Piezoelectric Vibration Research Articles

Adaptive and Robust Operation with Active Fuzzy Harvester under Nonstationary and Random Disturbance Conditions.

The objective of this paper is to amplify the output voltage magnitude from a piezoelectric vibration energy harvester under nonstationary and broadband vibration conditions. Improving the transferred energy, which is converted from mechanical energy to electrical energy through a piezoelectric transducer, achieved a high output voltage and effective harvesting. A threshold-based switching strategy is used to improve the total transferred energy with consideration of the signs and amplitudes of the electromechanical conditions of the harvester. A time-invariant threshold cannot accomplish effective harvesting under nonstationary vibration conditions because the assessment criterion for desirable control changes in accordance with the disturbance scale. To solve this problem, we developed a switching strategy for the active harvester, namely, adaptive switching considering vibration suppression-threshold strategy. The strategy adopts a tuning algorithm for the time-varying threshold and implements appropriate intermittent switching without pre-tuning by means of the fuzzy control theory. We evaluated the proposed strategy under three realistic vibration conditions: a frequency sweep, a change in the number of dominant frequencies, and wideband frequency vibration. Experimental comparisons were conducted with existing strategies, which consider only the signs of the harvester electromechanical conditions. The results confirm that the presented strategy achieves a greater output voltage than the existing strategies under all nonstationary vibration conditions. The average amplification rate of output voltage for the proposed strategy is 203% compared with the output voltage by noncontrolled harvesting.

Design and test of a piezoelectric micropump based on hydraulic amplification

To solve the problem of the small deformation of piezoelectric vibrators and improve the overall performance of piezoelectric micro-pumps, a flexible-diaphragm piezoelectric micropump is designed based on hydraulic amplification. The micropump uses a piezoelectric vibrator to provide its driving force, and fluid is delivered by driving the liquid to amplify the displacement of the piezoelectric vibrator. First, the working principle of the piezoelectric micropump is analyzed, and then theoretical analysis and displacement output tests of the hydraulic amplifier unit are carried out. The test results are consistent with those of the theoretical analysis, and the amplification factor of the hydraulic amplifier unit is 3.29. Finally, prototypes are produced and an experimental platform is built for testing. The results indicate that the best-performing piezoelectric micropump has a self-priming height of 1200 mm, an output pressure of 22.16 kPa, and an output flow of 23.18 ml/min. Compared with an ordinary piezoelectric pump, the overall performance of the piezoelectric micropump is greatly improved.

Piezoelectric vibration energy harvesting device based on water sloshing-inspired extensions

Inspired by shallow-water sloshing in a moving tank, a novel type of vibration-based piezoelectric energy harvesting device composed of a piezoelectric bimorph beam and an extension tank is proposed in this paper. The structure and working principle of the proposed device are provided. Then, the effects of different heights of water filling in the tank on the performances of the harvester are studied and analyzed. Experiments are set up to investigate the actual device performance by changing the base excitation frequency and load resistance for different water heights. The results show that by modulating the water height, the resonant frequency and bandwidth can be adjusted, which can enhance the energy harvesting performance of the device at different ambient vibration frequencies. This study provides some clues to improve the performance of the vibration-based energy harvesting devices.

Resonance response analysis of nonlinear vibration energy harvesting system under bounded noise excitation

In this paper, the resonance response of piezoelectric vibration energy harvester (VEH) driven by bounded noise is discussed through the quasi-conservative stochastic averaging method. A nonlinear transformation based on the total energy is firstly established to transform piezoelectric VEH system from an electromechanical coupled nonlinear system into a single-degree-of-freedom (SDOF) system. Then the SDOF system is rewritten as It\^o stochastic system about the energy and residual phase under the case of p:q resonance through the quasi-conservative stochastic averaging method. And the joint probability density function (JPDF) of the stationary response is obtained by solving the corresponding two-dimensional Fokker-Planck-Kolmogorov (FPK) equation using the finite difference method. Meanwhile, the mean-square electric voltage and the mean output power are further analytically given through the JPDF. Finally, the resonance response of piezoelectric VEH system is analyzed in detail in case of the primary resonance, and the Monte Carlo (MC) simulation technique is adopted to validate the effectiveness of the finite difference method.

