the variation law of the electrical LC resonance frequency, and increased resistance widens the attenuation coefficient range albeit with decreased peak values. The incorporation of negative capacitance significantly expands the low-frequency bandgap range. Visualized through vibration transfer simulations, the vibration-damping ability of the piezoelectric phononic crystal is demonstrated. Experimentally, this paper finds that two propagation modes of bending waves (symmetric and anti-symmetric) result in variable voltage amplitudes, and the average vibration of the system decreases by 4-5 dB within the range of 1710-1990 Hz. The comparison between experimental and model-generated data confirms the accuracy of the attenuation coefficient calculation model. This convergence between experimental and computational results emphasizes the validity and usefulness of the proposed model, and this paper provides theoretical support for the application of piezoelectric phononic crystals in the field of plate-shell vibration reduction.

Flexural–torsional modal interaction in MEMS actuators initiated by minuscule asymmetry

AbstractAn efficient actuation technique for electrostatic MEMS actuators exploiting electro-mechanical-mechanical modal interactions is proposed. The flexural–torsional equations of motion are established, and we manifest that the initiation of a 2:1 autoparametric modal interaction between in-plane bending and torsional modes of the actuator that is supposed to be symmetrical with respect to its axis of rotation is contingent upon the presence of a quadratic stiffness term, which arises from the existence of non-zero first moments of area of the actual cross-section in prismatic microbeams. In order to efficiently reduce the AC voltage value required to reach the activation of the 2:1 mechanical modal interaction, the electrical resonant frequency is syntonized to half of the natural frequency of the in-plane bending mode. The results indicate that the amplitude of the in-plane motion saturates upon the initiation of an energy exchange between the bending and torsional motions. Through suitable tuning of the AC frequency, the amplitude of the in-plane motion is minimized, while the amplitude of the torsional motion, the indirectly excited mode, is maximized. Our results demonstrate that the actuator's torsional motion, when subjected to a 1:2:1 electro-flexural–torsional modal interactions, is triggered by applying a maximum voltage of 10 V, resulting in about 20 degrees rotational angle. Furthermore, prolific frequency combs are generated as a result of secondary Hopf bifurcations along the large-amplitude response branches, inducing quasi-periodicity in the MEMS dynamics.

Resonant Electro-Mechanical Coupling – A Possible Renewable Energy Source

This paper looks at a simple Electro-Mechanical System that is tuned to resonate with both mechanical and electrical resonance. The intention is to couple the system resonance such that the amplitude of the output voltage is increased. The basic setup consists of a forced Mass-Spring System consisting of a speaker driving a mass attached to a tension-spring. The mass is a Neodymium cylindrical magnet. The vertically driven system couples to a magnet coil which sits over the magnet. Thus, by induction a voltage is generated within the coil. The coil is connected in series with a set of electrolytic capacitors. The resulting Resistor-Capacitor-Inductor (RCL) circuit is so designed as to resonate. The idea behind this coupling is to increase the output voltage of the circuit, thereby creating a voltage supply that could be boosted via transformer action, if necessary. Noting that the resulting circuit provides a source of single-phase electricity, such a setup could be used to charge small electronic devices like cellphones and mobile earphone sets. Mechanical resonance is indicated by the erratic vibration of the speaker, spring and magnet system. Knowing the magnet mass and measured resonant frequency the approximate spring constant can be calculated. The resonant frequency is then used as the driving frequency for the electrical circuit consisting of the RCL components. Noting the electric circuit resonance frequency, the approximate capacitance needed can be calculated using the driving frequency and the inductance of the said magnet coil. Using the circuit capacitance and appropriate circuit resistance, the maximised quality factor is sought, therefore the objective of the electric circuit design is to maximise the output voltage. The power generated by the device was found to be less than ~1 W. This system can be optimized to deliver maximum power output at the required resonant frequency, by greatly increasing the coil turns, using closer tolerances between the moving magnet and the wound coil and/or using materials that would ensure added magnetic coupling. Such a system can be used as a possible source of renewable energy especially on reciprocating engines, where exciting forces are available.

