Showing papers on "Bimorph published in 2011"

Piezoelectric Energy Harvesting

Abstract: About the Authors. Preface. 1. Introduction to Piezoelectric Energy Harvesting. 1.1 Vibration-Based Energy Harvesting Using Piezoelectric Transduction. 1.2 An Examples of a Piezoelectric Energy Harvesting System. 1.3 Mathematical Modeling of Piezoelectric Energy Harvesters. 1.4 Summary of the Theory of Linear Piezoelectricity. 1.5 Outline of the Book. 2. Base Excitation Problem for Cantilevered Structures and Correction of the Lumped-Parameter Electromechanical Model. 2.1 Base Excitation Problem for the Transverse Vibrations. 2.2 Correction of the Lumped-Parameter Base Excitation Model for Transverse Vibrations. 2.3 Experimental Case Studies for Validation of the Correction Factor. 2.4 Base Excitation Problem for Longitudinal Vibrations and Correction of its Lumped-Parameter Model. 2.5 Correction Factor in the Electromechanically Coupled Lumped-Parameter Equations and a Theoretical Case Study. 2.6 Summary. 2.7 Chapter Notes. 3. Analytical Distributed-Parameter Electromechanical Modeling of Cantilevered Piezoelectric Energy Harvesters. 3.1 Fundamentals of the Electromechanically Coupled Distributed-Parameter Model. 3.2 Series Connection of the Piezoceramic Layers. 3.3 Parallel Connection of Piezoceramic Layers. 3.4 Equivalent Representation of the Series and the Parallel Connection Cases. 3.5 Single-Mode Electromechanical Equations for Modal Excitations. 3.6 Multi-mode and Single-Mode Electromechanical FRFs. 3.7 Theoretical Case Study. 3.8 Summary. 3.9 Chapter Notes. 4. Experimental Validation of the Analytical Solution for Bimorph Configurations. 4.1 PZT-5H Bimorph Cantilever without a Tip Mass. 4.2 PZT-5H Bimorph Cantilever with a Tip Mass. 4.3 PZT-5A Bimorph Cantilever. 4.4 Summary. 4.5 Chapter Notes. 5. Dimensionless Equations, Asymptotic Analyses, and Closed-Form Relations for Parameter Identification and Optimization. 5.1 Dimensionless Representation of the Single-Mode Electromechanical FRFs. 5.2 Asymptotic Analyses and Resonance Frequencies. 5.3 Identification of Mechanical Damping. 5.4 Identification of the Optimum Electrical Load for Resonance Excitation. 5.5 Intersection of the Voltage Asymptotes and a Simple Technique for the Experimental Identification of the Optimum Load Resistance. 5.6 Vibration Attenuation Amplification from the Short-Circuit to Open-Circuit Conditions. 5.7 Experimental Validation for a PZT-5H Bimorph Cantilever. 5.8 Summary. 5.9 Chapter Notes. 6. Approximate Analytical Distributed-Parameter Electromechanical Modeling of Cantilevered Piezoelectric Energy Harvesters. 6.1 Unimorph Piezoelectric Energy Harvester Configuration. 6.2 Electromechanical Euler-Bernoulli Model with Axial Deformations. 6.3 Electromechanical Rayleigh Model with Axial Deformations. 6.4 Electromechanical Timoshenko Model with Axial Deformations. 6.5 Modeling of Symmetric Configurations. 6.6 Presence of a Tip Mass in the Euler-Bernoulli, Rayleigh, and Timoshenko Models. 6.7 Comments on the Kinematically Admissible Trial Functions. 6.8 Experimental Validation of the Assumed-Modes Solution for a Bimorph Cantilever. 