Transient response of a nonlinear energy sink based piezoelectric vibration energy harvester coupled to a synchronized charge extraction interface

Integration of a piezoelectric transducer with a nonlinear energy sink (NES) has been realized for both vibration mitigation and broadband energy harvesting. However, to ensure that a harvester can generate power in a truly broadband manner, the impedance matching issue of the interface circuit should be addressed. The synchronized charge extraction (SCE) is one technology that has been proved to be able to address this issue for linear energy harvesters. This work intends to investigate the transient response of an NES-based piezoelectric vibration energy harvesting system interfaced with an SCE interface (NESVEH-SCE). The nonlinear normal mode of such an electromechanically coupled system is analyzed on the basis of the equivalent impedance method and complexification-averaging method. The frequency-energy plots are depicted and verified by wavelet analysis. The effects of electromechanical coupling strength, electrical load in the SCE interface and initial input energy level on the performance of the proposed system are discussed by using the circuit simulation tool. Finally, experiments are performed to verify the consequences obtained from the theoretical and numerical methods, and demonstrate that the energy harvested during the transient response of the NESVEH-SCE system is independent of the electrical load in the SCE interface.

Auxetic clamped-clamped resonators for high-efficiency vibration energy harvesting at low-frequency excitation

Here, we utilize the auxetic concept to improve output electrical power and reduce resonance frequency for the piezoelectric vibration energy harvesting. An energy harvester consists of a proof mass and two supporter beams with piezoelectric patches, is proposed. Presented energy harvester prototype is appropriate for applications with limited allowable displacement. Three different auxetic structures are proposed and their performances are compared to the conventional plain system. Finite element (FE) modelling is provided to evaluate these structures and optimize their geometrical parameters and electrical resistance to achieve the best energy harvesting performance. The FE model is validated through experimental tests in which the energy harvesters with optimized parameters are excited by an electrodynamic shaker in different frequencies. It is shown that the proposed designs are able to remarkably enhance the harvested electrical power with respect to the plain structure. The experimental tests show that the Auxetic-I, II and III could enhance the output electrical power with a magnification factor of 10, 6.7 and 6.1 respectively, compared to the conventional structure. The resonant working frequency reduced up to 30.45%, 19.55% and 27.53% for different designs.

Fabrication and Characterization of a Microscale Piezoelectric Vibrator Based on Electrohydrodynamic Jet Printed PZT Thick Film.

This paper proposes a novel way of preparing a PZT thick film micro vibrator using the electrohydrodynamic jet (E-Jet) printing technique. Initially, a micro piezoelectric vibrator was simulated and designed for obtaining optimized structure, which has a total thickness of less than 600 µm. Subsequently, the PZT thick film element was directly printed on the elastic body using the E-Jet printing. This method avoids the glue fabrication process involved in the bulk piezoelectric fabrication, thus avoiding the limits of voltage drops, isolating and absorbing amplitude usually occurred in the vibrator having glue interface. It was observed that B02 and B03 modes were generated at frequencies of 29.74 and 79.14 kHz, respectively, and the amplitudes of B02 and B03 modes were 406 and 176 nm, respectively. The error between the simulation and test result in the B03 modal is only 0.35%, which indicates the accuracy of the simulation analysis and the fabrication process. The PZT thick film traveling-wave micro vibrator successfully realized bidirectional rotation of a rotor, with a maximum speed of 681 rpm, which also shows a linear relationship between excitation voltage and rotary speed. This paper provides an effective method for preparing a micro piezoelectric vibrator for MEMS ultrasonic devices, which simplifies the manufacturing process and enhances the performance of the piezoelectric vibrator.