Low-voltage dielectric elastomer actuators by electro-mechanical resonance syntonization

Generally, a serious practical limitation of dielectric elastomer (DE)-based capacitors is the need for high voltage supply (in the order of 1 kV) to activate them. High voltages require a power level that is currently challenging due to the limit in the operating range of existing function generators. These high voltages are also dangerous for humans, thereby overshadowing many applications of dielectric elastomers. The purpose of this work is to develop a new simple actuation technique to introduce low-voltage driven DE-based capacitors, in which the electrical resonant frequency is syntonized to the mechanical natural frequency by tuning the circuit inductance. This results in extensive voltage amplification across the DE capacitor. In turn, this leads the DE membrane to oscillate with a remarkable large motion using a small voltage which is of one-tenth the magnitude of the input voltage required to drive such systems in the absence of electro-mechanical (EM) resonance syntonization. The efficiency of the proposed approach is demonstrated in the context of nonlinear vibration analysis. The results show that the voltage amplitude across the DE capacitor is amplified substantially while the electrical mode is syntonized with the mechanical one, and as a result, the DE motion’s amplitude is at least two hundred times greater than that of the unmatched system. Furthermore, for unbiased AC voltages with large amplitudes, the electro-mechanical modal interaction causes the system to exhibit the formation of frequency combs in the frequency spectrum of the system’s response. The implementation of this method using a simple electrical circuit just requires adequate matching between the electrical and the mechanical natural frequencies that depends on the inductance value. Our proposal effectively eliminates the need for a high source voltage generator which has been the main limitation in designing DE-based capacitors.

A Study of Dielectric Effects on Resonance Frequency of a Spit Ring Shaped Inclusion

Resonator designs are central to the development of subwavelength unit structures of metasurfaces to create exotic and unique electromagnetic properties by modifying the host structure to tune impinging electromagnetic waves. The act of intentional control of propagating electromagnetic fields are actively being explored in wireless radio environment control for sixth generation (6G) and beyond. In this paper, we study the effect of dielectric properties on electric field distribution and resonance frequency of a circular split ring resonator (SRR). The subwavelength resonator structure is modelled and simulated using High Frequency Structure Simulation (HFSS) software. Rogers RO3003 and RO3210 were used at different thickness to study the field distribution and its effect on resonance frequency of the SSR. The results show a decrease in resonance frequency of 38.41% from RO3002 (lower relative permeability of 3) to RO3210 (higher relative permeability of 10.2). With change in Rogers RO3210 thickness from 1mm to 1.525mm, the resonance frequency has changed from 5.5GHz to 5.2313 GHz. This indicates that the material composition of the substrate and the physical dimension of the SRR unit cell affects the resonance frequency of the structure.   &nbsp

A nonlinear tunable piezoelectric resonant shunt using a bilinear component: theory and experiment

In this article, we propose a new concept for tuning a resonant piezoelectric shunt absorber thanks to the use of a nonsmooth electronic component. It consists in adding a voltage source in the resonant shunt circuit, which is a bilinear function of the voltage across the piezoelectric patch. The main advantage is the ability to change the electrical resonance frequency with the bilinear component gain, enabling a tuning as well as a possible reduction in the required inductance value. Furthermore, because of the intrinsic nonlinear nature of the bilinear component, a multi-harmonic response is at hand, leading to a nonlinear coupling between the mechanical and electrical modes. Two particular tunings between the electrical and the mechanical resonance frequencies are tested. The first one is one-to-one, for which the electrical resonance is tuned close to the mechanical one. It is proved to be similar to a classical linear resonant shunt, with the additional tuning ability. The second case consists in tuning the electrical circuit at half the mechanical resonance, leading to a two-to-one (2:1) internal resonance. The obtained response is also found to be similar to a classical resonant shunt near the main resonance. In either case, the shunt performances are analytically and numerically studied, leading to optimal values of the design parameters as well as an estimation of the amplitude reduction provided by the shunt. Finally, experimental validation is proposed, targeting the damping of the twisting mode of a hydrofoil structure, in which the bilinear component is realized with a diode.

