Performance Of Vibration Energy Harvester Research Articles

FEA analysis and working performance of micro vibration energy harvester based on diamagnetic levitation

A micro vibration energy harvester, based on diamagnetic levitation, is presented in this paper. It consists of a lifting permanent magnet, an upper pyrolytic graphite sheet, a floating permanent magnet, a lower pyrolytic graphite sheet and a copper coil on the two pyrolytic graphite sheets respectively. The gravity of the floating permanent magnet is balanced by the attractive force between the lifting magnet and the floating magnet. The diamagnetic force exerted on the floating permanent magnet by the two pyrolytic graphite sheets works as restoring force, which makes the floating permanent magnet return to its equilibrium position. By Ansoft Maxwell, comparative analysis between the attractive magnetic force and the diamagnetic force was carried out, so as to obtain appropriate key parameters of the structure. The maximum range of movement for the floating permanent magnet is 1.3 mm. The first resonant frequency is 11.3 Hz, at which the output voltage of the energy harvester is 98.18 mV. By eliminating mechanical contact during its movement, the energy harvester improves the efficiency of vibration energy harvesting, and it can provide sustainable power for micro-electro-mechanical system (MEMS).

Performance of bistable piezoelectric cantilever vibration energy harvesters with an elastic support external magnet

Based on the research results of conventional rigid support nonlinear energy harvesters, in this paper we conceive a kind of structure with an elastic support external magnet with the intent to keep the system in the state of bistable oscillation, even under low-intensity excitation conditions. It has been proved that elastic support systems have better power output performance than rigid support systems when excited at low-intensity vibrations. In addition, elastic support nonlinear energy harvesters do not need real-time adjustment of the magnet interval towards the variable-intensity random excitation source, consequently achieving maximum power output and sufficient electromechanical energy conversion of the system.

On Mathematical Modeling of Piezoelectric Energy Harvesters

Energy harvesting system has become one of important areas of ​​research and develops rapidly. How to improve the performance of the piezoelectric vibration energy harvester is a key issue in engineering applications. There are many literature on piezoelectric energy harvesting. The paper places focus on summarizing these literature of mathematical modeling of piezoelectric energy harvesting, ranging from the linear to nonlinear, from early a single mechanical degree to piezoaeroelastic problems.

Enhancement of the performance of a hybrid nonlinear vibration energy harvester based on piezoelectric and electromagnetic transductions

A multiphysics model of a hybrid piezoelectric–electromagnetic vibration energy harvester (VEH), including the main sources of nonlinearities, is developed. The continuum problem is derived on the basis of the extended Hamilton principle, and the modal Galerkin decomposition method is used in order to obtain a reduced-order model consisting of a nonlinear Duffing equation of motion coupled with two transduction equations. The resulting system is solved analytically using the method of multiple time scales and numerically by means of the harmonic balance method coupled with the asymptotic numerical continuation technique. Closed-form expressions for the moving magnet critical amplitude and the critical load resistance are provided in order to allow evaluation of the linear dynamic range of the proposed device. Several numerical simulations have been performed to highlight the performance of the hybrid VEH. In particular, the power density and the frequency bandwidth can be boosted, by up to 60% and 29% respectively, compared to those for a VEH with pure magnetic levitation thanks to the nonlinear elastic guidance. Moreover, the hybrid transduction permits enhancement of the power density by up to 84%.

Energy Harvesting from Ambient Vibrations with Arbitrary In-Plane Motion Directions Using a Magnetostrictive/Piezoelectric Laminate Composite Transducer

A magnetoelectric (ME) vibration energy harvester has been designed to scavenge sufficient energy from ambient vibration with arbitrary motion directions in a plane and over a range of frequencies. In the harvester, a circular-cross-section cantilever rod is adopted to extract the vibration energy due to its ability to host accelerations in arbitrary in-plane motion directions. The magnetic coupling between the magnet and the ME transducer results in nonlinear oscillation of the cantilever rod with increased frequency bandwidth. To achieve optimal vibration energy harvesting performance, the effects of the nonlinear vibration and the harvester parameters including the magnetic circuit and the separation distance on the electrical output and the␣working bandwidth are analyzed. The experimental results show that the harvester can scavenge vibration energy in arbitrary in-plane directions, exhibiting a bandwidth of 4.0 Hz and maximum power of 0.22 mW at acceleration of 0.6g (with g = 9.8 m s−2).

