Showing papers on "Bimorph published in 2016"

Construction of a Fish-like Robot Based on High Performance Graphene/PVDF Bimorph Actuation Materials.

Abstract: Smart actuators have many potential applications in various areas, so the development of novel actuation materials, with facile fabricating methods and excellent performances, are still urgent needs. In this work, a novel electromechanical bimorph actuator constituted by a graphene layer and a PVDF layer, is fabricated through a simple yet versatile solution approach. The bimorph actuator can deflect toward the graphene side under electrical stimulus, due to the differences in coefficient of thermal expansion between the two layers and the converse piezoelectric effect and electrostrictive property of the PVDF layer. Under low voltage stimulus, the actuator (length: 20 mm, width: 3 mm) can generate large actuation motion with a maximum deflection of about 14.0 mm within 0.262 s and produce high actuation stress (more than 312.7 MPa/g). The bimorph actuator also can display reversible swing behavior with long cycle life under high frequencies. on this basis, a fish-like robot that can swim at the speed of 5.02 mm/s is designed and demonstrated. The designed graphene-PVDF bimorph actuator exhibits the overall novel performance compared with many other electromechanical avtuators, and may contribute to the practical actuation applications of graphene-based materials at a macro scale.

Efficient Piezoelectric Energy Harvesters Utilizing (001) Textured Bimorph PZT Films on Flexible Metal Foils

Abstract: Extracting energy from low vibration frequencies (<10 Hz) using piezoelectric energy harvester promises continuous self-powering for sensors and wearables The piezoelectric compliant mechanism (PCM) design provides a significantly higher efficiency by fostering a uniform strain for its 1st mode shape, and so is interesting for this application In this paper, a PCM energy harvester with bimorph Pb(Zr,Ti)O3 (PZT) films on Ni foil deposited by rf magnetron sputtering is shown to have high efficiency and large power for low frequency mechanical vibration In particular, {001} textured PZT films are deposited on both sides of polished Ni foils with (100) oriented LaNiO3 seed layers on HfO2 buffer layers The performance of PCM with an active area of 52 cm2 is explored for various excitation accelerations (002–016 g [g = 98 m s−2]) around 6 Hz The PCM device provides a power level of 39 mW cm−2 g2 and 65% mode shape efficiencies

Design and characterisation of a piezoelectric knee-joint energy harvester with frequency up-conversion through magnetic plucking

Abstract: Piezoelectric energy harvesting from human motion is challenging because of the low energy conversion efficiency at a low-frequency excitation. Previous studies by the present authors showed that mechanical plucking of a piezoelectric bimorph cantilever was able to provide frequency up-conversion from a few hertz to the resonance frequency of the cantilever, and that a piezoelectric knee-joint energy harvester (KEH) based on this mechanism was able to generate sufficient energy to power a wireless sensor node. However, the direct contact between the bimorph and the plectra leads to reduced longevity and considerable noise. To address these limitations, this paper introduces a magnetic plucking mechanism to replace the mechanical plucking in the KEH, where primary magnets (PM) actuated by knee-joint motion excite the bimorphs through a secondary magnet (SM) fixed on the bimorphs tip and so achieve frequency up-conversion. The key parameters of the new KEH that affect the energy output of a plucked bimorph were investigated. It was found that the bimorph plucked by a repulsive magnetic force produced a higher energy output than an attractive force. The energy output peaked at 32 PMs and increased with a decreasing gap between PM and SM as well as an increasing rotation speed of the PMs. Based on these investigations, a KEH with high energy output was prototyped, which featured 8 piezoelectric bimorphs plucked by 32 PMs through repulsive magnetic forces. The gap between PM and SM was set to 1.5 mm with a consideration on both the energy output and longevity of the bimorphs. When actuated by knee-joint motion of 0.9 Hz, the KEH produced an average power output of 5.8 mW with a life time >7.3 h (about 3.8 × 105 plucking excitations).

