Дисертації: "PIEZOELECTRIC PERFORMANCE"

1

Gupta, Shashaank. "High Performance Lead--free Piezoelectric Materials." Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/50959.

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Piezoelectric materials find applications in number of devices requiring inter-conversion of mechanical and electrical energy. These devices include different types of sensors, actuators and energy harvesting devices. A number of lead-based perovskite compositions (PZT, PMN-PT, PZN-PT etc.) have dominated the field in last few decades owing to their giant piezoresponse and convenient application relevant tunability. With increasing environmental concerns, in the last one decade, focus has been shifted towards developing a better understanding of lead-free piezoelectric compositions in order to achieve an improved application relevant performance. Sodium potassium niobate (KxNa1-xNbO3, abbreviated as KNN) is one of the most interesting candidates in the class of lead-free piezoelectrics. Absence of any poisonous element makes it unique among all the other lead-free candidates having presence of bismuth. Curie temperature of 400"C, even higher than that of PZT is another advantage from the point of view of device applications.
Present work focuses on the development of fundamental understanding of the crystallographic nature, domain structure and domain dynamics of KNN. Since compositions close to x = 0.5 are of primary interest because of their superior piezoelectric activity among other compositions (0 < x < 1), crystallographic and domain structure studies are focused on this region of the phase diagram. KNN random ceramic, textured ceramic and single crystals were synthesized, which in complement to each other help in understanding the behavior of KNN.
K0.5Na0.5NbO3 single crystals grown by the flux method were characterized for their ferroelectric and piezoelectric behavior and dynamical scaling analysis was performed to reveal the origin of their moderate piezoelectric performance. Optical birefringence technique used to reveal the macro level crystallographic nature of x = 0.4, 0.5 and 0.6 crystals suggested them to have monoclinic Mc, monoclinic MA/B and orthorhombic structures respectively. Contrary to that, pair distribution function analysis performed on same composition crystals implies them to belonging to monoclinic Mc structure at local scale. Linear birefringence and piezoresponse force microscopy (PFM) were used to reveal the domain structure at macro and micros scales respectively.
A noble sintering technique was developed to achieve > 99% density for KNN ceramics. These high density ceramics were characterized for their dielectric, ferroelectric and piezoelectric properties. A significant improvement in different piezoelectric coefficients of these ceramics validates the advantages of this sintering technique. Also lower defect levels in these high density ceramics lead to the superior ferroelectric fatigue behavior as well. To understand the role of seed crystals in switching behavior of textured ceramic, highly textured KNN ceramics (Lotgering factor ~ 88 %) were synthesized using TGG method. A sintering technique similar to one employed for random ceramics, was used to sinter textured KNN ceramics as well. Piezoresponse force microscopy (PFM) study suggested these textured ceramics to have about 6¼m domains as compared to 2¼m domain size for random ceramics. Local switching behavior studied using switching spectroscopy (SS-PFM) revealed about two and half time improvement of local piezoresponse as compared to random counterpart.

Ph. D.

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2

Almajid, Abdulhakim A. "Design of high performance piezo composites actuators /." Thesis, Connect to this title online; UW restricted, 2002. http://hdl.handle.net/1773/7130.

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3

Mtawa, Alexander Nikwanduka. "Influence of geometry and material properties on the optimum performance of the C-shape piezo-composite actuator." Thesis, Cape Peninsula University of Technology, 2008. http://hdl.handle.net/20.500.11838/1301.

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Thesis (DTech (Mechanical Engineering))--Cape Peninsula University of Technology, 2008
In recent years, due to rapid advances in technology there has been an increasingly high demand for large displacement and large force, precise positioning, fast response, low power consuming miniature piezoelectric actuators. In certain smart structure applications, the use of curved piezoelectric actuators is necessary. The present work extends the earlier investigations on the C- shape actuator by providing a detailed investigation on the influence of geometric and material properties of the individual layers of the C-shape piezocomposite for its optimal performance as an actuator. Analytical models have. been used to optimize the geometry of the actuator. Experimental and finite element analyses (using general purpose finite element software i.e. CoventerWare and MSC. Marc) have been used for validation. The present work has established that, by maintaining the thickness of the substrate and piezoceramic layers constant; changing the external radius, for example increasing it, the stiffness of the structure decreases and thus yielding large displacement This has a negative effect on the force produced by the actuator. With fixed thickness of the substrate and varying the thickness of the piezoceramic (for fixed external radius) the result is as follows: Increasing the thickness of the piezoceramic layer has the effect of decreasing the displacement while the force increases. With fixed PZT thickness as well as the external radius, varying the substrate thickness has the following effect: As the thickness of the substrate increases the displacement increases reaching a maximum. Subsequent increase in the thickness of the substrate the displacement is reduced. The force continues increasing at least for the ratios up to 1.0, further increase of the substrate, subsequent decrease of force is also noted. In addition to changing the thickness of the substrate, the choice of different material for the substrate has the following effect: For substrate/PZT ratios of up to 0.6. an actuator with substrate material having higher elastic modulus will produce larger displacement while for ratios beyond this ratio the situation is reversed. The causes for this kind of behaviour have been addressed. In all cases both force and displacement are found to be directly proportional to applied voltage.

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4

Robinson, Michelle Christina. "Microstructural and geometric effects on the piezoelectric performance of PZT MEMS." Online access for everyone, 2007. http://www.dissertations.wsu.edu/Dissertations/Fall2007/m_robinson_091307.pdf.

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5

Rosatti, Lyric Michael. "Fatigue performance of macro-fiber piezoelectric composite actuator with respect to variable beam geometry." Thesis, Montana State University, 2012. http://etd.lib.montana.edu/etd/2012/rosatti/RosattiL1212.pdf.

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This study is an investigation into the reliability and performance over the lifetime of the piezoelectric fiber composite, macro fiber composite (MFC), with respect to variable beam geometry. MFC's are a class of smart structure utilizing the piezoelectric effect. The MFC is a thin flexible composite system that can be laminated to surfaces or embedded in classic composite structures for actuation and sensing. These piezocomposite structures are rectangular patches made of Lead-Zirconium-Titinate (PZT) piezoceramic fibers, copper-clad polyimide film, and epoxy. MFC's were originally developed at NASA Langley Research Center and are now commercially available from a single manufacturer. In this study, lifespan and performance were characterized by using the MFC as an actuator to impart deflection in a substrate. This structure is referred to as a Unimorph. The beam geometry affects the bending stiffness of the beam, and thus affects the reaction of the MFC. The only free geometrical dimension in this study was beam height. The unimorph was actuated cyclically by an electrical field of 3E+6 volts per micron at a frequency of 3750 Hz. Expected cycles to failure was 10 â¹ cycles. The test specimens consisted of cantilevered A2 tool steel beams, with six discrete beam heights, and an MFC patch laminated to one surface by a two-part epoxy. Beam tip displacement measurements were taken using a laser displacement sensor as an indication of cyclical performance over time. The beams were cycled until failure or 10 â¹ cycles for all beam geometries. The results of the experiment indicate a severe drop off in life with an increase of work energy out of the system. This is a function of the ratio of beam stiffness to MFC stiffness. After a break-in period of less than 250E+6 cycles, no significant degradation in operational performance was indicated by the recorded tip displacement despite an immense amount of crack propagation in the piezoceramic fibers. The results of this testing can be used in designing piezoelectric actuators and as a basis for further study of MFC's.

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6

Roberts, Patrick James. "An Experimental Study of Concurrent Methods for Adaptively Controlling Vertical Tail Buffet in High Performance Aircraft." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/19863.

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High performance twin-tail aircraft, like the F-15 and F/A-18, encounter a condition known as tail buffet. At high angles of attack, vortices are generated at the wing fuselage interface (shoulder) or other leading edge extensions. These vortices are directed toward the twin vertical tails. When the flow interacts with the vertical tail it creates pressure variations that can oscillate the vertical tail assembly. This results in fatigue cracks in the vertical tail assembly that can decrease the fatigue life and increase maintenance costs. For many years, research has been conducted to understand this phenomenon of buffet and to reduce its adverse effects on the fatigue life of aerospace structures. Many proposed solutions to this tail buffet problem have had limited success. These include strengthening the tail, modifying the vortex flow, using an active rudder control, and leading edge extensions. Some of the proposed active controls include piezoelectric actuators. Recently, an offset piezoceramic stack actuator was used on an F-15 wind tunnel model to control buffet induced vibrations at high angles of attack. The controller was based on acceleration feedback control methods. In this thesis a procedure for designing the offset piezoceramic stack actuators is developed. This design procedure includes determining the quantity and type of piezoceramic stacks used in these actuators. The changes of stresses, in the vertical tail caused by these actuators during an active control, are investigated. In many cases, linear controllers are very effective in reducing vibrations. However, during flight, the natural frequencies of the vertical tail structural system changes as the airspeed increases. This in turn, reduces the effectiveness of a linear controller. Other causes such as the unmodeled dynamics and nonlinear effects due to debonds also reduce the effectiveness of linear controllers. In this thesis, an adaptive neural network is used to augment the linear controller to correct these effects.

