Showing papers on "Bimorph published in 2017"
TL;DR: Two applications of this type of soft actuators were demonstrated towards biomimetic robotics - a crawling robot that can walk spontaneously on ratchet surfaces and a soft gripper that is capable of manipulating lightweight and delicate objects.
Abstract: Low-voltage and extremely flexible electrothermal bimorph actuators were fabricated in a simple, efficient and scalable process. The bimorph actuators were made of flexible silver nanowire (AgNW) based heaters, which exhibited a fast heating rate of 18 °C s−1 and stable heating performance with large bending. The actuators offered the largest bending angle (720°) or curvature (2.6 cm−1) at a very low actuation voltage (0.2 V sq−1 or 4.5 V) among all types of bimorph actuators that have been reported to date. The actuators can be designed and fabricated in different configurations that can achieve complex patterns and shapes upon actuation. Two applications of this type of soft actuators were demonstrated towards biomimetic robotics – a crawling robot that can walk spontaneously on ratchet surfaces and a soft gripper that is capable of manipulating lightweight and delicate objects.
134 citations
TL;DR: In this paper, the suspension angle of the individual bimorph cantilever in air can be precisely controlled through electrostatic actuation that determines the operative phase diagram of the metadevice.
Abstract: Metasurfaces have provided a novel route to control the local phase of electromagnetic radiation through subwavelength scatterers where the properties of each element remain passive. A passive metasurface design can only achieve a specific functionality as it is extremely challenging to reconfigure each element that contributes toward the control of the radiation. In this work, the authors propose a different scheme based on microelectromechanical system (MEMS) to reconfigure the resonance and radiation phase via control of each dipolar element. The suspension angle of the individual bimorph cantilever in air can be precisely controlled through electrostatic actuation that determines the operative phase diagram of the metadevice. The dynamic polarization conversion is demonstrated through global control. In addition, it is proposed that a multifunctional operation such as dynamic wavefront deflection and rewritable holographic display can be accomplished by using 1D and 2D control of the cantilever array when each cantilever in the MEMS metadevice array is uniformly and accurately controlled in the large-area samples. Such a rewritable proposition can enable myriad of applications of MEMS-based metadevices in polarization-division multiplexing and dynamic flat lenses.
103 citations
TL;DR: The robust magnetic behaviors against mechanical bending were characterized by hysteresis measurements and magnetic force microscopy, which maintain a saturation magnetization of ∼120-150 emu/cm3 under different bending states.
Abstract: A bimorph composed of ferrimagnetic cobalt ferrite (CoFe2O4, CFO) and flexible muscovite was fabricated via van der Waals epitaxy. The combination of X-ray diffraction and transmission electron microscopy was conducted to reveal the heteroepitaxy of the CFO/muscovite system. The robust magnetic behaviors against mechanical bending were characterized by hysteresis measurements and magnetic force microscopy, which maintain a saturation magnetization (Ms) of ∼120–150 emu/cm3 under different bending states. The large magnetostrictive response of the CFO film was then determined by digital holographic microscopy, where the difference of magnetostrction coefficient (Δλ) is −104 ppm. The superior performance of this bimorph is attributed to the nature of weak interaction between film and substrate. Such a flexible CFO/muscovite bimorph provides a new platform to develop next-generation flexible magnetic devices.
101 citations
TL;DR: This study develops flexible, all-inorganic actuators based on bimorph structures composed of vanadium dioxide (VO2) and carbon nanotube (CNT) thin films that find applications in biomimetic inspect wings, millimeter-scale fingers, and physiological-temperature driven switches.
Abstract: Flexible actuators responsive to multiple stimuli are much desired in wearable electronics. However, general designs containing organic materials are usually subject to slow response and limited lifetime, or high triggering threshold. In this study, we develop flexible, all-inorganic actuators based on bimorph structures composed of vanadium dioxide (VO2) and carbon nanotube (CNT) thin films. The drastic, reversible phase transition of VO2 drives the actuators to deliver giant amplitude, fast response up to ∼100 Hz, and long lifetime more than 1 000 000 actuation cycles. The excellent electrical conductivity and light absorption of CNT thin films enable the actuators to be highly responsive to multiple stimuli including light, electric, and heat. The power consumption of the actuators can be much reduced by doping VO2 to lower its phase transition temperature. These flexible bimorph actuators find applications in biomimetic inspect wings, millimeter-scale fingers, and physiological-temperature driven swit...