Linear and nonlinear analysis of traditional and non-traditional piezoelectric vibration absorber with time delay feedback for simultaneous resonance conditions

In the present work, vibration suppression of a single degree of freedom nonlinear spring-mass primary (main) system subjected to simultaneous external harmonic and parametric excitation by using traditional and non-traditional active nonlinear vibration absorber (ANVA) is carried out. The traditional and non-traditional ANVA consists of a PZT (lead zirconate titanate) stack actuator in series with a nonlinear spring and a damper. In the traditional ANVA, the damper is connected to the main system whereas, in non-traditional ANVA, the damper is connected to the base of the main system. The governing nonlinear equations of motion for the system have been derived using weighted modal matrix approach considering novel actuation force by time delay in displacement, velocity and acceleration feedback of the main system by the PZT stack actuator and the nonlinear spring in series combination. The method of multiple scales (MMS) is used to obtain the reduced equations which are solved using Newton’s method. The responses of the system for the primary, principal parametric and simultaneous primary and principal parametric resonance conditions have been studied. The results are compared with those obtained by using the harmonic balance method (HBM), numerical method and with previous literature. From these results, two resonating peaks in the frequency response of the main system are shown by using the reduced equation of the MMS which was not reported in earlier literature. It is shown that for the active case the vibration of the undamped main system is completely reduced at the specified operating frequency for both the linear and nonlinear systems. Also, for a wider range of operating frequencies, the vibration of the main system is reduced by actively tuning the absorber for various mass ratios. Further, the efficacy of the active force is observed in reducing the instability regions and improving the critical value of excitations in the trivial state.

Piezoelectric autoparametric vibration energy harvesting with chaos control feature

To extend the working bandwidth for piezoelectric vibration energy harvesting, autoparametric internal resonant system is proposed. Unstable quasiperiodic motion and chaos, however, are accompanied by broadband characteristic in nonlinear energy conversion. In order to control unwanted irregular motions for power management, we presented a new autoparametric vibration energy harvester coupled by nonlinear energy sink. Mathematical model considering the electromechanical coupling and modal coupling for the high-order nonlinear energy harvesting system is established. Nonlinear analyses via power spectrum, phase portrait and Poincaré map illustrate the effectiveness of chaos control using nonlinear energy sink. In addition, average power of the lower boundary of the harvesting band is enhanced by increasing the stiffness and damping of nonlinear energy sink. Average power of the upper boundary of the harvesting band is improved by increase of the nonlinear energy sink mass and substructural natural frequency ratio. The maximum average power of the proposed piezoelectric autoparametric vibration energy harvester is enhanced 200%, compared to the power harvested by the system without the nonlinear energy sink. This study provides a chaos control method for stable broadband vibration energy harvesting. With simultaneous energy harvesting and chaos control, such system can fit in with more applications.

A cantilevered piezoelectric energy harvester excited by an axially pushed wedge cam using repulsive magnets for rotary motion

Harvesting energy from the rotary environment to replace the conventional electrochemical batteries has gained considerable interest. Different from the existing rotation-induced energy harvesters based on the bidirectional deformation of piezoelectric vibrators, a novel cantilevered piezoelectric energy harvester excited by an axially pushed wedge cam using repulsive magnets for rotary motion was presented and fabricated in this paper. The new piezoelectric rotary energy harvester (PREH) was characterized by the simultaneous realization of unidirectional deformation and limited amplitude for piezoelectric vibrators. To verify the feasibility of the proposed principle and design, a theoretical model was established based on Fourier series as well as superposition principle. Meanwhile, the influence of the system parameters on the response characteristic of the presented PREH were obtained by simulation. And then, the experiments of rotating speed response were performed to evaluate the energy harvesting performance in terms of the deformation and open-circuit voltage. Both simulation and experimental results showed that the amplitude of the piezo-cantilever could be limited by using the cam mechanism and there were obvious resonance peaks on the amplitude-rotary speeds curves. Thus, the relatively stable output voltage could be maintained over a broad rotating speed range. Also, the stable voltage increased with the increasing of cam lift, but the effective rotating speed range became narrow. With the increasing of the cam angle, the effective rotating speed bandwidth could be increased, whereas the self-locking phenomenon of the piezo-cantilever would occur when the angle was increased to some extent. Besides, the bandwidth could be adjusted by changing the number of exciting magnets and stiffness of cam system. Under the optimum matching parameters, the maximum power 10.88 mW was reached for the presented PREH.