6.9 Experimental Validation for a Two-Segment Cantilever. 6.10 Summary. 6.11 Chapter Notes. 7. Modeling of Piezoelectric Energy Harvesting for Various Forms of Dynamic Loading. 7.1 Governing Electromechanical Equations. 7.2 Periodic Excitation. 7.3 White Noise Excitation. 7.4 Excitation Due to Moving Loads. 7.5 Local Strain Fluctuations on Large Structures. 7.6 Numerical Solution for General Transient Excitation. 7.7 Case Studies. 7.8 Summary. 7.9 Chapter Notes. 8. Modeling and Exploiting Mechanical Nonlinearities in Piezoelectric Energy Harvesting. 8.1 Perturbation Solution of the Piezoelectric Energy Harvesting Problem: the Method of Multiple Scales. 8.2 Monostable Duffing Oscillator with Piezoelectric Coupling. 8.3 Bistable Duffing Oscillator with Piezoelectric Coupling: the Piezomagnetoelastic Energy Harvester. 8.4 Experimental Performance Results of the Bistable Peizomagnetoelastic Energy Harvester. 8.5 A Bistable Plate for Piezoelectric Energy Harvesting. 8.6 Summary. 8.7 Chapter Notes. 9. Piezoelectric Energy Harvesting from Aeroelastic Vibrations. 9.1 A Lumped-Parameter Piezoaeroelastic Energy Harvester Model for Harmonic Response. 9.2 Experimental Validations of the Lumped-Parameter Model at the Flutter Boundary. 9.3 Utilization of System Nonlinearities in Piezoaeroelastic Energy Harvesting. 9.4 A Distributed-Parameter Piezoaeroelastic Model for Harmonic Response: Assumed-Modes Formulation. 9.5 Time-Domain and Frequency-Domain Piezoaeroelastic Formulations with Finite-Element Modeling. 9.6 Theoretical Case Study for Airflow Excitation of a Cantilevered Plate. 9.7 Summary. 9.8 Chapter Notes. 10. Effects of Material Constants and Mechanical Damping on Power Generation. 10.1 Effective Parameters of Various Soft Ceramics and Single Crystals. 10.2 Theoretical Case Study for Performance Comparison of Soft Ceramics and Single Crystals. 10.3 Effective Parameters of Typical Soft and Hard Ceramics and Single Crystals. 10.4 Theoretical Case Study for Performance Comparison of Soft and Hard Ceramics and Single Crystals. 10.5 Experimental Demonstration for PZT-5A and PZT-5H Cantilevers. 10.6 Summary. 10.7 Chapter Notes. 11. A Brief Review of the Literature of Piezoelectric Energy Harvesting Circuits. 11.1 AC-DC Rectification and Analysis of the Rectified Output. 11.2 Two-Stage Energy Harvesting Circuits: DC-DC Conversion for Impedance Matching. 11.3 Synchronized Switching on Inductor for Piezoelectric Energy Harvesting. 11.4 Summary. 11.5 Chapter Notes. Appendix A. Piezoelectric Constitutive Equations. Appendix B. Modeling of the Excitation Force in Support Motion Problems of Beams and Bars. Appendix C. Modal Analysis of a Uniform Cantilever with a Tip Mass. Appendix D. Strain Nodes of a Uniform Thin Beam for Cantilevered and Other Boundary Conditions. Appendix E. Numerical Data for PZT-5A and PZT-5H Piezoceramics. Appendix F. Constitutive Equations for an Isotropic Substructure. Appendix G. Essential Boundary Conditions for Cantilevered Beams. Appendix H. Electromechanical Lagrange Equations Based on the Extended Hamilton s Principle. Index.