Improve efficiency of harvesting random energy by snap-through in a quad-stable harvester

Abstract: In response to the defects of the bi-stable energy harvester (BEH), we develop a novel quad-stable energy harvester (QEH) to improve the harvesting efficiency. The device is made up of a bimorph cantilever beam having a tip magnet and three external fixed magnets. By introducing the repulsion forces between magnets, the function of potential energy of the QEH is given. It owns four potential wells. It is proved that the quad-stable harvester can cross the barriers and realize snap-through easier. Validation experiments were performed by frequency sweeping and random excitations. Results show that compared to the BEH the frequency bandwidth of snap-through of the novel device is much wider. The QEH can make a dense snap-through in response under random excitation, and give out a large output voltage. This shows that the proposed QEH is more effective in energy harvesting applications.

Bimorph Piezoelectric Micromachined Ultrasonic Transducers

Abstract: This paper presents the concept, basic theory, fabrication, and testing results of dual-electrode bimorph piezoelectric micromachined ultrasonic transducers (pMUTs) for both air- and liquid-coupled applications. Both the theoretical analyses and experimental verifications under the proposed differential drive scheme display high drive sensitivity and an electromechanical coupling energy efficiency that is as high as $4\times $ of the state-of-the-art pMUT with a similar geometry and frequency. The prototype transducers are fabricated in a CMOS-compatible process with the radii of 100–230 $\mu \text{m}$ using aluminum nitride as the piezoelectric layers with the thicknesses varying from 715 to 950 nm and molybdenum (Mo) as the electrodes with a thickness of 130 nm. The tested operation frequencies of the prototype transducers are 200–970 kHz in air for possible ranging and motion detection applications, and from 250 kHz to 1 MHz in water for medical ultrasound applications such as fracture healing, tumor ablation, and transcranial sonothrombolysis. A $12\times 12$ array structure is measured to have the highest intensity per voltage squared, per number of pMUTs squared, and per piezoelectric constant squared ( $I_{n}= I/(VNd_{31})^{2})$ among all reported pMUT arrays. The generated acoustic intensity is in the range of 30–70 mW/cm2 up to 2.5 mm from the transducer surface in mineral oil with a driving voltage of 5 $\text{V}_{{\mathrm{ac}}}$ , which is suitable for battery-powered therapeutic ultrasound devices. [2015-0305]

Nonlinear analysis and power improvement of broadband low-frequency piezomagnetoelastic energy harvesters

Abstract: A significant impediment to the deploy- ment of vibration-based energy harvesting devices has been the limitation of most low-frequency transduc- ers, usually in the form of unimorph or bimorph can- tileverbeam,toextractenergyfromaverynarrowband- width around the transducer's fundamental frequency. In such devices, a slight deviation from the fundamen- tal frequency causes a significant reduction in the level of harvested power by several orders of magnitudes. Additionally,mostofthecurrentresearcheffortsonthe design of piezoelectric energy harvesters have had lim- ited success in achieving low resonance frequency. To overcome these challenges, we introduce an enhanced broadband low-frequency piezomagnetoelastic energy harvester. This harvester consists of a partially cov- ered piezoelectric cantilever beam with a fixed magnet mass at the top of the magnet tip mass. A nonlinear distributed-parameter model based on Euler-Bernoulli beam theory and Galerkin discretization is developed. This electromechanical model is validated with previ- ous experimental measurements for a specific value of the spacing distance between the two magnets. A para- metric study is performed to determine the effects of the spacing distance between the two magnets on the static position of the harvester, natural frequency, and level of the harvested power. It is demonstrated that a decrease between the two attractive magnets results in a decrease in the natural frequency of the harvester withastrongsofteningbehaviorwhichgivestheoppor- tunity to harvest energy at broadband low-frequency range. The results also show that the presence and importance of the softening behavior depends on the electrical load resistance. In conclusion, the results show that depending on the available low excitation frequency, an enhanced piezoelectric energy harvester can be tuned and optimized by changing the spacing distance between the two tip magnets.

