Electromagnetic Transducer Research Articles

Sound to electric energy generating device

This paper presents the potential of an electromagnetic transducer device in a form of audio speaker that is used to capture sound waves to be converted into electricity. It is an interesting concept but less explored by researchers. The objective of the study is to measure the potential of electromagnetic transducer as a way to generate electricity. It deals with the creation of electricity through movement and magnetism. Sound waves can induce movement on the surface which in turn moves the transducer thus creating electricity. The source of sound was coming from an 8-inch subwoofer speaker with a frequency of 80 Hz that was held constant throughout the experiment. Furthermore, using simple linear regression analysis, the study showed that for every linear increase of sound intensity level and distance of the source, there is an exponential increase and an exponential decrease in the voltage root mean square (RMS) respectively. The functionality assessment of the device was statistically analyzed using completely randomized design. It was found that the energy level significantly increased as the sound intensity level increases given a fixed distance of 15 mm from the source. The device could generate enough energy to power small electronics such as light emitting diodes (LED), transistor and resistor.

Tuning of a shunted electromagnetic vibration absorber based on the maximisation of the electrical power dissipated

This paper investigates a local tuning approach for a shunted electromagnetic vibration absorber, which is based on the maximisation of the electrical power dissipated by the coil and shunt components. The study considers a simplified problem with a single-degree-of-freedom mechanical hosting system, which is excited by a white noise stochastic force. The hosting system is equipped with a coil-magnet seismic transducer, which is connected to a resistive-inductive shunt. The study examines the effectiveness of the shunted electromagnetic vibration absorber with respect to the following cost functions. Firstly, the reference cost function, which is based on the minimisation of the time-averaged kinetic energy of the hosting system. Secondly, the local cost functions, which are based on: the maximisation of the time-averaged vibration power absorbed by the shunted electromagnetic vibration absorber; the maximisation of the time-averaged mechanical power dissipated by the electromagnetic transducer and the maximisation of the time-averaged electrical power dissipated by the coil and the shunt. The study shows that, provided the transducer is lightly damped, the local cost function based on the maximisation of the electrical power dissipated by the coil and the shunt gives the same optimal tuning parameters than the reference cost function. Therefore, provided the electromagnetic transducer is properly designed, the shunt can be suitably tuned by maximising the time-averaged electrical power dissipated by the coil and shunt. This is a rather appealing practical solution since it can be implemented locally without the need of measuring the response of the hosting system and also it can be implemented in the shunt circuit without the need of extra sensors.

Design of a new type of omnidirectional shear-horizontal EMAT by the use of half-ring magnets and PCB technology

In this paper, an electromagnetic acoustic transducer (EMAT) for generating and receiving omnidirectional shear-horizontal (OSH) wave in aluminum plate is developed. The proposed OSH-EMAT consists of a specially designed printed circuit board (PCB) coil and a pair of half-ring magnets. Vertical oriented static magnetic field and the radial alternative eddy current are applied to excite the Lorentz force along the circumferential direction. A three-dimensional finite element model has been established to simulate the distributions of the static magnetic flux, the eddy current, and the exciting process of SH wave. Further experimental results show that the proposed electromagnetic ultrasonic transducer has good consistency in the performance of omnidirectional excitation and reception. The new OSH-EMAT design has the potential for many non-destructive testing applications owing to its low cost, acceptable accuracy and convenient processing and fabrication.

Vibration damping of an offshore wind turbine by optimally calibrated pendulum absorber with shunted electromagnetic transducer

This paper investigates the use of an augmented pendulum absorber for damping of tower vibrations in monopile-supported wind turbines. A shunted electromagnetic transducer is proposed to replace the classic viscous dashpot for pendulum absorbers, in order to improve performance and durability of the absorber. A series RCL (resistive-capacitative-inductive) network is designed as the supplemental shunt for the electromagnetic transducer, which together with the intrinsic resistive-inductive properties of the transducer coil results in an additional resonance. The system equations of motion are established, from which closed-form expressions for optimal calibration are derived using pole-placement. A fully-coupled 14-degree-of-freedom aero-hydro-servo-elastic wind turbine model is established to evaluate the pendulum absorber performance under realistic conditions by non-linear time-domain simulations. Both frequency- and time-domain results show that the calibration procedure results in an optimal absorber that outperforms the classic dashpot-based pendulum absorber with respect to vibration mitigation.