Study on effects of the damping ratio on output performance of micro electromagnetic vibration energy harvesters

The damping ratio plays an important role in the energy acquisition and energy conversion of micro vibration energy harvester. The paper focused on damping effects of electromagnetic vibration energy harvesters and discussed the effects of the electrical damping/mechanical damping on the output performance of micro electromagnetic vibration energy harvesters. In our experiments, the damping effects on the output voltage, resonant frequency, power and efficiency of the vibration energy harvester were investigated. Both experiments and theoretical analysis suggest that the amplitude of output voltage increases firstly with electrical damping and then decreases slowly. Moreover, the increasing mechanical damping can reduce the efficiency of micro vibration energy harvesters.

22am2-E7 選択的電極配置によるスパイラル型振動発電素子の性能向上

In this study, we have improved the performance of a spiral vibration energy harvester by selective electrode placement. In our previous study, we had developed a spiral vibration energy harvester and evaluated its electrical property quantitatively. However, the electrical property of the previous device was insufficient for practical use. To improve the electrical property, we intended to optimize the electrode pattern of the spiral element. First, we simulated the distribution of electrical potential of the spiral element. From the result, we found an output voltage of the selective electrode was 12 times higher than that of selective electrode according to the charge distribution. In order to verify the analytical result, we carried out vibration tests using the spiral energy harvester with selective electrode placement and uniform electrode. As a result, it was demonstrated that the maximum output voltage of selective electrode was 2.5 times higher than that of uniform electrode.

Design and analysis of a 2D broadband vibration energy harvester for wireless sensors

This paper presents a design for a novel vibration energy harvester using a magnetoelectric (ME) transducer, which is efficiently applicable in two-dimensional (2D) motion and over a range of vibration frequencies. This harvester adopts a circular cross-section cantilever rod to extract the ambient vibration energy because of its ability to host accelerations in arbitrary motion directions. Moreover, the magnetic interactions between the magnets and the ME transducer will lead to the nonlinear oscillation of the rod with increased frequency bandwidth. The influences of the nonlinear vibration factor and magnetic field distribution on the electrical output and bandwidth of the harvester are investigated to achieve optimal vibration energy harvesting performances. The experimental results showed that, the harvester was sensitive to the vibration with arbitrary in-plane directions. With an acceleration of 0.6g (where g=9.8ms−2), it had the working bandwidths of 4.2Hz, 2.6Hz, 2.3Hz, 2.5Hz and 3.2Hz, and the output powers of 0.6mW, 0.49mW, 0.33mW, 0.5mW and 0.56mW at the in-plane excitation angles of−90°, −45°, 0°, 45° and 90°, respectively.

외팔보 압전 진동 에너지 수확 장치의 직류 전기 출력 해석을 위한 전용 알고리즘 개발

For most applications of the vibration energy harvesting technology as in wireless sensor networks for smart buildings and plants, the evaluation of DC output performance of vibration energy harvesters is typically required. However, there is no dedicated algorithm for the evaluation. The lack of a dedicated algorithm results from difficulties in the direct incorporation of nonlinear rectifying and regulating circuitry into finite element models of piezoelectric vibration energy harvesters. In this study, we develop a dedicated algorithm and present software based on it for the evaluation of not only AC but also DC electrical quantities. Here, an equivalent electrical circuit model is employed. The COMSOL multiphysics simulation tool is adopted for extracting equivalent electrical circuit parameters of a piezoelectric vibration energy harvester and MATLAB is used to make a graphical user interface. The AC voltage and power outputs calculated by the proposed algorithm under various conditions are compared with those by a traditional finite element analysis. The DC output voltage and power through a rectifier are obtained for varying values of smoothing capacitance and external resistance.