An experimental study on a piezoelectric vibration energy harvester for self-powered cardiac pacemakers.

BackgroundOver the past half-century, cardiac pacing technology has been reported. In this study, we designed, prepared, and tested the performance of a self-energized cardiac pacemaker driven by piezoelectric vibration energy collection technology, which converts the kinetic energy of the heart into electrical energy. A record in vivo output current of 54 nA was obtained in an adult rat by the implanted piezoelectric transducer.MethodsFirst, the kinetic energy of the heart was collected by an implanted piezoelectric energy collector and supplied to the cardiac pacemaker. Then, the heart was pierced from the outside, and the cardiac tissue was stimulated by the pacing electrode, and self-powered pacing.ResultsThe average voltage and average current of the piezoelectric vibration energy harvester in vitro were 3.5 mV and 60 nA, respectively. After implantation of the device into rats, the average voltage and current were measured immediately and reached 3.2 mV and 54 nA, respectively. The average voltage and average current reached 3.0 mV and 48 nA after 1 week, and 2.1 mV and 31 nA after 12 weeks. The electrical performance of the self-powered pacemaker in this study is based on piezoelectric energy collection technology. The implanted piezoelectric vibration energy collector drives the pacemaker to generate electrical pulses, which directly stimulates the myocardial tissue through the epicardium to achieve the pacing effect.ConclusionsThese results evidence the feasibility of the in-situ epicardial pacing strategy. This research will promote the design and development of self-powered cardiac pacemakers.

Potential energy analysis based on piezoelectric cantilever beam structure

The piezoelectric vibration energy collection technology utilizes the positive piezoelectric effect of the piezoelectric material, and collects the energy by attaching the material to a clamping structure and deforming under the external excitation, thus accumulating the charge and generating the potential difference. In this paper, the cantilever beam is used as a clamping structure because of its large deflection and simple structure. In this paper, the raindrop impulsion is applied to the piezoelectric material, the piezoelectric vibration energy capture device is used to improve the energy collection efficiency, and the electromechanical coupling model is established to simplify the potential energy analysis by using the conservation of energy and Newton’s second law. In this paper, Runge-kutta method is used to simulate the differential equation, which reduces the computational cost of the system and has a certain precision for analysis and solution. Based on Al-‘Ula’s Bernoulli beam theory, the model was simulated by using the differential equation method and the ordinary differential equation group.

In vitro and in vivo studies on the biocompatibility of a self-powered pacemaker with a flexible buckling piezoelectric vibration energy harvester for rats.

BackgroundScavenging energy from biomechanical motions in vivo by energy converting devices, i.e., implantable harvesters, to obtain sustainable electrical energy is the ideal way to power implantable medical devices which require long term and continuous power supply. A novel self-powered cardiac pacemaker is designed to achieve self-powered pacing. The kinetic energy of the heart was collected by an implanted piezoelectric energy collector and supplied to the cardiac pacemaker, and then the cardiac tissue was stimulated by the pacing electrode pierced from the outside of the heart to realize effective pacing effect and self-powered pacing. In this study, we evaluated the stability and biocompatibility of our previously described flexible buckling piezoelectric vibration energy harvester in vitro and in vivo. The biocompatibility, in vivo stability, and safety of the self-powered pacemaker with a flexible flexion piezoelectric vibratory energy harvesting device prepared were analyzed by performing cell and in vivo animal experiments.MethodsThe MTT(3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay was used to detect the cell proliferation of H9C2 cells and HUVECs at 24, 48, and 72 hours. Computed tomography (CT) and cardiac ultrasound were used to evaluate the position and heart rate of pacemakers 12 weeks after implantation, and the changes of plasma biochemical indexes were detected by a biochemical detector.ResultsAt 12 weeks after implantation, CT results showed that there were no changes in the position of the self-powered pacemaker. The device implanted into the thoracic cavity of rats demonstrated certain effects on cardiac function, while it did not have a significant effect on their blood biochemical indexes.Conclusionsthe flexible buckling piezoelectric vibratory energy collector did not produce adverse effects on the myocardial tissue or on the normal proliferation of myocardial cells.