Fabrication and performance evaluation of a metal-based bimorph piezoelectric MEMS generator for vibration energy harvesting

Abstract: This paper presents the development of a bimorph microelectromechanical system (MEMS) generator for vibration energy harvesting. The bimorph generator is in cantilever beam structure formed by laminating two lead zirconate titanate thick-film layers on both sides of a stainless steel substrate. Aiming to scavenge vibration energy efficiently from the environment and transform into useful electrical energy, the two piezoelectric layers on the device can be poled for serial and parallel connections to enhance the output voltage or output current respectively. In addition, a tungsten proof mass is bonded at the tip of the device to adjust the resonance frequency. The experimental result shows superior performance the generator. At the 0.5 g base excitation acceleration level, the devices pooled for serial connection and the device poled for parallel connection possess an open-circuit output voltage of 11.6 VP–P and 20.1 VP–P, respectively. The device poled for parallel connection reaches a maximum power output of 423 μW and an output voltage of 15.2 VP–P at an excitation frequency of 143.4 Hz and an externally applied based excitation acceleration of 1.5 g, whereas the device poled serial connection achieves a maximum power output of 413 μW and an output voltage of 33.0 VP–P at an excitation frequency of 140.8 Hz and an externally applied base excitation acceleration of 1.5 g. To demonstrate the feasibility of the MEMS generator for real applications, we finished the demonstration of a self-powered Bluetooth low energy wireless temperature sensor sending readings to a smartphone with only the power from the MEMS generator harvesting from vibration.

A large-deformation phase transition electrothermal actuator based on carbon nanotube–elastomer composites

Abstract: An electrothermal phase transition actuator based on a superaligned carbon nanotube film and elastomers has been designed and fabricated. Compared with a conventional electrothermal bimorph actuator using cantilever structures, this new-type actuator introduces a novel concept of phase transition large-deformation actuation. The actuator consists of an enclosed cavity made up of highly elastic elastomers and an embedded carbon nanotube based electrical heater. A low-boiling liquid was injected into the cavity and it can vaporize rapidly to make the elastic cavity expand significantly when electrically heated. The size and speed of the expansion can be easily controlled by the applied voltage (electrical power). The expanded elastomer membrane can lift more than 1000 times of its own weight. The cyclic actuation test shows the excellent durability of the actuator. A heart-shaped closed liquid circulation system based on the phase transition pump-type actuators has been made, which can work like a real heart. Owing to the advantages of low driving voltage, large deformation, simple fabrication, easy operation, lightweight and durability, we think that the phase transition actuator will have great potential usage in various areas, such as artificial muscles, soft robots, sensors, and especially in the biomedical field.

Hydroelectromechanical modelling of a piezoelectric wave energy converter

Abstract: We investigate the hydroelectromechanical-coupled dynamics of a piezoelectric wave energy converter. The converter is made of a flexible bimorph plate, clamped at its ends and forced to motion by incident ocean surface waves. The piezoceramic layers are connected in series and transform the elastic motion of the plate into useful electricity by means of the piezoelectric effect. By using a distributed-parameter analytical approach, we couple the linear piezoelectric constitutive equations for the plate with the potential-flow equations for the surface water waves. The resulting system of governing partial differential equations yields a new hydroelectromechanical dispersion relation, whose complex roots are determined with a numerical approach. The effect of the piezoelectric coupling in the hydroelastic domain generates a system of short- and long-crested weakly damped progressive waves travelling along the plate. We show that the short-crested flexural wave component gives a dominant contribution to the generated power. We determine the hydroelectromechanical resonant periods of the device, at which the power output is significant.

Piezoelectric type acoustic energy harvester with a tapered Helmholtz cavity for improved performance

Abstract: This paper reports an improved acoustic energy harvester with a tapered Helmholtz cavity. The harvester consists of a bimorph piezoelectric composite plate and a Helmholtz resonator (HR) with a tapered cavity. The architecture, operational mechanism, fabrication, and characterization of the harvesters are described. The harvesters are tested under sinusoidal sound pressure levels (SPLs) inside a lab as well as random SPLs in a real ambient acoustical environment. When a harvester with a tapered HR and without proof mass attached to its piezoelectric plate is characterized at a sinusoidal SPL of 130 dB, a maximum power of 90.6 μW is delivered to 1 kΩ load. In comparison, a similar harvester with a cylindrical shape HR produced a maximum power of 51.4 μW under the similar acoustic conditions. It is found that 76.26% increase in power is achieved with the tapered cavity for the HR. Furthermore, due to the attachment of a proof mass (0.84 g) with the harvester, its power production capability is further increased by 103.3%, from 90.6 to 184.18 μW. Moreover, in a real environment, the maximum voltage amplitudes of about 260 and 280 mV are produced by the harvester when placed in the surrounding of a motorbike and domestic electric generator, respectively.