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7

Xiong, Xingyu. "Development of vibration-based multi-resonance energy harvesters using piezoelectric materials." Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/development-of-vibrationbased-multiresonance-energy-harvesters-using-piezoelectric-materials(62d0d760-8b9c-4958-94a9-677b0e57082d).html.

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The development of self-powered wireless sensor networks for structural and machinery health monitoring has attracted considerable attention in the research field during the last decade. Since the low-duty-cycle wireless sensor networks have significantly reduced the power requirements to the range of tens to hundreds of microwatts, it is possible to harvest environmental energy as the power supply instead of using batteries. Vibration energy harvesting using piezoelectric materials has become the most popular technique, which has a good potential to generate adequate power. However, there is a limitation for the conventional beam-shaped harvester designs in real applications due to their limited bandwidth. In order to overcome this limitation, the essential objective of this thesis is to develop harvesters with multi-resonance structures. The multi-resonance harvester with good broadband performance can achieve close resonance frequencies and relatively large power output in each vibration mode. The main tasks and contributions of this thesis are summarised as follows: • A parametric analysis is presented to determine how the modal structural and electromechanical performances of cantilevered beam harvesters are affected by two modal factors designated as mass ratio and electromechanical coupling coefficient (EMCC). The modal performance of using rectangular, convergent and divergent tapered configurations with and without extra masses are systematically analysed by geometric variation using the finite element analysis (FEA) software ABAQUS. • A modal approach using the two modal factors to evaluate the modal performance of harvesters is introduced and a configurational optimization strategy based on the modal approach is developed to pre-select the configurations of multi-resonance harvesters with better modal structural performance and close resonance frequencies in multiple modes. Using this optimization strategy obviates the need to run the full analysis at the first stage. • A novel two-layer stacked harvester, which consists of a base cantilevered beam that is connected to an upper beam by a rigid mass, is developed. By altering the dimensions and the locations of the masses, the two-layer harvester can generate two close resonance frequencies with relatively large power output. The effects of using rectangular, convergent and divergent tapered beam configurations are systematically analysed. • Multi-layer stacked harvesters with up to five layers are developed. The three-layer harvesters with different mass positions, which can generate three close resonance frequencies, are optimized using the configurational optimization strategy. • A novel doubly-clamped multi-layer harvester, which is able to generate five close resonance frequencies with relatively large power output, is developed and thoroughly analysed. • An experimental study of the multi-layer stacked harvester is presented to validate the simulated results and the configurational optimization strategy. • An experimental study of the two-layer stacked harvester using high performance single crystal piezoelectric material PIMNT is presented. The harvester using PIMNT can generate nearly 10 times larger power output and 3.5 times wider bandwidth than using PZT. Besides, by modifying the location of the piezoelectric layer, anti-resonances between two adjacent modes can be eliminated.

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8

Mei, Jie. "Simulation and characterization on optimum performance of piezoelectric energy harvesters by utiliizing multimode mechanical response." Thesis, Swansea University, 2015. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.678400.

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9

Zhang, Wenli. "HIGH PERFORMANCE PIEZOELECTRIC MATERIALS AND DEVICES FOR MULTILAYER LOW TEMPERATURE CO-FIRED CERAMIC BASED MICROFLUIDIC SYSTEMS." UKnowledge, 2011. http://uknowledge.uky.edu/gradschool_diss/200.

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The incorporation of active piezoelectric elements and fluidic components into micro-electromechanical systems (MEMS) is of great interest for the development of sensors, actuators, and integrated systems used in microfluidics. Low temperature cofired ceramics (LTCC), widely used as electronic packaging materials, offer the possibility of manufacturing highly integrated microfluidic systems with complex 3-D features and various co-firable functional materials in a multilayer module. It would be desirable to integrate high performance lead zirconate titanate (PZT) based ceramics into LTCC-based MEMS using modern thick film and 3-D packaging technologies. The challenges for fabricating functional LTCC/PZT devices are: 1) formulating piezoelectric compositions which have similar sintering conditions to LTCC materials; 2) reducing elemental inter-diffusion between the LTCC package and PZT materials in co-firing process; and 3) developing active piezoelectric layers with desirable electric properties. The goal of present work was to develop low temperature fired PZT-based materials and compatible processing methods which enable integration of piezoelectric elements with LTCC materials and production of high performance integrated multilayer devices for microfluidics. First, the low temperature sintering behavior of piezoelectric ceramics in the solid solution of Pb(Zr0.53,Ti0.47)O3-Sr(K0.25, Nb0.75)O3 (PZT-SKN) with sintering aids has been investigated. 1 wt% LiBiO2 + 1 wt% CuO fluxed PZT-SKN ceramics sintered at 900oC for 1 h exhibited desirable piezoelectric and dielectric properties with a reduction of sintering temperature by 350oC. Next, the fluxed PZT-SKN tapes were successfully laminated and co-fired with LTCC materials to build the hybrid multilayer structures. HL2000/PZT-SKN multilayer ceramics co-fired at 900oC for 0.5 h exhibited the optimal properties with high field d33 piezoelectric coefficient of 356 pm/V. A potential application of the developed LTCC/PZT-SKN multilayer ceramics as a microbalance was demonstrated. The final research focus was the fabrication of an HL2000/PZT-SKN multilayer piezoelectric micropump and the characterization of pumping performance. The measured maximum flow rate and backpressure were 450 μl/min and 1.4 kPa respectively. Use of different microchannel geometries has been studied to improve the pumping performance. It is believed that the high performance multilayer piezoelectric devices implemented in this work will enable the development of highly integrated LTCC-based microfluidic systems for many future applications.

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10

Mettananda, E. A. C. Himanga. "A high performance winding traverse mechanism for textile precision winders using electromagnetic/piezoelectric dual-stage positioning." Thesis, University of Leeds, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.410965.

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11

Bayon, De Noyer Maxime P. "Tail buffet alleviation of high performance twin tail aircraft using offset piezoceramic stack actuators and acceleration feedback control." Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/12499.

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12

Aridogan, Mustafa Ugur. "Performance Evaluation Of Piezoelectric Sensor/actuator On Investigation Of Vibration Characteristics And Active Vibration Control Of A Smart Beam." Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12612005/index.pdf.

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In this thesis, the performance of piezoelectric patches on investigation of vibration characteristics and active vibration control of a smart beam is presented. The smart beam is composed of eight surface-bonded piezoelectric patches symmetrically located on each side of a cantilever aluminium beam. At first, vibration characteristics of the smart beam is investigated by employment of piezoelectric patches as sensors and actuators. Smart beam is excited by either impact hammer or piezoelectric patch and the response of the smart beam particular to these excitations is measured by piezoelectric patches used as sensors. In order to investigate the performance of piezoelectric patches in sensing, the measurements are also conducted by commercially available sensing devices. Secondly, active vibration suppression of the smart beam via piezoelectric sensor/actuator pair is considered. For this purpose, system identification of the smart beam is conducted by using four piezoelectric patches as actuators and another piezoelectric patch as a sensor. The designed robust controller is experimentally implemented and active vibration suppression of the free and first resonance forced vibration is presented. Thirdly, active vibration control of the smart beam is studied by employment of piezoelectric patches as self-sensing actuators. Following the same approach used in the piezoelectric sensor/actuator pair case, system identification is conducted via self-sensing piezoelectric actuators and robust controller is designed for active vibration suppression of the smart beam. Finally, active vibration suppression via self-sensing piezoelectric actuators is experimentally presented.

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13

Agnes, Gregory Stephen. "Performance of Nonlinear Mechanical, Resonant-Shunted Piezoelectric, and Electronic Vibration Absorbers for Multi-Degree-of-Freedom Structures." Diss., Virginia Tech, 1997. http://hdl.handle.net/10919/30740.

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Linear vibration absorbers are a valuable tool used to suppress vibrations due to harmonic excitation in structural systems. Limited evaluation of the performance of nonlinear vibration absorbers for nonlinear structures exists in the current literature. The state of the art is extended in this work to vibration absorbers in their three major physical implementations: the mechanical vibration absorber, the inductive-resistive shunted piezoelectric vibration absorber, and the electronic vibration absorber (also denoted a positive position feedback controller). A single, consistent, physically similar model capable of examining the response of all three devices is developed. The performance of vibration absorbers attached to single-degree-of-freedom structures is next examined for performance, robustness, and stability. Perturbation techniques and numerical analysis combine to yield insight into the tuning of nonlinear vibration absorbers for both linear and nonlinear structures. The results both clarify and validate the existing literature on mechanical vibration absorbers. Several new results, including an analytical expression for the suppression region's location and bandwidth and requirements for its robust performance, are derived. Nonlinear multiple-degree-of-freedom structures are next evaluated. The theory of Nonlinear Normal Modes is extended to include consideration of modal damping, excitation, and small linear coupling, allowing estimation of vibration absorber performance. The dynamics of the N+1-degree-of-freedom system reduce to those of a two-degree-of-freedom system on a four-dimensional nonlinear modal manifold, thereby simplifying the analysis. Quantitative agreement is shown to require a higher order model which is recommended for future investigation. Finally, experimental investigation on both single and multi-degree-of-freedom systems is performed since few experiments on this topic are reported in the literature. The experimental results qualitatively verify the analytical models derived in this work. The dissertation concludes with a discussion of future work which remains to allow nonlinear vibration absorbers, in all three physical implementations, to enter the engineer's toolbox.
Ph. D.