An electromagnetic/magnetoelectric transducer based on nonlinear RMSHI circuit for energy harvesting and sensing

Random mechanical switching harvester on inductor (RMSHI) circuits for voltage rectification present a promising approach to enable the use of low output voltages from electromagnetic transducers under weak vibration conditions. In this paper, an electromagnetic transducer, which is suitable for noisy environments and realizes a high energy income even under a boradband excitation is presented. The proof-of concept system is realized and functionally tested. Further, in order to characterize the behavior of the mechanical bistable switch relative to the applied vibration, a passive solution is proposed. It consists of the use of two magnetoelectric (ME) transducers added to the bistable structure. The proposed solution is investigated with different random vibration profiles and vibration frequency bandwidths. Results have shown that the performance of the electromagnetic transducer due to the bistable RMSHI solution and in presence of random kinetic sources, is significantly improved. Further, the mechanical power is passively evaluated relative to the output of the two ME transducers based on the commutation of the cantilever between the two ME transducers. The achieved results have a high potential for the development of an integrated energy harvesting solution from weak and random kinetic sources with sensing capabilities.

Passive Resonant Sensors: Trends and Future Prospects

Sensors based on “resonance phenomenon” span a broad spectrum of important current applications including detection of biological and chemical agents, and measurements of physical quantities. Resonance phenomena occur with all types of waves: electromagnetic, optic, and acoustic. This review reports about the most recent advances in the design and applications of resonant “passive” sensors, i.e. resonant sensors able to operate with a distant power source and/or able to communicate with a distant transceiver. The sensors considered in this review include acoustic, magnetoelastic, and electromagnetic transducers. They are presented through their relevant technological aspects and through they major advantages which include their integrability within embedded systems and/or systems requiring energy autonomy. Furthermore, the use of these resonant sensors is illustrated in a large variety of applications, ranging from environmental monitoring, structural health monitoring, food packaging monitoring, wearable or implanted sensors for the monitoring of physiological parameters in healthcare related applications, to IoT and future industry monitoring applications.

Computer simulation and full-scale measurements of the load flow in a functioning heating network

The article aims to identify patterns in the distribution of heating energy to consumers with a varying availability of regulation equipment under real conditions of a central heating network, as well as to compare the results of computer simulation with full-scale measurements. For computer simulation, well-known mathematical methods for calculating the load flow in hydraulic circuits were used. Experimental studies of the operation modes of heat supply systems were carried out using the data of the control and monitoring systems of thermal power plants using the Siemens Simatic PCS7 software, a Portaflow 300 ultrasonic flow meter, stationary electromagnetic flow transducers, verified and certified manometers and thermometers. The graphs of the actual hydrodynamic modes of the heating network under study were obtained at outdoor air temperatures from +8 to -37°C, as well as under abnormal conditions (temperature drop in the supply pipeline and pressure drop at the heating network input). It was proposed to use jointly the simulation by means of the JA_Net software and full-scale measurements of the thermohydraulic operating modes of a centralised heat supply system, whose consumers have a various degree of regulation equipment. It was shown that the proposed complex method of qualitative and quantitative assessment of the efficiency of district heating networks makes it possible to identify the features of control of their hydraulic modes when connecting new consumers with a varying degree of automation. According to the obtained characteristics of changes in the flow rate of the coolant in the consumers’ internal systems depending on the pressure drop at the tie-in point, the lack of response to emergency situations on part of the consumers whose heat supply systems are equipped with the means of qualitative and quantitative regulation of the heat load, is associated with the process of automatic adjustment of the degree of opening of flow controllers and control valves at individual points. In future work, we will develop guidelines for levelling the imbalance of the heating network under the conditions of uneven provision of facilities with automation equipment when implementing projects for the complex modernisation of heat consumers or connecting new facilities to existing heat supply networks.