Design of a Charge Drive for Reducing Hysteresis in a Piezoelectric Bimorph Actuator

Abstract: This paper describes the design of a charge drive for reducing the hysteresis exhibited by a piezoelectric bimorph bender. Existing charge drive circuits cannot be directly applied to bimorph benders since they share a common electrode. In this paper, a new charge drive circuit and electrical configuration are implemented that allows commonly available piezoelectric bimorphs to be linearized. This circuit consists of four major components, including, a high voltage amplifier, a differential amplifier, a piezoelectric load, and a PI feedback controller. An isolation amplifier was used to achieve a differential amplifier with a high common-mode rejection ratio. The charge drive was tested by driving a series poled three layer bimorph bender. The experiment showed a significant improvement to the hysteresis of the bender when compared to a typical voltage drive. This paper has identified an alternative Feedback method to improve the ac hysteresis performance of a piezoelectric bender by using a charge drive.

Wide aperture piezoceramic deformable mirrors for aberration correction in high-power lasers

Abstract: The deformable mirror with the size of controlled by the bimorph piezoceramic plates and multilayer piezoceramic stacks was developed. The results of the measurements of the response functions of all the actuators and of the surface shape of the deformable mirror are presented in this paper. The study of the mirror with a Fizeau interferometer and a Shack–Hartmann wavefront sensor has shown that it was possible to improve the flatness of the surface down to a residual roughness of (RMS). The possibility of correction of the aberrations in high-power lasers was numerically demonstrated.

Development of a self-sensing piezoelectric pump with a bimorph transducer

Abstract: This article presents a self-sensing piezoelectric pump with a bimorph transducer. The proposed method is able to realize the functions of fluid transportation and output flow and pressure self-testing simultaneously through only a single piezoelectric element. The simultaneous function is achieved through separating one lead zirconium titanate disk from the piezoelectric bimorph to detect the pumping flow or pressure in direct proportion to the bimorph deflection generated by the other actuated lead zirconium titanate disk. A prototype pump is fabricated with the size of 40 mm × 40 mm × 17 mm and tested according to the actuation frequency characteristics and voltage characteristics of the flow rate, backpressure, and sensing voltages. The testing results show that the sensing voltages are changed with the flow rate and backpressure as a function of frequency while either lead zirconium titanate disk of the bimorph act as the integrated sensor. It is found that when the pump with two distinct disks succe...

A Broadband Vibration-Based Energy Harvester Using an Array of Piezoelectric Beams Connected by Springs

Abstract: Piezoelectric cantilevered beams have been widely used as vibration-based energy harvesters. Nevertheless, these devices have a narrow frequency band and if the excitation is slightly different there is a significant drop in the level of power generated. To handle this problem, the present investigation proposes the use of an array of piezoelectric cantilevered beams connected by springs as a broadband vibration-based energy harvester. The equations for the voltage and power output of the system are derived based on the analytical solution of the piezoelectric cantilevered energy harvester with Euler-Bernoulli beam assumptions. To study the advantages and disadvantages of the proposed system, the results are compared with those of an array of disconnected beams (with no springs). The analytical model is validated with experimental measurements of three bimorph beams with and without springs. The results show that connecting the array of beams with springs allows increasing the frequency band of operation and increasing the amount of power generated.