Plucked piezoelectric bimorphs for knee-joint energy harvesting: modelling and experimental validation

Abstract: The modern drive towards mobility and wireless devices is motivating intensive research in energy harvesting technologies. To reduce the battery burden on people, we propose the adoption of a frequency up-conversion strategy for a new piezoelectric wearable energy harvester. Frequency up-conversion increases efficiency because the piezoelectric devices are permitted to vibrate at resonance even if the input excitation occurs at much lower frequency. Mechanical plucking-based frequency up-conversion is obtained by deflecting the piezoelectric bimorph via a plectrum, then rapidly releasing it so that it can vibrate unhindered; during the following oscillatory cycles, part of the mechanical energy is converted into electrical energy. In order to guide the design of such a harvester, we have modelled with finite element methods the response and power generation of a piezoelectric bimorph while it is plucked. The model permits the analysis of the effects of the speed of deflection as well as the prediction of the energy produced and its dependence on the electrical load. An experimental rig has been set up to observe the response of the bimorph in the harvester. A PZT-5H bimorph was used for the experiments. Measurements of tip velocity, voltage output and energy dissipated across a resistor are reported. Comparisons of the experimental results with the model predictions are very successful and prove the validity of the model.

Graphene-based bimorph microactuators.

Abstract: A novel graphene-on-organic film fabrication method that is compatible with a batch microfabrication process was developed and used for electromechanically driven microactuators. A very thin layer of graphene sheets was monolithically integrated and the unique material characteristics of graphene including negative thermal expansion and high electrical conductivity were exploited to produce a bimorph actuation. A large displacement with rapid response was observed while maintaining the low power consumption. This enabled the successful demonstration of transparent graphene-based organic microactuators.

Superfast-Response and Ultrahigh-Power-Density Electromechanical Actuators Based on Hierarchal Carbon Nanotube Electrodes and Chitosan

Abstract: Here we report a novel single-walled carbon nanotube (SWNT) based bimorph electromechanical actuator, which consists of unique as-grown SWNT films as double electrode layers separated by a chitosan electrolyte layer consisting of an ionic liquid. By taking advantage of the special hierarchical structure and the outstanding electrical and mechanical properties of the SWNT film electrodes, our actuators show orders-of-magnitude improvements in many aspects compared to previous ionic electroactive polymer (i-EAP) actuators, including superfast response (19 ms), quite wide available frequency range (dozens to hundreds of Hz), incredible large stress generating rate (1080 MPa/s), and ultrahigh mechanical output power density (244 W/kg). These remarkable achievements together with their facile fabrication, low driving voltage, flexibility, and long durability enable the SWNT-based actuators many applications such as artificial muscles for biomimetic flying insects or robots and flexible deployable reflectors.

Underwater thrust and power generation using flexible piezoelectric composites: an experimental investigation toward self-powered swimmer-sensor platforms

Abstract: Fiber-based flexible piezoelectric composites offer several advantages to use in energy harvesting and biomimetic locomotion These advantages include ease of application, high power density, effective bending actuation, silent operation over a range of frequencies, and light weight Piezoelectric materials exhibit the well-known direct and converse piezoelectric effects The direct piezoelectric effect has received growing attention for low-power generation to use in wireless electronic applications while the converse piezoelectric effect constitutes an alternative to replace the conventional actuators used in biomimetic locomotion In this paper, underwater thrust and electricity generation are investigated experimentally by focusing on biomimetic structures with macro-fiber composite piezoelectrics Fish-like bimorph configurations with and without a passive caudal fin (tail) are fabricated and compared The favorable effect of having a passive caudal fin on the frequency bandwidth is reported The presence of a passive caudal fin is observed to bring the second bending mode close to the first one, yielding a wideband behavior in thrust generation The same smart fish configuration is tested for underwater piezoelectric power generation in response to harmonic excitation from its head Resonant piezohydroelastic actuation is reported to generate milli-newton level hydrodynamic thrust using milli-watt level actuation power input The average actuation power requirement for generating a mean thrust of 19 mN at 6 Hz using a 10 g piezoelastic fish with a caudal fin is measured as 120 mW This work also discusses the feasibility of thrust generation using the harvested energy toward enabling self-powered swimmer-sensor platforms with comparisons based on the capacity levels of structural thin-film battery layers as well as harvested solar and vibrational energy (Some figures may appear in colour only in the online journal)

Piezoelectric Energy Harvesting for Civil Infrastructure System Applications: Moving Loads and Surface Strain Fluctuations

Abstract: This article formulates the problem of vibration-based energy harvesting using piezoelectric transduction for civil infrastructure system applications with a focus on moving load excitations and surface strain fluctuations. Two approaches of piezoelectric power generation from moving loads are formulated. The first one is based on using a bimorph cantilever located at an arbitrary position on a simply supported slender bridge. The fundamental moving load problem is reviewed and the input to the cantilevered energy harvester is obtained to couple with the generalized electromechanical equations for transient excitation. The second approach considers using a thin piezoceramic patch covering a region on the bridge. The transient electrical response of the surface patch to moving load excitation is derived in the presence of a resistive electrical load. The local way of formulating piezoelectric energy harvesting from two-dimensional surface strain fluctuations of large structures is also discussed. For a thi...