High performance piezoelectric vibration energy harvesting by electrical resonant frequency tuning

Extending the frequency bandwidth (BW) of vibration energy harvesters (VEH) that power wireless sensor nodes is of scientific and industrial interest. In this aim, electrical methods to tune the resonant frequency of piezoelectric harvesters with strong electromechanical coupling coefficients have been developed. In this work, we provide guidelines for designing such strongly coupled VEH and present a broadband harvester with high normalized power density (NPD). Through an analytical model, we explain how the coupling coefficient and the quality factor of a cantilever can be jointly maximized, thereby maximizing the figure of merit . The proposed cantilever prototype made of PZN-5.5PT and aluminum offers one of the best coupling coefficients among the state-of-the-art (k 2= 49.8%) and a high quality factor (Qm = 140). Associated to an appropriate tunable electrical interface (short-circuit synchronous electric charge extraction (SECE) in our case), the prototype exhibits a NPD of 12.0 mW g−2 cm−3 and a frequency BW of 36.0% (56.5 Hz around 157 Hz) at 0.34 m s−2 with a tunable electrical interface: the short-circuit SECE. This represents the highest product NPW × BW from state of the art.

Study on Early-Age Elastic Modulus of FRC Using Electrical Resistivity and Resonance Frequency

The correlation between surface electrical resistivity and modulus of elasticity of fiber-reinforced concrete (FRC) was studied within early ages in this study as a novel nondestructive method for predicting the modulus of elasticity of FRC. In addition to the relationship of the two quantities, the influence of various discrete fibers such as glass, nylon, polypropylene, and steel on the early age properties of FRC was investigated. Twenty-one FRC mixes were designed and tested; including four fiber types, three different fiber volume fractions for each fiber type, and three different water-to-cement ratios for all the different mixes. The surface electrical resistivity meter and resonance testing gauge were used to measure each specimen’s surface electrical resistivity and modulus of elasticity. Early-age dynamic modulus of FRC may be predicted using the mechanical properties and dimension of the fiber, according to proposed mathematical calculations. Statistical analysis was performed on the experimental results and the results acquired by the proposed equations, to examine and proof the accuracy of the proposed equations. The acceptable coefficient of variation of 5–9 percent confirmed the good agreement between the measured and predicted values.

Application of the meta-substrates for power amplification in rotary piezoelectric energy harvesting systems: Design, fabrication and testing

In this paper we numerically and experimentally investigate a new proposal of utilizing the auxetic meta-structure concepts to enhance the efficiency of piezoelectric energy harvesters in rotating systems. The proposed energy harvester is designed to be installed on the freight train axel to provide necessary power for the self-powered sensors. The harvester is a resonator consists of a cantilever beam with a tip mass and a piezoelectric patch mounted on its latticed substrate. Three various auxetic patterns are suggested and implemented on the base of the cantilever in order to enhance the harvested powers. The efficiency enhancement of the suggested concepts is compared with a conventional plain resonator. In order to optimize the geometrical parameters of the auxetic patterns and investigate the efficiency of various resonator’s output power, the finite element modeling (FEM) is employed. Maximum output powers according to the optimum electrical resistance and resonance frequency are achieved. Also, the effects of different PZT types on the extracted energy are taken into investigation. Two different substrate materials (aluminum and steel) are used in the fabrication of resonators. The​ numerical models are validated by experimental results in the rotating speed at the range of 6–7 Hz, which is tuned to the operational rotational frequency of the freight train axles. It is shown that for Auxetic-I, Auxetic-II, and Auxetic-III, the magnification factors are 3.28, 2.5, and 2.14 are achieved for the aluminum substrate. These factors are 3.0, 2.6, and 2.3 for the steel resonator, respectively. The experimental results show that the auxetic resonators are able to considerably enhance the efficiency of rotary energy harvesting systems.