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14

Glenn, Timothy Scott 1971. "Mixed-domain performance model of the piezoelectric traveling-wave motor and the development of a two-sided device." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/16875.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2002.
Page 226 blank.
Includes bibliographical references (p. 221-225).
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
In recognition of the growing consideration of piezoelectric traveling-wave motors as suitable replacements for small-scale electromagnetic motors, the present work addresses two parallel objectives: (1) to develop an advanced modeling approach for the accurate prediction of steady-state performance of piezoelectric traveling-wave motors, and (2) to improve upon the typical piezoelectric traveling-wave motor configuration by investigating the novel implementation of two-sided operation. Firstly, a performance model of the piezoelectric traveling-wave motor has been developed that accounts for loss at the material level through the integration of complex material constants. In effect, all model parameters can be attributed to physically relevant properties, and, as demonstrated by the success of several experimental correlation studies, motor performance can be predicted independently of the measured characteristics of an existing device. Other key features of the model include a dynamic rotor model, a hysteretic stick-slip friction contact model, and generalization to accommodate non-ideal traveling-wave excitation. Critical to the cohesion of the model, a mixed-domain formulation combines the ease and accuracy of deriving the nonlinear contact forces in the time domain and the efficiency of equilibrating the modal forces in the frequency domain.
(cont.) Secondly, a two-sided motor configuration has been developed that is theoretically capable of doubling the torque and power output of the typical configuration with little or no increase in size or mass. Controlled experimental testing has been performed concurrently on essentially identical one-sided and two-sided prototypes, and the results verify a dramatic performance improvement due to the implementation of two-sided operation.
by Timothy Scott Glenn.
Ph.D.

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15

Llorens, Balada Eduard. "Study of HfN as seed layer for next generation of BAW RF filters : synthesis, characterization, and investigation of piezoelectric performance." Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-80960.

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Micro-electro-mechanical systems (MEMS) have become an essential component of a wide range ofelectronic devices over the last decades such as accelerometers, microphones, gas sensors, and filters.During this new millennium, a new radio frequency (RF) technology has been developed to satisfy thetough demands that arose due to the implementation of 5G wireless communication: bulk acoustic wave(BAW) filters.BAW devices use the piezoelectric effect, converting mechanical vibrations to electrical signals, topower wireless devices. BAW filters can operate between 3.5 GHz and 6 GHz, therefore, within therange of the new 5G. BAW technology offers lower insertion loss, higher heat dissipation, andperformances at higher power and frequency which increases the data speed considerably.This thesis will be focused on the study of the materials used in BAW devices. A common BAW filteris made from different layers distributed in a stack, from the bottom to the upper part, the BAW filteris composed of a substrate, a transducer layer made of a piezoelectric layer in between of two electrodes,and intermediate layers that can enhance the addition of the deposited layers on top called buffer layers,or the crystal quality of the films on top called seed layers.The main characteristic that a buffer layer must possess is an intermediate lattice parameter betweenthat of the substrate and the top layer. When these two layers present a high lattice mismatch, theinterface quality is rather poor. By using a buffer layer, and therefore, by adding two different interfaces,the crystal quality is improved by decreasing the internal stress and the crystal distortion. Buffer layermaterials depend on the type of materials that will be in contact with them.A seed layer is usually used to improve the crystal quality of a layer that requires extreme sputteringparameters to be used to be deposited possessing a high crystal quality and a preferred orientation. Seedlayers used in BAW devices, whose piezoelectric layer is made of AlScN or AlN, are usually made ofhighly c-axis oriented and highly crystalline AlN.The objective of this study is to analyze the deposition of AlN and HfN by means of reactive radiofrequency magnetron sputtering and reactive pulsed-direct current magnetron sputtering, respectively.AlN is largely used as a buffer layer and as a seed layer, however, the new approach of this report is tostudy the sputtering of HfN and compare it as a possible candidate to replace AlN as a seed layer.

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16

Kim, Jina. "Low-Power System Design for Impedance-Based Structural Health Monitoring." Diss., Virginia Tech, 2007. http://hdl.handle.net/10919/40400.

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Maintenance of the structural integrity and damage detection are critical for all massive and complicated new and aging structures. A structural health monitoring (SHM) system intends to identify damage on the structure under monitoring, so that necessary action can be taken in advance to avoid catastrophic results. Impedance-based SHM utilizes a piezoelectric ceramic as a collocated actuator and sensor, which measures the electrical impedance of the piezoelectric ceramic over a certain frequency range. The impedance profile of a structure under monitoring is compared against a reference profile obtained from the healthy structure. An existing approach called the sinc method adopts a sinc wave excitation and performs traditional discrete Fourier transform (DFT) based structural condition assessment. The sinc method requires rather intensive computing and a digital-to-analog converter (DAC) to generate a sinc excitation signal. It also needs an analog-to-digital converter (ADC) to measure the response voltage, from which impedance profile is obtained through a DFT. This dissertation investigates system design approaches for impedance-based structural health monitoring (SHM), in which a primary goal is low power dissipation. First, we investigated behaviors of piezoelectric ceramics and proposed an electrical model in order to enable us to conduct system level analysis and evaluation of an SHM system. Unloaded and loaded piezoelectric ceramics were electrically modeled with lumped linear circuit components, which allowed us to perform system level simulations for various environmental conditions. Next, we explored a signaling method called the wideband method, which uses a pseudorandom noise (PN) sequence for excitation of the structure rather than a signal with a particular waveform. The wideband method simplifies generation of the excitation signal and eliminates a digital-to-analog converter (DAC). The system form factor and power dissipation is decreased compared to the previously existing system based on a sinc signal. A prototype system was implemented on a digital signal processor (DSP) board to validate its approach. Third, we studied another low-power design approach which employs binary signals for structural excitation and structural response measurement was proposed. The binary method measures only the polarity of a response signal to acquire the admittance phase, and compares the measured phase against that of a healthy structure. The binary method eliminates the need for a DAC and an ADC. Two prototypes were developed: one with a DSP board and the other with a microcontroller board. Both prototypes demonstrated reduction of power dissipation compared with those for the sinc method and for the wideband method. The microcontroller based prototype achieved an on-board SHM system. Finally, we proposed an analytical method to assess the quality of the damage detection for the binary method. Using our method, one can obtain the confidence level of a damage detection for a given damage distance.
Ph. D.

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17

Xu, Changting. "Investigation of Modulation Methods to Synthesize High Performance Resonator-Based RF MEMS Components." Research Showcase @ CMU, 2018. http://repository.cmu.edu/dissertations/1135.

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The growing demand for wireless communication systems is driving the integration of radio frequency (RF) front-ends on the same chip with multi-band functionality and higher spectral efficiency. Microelectromechanical systems (MEMS) have an overarching applicability to RF communications and are critical components in facilitating this integration process. Among a variety of RF MEMS devices, piezoelectric MEMS resonators have sparked significant research and commercial interest for use in oscillators, filters, and duplexers. Compared to their bulky quartz crystal and surface acoustic wave (SAW) counterparts, MEMS resonators exhibit impressive advantages of compact size, lower production cost, lower power consumption, and higher level of integration with CMOS fabrication processes. One of the promising piezoelectric MEMS resonator technologies is the aluminum nitride (AlN) contour mode resonator (CMR). On one hand, AlN is chemically stable and offers superior acoustic properties such as large stiffness and low loss. Furthermore, CMRs offer low motional resistance over a broad range of frequencies (few MHZ to GHz), which are lithographically-definable on the same silicon substrates. To date, RF MEMS resonators (include CMRs) have been extensively studied; however, one aspect that was not thoroughly investigated is how to modulate/tune their equivalent parameters to enhance their performance in oscillators and duplexers. The goal of this thesis is to investigate various modulation methods to improve the thermal stability of the resonator, its “effective” quality factor when used in an oscillator, and build completely novel non-reciprocal components. Broadly defined, modulation refers to the exertion of a modifying or controlling influence on something, herein specifically, the resonator admittance. In this thesis, three categories of modulation methods are investigated: thermal modulation, force modulation, and external electronic modulation. Firstly, the AlN CMR’s center frequency can be tunned by the applied thermal power to the resonator body. The resonator temperature is kept constant (for example, 90 °C) via a temperature sensor and feedback control such that the center frequency is stable over the whole operation temperature range of interest (e.g. –35 to 85 °C). The maximum power consumption to sustain the maximum temperature difference (120 ºC in this thesis) between resonator and ambient is reduced to a value as low as 353 μW – the lowest ever reported for any MEMS device. These results were attained while simultaneously maintaining a high quality factor (up to 4450 at 220 MHz device). The feedback control was implemented by either analog circuits or via a microprocessor. The analog feedback control, which innovatively utilized a dummy resistor to compensate for temperature gradients, resulted in a total power consumption of 3.8 mW and a frequency stability of 100 ppm over 120 ºC. As for the digital compensation, artificial neural network algorithm was employed to facilitate faster calibration of look-up tables for multiple frequencies. This method attained a frequency stability of 14 ppm over 120 ºC. The second modulation method explored in this thesis is based on the use of an effective external force to enhance the 3-dB quality factor of AlN CMRs and improve the phase noise performance of resonator-based oscillators. The force modulation method was embodied in a two-port device, where one of the two ports is used as a one-port resonator and the other is driven by an external signal to effectively apply an external force to the first port. Through this technique, the quality factor of the resonator was boosted by 140 times (up to 150,000) and the phase noise of the corresponding oscillator realized using the resonator was reduced by 10 dBc/Hz. Lastly, a novel magnetic-free electrical circulator topology that facilitates the development of in-band full duplexers (IBFD) for simultaneous transmit and receive (STAR) is proposed and modeled. Fundamentally, a linear time-invariant (LTI) filter network parametrically modulated via a switching matrix is used to break the reciprocity of the filter. The developed model accurately predicts the circulator behavior and shows very good agreement with the experimental results for a 21.4 MHz circulators built with MiniCircuit filter and switch components. Furthermore, a high frequency (1.1 GHz) circulator was synthesized based on AlN MEMS bandpass filters and CMOS RF switches, hence showing a compact approach that can be used in handheld devices. The modulation frequency and duty cycle are optimized so that the circulator can provide up to 15 dB of isolation over the filter bandwidth while good power transfer between the other two ports is maintained. The demonstrated device is expected to intrinsically offer low noise and high linearity. The combination of the first two modulation methods facilitates the implementation of monolithic, temperature-stable, ultra-low noise, multi-frequency oscillator banks. The third modulation technique that was investigated sets the path for the development of CMOS-compatible in-band full duplexers for simultaneous transmit and receive and thus facilitates the efficient utilization of the electromagnetic spectrum. With the aid of all these three modulation approaches, the author believes that a fully integrated, multi-frequency, spectrum-efficient transceiver is enabled for next-generation wireless communications.