Improving functionality of vibration energy harvesters using magnets

In recent years, several strategies have been proposed to improve the functionality of energy harvesters under broadband vibrations, but they only improve the efficiency of energy harvesting under limited conditions. In this work, a comprehensive experimental study is conducted to investigate the use of magnets for improving the functionality of energy harvesters under various vibration scenarios. First, the nonlinearities introduced by magnets are exploited to improve the performance of vibration energy harvesting. Both monostable and bistable configurations are investigated under sinusoidal and random vibrations with various excitation levels. The optimal nonlinear configuration (in terms of distance between magnets) is determined to be near the monostable-to-bistable transition region. Results show that both monostable and bistable nonlinear configurations can significantly outperform the linear harvester near this transition region. Second, for ultra-low-frequency vibration scenarios such as wave heave motions, a frequency up-conversion mechanism using magnets is proposed. By parametric study, the repulsive configuration of magnets is found preferable in the frequency up-conversion technique, which is efficient and insensitive to various wave conditions when the magnets are placed sufficiently close. These findings could serve as useful design guidelines when nonlinearity or frequency up-conversion techniques are employed to improve the functionality of vibration energy harvesters.

An experimental study on self-powered vibration control and monitoring system using electromagnetic TMD and wireless sensors

This paper proposed and validated a self-powered vibration control and monitoring (SVCM) system which consists of a pendulum-type tuned mass damper (TMD), a rotary electromagnetic (EM) device, an energy harvesting circuit (EHC) and a wireless smart sensor (WSS). As the key element in the system, the regenerative electromagnetic TMD (EMTMD) is able to convert vibration energy of structures to electrical energy, and thus plays dual functions, namely, vibration mitigation and energy harvesting. With the aid of EHC, the electrical energy can be further stored and used to power WSS that closely monitor structural vibration responses. The feasibility of the proposed SVCM system was validated via shaking table tests, in which a single-degree-of-freedom (SDOF) structural model equipped with the SVCM system was tested under random excitations. The functionality of the SVCM system was discussed with regard to the vibration control, energy harvesting and vibration monitoring performance. The experimental results revealed that the proposed regenerative EMTMD device can provide regenerative and economical power to WSS. The harvested power reaches about 312.4mW under random ground motions with root-mean-square (RMS) acceleration equal to 0.05g. Meanwhile, the comparison shows that the peak magnitude of the frequency response function of structural displacement is reduced by 10dB with the aid of the EMTMD. This study demonstrates that the SVCM system provides a novel and promising solution to the power supply problem associated with wireless sensing technology, and will stimulate the integration of vibration control and monitoring system.

Design and characterization of miniature piezoelectric generators with low resonant frequency

In this study, both materials selection and device configuration design were considered for developing miniature piezoelectric generators with low resonant frequency. Instead of single crystal Si, stainless steel (SUS) was chosen as the substrate of AlN thin films owing to its higher fracture toughness, which made it possible that millimeter-scale generators had resonant frequency of less than 100Hz. The device configuration including the aspect ratio (the length of the cantilever to the width of the cantilever) and the thickness ratio (the substrate layer to the AlN film layer) were analyzed for optimizing transverse electromechanical coupling coefficient of generators. Using AlN thin films deposited on stainless steel, millimeter-scale generators were fabricated and their vibration energy harvesting performance was characterized. Output power and resonant frequency of the devices are, respectively, 5.130μW and 69.8Hz when they were vibrated at 1g acceleration and connected with 0.7MΩ electric loading.

Performance of Linear Vibration Energy Harvesters under Broadband Vibrations with Multiple Frequency Peaks

This paper studies the performance of linear Vibration Energy Harvesters (VEH) under broadband vibrations with multiple frequency peaks. The output power of both electromagnetic and piezoelectric linear VEH is determined when excited by a single frequency excitation and when excited by two frequency peaks, one at resonance and the other at a different frequency (defined as the interference frequency). Experimentally, it was found that when a linear VEH is excited by two-peak vibrations, its output power is lower than in the case of the single frequency excitation. Furthermore, the larger the amplitude at the interference frequencies, the lower the output power of the VEH. Also, for the same interference peak amplitudes, the further the interference frequency is from the resonant frequency, the lower the output power is. These results suggest that when designing a linear VEH for multiple-peak broadband vibrations, the VEH should be matched to the lowest peak frequency and that pure sinusoidal excitation should be avoided when laboratory testing VEH for use in applications with multiple frequencies.