A Multidirectional Piezoelectric Vibration Energy Harvester With Direction-Dependent Dual Resonance.

A multidirectional base-mounted piezoelectric vibration energy harvester with a 2 mm ×2 mm ×20 mm polyurethane resonating beam, an 8.36-g tip mass, and a lead zirconium titanate (PZT) transducer was designed, fabricated, and tested. The harvester was shown to operate in any direction in a 2-D plane and produced as much as [Formula: see text] across a 50- [Formula: see text] load under harmonic base excitations with peak acceleration of 0.25 g at an angle of 45°. Experiments showed that, in some directions, the harvester had two resonant frequencies, one at 36.0 Hz and one at 38.5 Hz. Analysis shows that this phenomenon is caused by deviations in the shape of the polyurethane beam from the intended square cross section. This analysis is used to propose a method for designing harvesters with any two desired resonant frequencies. The possibility of using this design method to increase the harvester's bandwidth is discussed.

A Review of Piezoelectric Vibration Energy Harvesting with Magnetic Coupling Based on Different Structural Characteristics.

Piezoelectric vibration energy harvesting technologies have attracted a lot of attention in recent decades, and the harvesters have been applied successfully in various fields, such as buildings, biomechanical and human motions. One important challenge is that the narrow frequency bandwidth of linear energy harvesting is inadequate to adapt the ambient vibrations, which are often random and broadband. Therefore, researchers have concentrated on developing efficient energy harvesters to realize broadband energy harvesting and improve energy-harvesting efficiency. Particularly, among these approaches, different types of energy harvesters adopting magnetic force have been designed with nonlinear characteristics for effective energy harvesting. This paper aims to review the main piezoelectric vibration energy harvesting technologies with magnetic coupling, and determine the potential benefits of magnetic force on energy-harvesting techniques. They are classified into five categories according to their different structural characteristics: monostable, bistable, multistable, magnetic plucking, and hybrid piezoelectric–electromagnetic energy harvesters. The operating principles and representative designs of each type are provided. Finally, a summary of practical applications is also shown. This review contributes to the widespread understanding of the role of magnetic force on piezoelectric vibration energy harvesting. It also provides a meaningful perspective on designing piezoelectric harvesters for improving energy-harvesting efficiency.

Bio-inspired bistable piezoelectric vibration energy harvester: Design and experimental investigation

Inspired by the flight mechanism of dipteran, a novel bionic-dipteran energy harvester (BDEH) was proposed to collect ultralow-frequency vibration energy. Mimicking the skeletal structure of dipteran wing, two flexible beams and two rigid links are hinged together to form a bistable mechanism. Piezoelectric patches attached onto the flexible beams generate electricity as the proof mass is driven to oscillate by base excitations. A lumped-mass-spring model is built for theoretical analysis, which is verified by both finite element simulations and experiments. The dynamic responses of displacement and output voltage are achieved under different conditions, which indicate that the BDEH has the highest efficiency when the system undergoes cross-well vibration pattern. Both light damping and large excitation are beneficial to trigger cross-well vibration and thus enhance energy harvesting efficiency. A rectifier circuit is built to measure output power of the prototype under different excitations. Maximum power of 0.143 mW is generated under cross-well vibration pattern at an excitation frequency of 4 Hz and acceleration of 0.7g (g = 9.8 m/s2), which implies that the BDEH should be a feasible solution for ultralow-frequency energy harvesting even under low excitation.