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18

Headings, Leon Mark. "Modeling, characterization, and design of smart material driven stick-slip actuation mechanisms." Connect to resource, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1141700440.

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19

Jenne, Kirk E. "Acoustic cymbal transducers-design, hydrostatic pressure compensation, and acoustic performance." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Mar%5FJenne.pdf.

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Thesis (M.S. in Engineering Acoustics)--Naval Postgraduate School, March 2004.
Thesis advisor(s): Thomas R. Howarth, Dehua Huang. Includes bibliographical references (p. 67-69). Also available online.

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20

Peng, Jiangguli. "Effect of the microstructure and orientation of grains on the performance of perovskite ferroelectric ceramics." Thesis, Le Mans, 2020. http://www.theses.fr/2020LEMA1013.

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Les matériaux ferroélectriques sont largement utilisés dans d’importantes technologies incluant les transducteurs, actionneurs, capteurs... Parmi les structures ferroélectriques les plus exploitées, celles à base de Pb(Zr,Ti)O3 (PZT) offrent de bonnes performances dans des dispositifs opérationnels. Malgré cet aboutissement en terme de valorisation, la compréhension fondamentale des caractéristiques physiques des systèmes basés sur les céramiques PZT continue de susciter l’intérêt d’une large communauté scientifique. Cependant, un intérêt croissant porte sur la mise en œuvre de structures ferroélectriques exemptes d’éléments chimiques nocifs pour l’environnement dont la teneur en plomb. Dans ce cadre, les systèmes à base de BiFeO3-BaTiO3 (BF-BT) ont suscité beaucoup d'intérêt en tant que matériaux ferroélectriques sans plomb. Ce travail de thèse porte sur des études systématiques portant sur les céramiques à base de PZT et celles à base de BF-BT. Trois contributions ont été développées doant la première dédiée à l'analyse des microstructures, des phases cristallines et des propriétés ferroélectriques dans les systèmes PZT dopés. Les travaux ont montré le rôle du dopage Soft-Hard sur les propriétés structurales, morphologiques et électriques des matériaux dopés accepteurs. Dans une deuxième partie, l'interaction des microstructures et des propriétés électriques a été étudiée dans les systèmes BF-BT. L’optimisation des conditions de fabrication à travers la composition chimique et le traitement thermique contribue aux propriétés piézoélectriques améliorées dans ces systèmes sans plomb. Pour la troisième partie des travaux, des études expérimentales de fabrication, texturation et les caractérisations des propriétés ferroélectriques et électromécaniques ont été corrélées avec l’organisation structurale et morphologique des céramiques texturées
Ferroelectric materials have been widely applied in transducers, high-pressure generators, actuators, sensors... In this context, the ferroelectric materials are generally regarded as being related to an important class of smart materials. Among the most popular ferroelectric materials, those based on Pb(Zr,Ti)O3 (PZT) structures show the best performances in operating devices. Despite such achievements, the fundamental understanding of the physical characteristics continues to arouse the interest of a wide scientific community. On the other hand, in view of the environmental-friendly requirement, more attention have been paid by the researchers to lead-free ferroelectric materials. Thus, BiFeO3-BaTiO3 (BF-BT) systems have attracted a great deal of interest as promising candidate for lead-free ferroelectric materials. In this dissertation, PZT-based and BF-BT-based ceramics were investigated systematically. Three contributions have been developed with the first dealing with the analysis of microstructures, crystalline phases and electric properties in doped PZT systems. It was revealed the involvement of softening-hardening features and the relation between defect dipoles and electric properties in acceptor doped materials. In a second part, the interplay of microstructures and electric properties was studied in BF-BT systems, providing the relevant analysis of the optimized performance such as the enhanced piezoelectric properties of lead-free systems. In the third contribution, experimental methods of synthesis and texturing BF-BT systems by BT templates ad the characterization of ferroelectric and electromechanical properties have been correlated with the structural and morphological organization of textured ceramics

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21

Porfiri, Maurizio. "Performances of passive electric networks and piezoelectric transducers for beam vibration control." Doctoral thesis, La Sapienza, 2005. http://hdl.handle.net/11573/917115.

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This thesis is focused on beam vibration control using piezoelectric transducers and passive electric networks. The first part of this study deals with the modeling and the analysis of stepped piezoelectric beams. A refined one-dimensional model is derived and experimentally validated. The modal properties are determined with four numerical methods. A homogenized model of stepped periodic piezoelectric beams is derived by using two-scale convergence. The second part deals with the performance analysis of three passive circuits in damping structural vibrations: the piezoelectric shunting, the second order transmission line and the fourth order transmission line. The effects of uncertainties of the electric parameters on the system performances are analyzed. Theoretical predictions are validated through different experimental setups

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22

Grinberg, Daniel. "Multi-physical approach for the assessment of objective consequences of mitral valve repair." Thesis, Lyon, 2020. http://www.theses.fr/2020LYSEI110.

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L’insuffisance mitrale est la cardiopathie valvulaire ayant l’incidence la plus élevée dans les pays occidentaux. Néanmoins les stratégies thérapeutiques médicales et les pratiques chirurgicales ainsi que leurs résultats sont hétérogènes, entre les différents opérateurs, centres de soins et pays. L’évaluation de la qualité d'une réparation Chirurgicale repose aujourd'hui sur une évaluation principalement morphologique peropératoire (aspect visuel de la valve), et une évaluation fonctionnelle approximative (test à l’eau) alors que le cœur est encore arrêté et immobile. L’hypothèse de ce travail de thèse est qu’une meilleure compréhension des modifications physiques Survenant au cours des réparations mitrales permettrait d’améliorer des pratiques médicales de multiples façons : sélection des stratégies thérapeutiques idéales (réalisation de chirurgies “à la carte” adaptées à chaque patient), évaluation objective et quantitative Peropératoire (concept de “réparation à faible stress”), développement de nouveaux outils réalisant des réparations percutanées à bas stress. Depuis les cinq dernières années, une collaboration d'experts chirurgicaux et scientifiques Français (Hospices Civils de Lyon et Laboratoire de Génie Ðu201Électrique et Ferroélectricité) et Américains (Mount Sinai Hospital and Sinai BioDesign lab.) a été initiée, afin de développer des outils innovants permettant la mesure de certains paramètres objectifs (physique) de l'appareil valvulaire mitral
Mitral regurgitation is the most frequent valvular disease in western populations. However medical strategies and surgical techniques and results widely diverge between centers and countries. Current intraoperative assessment during surgeries relies on a rough intraoperative morphological assessment. A comprehensive understanding of the physical changes occurring during such surgeries could help us optimize the current repair strategies in different manners: selection of the ideal strategy (tailored surgical strategy to patient’s needs), intraoperative assessment of the objective parameters (low-stress repair procedures) and development of innovative surgical devices performing low-stress percutaneous repairs. A five-year collaboration of surgical and scientific experts in France (Hospices Civils de Lyon, and the Laboratoire de Génie Electrique et Ferroélectricité), and in the USA (Mount Sinai Hospital and Sinai BioDesign laboratory) was carried out in order to develop innovative tools enabling the measurement of objective (physical) parameters in the mitral valve

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23

FORLANI, Mauro. "Investigation on the dynamic performances of piezoelectric multilayer actuators." Doctoral thesis, Università degli studi di Bergamo, 2011. http://hdl.handle.net/10446/875.