92 citations
TL;DR: In this article, a 2D auxetic substrate is sandwiched between two piezoelectric layers, which is capable of introducing auxetic behaviors and thus increasing the transverse stress in the piezelectric layer when subjected to a longitudinal stretching load.
Abstract: This letter presents a piezoelectric bimorph with auxetic (negative Poisson’s ratio) behaviors for increased power output in vibration energy harvesting. The piezoelectric bimorph comprises a 2D auxetic substrate sandwiched between two piezoelectric layers. The auxetic substrate is capable of introducing auxetic behaviors and thus increasing the transverse stress in the piezoelectric layers when the bimorph is subjected to a longitudinal stretching load. As a result, both 31- and 32-modes are simultaneously exploited to generate electric power, leading to an increased power output. The increasing power output principle was theoretically analyzed and verified by finite element (FE) modelling. The FE modelling results showed that the auxetic substrate can increase the transverse stress of a bimorph by 16.7 times. The average power generated by the auxetic bimorph is 2.76 times of that generated by a conventional bimorph.
63 citations
TL;DR: Kim et al. as discussed by the authors presented a photothermally foldable soft bimorph by dry transfer of poly(3,4-ethylenedioxythiophene)s (PEDOT) onto poly(dimethylsiloxane) film.
Abstract: A photothermally foldable soft bimorph was prepared via the dry transfer of poly(3,4-ethylenedioxythiophene) (PEDOT) doped with tosylate onto a poly(dimethylsiloxane) film. The photothermal folding was optimized via reversible actuation by controlling the thickness of each layer and the temperature increase to afford large deflection and displacement up to 150° and >20 mm, respectively, upon exposure to near-infrared (NIR) light (808 nm). A two-dimensional array of the bimorph converted into complex three-dimensional architectures, such as a Venus flytrap, under light and reversibly unfolded in the dark. Taking advantage of the photothermal nature of PEDOT, a localized heat pocket was generated inside the folding structure. Thus, a Venus flytrap with a hot pocket reaching 100 °C was realized for the first time. The Venus flytrap could trap and move an object within a few seconds of NIR exposure. A bilayer material that behaves like a Venus flytrap when illuminated by infrared light has been created by researchers in South Korea. Biomimetic materials – substances that replicate the behavior of biological organisms and structures – offer a route to producing engineered devices with novel functionality. The biomimetic material made by Eunkyoung Kim and colleagues from Yonsei University consists of two soft polymers – a spin–coated layer of polydimethylsiloxane (PDMS) on a spin-coated film of poly (3, 4–ethylenedioxythiophene) (PEDOT) doped with tosylate. PEDOT has photothermal properties, meaning that incident light leads to localized heating. This heat then changes the volume of the PDMS, which makes the bilayer fold. The team used this effect to create complex three–dimensional architectures and hot trap including a Venus flytrap, which snapped close within a few seconds of being exposed to near–infrared radiation. A photothermally foldable soft bimorph was prepared by dry transfer of poly(3,4-ethylenedioxythiophene)s (PEDOT) onto poly(dimethylsiloxane) film. The reversible folding nature of the soft bimorph was programmable to convert the two-dimensional (2D) array of bimorph into complex three-dimensional (3D) architectures such as Venus flytrap under light. These 3D structures were returned reversibly to the original unfolded 2D structures under dark. The Venus flytrap could perform a task to snap and move an object within few second of near-infrared exposure. A localized heat pocket was generated inside the folding structure due to the large photothermal effect of PEDOT.
63 citations
TL;DR: In this article, a high performance bimorph piezoelectric MEMS harvester with bulk PZT thick films on both sides of a flexible thin beryllium-bronze substrate via bonding and thinning technologies is presented.