215 圧電コンポジットを利用した振動発電装置のエネルギー変換効率の評価(セッション8 エナジーハーベスティングと評価システム技術)

In the previous authors' study, the vibration energy harvester of the piezoelectric bimorph cantilever type was proposed for vibration condition monitoring applications of rotating machinery. Authors assumed that the typical casing or pedestal vibration amplitude of the rotating machinery was 0.71 mm/sec rms and this low intensity excitation condition was the input for experimental evaluation of the voltage generation performance of the piezocomposite vibration energy harvester. Proposed energy harvester consists of the surface bonded two Macro-Fiber Composites (MFCs). In this study, energy transfer efficiency was derived from the system energy balance during the natural period of the proposed vibration energy harvester. Energy balance equations were successfully obtained from the governing equations of the piezoelectrically coupled electro-mechanical system. In this study, the two types of cantilever, milling plate and thin plate, were used for evaluating the effect of the mechanical damping property of the clamped end. The maximum AC power of milling plate through 51.0 Kilo-Ohm resistor which includes instrument internal resistances experimentally obtained 408.8 microwatt at the resonant frequency of the harvester (58.40 Hz). The impedance matching between MFCs and the electrical resistive load was effective for maximizing AC power transfer of the vibration energy harvester. Estimated energy transfer from mechanical system to electrical system shows the agreement with the experimentally evaluated generating power during the natural period of the vibration energy harvester with about 3 (%) difference. Estimated energy transfer efficiency was about 30 % for different excitation magnitudes: 0.71, 0.568, and 0.355 mm/sec rms.

A New Vibration Energy Harvester Using Magnetoelectric Transducer

Magnetoelectric (ME) transducers were originally intended for magnetic field sensors but have recently been used in vibration energy harvesting. In this paper, a new broadband vibration energy harvester has been designed and fabricated to be efficiently applicable over a range of source frequencies, which consists of two cantilever beams, two magnetoelectric (ME) transducers and a magnetic circuit. The effects of the structure parameters, such as the non-linear magnetic forces of the ME transducers and the magnetic field distribution of the magnetic circuit, are analyzed for achieving the optimal vibration energy harvesting performances. A prototype is fabricated and tested, and the experimental results on the performances show that the harvester has bandwidths of 5.6 Hz, and a maximum power of 0.25 mW under an acceleration of 0.2 g (with g = 9.8 ms 2 ).

Temperature effects on output power of piezoelectric vibration energy harvesters

The performance of piezoelectric vibration energy harvesters was studied as a function of environment temperature. The devices fabricated by soft or hard PZTs were used to investigate the effect of material parameters on the thermal degradation of the devices. PZT MEMS device was also prepared and compared with the bulk devices to investigate scaling effect on the thermal degradation. All devices were heated up to 150°C in an insulating chamber. Output power was estimated by Roundy’s equivalent circuit model and compared with experimental data. The output power of all devices decreased with the increase of the temperature. The output power as a function of temperature can be predicted by the change of piezoelectric coupling coefficient that is proportional to piezoelectric constant and inverse of square root of dielectric constant. Such combined influence on the output power leads to a lower thermal degradation rate of the soft PZT-based device at a lower temperature. For MEMS scale device based on PZT films, temperature dependence of the output power was reduced. This result can be attributed to decreased temperature dependence of dielectric and piezoelectric constants mainly due to constrained domain motions.