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24

Probst, Troy Anthony. "Evaluating the Aerodynamic Performance of MFC-Actuated Morphing Wings to Control a Small UAV." Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/19190.

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The purpose of this research is to evaluate certain performance characteristics of a morphing
wing system that uses Macro Fiber Composites (MFC) to create camber change. This
thesis can be broken into two major sections. The first half compares a few current MFC
airfoil designs to each other and to a conventional servomechanism (servo) airfoil. Their
performance was measured in terms of lift and drag in a 2-D wind tunnel. The results
showed MFC airfoils were effective but limited by aeroelasticity compared to the servo. In
addition, a morphed airfoil and a flapped airfoil were rapid prototyped and tested to isolate
the effects of discontinuity. The continuous morphed airfoil produced more lift with less
drag.
The second half of this thesis work focused on determining the ideal MFC configurations for
a thin wing application. Simulations were run on a thin wing with embedded MFCs such
that the whole wing morphed. Finite element and vortex lattice models were used to predict
deflections and rolling moment coefficients. Different configuration parameters were then
varied to quantify their effect. The comparisons included MFC location, number of MFCs,
material substrate, and wing thickness. A prototype wing was then built and flight tested.
While the simulations overestimated the wing deflection, the flight results illustrated the
complexity and variability associated with the MFC morphing system. The rolling moment
coefficients from flight were consistent with the simulation given the differences in deflection.
Master of Science

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25

Pokharel, Alok. "Analyse par des méthodes de “reverse engineering” de résonateurs piézoélectriques hautes performances et modélisation du bruit." Thesis, Bourgogne Franche-Comté, 2020. http://www.theses.fr/2020UBFCD025.

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Les résonateurs à ondes acoustiques de volume (BAW) ont été étudiés dans le domaine temps-fréquence à FEMTO-ST depuis longtemps et ont montré un rôle essentiel dans de nombreuses applications métrologiques telles que dans les dispositifs de positionnement comme GPS, Glonass, Galileo, etc. Ce travail de thèse présente la technique passive utilisée pour des mesures du bruit de phase dans les résonateurs BAW à quartz. Les résonateurs BAW de hautes performances ont été fabriqués par plusieurs fabricants européens et fournis par le CNES pour une étude de “reverse engineering” durant cette thèse. Le manuscrit commence par rappeler les bases de cristallographie du quartz, de piézoélectricité et de caractérisation du bruit dans les résonateurs ultra-stables. La deuxième partie du travail donne des détails sur la mesure de bruit dans les résonateurs par une technique de suppression de porteuse et sur une adaptation pour les résonateurs LGT d’impédance très faible (< 10 ohms).La troisième partie concerne l’interprétation avec le modèle de Steven-Tiersten des résultats de mesures du bruit de phase à différentes températures et leur classification en fonction du bruit. Une simulation par méthode d’éléments finis (FEM) permet de comparer ces résultats avec la théorie de Steven-Tiersten. La quatrième partie, présente un test de modélisation du bruit de phase à l'aide d’un modèle d’intermittence. Des comparaisons de nos résultats avec la distribution de Mittag-Leffler ainsi que des distributions stables semblent indiquer un rejet du modèle d’intermittence en loi de puissance, dans notre cas. Enfin, le travail de “reverse engineering” est réalisé en démontant les résonateurs pour l'analyse des défauts par diffraction des rayons X et diffusion laser. Le démontage du résonateur a révélé des imperfections macroscopiques. Les résultats préliminaires de diffraction des rayons X montrent la présence de dislocations qui pourraient être une cause de bruit de phase dans les résonateurs. Ceci devra être confirmé sur d’autres résonateurs
Bulk Acoustic Wave Resonators (BAW) have been studied in Time and Frequency domain for a long time, particularly at FEMTO-ST. They have an essential role in many metrological applications such as in positioning devices like GPS, Glonass, Galileo, etc. This thesis work presents the passive technic used for phase noise measurement in high-performance BAW resonators. These resonators were fabricated by several European manufacturers and provided for the thesis work by CNES for reverse engineering investigations.The work begins with recalling the basics of piezoelectricity in quartz and noise in ultra-stable resonators.The second part of the work gives details on noise measurement by carrier suppression technic with an alternative technic for low impedance resonators (< 10 ohms).The third part is about the comparison of Steven-Tiersten’s model with our phase noise measurement results at different temperatures and classification of resonators according to their short-term stability. A finite element simulation is used to compare the theory and experimental results.The fourth part presents tests using Mittag-Leffler distribution and stable distributions of a model of phase noise due to power law intermittency.Finally, the “reverse engineering” work is carried out by dismantling some resonators for defects analysis using X-rays diffraction and laser scattering. This revealed macroscopic imperfections and a few dislocations which could be a possible cause for phase noise in the resonators. This will have to be confirmed and quantified with other resonators

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26

Allani, Maroua. "Effets des propriétés physico-chimiques du cristal LGT (La3Ga5.5Ta0.5O14) sur les performances des résonateurs piézoélectriques." Thesis, Bourgogne Franche-Comté, 2017. http://www.theses.fr/2017UBFCD041/document.

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Nous avons caractérisé différents cristaux piézoélectriques de Langatate La3Ga5.5Ta0.5O14 (LGT), de différentes couleurs afin d’évaluer l’influence des défauts sur la qualité de dispositifs du domaine Temps-Fréquence (résonateurs acoustiques).Nous avons étudié la composition de ces cristaux dont les variations autour de la composition stoechiométrique sont surtout dues à l’évaporation du Ga2O au cours de la croissance compensée par un excès de Ga2O3 dans le mélange initial. Pour déterminer cette composition, la technique ICP-AES, précédée par une mise en solution par fusion alcaline, est la plus fiable.La présence d’impuretés chimiques, telles que les éléments métalliques ou les terres rares, liée à la pureté des oxydes de base, au frittage de la charge dans un creuset alumine… est étudiée. Nous expliquons ainsi la nature des centres colorés qui évolue selon l’atmosphère de tirage ou lors d’un recuit particulier.C’est ainsi que nous avons déterminé certaines propriétés de LGT permettant l’obtention de dispositifs comme les résonateurs à ondes de volume dont le produit Q.f est supérieur à celui des résonateurs à quartz. Pour cela, nous montrons notamment qu’il est nécessaire que :- la composition du cristal soit la plus proche possible de la stoechiométrie,- la résistivité électrique soit la plus grande possible,- l’étude spectroscopique ne révèle aucune absorption dans le domaine du visible.Dans ces conditions, le facteur de qualité Q d’une résonance à 10 MHz peut être de 1.44 million au point d’inversion de la courbe fréquence-température (1.35 pour le quartz) mais qu’il diminue notablement pour atteindre 0.35 million si nous pratiquons un recuit sous air à 1000°C pendant 48 h
We have characterized Langatate piezoelectric crystals La3Ga5.5Ta0.5O14 (LGT), differently colored in order to evaluate the defects influence on the quality of Bulk Acoustic Waves resonators for the Time and Frequency domain.We have analyzed the composition of crystals whose variations around stoichiometric composition are mainly due to the evaporation of the Ga2O during growth compensated by adding an excess of Ga2O3 in the initial mixture. Among different techniques, the ICP-AES spectrometry, preceded by a dissolution by alkaline fusion seems to be the most accurate technique to determine the composition.The inevitable presence of chemical impurities, such as metallic elements, rare earth… linked to the purities of the raw materials, to the sintering of the load in an alumina crucible… is also studied. We try to explain in particular the nature of the color centers that evolve according to the growth atmosphere or during a particular annealing.So, we conclude by a list of necessary properties to obtain BAW resonators exhibiting a Q.f product higher than quartz. For this, we establish that it is necessary that:- the crystal composition is as close as possible to the stoichiometric composition,- the electrical resistivity is the highest possible,- the spectroscopic study does not reveal any absorption band in the visible domain.In these conditions, we were able to highlight that the quality factor of a 10 MHz resonance is of 1.44 million at the inversion temperature of the frequency-temperature curve (1.35 for the quartz crystal in the same conditions), but that this one decreases significantly to reach 0.35 million if we perform an annealing under air at 1000 °C during 48 hours

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27

Charng, Jie-Yann, and 常嘉彥. "Analysis on Performance of Piezoelectric Accelerometer." Thesis, 1996. http://ndltd.ncl.edu.tw/handle/77342756508756970797.

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碩士
國立成功大學
機械工程研究所
84
Consider a piezoelectric beam. Based on the piezoelectricity with consideration for the coupling between the strain field and the electric field, a finite element formulation is developed. This study uses this code to analyze the response of the structure subjected to boundary vibration and the sensor electrical outputs as well as to determine the boundary condition from output voltage. Besides,this study also analyze performance limitations of the accelerometers as well as to determine the design parameter from some performance limitation.