Screen printed PZT/PZT thick film bimorph MEMS cantilever device for vibration energy harvesting

Abstract: We present a MEMS-based PZT/PZT thick film bimorph vibration energy harvester with an integrated silicon proof mass. The most common piezoelectric energy harvesting devices utilize a cantilever beam of a non piezoelectric material as support beneath or in-between the piezoelectric material. It provides mechanical support but it also reduces the power output. Our device replaces the support with another layer of the piezoelectric material, and with the absence of an inactive mechanical support all of the stresses induced by the vibrations will be harvested by the active piezoelectric elements.

A credit card sized self powered smart sensor node

Abstract: This paper reports a self powered smart sensor node (also called ‘smart tag’) consisting of a piezoelectric vibration energy harvester, a power conditioning circuit, sensors and an RF transmitter. The smart tag has dimensions similar to a credit card and can be easily integrated into various applications such as the surface of the aircraft. The smart tag is powered by an integrated bimorph piezoelectric generator that extracts energy from ambient vibrations. The generator is fabricated using thick film printing technology. Experimentally, the generator produced a maximum RMS output power of 240W when excited at vibration with a frequency of 67 Hz and peak amplitude of 0.4 g (3.9 m s −2 ). This generated power is sufficient to enable periodic sensing and transmission. Details of the experimental results of the piezoelectric generator and the power conditioning circuit are presented. Test shows that the waiting time of the system between two consecutive transmissions is around 800 s. © 2011 Elsevier B.V. All rights reserved.

Corrugated aluminum nitride energy harvesters for high energy conversion effectiveness

Abstract: Aluminum nitride energy harvesters based on corrugated cantilever structures have been proposed, designed and demonstrated by means of micromachining processes with high energy conversion effectiveness. Corrugated cantilever design with a single piezoelectric layer prevents the common problem of an energy cancellation issue in a piezoelectric cantilever, by using a simple fabrication process similar to those in making the unimorph energy harvesters. Furthermore, corrugated structure can have an energy conversion effectiveness comparable to a conventional bimorph design. Experimentally, a prototype energy harvester with measured resonance frequency of 2.56 kHz has been fabricated. Under an input acceleration of 0.25 G, the amplitude of output voltage from the energy harvester has been recorded as 92 mV at a load resistance of 0.86 MΩ and the calculated output power is 4.9 nW. Furthermore, a multifold device resonating at 853 Hz with output power of 0.17 µW under acceleration of 1 G has been recorded.

Wireless temperature microsensors integrated on bearings for health monitoring applications

Abstract: This paper reports the performance of a wireless MEMS bimorph temperature sensor integrated on a bearing for component health monitoring applications. The sensor consists of a robust array of bimorphs consisting of gold and thermally-grown oxide operable to at least 300°C. Fabrication details are included, as well as the hermetic packaging information. Speed of actuation results from a high-speed camera is included showing the actuation time is less than 600 µs. Reliability testing of the bimorph array up to 400 million thermal cycles is also shown, after which the bimorphs still yield consistent behavior. Finally, dynamic testing is performed showing actual bearing temperature values at different speeds on a real-world helicopter bearing

Surface actuated variable-camber and variable-twist morphing wings using piezocomposites

Abstract: A surface actuated variable-camber morphing airfoil employing a type of piezoceramic composite actuator known as Macro-Fiber Composite is presented. The proposed airfoil employs two cascading active surfaces and a pair of optimized pinned boundary conditions. The optimized locations of pinned boundary conditions and the geometric features allow for a variable and smooth deformation in both directions from a flat camber line. The continuity of the airfoil surface is achieved by using a single substrate that wraps around the airfoil shape. This substrate forms the surface of the airfoil and it serves as the host material for the two cascading bimorph actuators. The cascading bimorphs are pinned together at the trailing edge with a compliant hinge, which is also formed by the substrate material. The paper focuses on the theoretical static-aeroelastic response characterization. A parametric study of the fluid-structure interaction problem is employed to optimize the geometric parameters and the boundary conditions of the variable-camber airfoil. The coupled treatment of the fluid-structure interaction allows the realization of a design that is not only feasible in a bench top experiment, but that can also sustain large aerodynamic loads. The paper identifies the effects of four important structural parameters to achieve the highest possible lift coefficient and lift-to-drag ratio. Practical recommendations are presented to achieve a working prototype.