Dual Resonator-Type Electromagnetic Energy Harvester for Structural Health Monitoring of Bridges

Abstract A dual resonator with electromagnetic transduction was developed to harvest bridge vibration energy at low acceleration and low frequency. The harvester had two cantilever beams: one to ca...

Frequency Up-Conversion Hybrid Energy Harvester Combining Piezoelectric and Electromagnetic Transduction Mechanisms

A hybrid energy harvester with frequency up-conversion structures is proposed. The harvester achieves a high power output by utilizing both piezoelectric and electromagnetic transduction mechanisms. The harvester comprises a flexible substrate and two (internal and external) cantilevers. The internal and external cantilevers used for piezoelectric and electromagnetic conversion, respectively, are arranged such that the piezoelectric internal cantilever can vibrate with a large displacement to produce high output power. We use a frequency up-conversion method to convert the bending of the harvester into the vibration of the structure so that the harvester can generate energy even from the mechanical motion with an extremely low frequency. Two harvester configurations are investigated to validate the effect of the relative positions of the coil and magnet on the output voltage of the harvester. The maximum power output of the hybrid harvester is 7.38 mW, with outputs of 1.35 and 6.03 mW for piezoelectric and electromagnetic conversion, respectively.

Design and Simulation of a Scalable Hybrid Energy Harvesting Device for Low Frequency Rotations

In this paper a design concept and a finite element analysis of a combined electromagnetic/piezoelectric scalable hybrid energy harvesting device is presented, which converts mechanical energy from low frequency rotations into electrical energy. The electromagnetic (EM) transducer comprises an electric coil and a permanent magnet which is moved by the changing gravitation force vector caused by the rotational movement. The piezoelectric (PE) transducer is based on a vibrational energy harvester excited through magnetic plugging, which is induced by the movement of the permanent magnet of the EM harvester. As the magnetic plugging mechanism acts as a frequency-up conversion the device can be used in a wide range of rotational frequencies. The performance of both transducers is evaluated by finite element simulations to estimate the output power.

An improved design of lamb wave EMAT for A0 wave generation and enhancement

A new structure of Lamb wave electromagnetic ultrasonic transducer (EMAT) is proposed in this work to suppress S0 mode Lamb wave (S0 wave) and enhance A0 mode lamb wave (A0 wave). The new EMAT consists of periodic magnet and meander-coil. Finite element models are established to analyze the static magnetic field and the excited ultrasonic signal. As a result, the local static magnetic field of the new EMAT is increased. S0 wave is suppressed obviously by new EMAT while A0 wave is enhanced significantly. Besides, the new EMAT structure is optimized. Finally, experiment has been performed on 2 mm thick aluminum. The experiment has verified that the amplitude of the A0 wave signal obtained by using new EMAT is increased by a factor of about 9.33. Besides, the experiment results have shown that the S0 wave obtained by using new EMAT is suppressed to be almost submerged in noise.

Heusler alloy-based heat engine using pyroelectric conversion for small-scale thermal energy harvesting

As an alternative to thermoelectric generators, heat engines show great interest thanks to their ability to convert temperature spatial gradient into time-domain temperature variations or vibrations. To this end, MultiPhysic Memory Alloys (MPMAs), combining shape memory characteristics with ferromagnetic properties, provide significant attractive characteristics such as sharp transition with reduced hysteresis as well as magnetic properties enabled by heating, thus allowing easier device development and implementation. In this study, we report the development of a heat engine for small-scale energy harvesting where the MPMA transfers its heat to a pyroelectric element that provides thermal to electrical energy conversion, yielding a more direct energy conversion path compared to conventional electromechanical heat engines. Furthermore, thermally decoupling the pyroelectric element from the MPMA allows a faster cooling of the latter, accounting for higher variation frequency. Compared to the use of electromagnetic transduction through a coil attached to the moving MPMA, this approach is shown to provide 3 to 9 times more power density (according to considered volume), with theoretical potential gains from 8 to 25 with the use of nonlinear electrical interfaces.