An electromechanical x-ray optical element based on a hysteresis-free monolithic bimorph crystal

Abstract: A hysteresis-free electrically controlled X-ray optical element based on a monolithic bi-domain bimorphic piezoelectric actuator that is made of lithium niobate crystal was proposed and successfully tested in practice. This element is used for electronically controlled adjustment of the angular position of an X-ray optical monochromator in a range of up to 200″ and is characterized by a high relative linearity (up to 98%), repeatability (the repeatability error is no more than 2%), and low control voltages (up to 100 V). The hysteresis- free behavior of the dependence of the angular position of the element on the control element, which demonstrates the high efficiency of the hysteresis-free monolithic bimorphic piezoactuators as controlled elements of X-ray optics, is shown.

Thermomechanical behavior of bulk NiTi shape-memory-alloy microactuators based on bimorph actuation

Abstract: Shape-memory-alloy (SMA) has attracted considerable attention in recent years as a smart and efficient material, due to its unique properties. SMA microactuators became one of the potential solutions for unresolved issues in microelectromechanical systems (MEMS). This paper presents a thermomechanical behavior analysis of bimorph SMA structure and studies the effect of varying the SMA layer thickness, the type of stress layer and its thickness, and the processing temperature on the displacement of the microactuator. Furthermore, the analyzed results were verified by experimental work, where the fabrication of the SMA microactuators followed the standards of the MEMS fabrication process. SiO2, Si3N4 and Poly-Si were used as stress layers. The fabrication results showed that the bimorph SMA structure achieved maximum displacement when SiO2 was used. The SMA structure with dimensions of 10 mm (length) × 2 mm (width) × 80 µm (thickness), had maximum displacement of 804 µm when 4.1 µm of SiO2 layer was deposited at a temperature of 400 °C.

Sensitivity Enhancement in Magnetic Sensors Based on Ferroelectric-Bimorphs and Multiferroic Composites

Abstract: Multiferroic composites with ferromagnetic and ferroelectric phases have been studied in recent years for use as sensors of AC and DC magnetic fields. Their operation is based on magneto-electric (ME) coupling between the electric and magnetic subsystems and is mediated by mechanical strain. Such sensors for AC magnetic fields require a bias magnetic field to achieve pT-sensitivity. Novel magnetic sensors with a permanent magnet proof mass, either on a ferroelectric bimorph or a ferromagnetic-ferroelectric composite, are discussed. In both types, the interaction between the applied AC magnetic field and remnant magnetization of the magnet results in a mechanical strain and a voltage response in the ferroelectric. Our studies have been performed on sensors with a Nd-Fe-B permanent magnet proof mass on (i) a bimorph of oppositely-poled lead zirconate titanate (PZT) platelets and (ii) a layered multiferroic composite of PZT-Metglas-Ni. The sensors have been characterized in terms of sensitivity and equivalent magnetic noise N. Noise N in both type of sensors is on the order of 200 pT/√Hz at 1 Hz, a factor of 10 improvement compared to multiferroic sensors without a proof mass. When the AC magnetic field is applied at the bending resonance for the bimorph, the measured N ≈ 700 pT/√Hz. We discuss models based on magneto-electro-mechanical coupling at low frequency and bending resonance in the sensors and theoretical estimates of ME voltage coefficients are in very good agreement with the data.

Energy harvesting using piezoelectric materials in aerospace structures

Abstract: Piezoelectric energy harvesters (PEHs) are piezoelectric architectures that are smartly designed to maximum capture ambient vibration/motion energy into piezoelectric material and convert the mechanical energy into electrical energy. The critical piezoelectric material properties for energy harvesting are briefly introduced to provide the reader with a basic background. The state-of-the-art piezoelectric energy harvesting technologies have been reviewed. These PEH concepts include the cantilever beam-based unimorph and bimorph PEHs, flextensional PEHs, edge-clamped PEHs, and the advanced PEHs. Flextensional PEHs are the most promising PEH technology on the market because their average power output is at least one order of magnitude higher than cantilever beam PEHs and edge-clamped PEHs. Flextensional PEHs are also relatively easily integrated into aerospace space systems with little effect on flow dynamic control. In addition, flextensional PEHs can be operated in both resonance and off-resonance modes. Cymbal-type flextensional PEH research opened the door to flextensional PEHs. The “33” mode multilayer stack-based flextensional PEH is one of the most promising PEHs for practical application, with advantages such as capturing more mechanical energy into the piezoelectric structure, increasing mechanical to electrical energy conversion efficiency three to fivetimes, and increasing energy storage efficiency with optimized multilayer configuration. The electrical power delivery from a piezoelectric structure to a resistive load and the energy storage issues are addressed. PEH characterization methods are briefly introduced. Finally, suggestions on PEHs for aerospace applications are discussed.