High-precision positioning using a self-sensing piezoelectric actuator control with a differential detection method

Abstract: We present a self-sensing control method for piezoelectric actuators, which enables high-resolution positioning without an external positioning sensor. One of the present authors previously proposed a self-sensing piezoelectric actuator control system (Kawamata et al. (2008) [1] and Ishikiriyama and Morita (2010) [2] ). In the previous studies, a linear relationship between piezoelectric displacement and permittivity change was discovered, and this linear relationship was applied for positioning control. To detect permittivity changes, a high frequency voltage signal (permittivity detection voltage), in addition to the driving voltage signal, was applied to the actuator. The permittivity change was monitored as the amplitude of the current at the same frequency as the permittivity detection voltage. From this current amplitude, the permittivity change was easily calculated in real time. However, the positioning resolution was insufficient compared to that of traditional external positioning sensors, such as a strain gage sensor. In this study, we improved the positioning resolution by introducing a differential current measurement using two piezoelectric elements, one on each side of a bimorph actuator. The phase of the detected current signal was taken into consideration using a lock-in amplifier. In other words, the conductivity-related current and the permittivity-related current were measured separately. With these improvements, the permittivity change related to the piezoelectric displacement could be measured precisely, and self-sensing feedback control with a positioning error of less than 0.4 μm over a movement range of 80 μm was demonstrated.

Modeling and Analysis of Piezoelectric Energy Harvesting Beams Using the Dynamic Stiffness and Analytical Modal Analysis Methods

Abstract: The modeling and analysis of base-excited piezoelectric energy harvesting beams have attracted many researchers with the aim of predicting the electrical output for a given base motion input. Despite this, it is only recently that an accurate model based on the analytical modal analysis method (AMAM) has been developed. Moreover, single-degree-of-freedom models are still being used despite the proven potential for significant error. One major disadvantage of the AMAM is that it is restricted to simple cantilevered uniform-section beams. This paper presents two alternative modeling techniques for energy harvesting beams and uses these techniques in a theoretical study of a bimorph. One of the methods is a novel application of the dynamic stiffness method (DSM) to the modeling of energy harvesting beams. This method is based on the exact solution of the wave equation and so obviates the need for modal transformation. The dynamic stiffness matrix of a uniform-section beam could be used in the modeling of beams with arbitrary boundary conditions or assemblies of beams of different cross sections. The other method is a much-needed reformulation of the AMAM that condenses the analysis to encompass all previously analyzed systems. The Euler-Bernoulli model with piezoelectric coupling is used and the external electrical load is represented by generic linear impedance. Simulations verify that, with a sufficient number of modes included, the AMAM result converges to the DSM result. A theoretical study of a bimorph investigates the effect of the impedance and quantifies the tuning range of the resonance frequencies under variable impedance. The neutralizing effect of a tuned harvester on the vibration at its base is investigated using the DSM. The findings suggest the potential of the novel concept of a variable capacitance adaptive vibration neutralizer that doubles as an adaptive energy harvester. The application of the DSM to more complex systems is illustrated. For the case studied, a significant increase in the power generated was achieved for a given working frequency through the application of a tip rotational restraint, the use of segmented electrodes, and a resized tip mass.