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28

Eitel, Richard E. "Novel piezoelectric ceramics development of high temperature, high performance piezoelectrics on the basis of structure /." 2003. http://etda.libraries.psu.edu/theses/approved/WorldWideIndex/ETD-435/index.html.

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29

Hasan, Zeaid. "Controlling Performance of Laminated Composites Using Piezoelectric Materials." Thesis, 2010. http://hdl.handle.net/1969.1/ETD-TAMU-2010-12-8686.

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Composite materials are increasingly used in aerospace, underwater, and automotive structures. Their use in structural applications is dictated by the outstanding strength and stiffness while being lightweight in addition to their flexibility in tailoring the desired performance in the design of structures. The present study focuses on the failure analysis and shape control of smart composite laminates under coupled hygrothermal, electric and mechanical stimuli. A linear thermo-electro-elastic constitutive model for transversely isotropic materials is used for each ply in the composite laminates. The first-ply failure and ultimate laminate failure criteria of composite laminates are used to predict the failure stress and mode of the composite laminate where we incorporate various commonly known macroscopic failure criteria including Tsai-Hill, Tsai Wu, maximum stress and maximum strain for each lamina. We study the use of piezoelectric materials such as lead zirconate titanate (PZT) and piezoelectric fiber composites as actuators for controlling deformation in composite laminates; this study focuses on bending deformation. The purpose is to minimize unwanted deformation, such as the one due to hygrothermal effect, by applying counter deformation to avoid failure in such composite laminates. In addition, analysis based on the Classical Laminate Theory (CLT) is performed for Carbon/Epoxy (AS4/3501-6) thin laminate with stacking sequence [90/45/-45/0]s under uniaxial and biaxial in-plane loading. One of the major types of failure in smart structures is caused by debonding of the actuator from the host structure which is caused by the high stress discontinuity between the interface of the host structure and the active part. By using embedded actuators, such that the active part is incorporated into one of the layers of the composite beam during the manufacturing process, the stress concentration effect can be reduced while obtaining similar actuation values. Moreover, a control algorithm is proposed that enables the composite laminate to overcome the failure load by using piezoelectric materials where a counter electric voltage could be applied which prevents failure from occurring. Furthermore, computer software called “Hyper Composite” was developed using Action Script® and Adobe Flash® in order to perform stress and failure analysis for general composite laminates. Several carpet plots were also generated to show the interacting behavior of two independent variables such as Young’s modulus, Poisson’s ratio, shear modulus and the coefficient of thermal and moisture expansion at different percentile constitutions for the laminate different plies. This computer software is useful for estimating overall properties of smart composite laminates in designing smart composite structures.

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30

Chiu, Zhu-Shin, and 邱智聖. "Fabrication and Performance of Piezoelectric Micro — Mechanical Filter." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/79025005652305868807.

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Анотація:

碩士
逢甲大學
機械工程學所
92
In this thesis, micro-mechanical filters are fabricated by bulk micromachining technique and sol- gel derived PZT (lead zirconate titanate, PbTixZr1-xO3) thin films. The vibration theory is applied to design the micro-mechanical filter in order to get the frequency response with bandpass characteristics. The processing of PZT thin films and interaction of the films with other layers in the MEMS filter are key factors for achieving a successful device. The major parameters include the influence of etching agent BOE (buffer oxide etchant) of PZT films on other layers, and sintering timing of PZT films in the process integration. It is found that PZT films remain complete on metal electrode, but are broken onto the silicon dioxide (SiO2) layer due to mismatch of lattice constants of coefficients of thermal expansion between PZT ＆ SiO2. This causes failure of pattering PZT films because of the infiltration of etching agent into broken PZT induces lift-off of the SiO2 layer. The fast etching rate of green PZT films suggests that PZT be patterned before sintering. The Euler beam theory is adopted to predict natural frequency of resonance beam in this PZT actuated filter. Frequency falls in the range between 226 KHz to 14.5 MHz due to variation of beam lengths.

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31

Tasy, Chain-Wei, and 蔡建維. "Fabrication, Analysis and Performance Study of Piezoelectric Transformers." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/02381405912258542484.

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Анотація:

碩士
國立成功大學
航空太空工程學系碩博士班
94
Compared with wire-wound magnetic transformer, piezoelectric transformer ( PT ) has main advantages which include small and thin size, high efficiency power, no electromagnetic radiation, and so on. PT is gradually replacing magnetic transformer, especially in the application of the power supply of the liquid crystal displays ( LCDs ), because the tendency of electrical appliances is toward small and thin units. Although piezoelectric transformer offers the advantages above, it is only used in high-price electronic appliances because of higher cost in PT than that in magnetic transformer. In addition, for higher thresholds of technologies needed, a few companies capably invest in PT fabrication in Taiwan. In this theme, the researches on the fabrication, design, and simulation are carried out. First, the electrical equivalent circuit of PT is derived based on mechanical and electrical theories to learn the PT voltage gain in terms of the ratio of poling lengths of output section to input section, and characteristic parameters of piezoelectric material. Then, with the ANSYS, the design and simulation of PT are done. The voltage gain versus frequency response and impedance versus frequency response can be obtained by finite element calculation. Third, the implementation of the PT with the dimension of 30.3 x 6.5 x 1.3 mm is completed by stages from mold patterning of piezoelectric ceramic dust, burning process to poling process. The performances of implemented PT are measured with instruments. The resonance and anti-resonance frequencies are 113.5 kHz and 111.3 kHz respectively. Finally, the data comparisons of the parameters data from theory calculation, ANSYS simulation and instrument measurement are performaned. The difference of resonance and anti-resonance frequencies between simulation and measured data are 2.5kHz and 1.8kHz that difference rates are less than 1.6%. This demonstrates that the ANSYS simulation data are available to be used as pre-design references. It is greatly convenient for new PT designs and analyses in the future.

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32

Chou, Yuan-Cheng, and 周源正. "The performance analysis for piezoelectric driven feeder system." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/28827615763915448485.

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Анотація:

碩士
國立臺灣大學
工程科學及海洋工程學研究所
92
he performance of piezoelectric driven feeder system is discussed and analyzed in this thesis, especially the vibration and the feed rate. First, we established the math model of the feeder system and find out the relationship between dimension parameter and its first resonance frequency by numerical analysis. Then, the dimension of system is determined and can be computed or anticipated its mechanical characteristic. The ANSYS software offers a method to check the correctness of our math model and hypothesis. At last, make a real piezoelectric driven feeder system as we want and measure its mechanical characteristic (e.g. first resonance frequency and vibratory amplitude of track) to compare with result of numerical analysis. The ideal feed model must be set up before figure out the feed rate of the feeder system. Three factors that have the most influence on the feed rate can be found out. They are first resonance frequency, slanting angle and amplitude of track. Finally, we can conclude that the feed rate of the feeder system calculated from the formula we proposed in this thesis can be applied to all materials and dimensions.

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33

Wei-YangHsu and 徐偉洋. "Improvement on performance for the Piezoelectric speaker and the Piezoelectric Energy Harvester by Circuit Design." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/38910169103296080369.

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Анотація:

碩士
國立成功大學
電機工程學系
102
Thesis is divided into two parts, the first part of thesis the design of a tank circuit for energy harvester can be capable of being used more widely. Wireless sensor is increasingly important in life. Because they use the occasion to replace the batteries for these devices is a difficult and impractical task. Therefore, the automatic triggering of the tank circuit for energy harvester can be widely used. This thesis will be designed to meet the load and has a storage tank circuit automatically trigger circuit. The second part will present the use of bass boost circuit to optimize its low-frequency response. As mobile phones, digital TVs thin, rapid advances in miniaturization technology, thin speaker emerged. However, the piezoelectric material itself is a problem because of the low-frequency response distortion high, shrill sound, the purpose of thesis is production bass boost circuit. Bass boost circuit can improve the low-frequency response and improve the piezoelectric speaker audio response. Finally, the successful design the automatic triggering of the tank circuit for energy harvester can be more convenient to use. Piezoelectric speaker low-frequency is improved by circuit. Compared to commonly circuit can be increased by about 10dB.

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34

Lin, Xin-yi, and 林新益. "High Performance Motion Control of Linear Piezoelectric Ceramic Motors." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/w6e933.

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Анотація:

碩士
國立臺灣科技大學
機械工程系
99
Linear Piezoelectric Ceramic Motors (LPCM) have been recognized as one kind of useful actuators in recent mechatronics and automation industries. Due to their dominant nonlinear effects such as friction and hysteresis, controller design for LPCM has become a challenging task for researchers. The current literature related to motion control of LPCM shows that the designers mostly suffer from either complicated friction modeling for compensation or numerous parameters tuning by using intelligent control algorithms. Following the idea of “add-ons” controller design, this thesis proposes a novel hybrid control structure, comprising of PID control, repetitive control, and neural network adaptive control, to achieve high performance and easy maintainability for motion control of LPCM. The experimental results on tracking motion control of a LPCM demonstrate the effectiveness of the proposed method. Moreover, the study also adds a LuGre friction model based feedforward compensator to the hybrid controller for comparison purposes and further performance improvement. Biaxial motion control experiments are finally provided to justify the applicability of this method.