Simultaneous vibration reduction and energy harvesting of a nonlinear oscillator using a nonlinear electromagnetic vibration absorber-inerter

Recently, considerable attention has been given to electromagnetic resonant shunt tuned mass damper-inerters (ERS-TMDI) for simultaneous vibration mitigation and energy harvesting. The application of this design is already well-established for linear structures, however, it is not extensively explored for nonlinear structures. This work, for the first time, aims to achieve both vibration mitigation and energy harvesting for nonlinear oscillating structures using a single device. For this, a novel nonlinear electromagnetic resonant shunt tuned mass damper-inerter (NERS-TMDI) is proposed with two different configurations. The proposed NERS-TMDI is coupled to a nonlinear oscillator via linear and nonlinear springs. For the first configuration, the electromagnetic and the inerter devices are grounded on one side and connected to the nonlinear vibration absorber on the other side. In the second configuration, the electromagnetic device is placed between the nonlinear vibration absorber and the primary structure. The nonlinear governing equations of motion are solved analytically using the method of harmonic balance in conjunction with the fixed arc-length continuation method. The analytical approach is validated using numerical simulations. A detailed parametric analysis for both configurations is conducted to identify the key design parameters that render the best performance of the NERS-TMDI. The results show that the proposed NERS-TMDI configurations perform better than the existing approaches, including the nonlinear tuned mass damper (NTMD), and the ERS-TMDI, in terms of vibration control. The results also show that the first configuration of NERS-TMDI always performs better for simultaneous vibration mitigation and energy harvesting than the second configuration of NERS-TMDI. This implies that grounding the electromagnetic transducer extends the range of effectiveness of the NERS-TMDI. Further, a sensitivity analysis on the optimal Configuration-1 showed that the NERS-TMDI is robust to variations in nonlinear stiffness, but its performance degrades for variations in inertance, resistance, inductance, and capacitance. Additionally, a parametric study demonstrates that higher values of nonlinear stiffness, inertance, and resistance, and lower values of inductance and capacitance render an optimal design of the Configuration-1 of the NERS-TMDI for energy harvesting. The findings are very promising and open a horizon of future opportunities to optimize the design of the NERS-TMDI for superior performance.

Semi-active vibration control unit tuned to maximise electric power dissipation

This paper proposes a local approach for the on-line tuning of a semi-active vibration control unit, which is set to reduce the resonant response of target low-order flexural modes of distributed structures subject to broadband stochastic disturbances. The idea is to have multiple self-contained units, which can be fixed on thin walled structures to reduce flexural vibration and sound radiation at low audio frequencies where the dynamics of the structures is controlled by the resonant response of low-order flexural modes. The unit is formed by an electromagnetic seismic transducer connected to a resistive-inductive shunt. The proposed local tuning criterion is based on the maximisation of the time-averaged electrical power dissipated by the shunt. Both simulation and experimental results are presented for a setup where a unit is mounted on a thin plate model wall-structure excited by a broadband random force and is set to reduce the resonant response of target flexural modes. The paper investigates the physics of four tuning criteria with reference to the resonant response of the target flexural natural modes. First, the minimisation of the time-averaged total flexural kinetic energy of the plate; second, the maximisation of the time-averaged vibration power absorbed by the unit; third, the maximisation of the time-averaged mechanical power dissipated by the transducer and fourth, the maximisation of the time-averaged electrical power dissipated by the coil and shunt. The paper shows that, for small mechanical and Eddy currents damping effects of the transducer, the maximisation of the time-averaged electric power dissipated by the coil and shunt gives similar tuning parameters, and thus comparable vibration control effects, than the reference cost function based on the minimisation of the time-averaged total flexural kinetic energy of the plate.