Abstract: This letter presents a high performance bimorph piezoelectric MEMS harvester with bulk PZT thick films on both sides of a flexible thin beryllium-bronze substrate via bonding and thinning technologies. The upper and lower PZT layers are thinned down to about 53 μm and 76 μm, respectively, and a commercial beryllium bronze with the thickness of about 50 μm is used as the substrate. The effective volume of this device is 30.6 mm3. The harvester with a tungsten proof mass generated the close-circuit peak-to-peak voltage of 53.1 V, the output power of 0.979 mW, and the power density of 31.99 mW/cm3 with the matching load resistance of 360 kΩ at the applied acceleration amplitude of 3.5 g and the applied frequency of 77.2 Hz. Meanwhile, in order to evaluate the stability, the device was measured continuously under applied acceleration amplitudes of 1.0 g and 3.5 g for one hour and demonstrated a good stability. Then, the harvester was utilized to light up LEDs and about twenty-one serial LEDs were lighted up a...
56 citations
TL;DR: In this paper, a coupled piezoelectric-circuit finite element (FE) model for a mechanically plucked bimorph energy harvester (Mech-KEH) was developed.
Abstract: This paper develops a coupled piezoelectric-circuit finite element (FE) model for a mechanically plucked piezoelectric energy harvester (Mech-PEH), which uses plastic plectra to pluck piezoelectric bimorph cantilevers. The Mech-PEH was modelled as a piezoelectric cantilever with either a displacement or a force applied at the tip, and a load resistor connected across its electrodes. The FE model was validated with a difference around 2.7% between the simulated and measured energy outputs and able to predict the vibration- and energy-related characteristics of the Mech-KEH. It was used to investigate the effects of the bimorph’s geometric parameters and the plucking frequency on the energy outputs. It is concluded that (1) when the same plucking force is used, the energy output of the Mech-PEH can be increased by reducing the stiffness of the bimorph through reducing its width or thickness, or increasing its length, and (2) a high plucking frequency with a free vibration period is beneficial in improving the energy output. It is pointed out that the bending fatigue strength of the piezoelectric material limits the designed highest energy output, and that when designing bimorph parameters for the Mech-PEH, both the energy output and the expected life time should be considered.
46 citations
TL;DR: In this article, the authors derived the mathematical model of a VEH with two piezoelectric cantilevers symmetrically located at two open ends of a guiding channel with a rolling steel ball inside as the proof mass.
Abstract: Impact-based vibration energy harvesters (VEHs) with a rolling proof mass are promising candidates for scavenging ambient low-level, broadband, and low-frequency vibration energy. This paper derives the mathematical model of a VEH with two piezoelectric cantilevers symmetrically located at two open ends of a guiding channel with a rolling steel ball inside as the proof mass. The model includes the equation of motion and coupled electrical circuit equation of the bimorphs under base excitation, the equations of motion of the rolling proof mass under base excitation, and the collision equations between the bimorphs and the proof mass. Simulation results show that the scavenging efficiency of low-level vibration can be improved by introducing the rolling proof mass. The numerical results agree well with the experiments when the harvester prototype is horizontally fixed on the base. Under the base excitation of 1 g(=9.8 m/s 2 ), the maximum output power of one bimorph is about 511 μW at 18.4 Hz.
38 citations
TL;DR: This paper proposes an alternative method for predicting the power output of a bimorph cantilever beam using a finite-element method for both static and dynamic frequency analyses.
Abstract: Piezoelectric materials are excellent transducers for converting mechanical energy from the environment for use as electrical energy. The conversion of mechanical energy to electrical energy is a key component in the development of self-powered devices, especially enabling technology for wireless sensor networks. This paper proposes an alternative method for predicting the power output of a bimorph cantilever beam using a finite-element method for both static and dynamic frequency analyses. A novel approach is presented for optimising the cantilever beam, by which the power density is maximised and the structural volume is minimised simultaneously. A two-stage optimisation is performed, i.e., a shape optimisation and then a "topology" hole opening optimisation.
37 citations
TL;DR: The experimental results show that the small-scale EH generates sufficient power for state of the art pacemakers and the robustness of the device to the heart rate is studied by measuring the relation between the power output and theheart rate.