Modal-based synthesis of passive electrical networks for multimodal piezoelectric damping

This work presents a new approach to design an electrical network which, when coupled to a structure through an array of piezoelectric transducers, provides multimodal vibration mitigation. The characteristics of the network are specified in terms of modal properties. On the one hand, the electrical resonance frequencies are chosen to be close to those of the targeted set of structural modes. On the other hand, the electrical mode shapes are selected to maximize the electromechanical coupling between the mechanical and electrical modes while guaranteeing the passivity of the network. The effectiveness of this modal-based synthesis is demonstrated using a free–free beam and a fully clamped plate.

Operating Characteristic Analysis and Verification of Short-Stroke Linear Oscillating Actuators Considering Mechanical Load

Linear oscillating machines are electric devices that reciprocate at a specific frequency and at a specific stroke. Because of their linear motion, they are used in special applications, such as refrigerators for home appliances and medical devices. In this paper, the structure and electromagnetic characteristics of these linear oscillating machines are investigated, and the stroke is calculated according to voltage and motion equations. In addition, static and transient behavior analysis is performed, considering mechanical systems such as springs, damping systems, and mover mass. Furthermore, in this study, the magnetic force is analyzed, experiments are conducted according to the input power, and the current magnitude and stroke characteristics are analyzed according to the input frequency. Finally, the study confirmed that the most efficient operation is possible when the electrical resonance frequency matches the resonance frequency of the linear oscillating machines.

Predictability of concrete damage level by non-destructive test methods

Non-destructive methods have many advantages over traditional test methods, especially since it does not damage the specimen, it can be used multiple times on the same specimen. These advantages also provide a great benefit in terms of following the property development in concrete as the same specimens are used which eliminates the variations related to the specimens. In this study, it is aimed to determine the damaged amount of concrete produced with different binders by electrical bulk resistivity, resonance frequency, and ultrasonic pulse velocity methods. Firstly, concretes containing different binders were produced, and along with the mechanical properties, ultrasonic wave velocity, resonance frequency, and electrical resistivity values of the produced concrete were determined at the 7, 28, and 90 days. Besides, the specimens were subjected to gradually increase compressive loads and non-destructive methods were used to estimate the extent of damage on specimens. It was attempted to establish a relationship between the damage on concrete specimens and the results obtained by non-destructive methods. Consequently, the compressive strength, electrical resistivity, ultrasonic pulse velocity and resonance frequency values of all specimens increased with the advancing age. It was concluded that the resonant frequency method is more successful than other methods in estimating the amount of damage in concrete.

(Invited) Multi-Modal Nanowire Sensors Using Electrical Resonance Approach

There is an ever increasing demand for nanosensors with enhanced characteristics such as miniature size, low power consumption, higher sensitivity and selectivity, ease of manufacturing, decreased cost, simultaneous detection of multi-analytes, etc. As a result, the area of nanoscale sensing remains an area of rich opportunity to develop new ideas for immediate applications ranging from health and environmental monitoring to military and homeland defense. Therefore, these sensor technologies have great potential to revolutionize science and to influence major economic, agricultural, environmental, social, and health issues. Recent advances in our understanding of 1-D nanomaterials are paving the way for developing novel platforms for sensors and devices based on multi-physics, multi-modal approaches. Optically induced surface state (or defect states) population-depopulation in nanomaterials with extremely small thermal mass changes its electrical resonance and serves as a bridge to nano-world for developing next-generation, miniature spectrometers and molecular sensors with unprecedented selectivity and sensitivity. Modulating the defect state population in wide bandgap materials using optically-induced thermal pathways offers a new approach for designing advanced sensors and devices based on nanowire resonators with extremely low thermal mass. Resonant excitation of molecules adsorbed on these nanowires using tunable mid-infrared radiation heats the nanowires during the de-excitation process affecting the surface state population which can be sensitively monitored as changes in the dissipation at its electrical resonance frequency as a function of illumination wavelength and mimics the infrared absorption spectra of the physisorbed molecules offering excellent molecular selectivity. Since the mid-IR spectra are free of overtones (molecular fingerprint regime) and the spectrum of individual molecular species are linearly independent, this approach offers a new paradigm for chemical vapor sensing with high sensitivity and selectivity. Further, monitoring the dissipation variations at resonance as a function of temperature can provide information on thermally induced desorption and polarization or depolarization of adsorbed chemical species. The temperature response of the nanowire at resonance can be used to discriminate different vapors based on differential calorimetry due to a difference in the dipole moments.