On the Optimization of a Multimodal Electromagnetic Vibration Energy Harvester Using Mode Localization and Nonlinear Dynamics

In this paper we study a generic model of a nonlinear quasiperiodic vibration energy harvester (VEH) based on electromagnetic transduction. The proposed device consists of multiple moving magnets guided by elastic beams and coupled by repulsive magnetic forces. A system of two degrees-of-freedom (DOFs) with tunable nonlinearity and mode localization is experimentally validated. The validated 2-DOFs harvester is optimized using a multiobjective optimization procedure to improve its harvested power and frequency bandwidth. An efficient criterion using the modal kinetic energy of the finite element model is proposed to quantify the energy localized in the structure perturbed zones. Afterward, this concept has been generalized to a 5-DOFs VEH with two perturbed DOFs oscillators and the optimal performances are derived using a multiobjective optimization. This proposed model enables a significant increase in the harvested power and frequency bandwidth by 101% and 79%, respectively, compared to that of the 2-DOFs device. Moreover, it has been shown that harvesting energy from two perturbed magnets among five provides almost the same amount of harvested energy and enhances the frequency bandwidth by 18% compared to those of the periodic system. Consequently, the harvester can be improved by reducing the transduction circuits number and the manufacturing cost.

A novel nonlinear mechanical oscillator and its application in vibration isolation and energy harvesting

The nonlinear design of a new vibration structure is an essential part of the development of vibration isolation and energy harvesting technologies, and is one of the most effective technical means to improve the efficiency of low-frequency excitation. Due to structural constraints, high-efficiency vibration isolation and energy harvesting from ultra-low frequency or low intensity excitation has been a theoretical bottleneck and technical challenge in this field. In this study, this paper firstly proposes the theory and method of vibration isolation and energy harvesting based on the high-order quasi-zero stiffness (HQZS) mechanism, which is expected to break through the above bottleneck. Secondly, a detailed study of the HQZS oscillator with electromagnetic transduction under both stochastic and harmonic excitations is emphasized. The HQZS oscillator can not only achieve arbitrarily small stiffness near the equilibrium position through geometrically nonlinear parameter design, but also achieve vibration isolation or high-energy interwell oscillation under ultra-low frequency or low intensity excitations. Finally, compared with quad-stable and quasi-zero stiffness (QZS) systems, the results show that the HQZS oscillator has better vibration isolation and energy harvesting performance for ultra-lower stochastic excitation intensity or harmonic excitation frequency. Also, the initial isolation frequencies and maximum harvested power frequencies of the HQZS oscillator are lower than that of the QZS oscillator. The results will not only help to deepen the understanding of HQZS systems, but also provide new theoretical support and technical approaches for vibration isolation and energy harvesting under ultra-low frequency or low intensity excitation.

Evaluation Methodology of a Smart Clothing Biomechanical Energy Harvesting System for Mountain Rescuers.

The article presents a methodology developed for the evaluation of biomechanical energy harvesting systems that permits avoiding long-duration outdoor tests while providing realistic input signals and preserving uniform conditions across repeated tests. It consists of two stages: transducer output signal recording and power conversion and storage system measurements. The proposed approach was applied to assess the usefulness of a commercial electromagnetic transducer for supplying a Global Positioning System (GPS) receiver used as an active component of a smart clothing dedicated for mountain rescuers. Electrical power yield measurements have been presented together with ergonomic tests results. They all involved diverse physical activities performed by mountain rescuers that simulated their true operations, but were conducted in a training room for the sake of standardization. By providing reliable data on the transducer’s performance under realistic use conditions, the proposed evaluation procedure revealed that the true energy yield was much smaller not only with respect to the manufacturer’s assertions, but also substantially lower than what was expected based on an independent review which used unrealistic and non-uniform excitations. On the other hand, ergonomics ratings given by potential end users were very high, which demonstrates that the evaluated transducer can still be useful for supplying active cloth components with a lower power demand. The study also revealed that transducer location and orientation strongly affect its performance, which must be taken into account at the first stage of the evaluation procedure. Moreover, physical activity type and conditions (such as motion speed and ground tilt) influence the output power and should be carefully considered when composing a typical case scenario for the second stage.