Abstract: This paper studies the fabrication and testing of a magnet free piezoelectric energy harvester (EH) for powering biomedical devices and sensors inside the body. The design for the EH is a fan-folded structure consisting of bimorph piezoelectric beams folding on top of each other. An actual size experimental prototype is fabricated to verify the developed analytical models. The model is verified by matching the analytical results of the tip acceleration frequency response functions (FRF) and voltage FRF with the experimental results. The generated electricity is measured when the EH is excited by the heartbeat. A closed loop shaker system is utilized to reproduce the heartbeat vibrations. Achieving low fundamental natural frequency is a key factor to generate sufficient energy for pacemakers using heartbeat vibrations. It is shown that the natural frequency of the small-scale device is less than due to its unique fan-folded design. The experimental results show that the small-scale EH generates sufficient power for state of the art pacemakers. The 1 cm3 EH with tip mass generates more than of power from a normal heartbeat waveform. The robustness of the device to the heart rate is also studied by measuring the relation between the power output and the heart rate.
TL;DR: In this article, the degradation of bimorph piezoelectric bending beams was investigated under symmetrical and asymmetrical sinusoidal loading and it was shown that besides a loss in output power, the most dramatic effect of degradation is a shift in resonance frequency.
Abstract: Piezoelectric energy harvesting is an attractive alternative to battery powering for wireless sensor networks. However, in order for it to be a viable long term solution the fatigue life needs to be assessed. Many vibration harvesting devices employ bimorph piezoelectric bending beams as transduction elements to convert mechanical to electrical energy. This paper introduces two degradation studies performed under symmetrical and asymmetrical sinusoidal loading. It is shown that besides a loss in output power, the most dramatic effect of degradation is a shift in resonance frequency which is highly detrimental to resonant harvester designs. In addition, micro-cracking was shown to occur predominantly in piezoelectric layers under tensile stress. This opens the opportunity for increased life time through compressive operation or pre-loading of piezoceramic layers.
TL;DR: In this article, the authors used very thin stainless-steel (SS) foils with thickness of 20μm as base substrates, and the PZT thin films were deposited on both surface of SS foils by radiofrequency (rf) magnetron sputtering.
Abstract: The airflow energy harvesters (AFEHs) of piezoelectric Pb(Zr,Ti)O 3 (PZT) thin films were developed. Electric power was generated by self-excited vibration of the piezoelectric bimorph cantilevers induced by a continuous airflow. To enhance the vibration in low wind speed, we used very thin stainless-steel (SS) foils with thickness of 20 μm as base substrates, and the PZT thin films were deposited on both surface of SS foils by radio-frequency (rf) magnetron sputtering. When the angle of attack (AOA) was 20° and above, stable self-excited vibration was generated at wind speeds larger than 4.5 m/s. When the wind speed was 8 m/s, the maximum output power reached 36.4 μW at the AOA of 20°. From the evaluation of the thickness effect of the base cantilevers, it was confirmed that the thinner substrate reduced not only cut-in wind speed but also maximum output voltage.
TL;DR: In this article, the authors demonstrate the successful synthesis, integration, and characterization of hybrid 2D material systems consisting of tandem repeat (TR) proteins inspired by squid ring teeth and graphene oxide (GO).
TL;DR: In this paper, a U-shaped bimorph actuator is constructed by cutting out the middle part of the composite/aluminum laminates, where the MWCNT-aligned direction is parallel to the length direction of the U-shape actuators, and the bending displacement and force output are modeled by combining strength-of-materials theories and rule of mixtures.
Abstract: By using aligned multi-walled carbon nanotube (MWCNT) reinforced epoxy composites possessing a negative coefficient of thermal expansion (CTE) as well as high Young’s modulus and aluminum foils, novel electrothermal bimorph actuators are fabricated. U-shaped bimorph actuators are formed by cutting out the middle part of the composite/aluminum laminates, where the MWCNT-aligned direction is parallel to the length direction of the U-shaped bimorph actuators. We demonstrate that the bimorph actuators with a free length of 16 mm show a large bending displacement and force output, and their values are 7.6–10.0 mm and 0.8–7.8 mN under a DC voltage of 5.2–6.0 V. Based on these results, the bending displacement and force output of the bimorph actuator are modeled by combining strength-of-materials theories and rule of mixtures (Voigt model and Turner’s model). By using these models, we indicate contributions from two sources toward the increased bending displacement and force output in the bimorph actuator: (i) designing the Young’s modulus and negative CTE of the composite layer by controlling the MWCNT volume fraction and the dimensional parameters (especially thickness) of the bimorph actuator; (ii) selecting materials having a high Young’s modulus as well as a large CTE as the second layer.