Exploring the parametric amplification phenomenon for energy harvesting

Abstract: Due to inherent system nonlinearities, many vibratory excitation sources possess a frequency spectrum which contains energy components at multiple integers of the fundamental frequency of the source. In this paper, we theoretically explore the prospect of enhancing the transduction of a vibratory energy harvester (VEH) by utilizing the parametric amplification phenomenon to channel energy from one of these superharmonics, namely the one at twice the fundamental frequency, to a purely resistive load. Towards that end, we consider a piezoelectric cantilevered-type bimorph harvester and show that by tilting the axis of the beam through a proper angle with respect to the direction of excitation, it is possible to utilize a parametric pump to enhance the output power at the fundamental frequency. Percentage improvement in the output power depends on the excitation’s parameters and the mechanical damping ratio. It is observed that when the mechanical damping ratio is small, significant enhancement in the output...

Design and verification of a smart wing for an extreme-agility micro-air-vehicle

Abstract: A special class of fixed-wing micro-air-vehicle (MAV) is currently being designed to fly and hover to provide range superiority as well as being able to hover through a flight maneuver known as prop-hanging to accomplish a variety of surveillance missions. The hover maneuver requires roll control of the wing through differential aileron deflection but a conventional system contributes significantly to the gross weight and complexity of a MAV. Therefore, it is advantageous to use smart structure approaches with active materials to design a lightweight, robust wing for the MAV. The proposed smart wing consists of an active trailing edge flap integrated with bimorph actuators with piezoceramic fibers. Actuation is enhanced by preloading the bimorph actuators with a compressive axial load. The preload is exerted on the actuators through a passive latex or electroactive polymer (EAP) skin that wraps around the airfoil. An EAP skin would further enhance the actuation by providing an electrostatic effect of the dielectric polymer to increase the deflection. Analytical modeling as well as finite element analysis show that the proposed concept could achieve the target bi-directional deflection of 30° in typical flight conditions. Several bimorph actuators were manufactured and an experimental setup was designed to measure the static and dynamic deflections. The experimental results validated the analytical technique and finite element models, which have been further used to predict the performance of the smart wing design for a MAV.

High-Fill-Factor Micromirror Array With Hidden Bimorph Actuators and Tip–Tilt-Piston Capability

Abstract: This paper presents the design, fabrication, packaging, and characterization of a novel high-fill-factor micromirror array (MMA) actuated by electrothermal bimorphs. In this paper, 4 × 4 MMA devices with an 88% area fill factor at normal incidence, 1.5 mm × 1.5 mm subaperture size, and single-crystal-silicon-supported mirror plates have been fabricated based on a single silicon-on-insulator wafer, without additional bonding/transfer processes. The bimorph actuators are hidden underneath the mirror plates, which are also protected by silicon walls. The MMA devices can directly be surface mounted onto driving circuit chips or printed circuit boards after fabrication. The subapertures can generate large tip-tilt-piston scanning and can individually be addressed. Static characterizations of the packaged devices show that each subaperture can achieve a piston stroke of ~310 μm and optical deflection angles greater than ±25° in both the x- and y-axes, all at 8-V dc. The preliminary laser-steering optical-phased-array capability of the obtained MMA device has also experimentally been demonstrated. This paper is based on the conference proceedings presented at the 23rd IEEE International Conference on Micro Electro Mechanical Systems (MEMS 2010), Hong Kong.

A magnetic thin film microrobot with two operating modes

Abstract: Magnetic principles have proved successful for untethered submillimeter microrobotics, although challenges still exist in areas of propulsion and control. This paper presents the design, analysis, and performance results for a bimorph thin film magnetic microrobot utilizing the magnetostrictive principle as a secondary oscillating operation mode. The microrobot is no larger than 580 µm in its planar dimension and its total thickness is less than 5 µm. As a robot with magnetic material, it can be operated in a pushing/pulling mode in orthogonal directions for movement in a plane, while it's powered with an external magnetic field as low as 1 mT. For the secondary oscillating operation mode utilizing the magnetostrictive principle, in-plane strain is induced, resulting in bending and blocking forces on the robot. These forces are theoretically calculated to prove enough drive force can be generated in this mode. The design is further abstracted and translated into a piezoelectric cantilever FEM model to confirm the theorectical results. Microrobot fabrication and test-bed development based on this analysis is shown, which enabled us to participate in the final competition in the 2010 NIST Mobile Microrobot Challenge, with good performance in the dash and freestyle events. Finally, we discuss the testing results in various dry and fluid environments along with recommendations for future investigation and improvements. Keywords: microrobot, magnetostrictive, bimorph