Evaluation of Vibrant® Soundbridge™ positioning and results with laser doppler vibrometry and the finite element model.

The etiology of hearing loss originates from genetic factors and includes several other events including infections, working or living environment, as well as several endocrine and metabolic disorders. The Vibrant® Soundbridge™ (VSB) is an implantable hearing aid whose floating mass transducer (FMT) is attached to the long process of the incus. The device is used for pure sensorineural hearing loss with an intact middle ear. Variations in the manner of attachment may occur. Knowledge of the impact of such variations on the overall device performance may guide towards optimal transducer attachment during surgery. A mechanical modelling of the ear was first reported by von Békésy and indicated that the tympanic membrane (TM) moves as a stiff plate, and that the mallear and incudal ligaments act as a rotation axis for the ossicular chain at low frequencies. Experimental investigations and simulations with the model yield the same main results. The first fitting situation, where the FMT floats freely in the middle ear, provides by far the worst possible results. Contact to the stapes supra-structure of the FMT is necessary for optimal performance of the FMT. The mastoid specimen preserves its acoustic properties that have been shown to be similar to those in the vital human ear, under these conditions. Properly coupling the electromagnetic transducer to the ossicles can be difficult and it requires a certain degree of experience. A finite-element model (FEM) is useful for functional evaluation of the VSB since it enables easy modelling of the complicated middle ear structures and simulation of their dynamic behavior which makes it easy to understand it in detail without experiments.

Hardware-in-the-Loop Testing of an Electromagnetic Transducer With a Tuned Inerter for Vibratory Energy Harvesting

Abstract This paper assesses the vibratory energy harvesting performance of a tuned inertial mass electromagnetic transducer (TIMET) through hardware-in-the-loop (HIL) testing under random vibration. The TIMET has been developed by adding a tuning spring and an extra rotational inertial mass to a conventional electromagnetic transducer (ET) with a motor. The authors have already shown that the energy harvesting efficiency of the TIMET can be increased by taking advantage of the mechanical resonance effect of the rotational inertial mass due to the tuning spring through numerical simulation studies. In addition, further improvement in power generation of the TIMET can be achieved theoretically by controlling the current to the motor based on the appropriately developed algorithms. In this paper, the superiority of the TIMET over the ET under random disturbances when the current to the motor is controlled by the algorithms proposed for the ET in the literature is experimentally verified. Moreover, the accuracy of the numerical simulation using the developed device models is validated by comparing with the test results.

Energy harvesters for rotating systems: Modeling and performance analysis

Abstract An exclusive reliance on batteries for miniature sensors has created the need for a self-sustained energy harvester to enable permanent power. This work introduces a pendulum-based energy harvester that is capable of harnessing kinetic energy from rotating structures to generate electric power through electromagnetic transduction. A computational model of the energy harvesting device is developed on Simscape to compute, analyze and compare the power generation capacities of the single, double and Rott’s pendulum systems. Simulation results are validated against their experimental counterparts reported in the literature. Results show an increase in the output voltage in a specific range of rotational speed for all three pendulum harvesters. The double pendulum exhibits the highest power generation potential among the simulated pendulum arrangements. A parametric study revealed that increasing the damping of the harvester decreased its output power, whereas an increase in mass and length of the harvester is observed to increase the output power and shift the optimal power generation subrange.