TL;DR: In this paper, an optical 2-axis Micro Electro-Mechanical System (MEMS) micromirror actuated by a pair of electrothermal actuators and a set of passive torsion bars is presented.
Abstract: This paper introduces an optical 2-axis Micro Electro-Mechanical System (MEMS) micromirror actuated by a pair of electrothermal actuators and a set of passive torsion bars. The actuated element is a dual-reflective circular mirror plate of 1 m m in diameter. This inner mirror plate is connected to a rigid frame via a pair of torsion bars in two diametrically opposite ends located on the rotation axis. A pair of electrothermal bimorphs generates a force onto the perpendicular free ends of the mirror plate in the same angular direction. An array of electrothermal bimorph cantilevers deflects the rigid frame around a working angle of 45 ∘ for side-view scan. The performed scans reach large mechanical angles of 32 ∘ for the frame and 22 ∘ for the in-frame mirror. We denote three resonant main modes, pure flexion of the frame at 205 Hz , a pure torsion of the mirror plate at 1.286 kHz and coupled mode of combined flexion and torsion at 1.588 kHz . The micro device was fabricated through successive stacks of materials onto a silicon-on-insulator wafer and the patterned deposition on the back-side of the dual-reflective mirror is achieved through a dry film photoresist photolithography process.
TL;DR: In this paper, a bending pneumatic actuator that can be mass-produced is presented, which is capable of generating blocking force up to 7.32 N and bending angle up to 224.3° with an input pressure of 0.675 MPa and an operating switching frequency of 20 Hz with no more than 7% radial expansion.
Abstract: Typical pneumatic actuators provide one directional linear motion, but in many applications bending motion is required. Achieving bending motion with a typical pneumatic actuator requires a complex mechanism to translate the linear motion into bending. Hence, a bending pneumatic actuator will be desirable. This paper presents a bending pneumatic actuator that can be mass-produced. This actuator was modelled by using finite element analysis over a range of parameters. Systematic experimentation was carried out to validate the FEA simulations. A pneumatic bending actuator of length 180–220 mm, inner diameter 7–11 mm, wall thickness 2–3.2 mm, is capable of generating blocking force up to 7.32 N and bending angle up to 224.3° with an input pressure of 0.675 MPa and an operating switching frequency of 20 Hz with no more than 7% radial expansion for the samples under test. The low profile, light weight, compliant nature and robustness of the actuators developed in this work lead to a large variety of potential applications.
TL;DR: In this paper, a Rayleigh-Ritz model of a thin cylindrical shell is developed to predict its response subject to concurrent active and passive damping treatments, which take the form of piezoelectric patches and a distributed cardboard liner.
TL;DR: A discrete-layout bimorph piezoelectric deformable mirror (DBPDM) is proposed and its realistic electromechanical model is developed and it is suggested that the stroke of the DBPDM is larger than 10 microns and its resonance frequency is 53.3 kHz.
Abstract: We have proposed a discrete-layout bimorph piezoelectric deformable mirror (DBPDM) and developed its realistic electromechanical model. Compared with the conventional piezoelectric deformable mirror (CPDM) and the bimorph piezoelectric deformable mirror (BPDM), the DBPDM has both a larger stroke and a higher resonance frequency by integrating the strengths of the CPDM and the BPDM. To verify the advancement, a 21-elements DBPDM is studied in this paper. The results have suggested that the stroke of the DBPDM is larger than 10 microns and its resonance frequency is 53.3 kHz. Furthermore, numerical simulation is conducted on the deformation of the mirror using the realistic electromechanical model, and the dependence of the influence function upon the size of the radius of push pad is analyzed.
26 Jul 2017
TL;DR: A wrist-worn eccentric rotor-based energy harvester utilizing multiple magnetically plucked flower petal-shaped bimorph lead zirconate titanate (PZT) thin-film beams was designed and fabricated as discussed by the authors.