A curved multimorph based electrothermal micromirror with large scan range and low drive voltage

Abstract: We report a circular micromirror with a 1 mm aperture that has an optical scan range of 60° at 0.68 V applied voltage and 11 mW power input. The mirror is actuated by a semicircular aluminum (Al)–tungsten (W) electrothermal multimorph that bends and twists upon controlled Joule heating. W acts as an active layer of the multimorph and a resistive heater. The curved actuator design not only maximizes the efficiency of chip area usage, but also achieves high resonant frequency due to torsional stiffness encountered during beam deformation. The first three resonant modes of the micromirror are at 104 Hz, 400 Hz and 416 Hz, respectively. Two-dimensional (2D) optical scanning is demonstrated by using the second resonant mode. The low power consumption may be attributed to the use of a single actuator beam. Mirror-center shift produced by actuator bending and twisting partially compensate each other and this results in 1.6 times lower center-shift compared to previously reported straight multimorph based designs. Device fabrication involves surface and bulk micromachining on an SOI wafer.

High-efficiency mems micro-vibrational energy harvester and process for manufacturing same

Abstract: The present invention relates generally to a High Efficiency MEMS Micro- Vibrational Energy Harvester (μVEH) having an thick beam bimorph architecture. The disclosed architecture is capable of producing a voltage of sufficient magnitude such that the requirement to connect a plurality of harvesters in series to produce an adequate voltage magnitude is eliminated.

Enhanced resonant magnetoelectric coupling in frequency-tunable composite multiferroic bimorph structures

Abstract: We report on a giant tunable enhanced resonant magnetoelectric (ME) coupling in multiferroic magnetostrictive/piezoelectric composite bimorph structures. The approach uses a magnetic/electric field assisted stress-reconfigurable resonance to produce frequency tuning of up to 100%. The studies were performed by laser Doppler spectroscopy. We also show that this principle of a continuously tuned resonance might be used to improve sensitivity for ME magnetic sensors.

Out-of-plane spiral-coil inductor self-assembled by locally controlled bimorph actuation

Abstract: A method to manufacture 3D microcoils based on locally controlled bimorph actuation is reported. A simple and batch-compatible method for producing out-of-plane spiral structures is developed to create inductors whose inductances are tuned independently of their base dimensions. A 500-nm-thick Cr layer used as the stress layer is patterned on a planar Cu coil to induce plastic deformation of the coil in the vertical direction uniformly, defining the final 3D coil shape. The Cr pattern, as well as the temperature of post-fabrication annealing, is varied to achieve different levels of vertical deformation and inductance of the coils. A maximum vertical expansion of 721 μm is demonstrated to yield a 12 inductance change. The Q factor of 17 and the self-resonance at ~1.2~GHz are obtained.

Comparison of collocation strategies of sensor and actuator for vibration control

Abstract: Some possible collocation strategies of sensor and actuator pairs for the application to active vibration control systems are analyzed, compared and discussed in this paper. This is becausea well-designed sensor — actuator collocation configuration can provide a simpler control algorithm with excellent performance and stability, especially when velocity feedback is adopted. As an ideal point collocation pair of a sensor and actuator shows high possibility in actual vibration control problems, the advantage of a collocated accelerometer — shaker pair is proven experimentally and discussed first. Then as a similar approach, a collocated piezosensor — piezoactuator pair is analyzed in depth with the in-plane motion coupling. Finally, two configurations of a practically collocated configuration with an accelerometer — piezoactuator pair and a non-overlapped collocated pair of a bimorph piezosensor — two bimorph piezoactuators are described in detail in terms of performance and stability with experimental results. Those two configurations are expected for the applications to more practical active control of vibration systems with the velocity feedback control scheme.