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35

楊博凱. "Structural Analysis and Performance Evaluation of Piezoelectric Inkjet-Heads." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/75590374841367157343.

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Анотація:

碩士
大葉大學
機械工程研究所碩士班
92
The purpose of this thesis is to make a study of characteristics of an inkjet-head, which actuated by a newly designed shear type piezoelectric actuator. Points of this thesis are: analyzing and forecasting of characteristics of the shear type piezoelectric actuator and the inkjet-head, performance evaluation of piezoelectric inkjet-head and experimental measurement of dynamic characteristics of piezoelectric actuator. As the influence of properties of piezoelectric actuator is toward the inkjet-head directly, a finite element model will be established first to make analyses of piezoelectric actuator. A structural, electrical and fluid coupling finite element model will be established secondly to analyzing influences of mass loading of ink on the diaphragm. Then a lumped element model of the piezoelectric inkjet-head system will be presented to obtain a transfer function of inkjet system. The transfer function is purposed to evaluating performance of piezoelectric inkjet-head, and to provide consultations for designing. Finally, an experimental measurement of dynamic characteristics of piezoelectric actuator is taken to provide contrast with system models.

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36

Sriramdas, Rammohan. "Vibrational Energy Harvesting : Design, Performance and Scaling Analysis." Thesis, 2016. http://etd.iisc.ac.in/handle/2005/3814.

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Анотація:

Low-power requirements of contemporary sensing technology attract research on alternate power sources that can replace batteries. Energy harvesters function as power sources for sensors and other low-power devices by transducing the ambient energy into usable electrical form. Energy harvesters absorbing the ambient vibrations that have potential to deliver uninterrupted power to sensing nodes installed in remote and vibration rich environments motivate the research in vibrational energy harvesting. Piezoelectric bimorphs have been demonstrating a pre-eminence in converting the mechanical energy in ambient vibrations into electrical energy. Improving the performance of these harvesters is pivotal as the energy in ambient vibrations is innately low. The present work is organized in three major sections: firstly, audit of the energy available in a vibrating source and design for effective transfer of the energy to harvesters, secondly, design of vibration energy harvesters with a focus to enhance their performance, and lastly, identification of key performance metrics influencing conversion efficiencies and scaling analysis for MEMS harvesters. Typical vibration levels in stationary installations such as surfaces of blowers and ducts, and in mobile platforms such as light and heavy transport vehicles, are determined by measuring the acceleration signal. The frequency content in the signal is determined from the Fast Fourier Transform. A method of determining the energy associated with the vibrating source and the associated power using power spectral density of the signal is proposed. Power requirements of typical sensing nodes are listed with an intent to determine the adequacy of energy harvesting. Effective transfer of energy from a given vibration source is addressed through the concept of dynamic vibration absorption, which is a passive technique for suppressing unintended vibrations. Optimal absorption of energy from a vibration source entails the determination of absorber parameters such as resonant frequency and damping. We propose an iterative method to obtain these parameters for a generic case of large number of identical vibration absorbers resembling harvesters by minimizing the total energy absorbed by the system. The proposed method is verified by analysing the response of a set of cantilever absorber beams placed on a vibrating cantilever plate. We find, using our method, the values of the absorber mass, resonant frequency and damping of the absorber at which significant amount of energy supplied to the system flows into the absorber, a scenario which is favourable for energy harvesting. We emphasize through our work that monitoring energies in the system and optimizing their flow is both rational and vital for designing multiple harvesters that absorb energy from a given vibration source optimally. Enhancing the performance of piezoelectric energy harvesters through a multilayer and, in particular, a multistep configuration is presented. Partial coverage of piezoelectric material in steps along the length of a cantilever beam results in a multistep piezoelectric energy harvester. We find that the power generated by a multistep beam is almost twice of that generated by a multilayer harvester made out of the same volume of polyviny-lidine fluoride (PVDF), further corroborated experimentally. Improvements observed in the power generated prove to be a boon for weakly coupled, low pro le, piezoelectric materials. Thus, in spite of the weak piezoelectric coupling observed in PVDF, its energy harvesting capability can be improved significantly by using it in a multistep piezoelectric beam configuration. Besides, the effect of piezoelectric step length and thickness in a piezoelectric unimorph harvester and performance metrics such as piezoelectric coupling factor and efficiency of conversion are presented. Modeling of a hybrid energy harvester composed of piezoelectric and electromagnetic mechanisms of energy conversion motivated by the need to determine the contribution of each domain to the power generated by the harvester is presented, particularly, when multiple domains exist in a single harvester. Two exclusive schemes of energy transduction are represented using equivalent circuits, which allow modeling any additional transduction scheme employed in the hybrid harvester with relative ease. Furthermore, a method of determining optimal loads in the respective domains using the equivalent circuit of the hybrid harvester is presented. Four different hybrid energy harvesters were fabricated and evaluated for their performance in comparison with that estimated from the proposed models. Additionally, scaling laws for hybrid energy harvesters are presented. The power developed by both piezoelectric and electromagnetic domains is observed to decrease with width and length cubed. Power indices and figures of merit in a hybrid harvester are proposed and are used to estimate the efficiencies of the four fabricated hybrid harvesters. The important design parameters for micro scale harvesting are identified by performing scaling analysis on MEMS piezoelectric harvesters. Performance of energy harvesters is directly related to the harvester attributes, viz., size, material, and end-mass. Depending on the contribution from each attribute, the power developed by MEMS harvesters can vary widely. A novel method of delineating the power developed by a harvester using five exclusive factors representing scaling, composition, inertia, material, and power (SCIMP) factors is presented. Although the proposed method can be extended to bi-morph and multilayer harvesters, in the present work, we elucidate it by applying it to a MEMS unimorph. We also present a unique coupling factor that ensures maximum power factor in a harvester. As any tiny increment in the power generated would considerably improve the power densities of MEMS harvesters, we focus on enhancing the power developed by maximizing each of the five exclusive factors irrespective of material and size. Furthermore, we demonstrate the competence of the proposed method by applying it on nine different MEMS harvesters reported in the literature. Considering the close match between the reported and predicted performance, we emphasize that monitoring the proposed factors is sufficient to attain the best performance from a harvester.

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37

劉勝富. "An Experimental Investigation of the Thermal Performance of Piezoelectric Fans." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/48478799536436781477.

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38

Lin, Shun-Chiu, and 林順區. "High performance piezoelectric MEMS generators based on stainless steel substrate." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/03883169256650798515.

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Анотація:

博士
國立臺灣大學
工程科學及海洋工程學研究所
102
In the past decade, the vibration energy harvesting technologies based on piezoelectric materials have been studied intensively and been improved constantly. The power outputs of piezoelectric MEMS generators are also steadily improved year by year. This dissertation presents the development of piezoelectric MEMS power generators which have the ability to harvest mechanical energy of surrounding vibrations and transform vibration energy into useful electrical power. The harvesting electrical power is able to use in energy storage applications. To improve and get high- efficiency piezoelectric MEMS generators, the lead zirconate titanate (PZT) material was directly deposited on the substrate by the aerosol deposition method which could deposit PZT thin film up to tens micron in minutes. The piezoelectric MEMS generators utilize the d31 and bimorph of PZT for transforming mechanical strain energy into electrical charge by using. For applications with higher vibration levels, the structure with PZT ceramic fabricated on silicon or SOI substrate may break under higher acceleration levels. To increase the mechanical strength of the piezoelectric MEMS generators structure, alternative substrate material, stainless steel substrate is proposed. Finally, we succeed to fabricate the piezoelectric MEMS generators based on stainless steel, piezoelectric MEMS generators based on silicon and piezoelectric MEMS bimorph generators by means of micro-electro-mechanical-systems (MEMS) process. We also compared the output performance of these devices and the lifetime of these devices in a long-term vibration. Experimental results confirm that the devices have the ability to generate power in the hundred micro-watt range and the output voltage is much higher than the minimum requirement for diode band-gaps in the rectifier circuit.

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39

Tu, Ping-Yung, and 杜彬湧. "Design、Fabrication and Performance Study Piezoelectric Micropump for Fuel Atomizer." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/02022500604184457176.

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Анотація:

碩士
國立中正大學
機械系
90
Environment and energy conservation are compelling issues of today. Transportation is a principal cause of environmental pollution and energy consumption. Due to the use of carburetor in motorcycle engines for fuel supply, injection timings cannot precisely controlled to match engine operation of conditions. This study is aimed to design and fabricate a low cost; high precision micropump for fuel atomizer. The design of micropump can also be used for other applications such as lubrication systems. In this study, an actuator using bimorph type of piezoelectric sheet was developed. The piezoelectric sheet compressed fluid in fluid chamber and generated localized pressure to spray through array of micro nozzles. High frequency oscillations create fluid atomization. UV laser machining, micro electro discharge machining, and silicon micromachining was used to fabricate array of micro nozzles. The developed piezoelectric micropump can be operated with frequency at 4~20 kHz with less than 1 watt energy and 10~20 voltage. Performance investigation shows that the amount flow rate increases with increasing voltage, bore diameter and angle of cone hole of nozzle. The results also show that changing the frequency of piezoelectric sheet can generate different flow characteristic. This phenomenon can be used for flow rate control.