Abstract: A wrist-worn eccentric rotor-based energy harvester utilizing multiple magnetically plucked flower petal-shaped bimorph lead zirconate titanate (PZT) thin-film beams was designed and fabricated. The bimorph beams were formed by depositing {001} oriented PZT films up to 5.4 μm in thickness on both sides of a 50 μm thick nickel foil. The prototype was characterized with an analytical system-level model and a bench-top swing-arm test set-up. The prototype can achieve approximately 40 μW power output from a bench-top pseudo walking motion input. Further simulation suggests that improvement can be made by growing thicker PZT layers.
TL;DR: A thermodynamic analysis of the composite hydrogel containing an embedding coupled chemistry for light-sensitized catalytic reactions that enables chemo-mechanical actuation of poly(acrylic acid)-based gels is described.
Abstract: We describe a composite hydrogel containing an embedding coupled chemistry for light-sensitized catalytic reactions that enables chemo-mechanical actuation of poly(acrylic acid)-based gels. In these materials, a photosensitizer and catalyst—ruthenium trisbipyridine and iridium dioxide nanoparticles, respectively—are incorporated into the hydrogel where together, with visible light irradiation, they undergo a catalytic water-oxidation reaction that lowers the pH and induces a dissipative/chemically-driven strain change in the gel. To demonstrate the capacity for 3D chemo-mechanical actuation, a layer of non-pH responsive poly(2-hydroxyethyl methacrylate) is added to the photo-active composite gel to create a model bimorph actuator. Triggering and terminating the water-oxidation reaction leads to a programmatic expansion and contraction of the active layer, which induces different modes of biomimetic curling motions in the bimorph actuator in light and dark environments. The efficiency of this system is fundamentally limited by the system-level design, which provides no capacity to sustain a local pH gradient against diffusive mixing. Even so, if the initial pH of the background solution is reestablished either actively or passively between each reaction cycle, it is possible to realize multiple cycles of reversible actuation. We describe a thermodynamic analysis of this system which identifies specific features mediating efficiency losses and conceptual requirements for mesoscopic design rules for optimization of this system and for advancing soft actuation systems in general.
TL;DR: In this paper, a vibrating bimorph actuator based on a bidomain bending-type crystal of lithium niobate has been used for time-resolved X-ray experiments at both laboratory X-Ray sources and synchrotron facilities.
Abstract: A new approach to time-resolved X-Ray experiments implementation at both laboratory X-Ray sources and synchrotron facilities is presented. A time resolution of few milliseconds per one rocking curve measurement can be reached by using a new X-Ray optics element – vibrating bimorph actuator based on a bidomain bending-type crystal of lithium niobate. The ranges of X-Ray beam angular or energy changeover are defined by the actuator operational mode and resonant response. The time and spatial parameters for X-ray optical element based on bimorph actuator have been estimated. The ranges of actuator angular changeover in a dynamical mode at various frequencies (including resonance) of bidomain crystal vibrations have reached up to 100 arcseconds in а quasistatic mode and more than 500 arcseconds in а resonance mode at the control voltage of 22 V and vibration frequency up to 8 kHz (which corresponds to time resolution of 0.125 milliseconds). The numerical algorithms for processing of the experimental data measured using the bimorph optical element have been developed. The examples of X-Ray beam angular changeover reached in different actuator vibration modes and possible application of such approach are presented in the work.
TL;DR: In this article, the authors analyzed the response of a piezoelectric bimorph actuator considering the effect of self-induced electric displacement field, which can significantly impact the tip deflection and the stiffness of the actuator.
TL;DR: In this article, the optimal configuration of anisotropic piezocomposite actuators for vibration control of flexible structures is investigated for unimorph and antisymmetric angle-placement.
Abstract: Optimal configuration of anisotropic piezocomposite actuators is investigated for vibration control of flexible structures. Actuation effects of the actuators in unimorph and antisymmetric angle-pl...