Passive control of multiple structural resonances with piezoelectric vibration absorbers

A novel sequential tuning procedure for passive piezoelectric shunts targeting multiple structural modes is proposed in this work. The control authority on each targeted mode can be quantitatively chosen ab initio and is shown to be limited by passivity requirements, which highlights the fundamental limitations of multimodal piezoelectric shunts. Based on effective characteristics of the piezoelectric system around resonance, electrical damping ratios and resonance frequencies are derived using well-established single-mode formulae from the literature, thereby fully specifying the characteristics of the shunt impedance. The proposed approach is numerically verified and experimentally validated on piezoelectric beams by emulating the shunt with a digital vibration absorber.

Low‐frequency nanocomposite piezoelectric energy harvester with embedded zinc oxide nanowires

AbstractSweeping developments in microelectromechanical systems and low power electronics have pushed the need for piezoelectric energy harvesters (PEHs). Increasing environmental and biocompatibility issues have drawn interest in lead‐free piezoelectric materials. In this paper, cantilever‐type PEHs at centimeter scale have been proposed to harvest the energies of low‐frequency vibrations caused by a human's movements. The proposed PEHs are made of a passive PDMS substrate sandwiched between two active nanocomposite layers with embedded piezoelectric zinc oxide (ZnO) nanowires. Moreover, two different morphologies including PEHs with constant and tapered thicknesses have been considered. The material properties of such piezoelectric nanocomposites are calculated by an electromechanical model. Afterward, these novel PEHs have been developed in COMSOL Multiphysics and their static and dynamic performances have been investigated. The static study shows that tapered PEHs endures lower stresses. However, the dynamic study discloses that the rectangular design outperforms the tapered one in electrical power and resonance frequency. It is found that the rectangular design can produce 4.1623 μW at the resonant frequency of 25.8 Hz.

Magnetic dipole absorption of light at intersubband transitions in quantum wells

We consider theoretically the magnetic dipole mechanism of IR-light absorption at intersubband transitions in wide-gap quantum wells (QWs). In contrast to the electric dipole resonance, the discussed mechanism manifests in the interaction with the s-polarized component of electromagnetic radiation. We demonstrated that (a) the frequencies of magnetic and electric dipole intersubband transitions in the 2D layer are equal in the framework of one-particle approximation; (b) collective plasma effects should lead to a significant frequency shift between the magnetic and electric dipole resonances in a typical QW. Consequently, independent measurements of the magnetic and electric dipole resonant frequencies could allow both the extraction of the QW parameters and the experimental verification of theoretical models of collective fermion interaction. Taking into account the relative weakness of the magnetic dipole absorption, we propose a waveguide scheme for its experimental observation.

Parametric Investigation and Analysis of an Electric-LC Resonator by Using LC Circuit Model

Electric-LC resonators (ELCs) metamaterials, as a kind of common structures, have been extensively investigated from microwave to terahertz frequencies. In this paper, we present a LC circuit model to analyze electric-LC resonator. With the reliable and closed formulas of the effective inductance and capacitance, the expressions of electric and magnetic resonance frequencies were obtained, which is suitable to discuss the resonance characteristic under the normal incidence case. Meanwhile, the mutual relationships among the permittivity, permeability, refractive index, and structure parameters can be explored by using the obtained expressions. Numerical simulations and theoretical calculations reveal that the width and length of the gaps are some of the critical parameters determining the resonator frequency of the example metamaterial. This study provides valuable information for designing the desired left-hand metamaterial at some specific frequency points.