Parameter identification for resonant piezoelectric energy harvesters in the low- and high-coupling regimes

Abstract: We demonstrate a method for identifying the parameters of piezoelectric harvesters by simple electrical measurements. The basic equations are derived from a simplified yet accurate model. The accuracy of the model is proven by comparison with the full model. Two beam harvesters, one with a unimorph beam and one with a bimorph beam, have been fabricated and characterized. The results coincide well with proposed theory and demonstrate the differences between harvesters with low and high coupling constants. It turns out that four parameters are sufficient to completely describe the electrical behavior of a harvester with a low coupling constant. For harvesters with high coupling constants, five parameters are needed.

Sound transducer for insertion in an ear

Abstract: The invention relates to a sound transducer for producing sound vibrations, which can be inserted in an ear and can be used in particular for an implantable hearing aid. The sound transducer has at least one carrier layer and at least one piezoelectric layer, as a result of which a deflection via a bimorph principle is achieved, or a deflection can be detected by picking up a voltage.

Piezoelectric composite morphing control surfaces for unmanned aerial vehicles

Abstract: The authors have explored the use of morphing control surfaces to replace traditional servo-actuated control surfaces in UAV applications. The morphing actuation is accomplished using Macro Fiber Composite (MFC) piezoelectric actuators in a bimorph configuration to deflect the aft section of a control surface cross section. The resulting camber change produces forces and moments for vehicle control. The flexible piezoelectric actuators are damage tolerant and provide excellent bandwidth. The large amplitude morphing deflections attained in bench-top experiments demonstrate the potential for excellent control authority. Aerodynamic performance calculations using experimentally measured morphed geometries indicate changes in sectional lift coefficients that are superior to a servo-actuated hinged flap airfoil. This morphing flight control actuation technology could eliminate the need for servos and mechanical linkages in small UAVs and thereby increase reliability and reduce drag.

Thermo-Electro-Mechanical Analysis of a Curved Functionally Graded Piezoelectric Actuator with Sandwich Structure.

Abstract: In this work, the problem of a curved functionally graded piezoelectric (FGP) actuator with sandwich structure under electrical and thermal loads is investigated The middle layer in the sandwich structure is functionally graded with the piezoelectric coefficient g31 varying continuously along the radial direction of the curved actuator Based on the theory of linear piezoelectricity, analytical solutions are obtained by using Airy stress function to examine the effects of material gradient and heat conduction on the performance of the curved actuator It is found that the material gradient and thermal load have significant influence on the electroelastic fields and the mechanical response of the curved FGP actuator Without the sacrifice of actuation deflection, smaller internal stresses are generated by using the sandwich actuator with functionally graded piezoelectric layer instead of the conventional bimorph actuator This work is very helpful for the design and application of curved piezoelectric actuators under thermal environment

A polymer-based bidirectional micropump driven by a PZT bimorph

Abstract: This paper presents a polymer-based micropump for liquid control or drug delivery. The dimension of the pump was 20 × 24 × 3 mm3. A pair of O-ring SU-8 passive valves was fabricated by lift-off technique to control the fluid movement. Micropumps with dimple, bridge, and cantilever valves were studied. The PZT bimorph acted on the polymer membrane to periodically drive fluid. The maximum flow rate was 16.4 ml/min, and the back pressure was 1,525 mmH2O at 150 V (Vp-p). In frequency sweeping experiments, two flow rate peaks and back pressure peaks were analyzed. Bidirectional flow rate was achieved by changing the valve seat from a one-size hole to a step hole. The maximum backward flow rate was 5.1 ml/min, and the driving frequency was about 355 Hz higher than the forward flow rate driving frequency.

Automated in-situ optimization of bimorph mirrors at Diamond Light Source

Abstract: Bimorph mirrors are used on many synchrotron beamlines to focus or collimate light. They are highly adaptable because not only their overall figure but also their local slope errors can be corrected. However, the optimization procedure is complex. At Diamond Light Source, highly repeatable and accurate pencil beam measurements are used to determine a mirror's slope errors. These data are then used by automated scripts to calculate the necessary corrections. This procedure may be applied to any type of active mirror, but for hard X-ray mirrors, diffraction from the slits must be considered.