01 Jul 2017-Microsystem Technologies-micro-and Nanosystems-information Storage and Processing Systems
TL;DR: In this paper, the vibratory behavior of bimorph resonant harvesters coupled to nonlinear circuits of energy harvesting including standard and switched techniques is investigated, and an analytical approach employing some perturbation technique is utilized to derive a closed-form solution for the generated power response of these electromechanically coupled devices in a general case where damping due to energy harvesting cannot be considered as negligible.
Abstract: Application of piezoelectric materials in vibration energy harvesters is expanding rapidly, especially in MEMS-based devices, due to their uncomplicated fabrication processes and reasonable power generation potential. In addition to standard power extraction methods, nonlinear switched techniques with capability of generated power enhancement, are previously developed and extensively applied in energy harvesting using piezoelectric materials. In this article, vibratory behavior of bimorph resonant harvesters coupled to nonlinear circuits of energy harvesting including standard and switched techniques is investigated. An analytical approach employing some perturbation technique, is utilized to derive a closed-form solution for the generated power response of these electromechanically coupled devices in a general case where damping due to energy harvesting cannot be considered as negligible. While linear models lead to significant errors in prediction of harvested power especially in the case of implementing switched techniques, results of the present nonlinear analysis are in a very good agreement with that of numerical solutions. Results indicate that the application of nonlinear switched techniques can lead to peak power enhancement and bandwidth broadening of weakly and moderately coupled devices, respectively, while in the case of strongly coupled devices switched harvesting techniques are not shown to be reasonably efficient.
TL;DR: In this paper, a folding beam-type piezoelectric phononic crystal model is proposed to isolate vibration, and the effects of geometrical and circuit parameters on the band gaps are analyzed.
Abstract: A folding beam-type piezoelectric phononic crystal model is proposed to isolate vibration. Two piezoelectric bimorphs are joined by two masses as a folding structure to comprise each unit cell of the piezoelectric phononic crystal. Each bimorph is connected independently by a resistive-inductive resonant shunting circuit. The folding structure extends the propagation path of elastic waves, while its structure size remains quite small. Propagation of coupled extension-flexural elastic waves is studied by the classical laminated beam theory and transfer matrix method. The theoretical model is further verified with the finite element method (FEM). The effects of geometrical and circuit parameters on the band gaps are analyzed. With only 4 unit cells, the folding beam-type piezoelectric phononic crystal generates two Bragg band gaps of 369Hz to 1 687Hz and 2 127Hz to 4 000Hz. In addition, between these two Bragg band gaps, a locally resonant band gap is induced by resonant shunting circuits. Appropriate circuit parameters are used to join these two Bragg band gaps by the locally resonant band gap. Thus, a low-frequency and broad band gap of 369Hz to 4 000Hz is obtained.
TL;DR: In this article, a monolithic mixed-hybrid finite element formulation for the predictive modeling and simulation of piezoelectric energy harvesting devices is proposed, which is capable of analyzing structures with non-uniform geometry and varying material properties.
Abstract: This paper is devoted to monolithic modeling of piezoelectric energy harvesting devices. From a modeling perspective, piezoelectric energy harvesting is a strongly coupled phenomenon with two-way coupling between the electromechanical effect of the piezoelectric material and the harvesting circuit. Even in applications related to shunt damping, where the attached electrical circuit is passive, accurate modeling of the strong coupling is crucial for proper evaluation of the relevant parameters. The article proposes a monolithic mixed-hybrid finite element formulation for the predictive modeling and simulation of piezoelectric energy harvesting devices. The governing equations of the coupled electromechanical problem are converted into a single integral form with six independent unknown fields. Such a holistic approach provides consistent solution to the coupled field equations which involve structural dynamics, electromechanical effect of the piezoelectric patches and the dynamics of the attached harvesting circuit. This allows accurate computation of the eigenvalues and corresponding mode shapes of a harvester for any finite resistive load coupled to the harvester. The fully three-dimensional mixed-hybrid formulation is capable of analyzing structures with non-uniform geometry and varying material properties. The results of the finite element model are verified against the analytical results of a bimorph harvester with tip mass reported in the literature.
11 Jan 2017-Microsystem Technologies-micro-and Nanosystems-information Storage and Processing Systems
TL;DR: In this article, a fuzzy logic controller (FLC) tuned proportional-integral-derivative (PID) system has been used where the smart bimorph piezo actuator is used as an active actuator for providing the dexterous behavior during robotic assembly.