DESIGN, MODELING, AND PERFORMANCE MEASUREMENTS OF A BROADBAND VIBRATION ENERGY HARVESTER USING A MAGNETOELECTRIC TRANSDUCER

This article presents a new broadband vibration energy harvester using a magnetoelectric (ME) transducer. In order for vibration energy harvesters to be efficiently applicable over a range of vibration frequencies, many techniques have recently been investigated to broaden the frequency ranges of the harvesters using piezoelectric, electromagnetic, or electrostatic transductions, but few have been studied in the harvesters using ME transducers. In this article, a new harvester using a ME transducer is proposed, which takes advantage of multi-cantilever beams and nonlinear behavior of the magnetic force to expand the working bandwidth in ambient low frequency vibration. A theoretical model is developed to analyze the nonlinear vibration of the harvester, and the effects of the structure parameters on the electrical output and the bandwidth of the harvester are analyzed to achieve the optimal vibration energy harvesting performances. The experimental results on the performances show that the harvester has bandwidths of 5.2 Hz, 6.3 Hz, and 7.2 Hz, and the maximum output power values of 0.21 mW, 0.6 mW, and 1.03 mW at the accelerations of 0.2 g, 0.4 g, and 0.6 g (with g = 9.8 ms−2), respectively.

A magnetoelectric-based broadband vibration energy harvester for powering wireless sensors

Scavenging vibration energy directly from environments is an attractive technique for potentially powering small and/or wireless electronic devices in a smart structure and system. In this paper, a novel broadband vibration energy harvester is designed and analyzed, which consists of three cantilever beams, two magnetoelectric (ME) transducers and a magnetic circuit. A theoretical model is developed to analyze the effects of the structure parameters on the frequency response and the electrical output for achieving the optimal vibration energy harvesting performances. A prototype is fabricated and tested. The experimental results show that the harvester has a bandwidth of 7.2 Hz and an average power of 0.21 mW at an acceleration of 0.2 g (with g=9.8 ms−2).

Modeling and experimental verification of proof mass effects on vibration energy harvesterperformance

An electromechanically coupled model for a cantilevered piezoelectric energy harvester witha proof mass is presented. Proof masses are essential in microscale devices to move deviceresonances towards optimal frequency points for harvesting. Such devices with proofmasses have not been rigorously modeled previously; instead, lumped mass orconcentrated point masses at arbitrary points on the beam have been used. Thus, thiswork focuses on the exact vibration analysis of cantilevered energy harvesterdevices including a tip proof mass. The model is based not only on a detailedmodal analysis, but also on a thorough investigation of damping ratios that cansignificantly affect device performance. A model with multiple degrees of freedom isdeveloped and then reduced to a single-mode model, yielding convenient closed-formnormalized predictions of device performance. In order to verify the analyticalmodel, experimental tests are undertaken on a macroscale, symmetric, bimorph,piezoelectric energy harvester with proof masses of different geometries. The modelaccurately captures all aspects of the measured response, including the location ofpeak-power operating points at resonance and anti-resonance, and trends such as thedependence of the maximal power harvested on the frequency. It is observed that even asmall change in proof mass geometry results in a substantial change of deviceperformance due not only to the frequency shift, but also to the effect on thestrain distribution along the device length. Future work will include the optimaldesign of devices for various applications, and quantification of the importanceof nonlinearities (structural and piezoelectric coupling) for device performance.

Methods for Multimodal Vibration Suppression and Energy Harvesting Using Piezoelectric Actuators

This paper presents a novel method for suppressing multimodal vibrations in structures by using the controlled harvesting and storage of vibration energy as electrical charge. Unlike a traditional semi-active system in which vibration energy is dissipated using a controlled variable dissipater, the proposed system harvests vibration energy for storage. The stored energy can then be recycled enabling the system to achieve a vibration reduction performance superior to that of a traditional semi-active system and approaching that of a fully active system. In the proposed method, an array of one or more precharged capacitors is employed to provide a selection of various voltages, which may be selected to approximate a desired control signal defined by an LQR multimodal vibration controller. The capacitors can apply a control voltage to the piezoelectric actuators and can also collect current generated by the actuators as the structure strains in vibration. Both a single capacitor system and a multi-capacitor system are considered and applied to a cantilevered beam. The response to impulse disturbances and random force disturbances are studied. The results are compared to a previously proposed energy harvesting based semi-active method. Advantages in both vibration suppression and energy harvesting performance over the previously proposed method are demonstrated. The multicapacitor method is found to be most effective due to its ability to apply sufficiently large control voltages while moderating large step inputs therefore reducing the excitation of higher frequency uncontrolled modes, which otherwise parasitically dissipate energy in the circuit resistance.