A Numerical and Experimental Study of a Low-Loss Wideband E-Shaped Meta-Atom for LHM Characteristics

A planar left-handed metamaterial (LHM) based on E-shaped resonator (ESR) configuration is demonstrated, which provides a methodology in designing loss wideband negative-refractive-index (NRI) materials. When a plane wave propagates perpendicularly toward the ESR metamaterial (MTM) layer, a left-handed (LH) transmission passband is realised from a frequency band of 4.31 GHz to 5.24 GHz, where both effective permittivity and effective permeability are negative. Numerical and experimental results predict a LH transmission band near 4.16-GHz resonance. The retrieval algorithm and dispersion characteristics confirm the double-negative (DNG) constitutive parameters and NRI passband. Simple expressions for the electric and magnetic resonance frequencies of an ESR MTM structure are also presented. CST Microwave Studio EM simulation was used to obtain the complex values of S-parameters data of the MTM unit cell and to examine E-field distribution. The implemented experimental results reveal that the proposed compact ESR MTM structure provides a wide left-handed transmission passband with small material losses and ease of fabrication, making the suggested ESR LHM a good candidate for radio-frequency (RF) and millimetre applications.

A temperature-controlled cryogen free cryostat integrated with transceiver-mode superconducting coil for high-resolution magnetic resonance imaging.

Small-sized High Temperature Superconducting (HTS) radiofrequency coils are used in a number of micro-magnetic resonance imaging applications and demonstrate a high detection sensitivity that improves the signal-to-noise ratio. However, the use of HTS coils could be limited by the rarity of cryostats that are suitable for the MR environment. This study presents a magnetic resonance (MR)-compatible and easily operated cryogen-free cryostat based on the pulse tube cryocooler technology for the cooling and monitoring of HTS coils below the temperature of liquid nitrogen. This cryostat features a real-time temperature control function that allows the precise frequency adjustment of the HTS coil. The influence of the temperature on the electrical properties, resonance frequency (f0), and quality factor (Q) of the HTS coil was investigated. Temperature control is obtained with an accuracy of over 0.55 K from 60 K to 86 K, and the sensitivity of the system, extracted from the frequency measurement from 60 K to 75 K, is of about 2 kHz/K, allowing a fine retuning (within few Hz, compared to 10 kHz bandwidth) in good agreement with experimental requirements. We demonstrated that the cryostat, which is mainly composed of non-magnetic materials, does not perturb the electromagnetic field in any way. MR images of a 10 × 10 × 15 mm3 liquid phantom were acquired using the HTS coil as a transceiver with a spatial resolution of 100 × 100 × 300 µm3 in less than 20 min under experimental conditions at 1.5 T.

Experimental researching of biological objects noninvasive passive acoustothermometry features

Experimental confirmation of the possibility of real-time measurement of the internal (deep) temperature of a biological object by thermal acoustic radiation with an accuracy of at least 0.2 °C using an acoustic thermometer implementing the modified zero modulation method is obtained. The model of a single-channel passive noninvasive focussed acoustic thermometer based on a plate piezoceramic electro-acoustic transducer, acoustic elliptical lens and blocks of two serial voltmeters is developed. Electronic switching of the output signals of the noise simulator and the equivalent circuit of the focused piezoelectric transducer is proposed, when resistance generates thermal noise with an intensity equal to the sum of intensities of acoustic radiation of the biological object and natural noise of the piezoelectric transducer. This circuitry solution made it possible to exclude the mechanical modulator (shutter) unit used in analogs from the acoustic thermometer circuit. When developing the original switching and detection unit, it was proposed to use the key mode of n-channel field-effect transistors to perform modulation of the input noise signal. Calculation of equivalent circuits of the piezoelectric electroacoustic transducer and noise simulator, which are connected circuits with a bandwidth in which the average noise voltage level is determined by the noise voltage at the electric resonance frequency of the piezoelectric element, is performed. The possibility of using the model of the single-channel passive noninvasive focussed acoustic thermometer, constructed according to the circuit implementing the modified zero modulation method, for measuring noise voltages in the range from 5 to 30 μV is proved. Since the process of manufacturing or operating a piezoceramic electroacoustic transducer may lead to a deviation of its parameters from theoretically calculated, a method is developed to measure the frequency response of the active and reactive components of electrical impedance. Using the proposed method, the assembly quality of the focused piezoelectric electro-acoustic transducer is monitored and the temperature dependence of electric noise voltage at the electrodes of the focused piezoelectric receiver is obtained.