Abstract: Piezoelectric actuator is one of the most versatile types of smart material based actuators which can be utilized for different industrial applications like robotics, MEMS, micro assembly, biological cell handling, self-assembly and optical component handling in photonics. By applying a potential to piezoelectric based smart actuator, it can produce micro level deflection with large force generation, very fast response and long term actuation as compared to other actuators. The characterization and performance evaluation of the bimorph piezoelectric cantilever beam using novel fuzzy logic controller (FLC) tuned proportional-integral-derivative (PID) system has been carried out where the smart bimorph piezo actuator is used as an active actuator for providing the dexterous behavior during robotic assembly. Fuzzy is introduced for fast tuning of PID and it provides the steady state characteristics. Experimentally, it is verified that the actuator produces steady state behavior of deflection for handling the object. A prototype is developed which shows the potential of handling the light weight objects for assembly.
01 May 2017-Microsystem Technologies-micro-and Nanosystems-information Storage and Processing Systems
TL;DR: In this article, the resonance frequencies of triangular bimorphs with and without a proof mass were investigated, and it was shown that triangular devices with matching resonance frequencies and volumes provide enhanced electromechanical coupling coefficients, which translate into lower optimal load resistances at the resonance (also the short-circuit resonance) frequency, and a higher optimal load resistance at the anti-resonance (also, the open circuit resonance), and a desired effect for circuitry applications.
Abstract: Energy harvesting from vibrations utilizing the d31 mode of operation via cantilevered bimorphs has been the subject of significant research over the past decade. The concept of tapering cantilevered rectangular bimorphs into triangular shapes to evenly distribute the axial strain along the surface of the cantilevered bimorphs has previously been presented in literature. However, an extensive experimental characterization of tapered and comparable rectangular bimorphs, with varying sizes, with and without the presence of a tip mass from an electronic standpoint has been elusive. In this embodiment, rectangular and triangular bimorphs of various sizes, designed with matching resonance frequencies have been investigated. It is shown that the resonance frequencies of triangular devices, with and without a proof mass match that of a rectangle when the length (i.e. altitude for isosceles triangles) to clamping widths aspect ratios match. Moreover, triangular devices with matching resonance frequencies and volumes when compared with rectangular counterparts provide enhanced electromechanical coupling coefficients, which translate into lower optimal load resistances at the resonance (also the short-circuit resonance) frequency, and a higher optimal load resistances at the anti-resonance (also the open-circuit resonance) frequency. With increasing bimorph sizes, and constant tip masses, resulting in lower maximum strains, the k2Q values improve, which shift the overall device impedance values to lower values, a desired effect for circuitry applications.
Patent•
10 May 2017
TL;DR: In this article, a power fluid coupling's non-linear vortex induced vibration energy gatherer, including last roof, a lower plate, the support column, the cantilever beam, bimorph symmetry, a cylinder body, upper and lower magnet power mechanism, rectifier circuit and super capacitor, the both ends of support column are fixed in respectively on roof and lower plate.
Abstract: The utility model discloses a power fluid coupling's non -linear vortex induced vibration energy gatherer, including last roof, a lower plate, the support column, the cantilever beam, bimorph, a cylinder body, upper and lower magnet power mechanism, rectifier circuit and super capacitor, the both ends of support column are fixed in respectively on roof and the lower plate, the one end of cantilever beam is installed on the support column, the other end is fixed at the cylinder, the cylinder is unsettled, the bimorph symmetry is fixed in on the cantilever beam, it includes the permanent magnet to go up magnetic mechanism, last repulsion magnet and two last appeal magnet, magnetic mechanism includes permanent magnet down, lower repulsion magnet and twice appeal magnet, last permanent magnet is fixed in respectively on the face of the upper and lower both ends of cylinder with lower permanent magnet, last repulsion magnet and two last appeal magnet all are fixed in on the roof, repulsion magnet and twice appeal magnet all are fixed in on the lower plate down, super capacitor passes through rectifier circuit and is connected with bimorph. This collector simple structure, and improve the energy and gather efficiency.