Influence of the Power Generation Capacity of the Structural Parameters of a Piezoelectric Unimorph

To explore the influence of the structural parameters of unimorph piezoelectric vibrators on the power generation capacity, a power generation model of cantilever rectangular unimorph piezoelectric vibrators was established. The power generation expressions of the unimorph piezoelectric vibrator were obtained, and the parameters influencing the power generation effect were determined. The influence relationship curve of the system output voltage and structural parameters was obtained through MATLAB simulations; the effecting laws of the output voltage, excitation amplitude, thickness ratio, width-length ratio were experimentally acquired. The test results are consistent with the theoretical results, and the accuracy of theoretical analyses was verified. The piezoelectric vibrator exhibited the optimum power generation effect and provided a theoretical basis and technical reference for applying piezoelectric ceramic materials to power generation at the thickness ratio, Young’s modulus, and aspect ratio of 0.5, 0.35, and 1, respectively.

A silicone based piezoelectric and electromagnetic hybrid vibration energy harvester

This paper describes the investigation of a novel low-cost silicone-based hybrid vibration energy harvester (SHVEH) for converting machine vibrations into useful electrical power for wireless sensor nodes. Due to a novel fabrication technique, the harvester has the benefit of incorporating two transduction mechanisms (electromagnetic and piezoelectric) into a single silicone housing for improved output power. In the devised fabrication technique, water-soluble tablets are used to develop a cavity inside the silicone structure for an embedded magnet to vibrate in. The developed device was characterized inside the lab at different acceleration levels. The SHVEH was found to be capable of delivering a combined output power of 1.12 mW and a power density of 52 µW cm−3. The SHVEH was able to deliver maximum open circuit voltages of 3 V and 28 mV AC via the piezoelectric and electromagnetic portions, respectively, at a resonant frequency of 110 Hz. Furthermore, after connecting the SHVEH to rectifier circuitry, the DC voltage levels obtained were 3.5 V and 35 mV from the piezoelectric and electromagnetic portions, respectively.

Research on a Piezoelectric Pump with Flexible Valves

Imitating the structure of the venous valve and its characteristics of passive opening and closing with changes in heart pressure, a piezoelectric pump with flexible valves (PPFV) was designed. Firstly, the structure and the working principle of the PPFV were introduced. Then, the flexible valve, the main functional component of the pump, was analyzed theoretically. Finally, an experimental prototype was manufactured and its performance was tested. The research proves that the PPFV can achieve a smooth transition between valved and valveless by only changing the driving signal of the piezoelectric (PZT) vibrator. The results demonstrate that when the driving voltage is 100 V and the frequency is 25 Hz, the experimental flow rate of the PPFV is about 119.61 mL/min, and the output pressure is about 6.16 kPa. This kind of pump can realize the reciprocal conversion of a large flow rate, high output pressure, and a small flow rate, low output pressure under the electronic control signal. Therefore, it can be utilized for fluid transport and pressure transmission at both the macro-level and the micro-level, which belongs to the macro–micro combined component.

Modeling of a Rope-Driven Piezoelectric Vibration Energy Harvester for Low-Frequency and Wideband Energy Harvesting.

In this work, a mechanical model of a rope-driven piezoelectric vibration energy harvester (PVEH) for low-frequency and wideband energy harvesting was presented. The rope-driven PVEH consisting of one low-frequency driving beam (LFDB) and one high-frequency generating beam (HFGB) connected with a rope was modeled as two mass-spring-damper suspension systems and a massless spring, which can be used to predict the dynamic motion of the LFDB and HFGB. Using this model, the effects of multiple parameters including excitation acceleration, rope margin and rope stiffness in the performance of the PVEH have been investigated systematically by numerical simulation and experiments. The results show a reasonable agreement between the simulation and experimental study, which demonstrates the validity of the proposed model of rope-driven PVEH. It was also found that the performance of the PVEH can be adjusted conveniently by only changing rope margin or stiffness. The dynamic mechanical model of the rope-driven PVEH built in this paper can be used to the further device design or optimization.