Dynamic Electromechanical Coupling of Piezoelectric Bending Actuators

Abstract: Electromechanical coupling defines the ratio of electrical and mechanical energy exchanged during a flexure cycle of a piezoelectric actuator. This paper presents an analysis of the dynamic electromechanical coupling factor (dynamic EMCF) for cantilever based piezoelectric actuators and provides for the first time explicit expressions for calculation of dynamic EMCF based on arrangement of passive and active layers, layer geometry, and active and passive materials selection. Three main cantilever layer configurations are considered: unimorph, dual layer bimorph and triple layer bimorph. The actuator is modeled using standard constitutive dynamic equations that relate deflection and charge to force and voltage. A mode shape formulation is used for the cantilever dynamics that allows the generalized mass to be the actual mass at the first resonant frequency, removing the need for numerical integration in the design process. Results are presented in the form of physical insight from the model structure and also numerical evaluations of the model to provide trends in dynamic EMCF with actuator design parameters. For given material properties of the active and passive layers and given system overall damping ratio, the triple layer bimorph topology is the best in terms of theoretically achievable dynamic EMCF, followed by the dual layer bimorph. For a damping ratio of 0.035, the dynamic EMCF for an example dual layer bimorph configuration is 9% better than for a unimorph configuration. For configurations with a passive layer, the ratio of thicknesses for the passive and active layers is the primary geometric design variable. Choice of passive layer stiffness (Young’s modulus) relative to the stiffness of the material in the active layer is an important materials related design choice. For unimorph configurations, it is beneficial to use the highest stiffness possible passive material, whereas for triple layer bimorph configurations, the passive material should have a low stiffness. In all cases, increasing the transverse electromechanical coupling coefficient of the active material improves the dynamic EMCF.

Optimization for the Harvesting Structure of the Piezoelectric Bimorph Energy Harvesters Circular Plate by Reduced Order Finite Element Analysis

Abstract: The power generation efficiency of piezoelectric energy harvesters is dependent on the coupling of their resonant frequency with that of the source vibration. The mechanical design of the energy harvester plays an important role in defining the resonant frequency characteristics of the system and therefore in order to maximize power density, it is important for a designer to be able to model, simulate and optimize designs to match new target applications. This paper gives a detailed calculation of piezoelectric energy harvesters that is in the form of a bimorph-circular plate fixed in the contour in the device frame by finite element (FE) analysis using the commercially available software package ANSYS, ACELAN. The piezoelectric bimorph is assumed to be driven into flexural vibration by an ambient acoustic source to convert the mechanical energies into electric energies. The optimal design was based on matching the resonant frequency of the device with the environmental exciting frequency, and balancing t...

Multi-objective shape design optimization of piezoelectric energy harvester using artificial immune system

Abstract: Energy harvesting is about deriving energy from environment and converting into electricity. In this paper, optimal design of a cantilever piezoelectric energy harvester is presented with the aim to capture electrical power from a vibratory feeder in mining industry. Rayleigh---Ritz method is utilized for the modeling of the cantilever piezoelectric, taking into account possible variation in the width, nonequivalent layer lengths and thickness for unimorph and bimorph configurations. Innovatively, intelligent artificial immune system is utilized for multi-objective optimization of the shape parameters of the system. To verify the presented analytical shape optimization method, finite element analysis of the designed system is also presented, to investigate the output voltage and stress distribution along the piezoelectric layer. Moreover, the experimental setup is generated and verification tests are performed to derive frequency response diagram of the system. The obtained results are encouraging, indicating good agreement between experiments, FE analysis and theoretical results.

Optical coherence tomography endoscopic probe based on a tilted MEMS mirror.

Abstract: This paper reports a compact microendoscopic OCT probe with an outer diameter of only 2.7 mm. The small diameter is enabled by a novel 2-axis scanning MEMS mirror with a preset 45° tilted angle. The tilted MEMS mirror is directly integrated on a silicon optical bench (SiOB). The SiOB provides mechanical support and electrical wiring to the mirror plate via a set of bimorph flexure, enabling a compact probe mount design without the requirement of a 45° slope, which is capable to dramatically reduce the probe size and ease the assembly process. Additionally, the SiOB also provides trenches with properly-designed opening widths for automatic alignment of the MEMS mirror, GRIN lens and optical fiber. The 45°-tilted MEMS mirror plate is actuated by four electrothermal bimorph actuators. The packaged 2.7 mm-diameter probe offers 2-axis side-view optical scanning with a large optical scan range of 40° at a low drive voltage of 5.5 Vdc in both axes, allowing a lateral scan area of 2.2 mm × 2.2 mm at a 3 mm working distance. High-resolution 2D and 3D OCT images of the IR card, ex vivo imaging of meniscus specimens and rat brain slices, in vivo imaging of the human finger and nail have been obtained with a TDOCT system.

Biomimetic flexible plate actuators are faster and more efficient with a passive attachment

Abstract: Using three-dimensional computer simulations, we probe biomimetic free swimming of an internally actuated flexible plate in the regime near the first natural frequency. The plate is driven by an oscillating internal moment approximating the actuation mechanism of a piezoelectric macro fiber composite (MFC) bimorph. We show in our simulations that the addition of a passive attachment increases both swimming velocity and efficiency. Specifically, if the active and passive sections are of similar size, the overall performance is the best. We determine that this optimum is a result of two competing factors. If the passive section is too large, then the actuated portion is unable to generate substantial deflection to create sufficient thrust. On the other hand, a large actuated section leads to a bending pattern that is inefficient at generating thrust especially at higher frequencies.

Modeling and analysis of piezoelectric beam with periodically variable cross-sections for vibration energy harvesting

Abstract: A bimorph piezoelectric beam with periodically variable cross-sections is used for the vibration energy harvesting. The effects of two geometrical parameters on the first band gap of this periodic beam are investigated by the generalized differential quadrature rule (GDQR) method. The GDQR method is also used to calculate the forced vibration response of the beam and voltage of each piezoelectric layer when the beam is subject to a sinusoidal base excitation. Results obtained from the analytical method are compared with those obtained from the finite element simulation with ANSYS, and good agreement is found. The voltage output of this periodic beam over its first band gap is calculated and compared with the voltage output of the uniform piezoelectric beam. It is concluded that this periodic beam has three advantages over the uniform piezoelectric beam, i.e., generating more voltage outputs over a wide frequency range, absorbing vibration, and being less weight.

Investigation on the Selection of Piezoelectric Materials for the Design of an Energy Harvester System to Generate Energy from Traffic

Abstract: This article investigates various existing piezoelectric materials and the structures of the piezoelectric transducers. Then the article explores the idea of using the electricity generated using piezoelectric elements and compares the energy requirement of this era of power electronics. Then, the most compatible piezoelectric transducer for producing sustainable energy from the road traffic was analyzed using the finite element analysis. This included the various structural designs of the piezoelectric harvester designs to determine the performance of the piezoelectric material. The structures focused on this article are namely the Pile type, Multilayered, Thunder, Bridge, Cymbal and Moonie piezoelectric generators. The finite element analysis was also used to categorize the chemical behavior of various piezoelectric elements. After which, the article focuses on the two main types of implementation of the piezoelectric generators on the road to produce the sustainable form of energy. This energy is captured by harnessing the wasted vibration and kinetic energy due to the moving vehicles on the surface of the road. These two main types of implementation include the cantilever beam type implementation such as the bimorph with a tip mass, which requires a fixed support. The other implementation was based on embedding the piezoelectric transducers into the road to harvest the strain and kinetic energy due to the vehicles directly.