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40

Gupta, Harshvardhan. "Development of High-Performance Piezoelectric Micromachined Transducers for Near Ultrasound." Thesis, 2022. https://etd.iisc.ac.in/handle/2005/6109.

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Анотація:

Near-ultrasound refers to sound with frequencies just above the range of human hearing, from about 18 to 40 kHz. This band is rarely used for typical ultrasound applications and is ignored for all except the most demanding audio applications. We highlight the advantages of using this band and present a design study on the development of high-efficiency, resonant transducers for near-ultrasound. Piezoelectric Micromachined Ultrasound Transducers, or PMUTs, are MEMS resonators that are used to generate and receive ultrasound and acoustic waves. They are fabricated as multilayered diaphragms consisting of a passive structural layer coated with a piezoelectric material sandwiched between metal films. In this dissertation, we report the realization of a novel near-ultrasound PMUT system especially designed for Data-over-Sound (DoS) applications. This realization includes investigation of new transducer designs, innovation in fabrication processes, and a significant advance in acoustics and electronics integration. We use analytical and coupled finite element models of clamped circular plates with in-plane stresses to generate design maps for PMUTs. Residual tensile stresses generated during fabrication processes have the effect of stiffening the diaphragms and increasing their resonant frequencies. We experimentally estimate the magnitude of these stresses in sol-gel PZT-coated SOI wafers and fabricate transducers with dimensions optimized for near-ultrasound. The transducers are 50 times smaller and 20 times more efficient than conventional electrodynamic micro speakers in the near-ultrasound range. We then present a novel design for PMUTs with “bossed” diaphragms that allows further reduction in device footprint and power consumption while improving sensitivity and efficiency. The dimensions of the central boss structure are optimized using simulations. The fabricated devices are found to be up to 10 times smaller than conventional PMUTs for the same frequencies, and less sensitive to variations in residual stress. We have studied and optimized the effects of packaging and the acoustic environment on the performance of the transducers using finite element and boundary element acoustic simulations. The devices are packaged with 3D-printed acoustic resonators and horns designed to boost sensitivity, improve bandwidth, and widen the directivity of the transducers. The results of the simulations are experimentally verified by scanning the acoustic field of the transducers. The transducers are finally integrated into battery- and solar-powered DoS beacons and wireless sensor nodes, complete with a low-power microcontroller for modulation/demodulation, a low Q-current amplifier, a MEMS microphone, an acoustic resonator, and the near-ultrasound transducer — all in a compact package with a transmission range of up to 30 meters and a battery reserve of up to 4 weeks.

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41

GAUTAM, GAURANG, and MOHIT KUMAR. "HIGH PERFORMANCE PIEZOELECTRIC ENERGY HARVESTING BASED ON PVDF-SnS2 NANOCOMPOSITE." Thesis, 2022. http://dspace.dtu.ac.in:8080/jspui/handle/repository/19541.

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Анотація:

This study focuses on fabricating flexile piezoelectric nanogenerators (PENGs) based on polyvinyl fluoride (PVDF) – tin diselenide (SnS2) composite. 2D-SnS2 was synthesized via simple hydrothermal method and was mixed with PVDF to form the nanocomposite solution, which was then drop casted to form flexible thin films. The prepared SnS2 was confirmed and characterized using X-ray diffractometry (XRD) and Raman spectroscopy. Different weight percentages of SnS2 were added to bare PVDF to study the role of weight percentage on the output performance of the PENGs. The enhanced beta (β) phase of PVDF-SnS2 based PENGs was studied using XRD analysis, where a steep rise in the intensity of β-phase peak is observed, as the SnS2 concentration (by wt. %) is increased. In order to analyse the piezoelectric outputs, the generation of piezo voltage (open circuit, Voc) and piezo current (short circuit, Isc) were recorded and compared. The Voc and Isc of fabricated PENGs composing different weight percentages of SnS2 in PVDF, were reported to have higher Voc and Isc as compared to bare PVDF based PENGs. The trends of increasing β-phase and hence, increasing piezoelectric output on increasing the wt. % of SnS2 were observed. Thus, the PENG fabricated from PVDF thin film with maximum SnS2 concentration, i.e., 7 wt.% shows maximum beta phase enhancement and hence, maximum piezoelectricity.

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42

Sriramdas, Rammohan. "Vibrational Energy Harvesting : Design, Performance and Scaling Analysis." Thesis, 2016. http://etd.iisc.ernet.in/2005/3814.

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Анотація:

Low-power requirements of contemporary sensing technology attract research on alternate power sources that can replace batteries. Energy harvesters function as power sources for sensors and other low-power devices by transducing the ambient energy into usable electrical form. Energy harvesters absorbing the ambient vibrations that have potential to deliver uninterrupted power to sensing nodes installed in remote and vibration rich environments motivate the research in vibrational energy harvesting. Piezoelectric bimorphs have been demonstrating a pre-eminence in converting the mechanical energy in ambient vibrations into electrical energy. Improving the performance of these harvesters is pivotal as the energy in ambient vibrations is innately low. The present work is organized in three major sections: firstly, audit of the energy available in a vibrating source and design for effective transfer of the energy to harvesters, secondly, design of vibration energy harvesters with a focus to enhance their performance, and lastly, identification of key performance metrics influencing conversion efficiencies and scaling analysis for MEMS harvesters. Typical vibration levels in stationary installations such as surfaces of blowers and ducts, and in mobile platforms such as light and heavy transport vehicles, are determined by measuring the acceleration signal. The frequency content in the signal is determined from the Fast Fourier Transform. A method of determining the energy associated with the vibrating source and the associated power using power spectral density of the signal is proposed. Power requirements of typical sensing nodes are listed with an intent to determine the adequacy of energy harvesting. Effective transfer of energy from a given vibration source is addressed through the concept of dynamic vibration absorption, which is a passive technique for suppressing unintended vibrations. Optimal absorption of energy from a vibration source entails the determination of absorber parameters such as resonant frequency and damping. We propose an iterative method to obtain these parameters for a generic case of large number of identical vibration absorbers resembling harvesters by minimizing the total energy absorbed by the system. The proposed method is verified by analysing the response of a set of cantilever absorber beams placed on a vibrating cantilever plate. We find, using our method, the values of the absorber mass, resonant frequency and damping of the absorber at which significant amount of energy supplied to the system flows into the absorber, a scenario which is favourable for energy harvesting. We emphasize through our work that monitoring energies in the system and optimizing their flow is both rational and vital for designing multiple harvesters that absorb energy from a given vibration source optimally. Enhancing the performance of piezoelectric energy harvesters through a multilayer and, in particular, a multistep configuration is presented. Partial coverage of piezoelectric material in steps along the length of a cantilever beam results in a multistep piezoelectric energy harvester. We find that the power generated by a multistep beam is almost twice of that generated by a multilayer harvester made out of the same volume of polyviny-lidine fluoride (PVDF), further corroborated experimentally. Improvements observed in the power generated prove to be a boon for weakly coupled, low pro le, piezoelectric materials. Thus, in spite of the weak piezoelectric coupling observed in PVDF, its energy harvesting capability can be improved significantly by using it in a multistep piezoelectric beam configuration. Besides, the effect of piezoelectric step length and thickness in a piezoelectric unimorph harvester and performance metrics such as piezoelectric coupling factor and efficiency of conversion are presented. Modeling of a hybrid energy harvester composed of piezoelectric and electromagnetic mechanisms of energy conversion motivated by the need to determine the contribution of each domain to the power generated by the harvester is presented, particularly, when multiple domains exist in a single harvester. Two exclusive schemes of energy transduction are represented using equivalent circuits, which allow modeling any additional transduction scheme employed in the hybrid harvester with relative ease. Furthermore, a method of determining optimal loads in the respective domains using the equivalent circuit of the hybrid harvester is presented. Four different hybrid energy harvesters were fabricated and evaluated for their performance in comparison with that estimated from the proposed models. Additionally, scaling laws for hybrid energy harvesters are presented. The power developed by both piezoelectric and electromagnetic domains is observed to decrease with width and length cubed. Power indices and figures of merit in a hybrid harvester are proposed and are used to estimate the efficiencies of the four fabricated hybrid harvesters. The important design parameters for micro scale harvesting are identified by performing scaling analysis on MEMS piezoelectric harvesters. Performance of energy harvesters is directly related to the harvester attributes, viz., size, material, and end-mass. Depending on the contribution from each attribute, the power developed by MEMS harvesters can vary widely. A novel method of delineating the power developed by a harvester using five exclusive factors representing scaling, composition, inertia, material, and power (SCIMP) factors is presented. Although the proposed method can be extended to bi-morph and multilayer harvesters, in the present work, we elucidate it by applying it to a MEMS unimorph. We also present a unique coupling factor that ensures maximum power factor in a harvester. As any tiny increment in the power generated would considerably improve the power densities of MEMS harvesters, we focus on enhancing the power developed by maximizing each of the five exclusive factors irrespective of material and size. Furthermore, we demonstrate the competence of the proposed method by applying it on nine different MEMS harvesters reported in the literature. Considering the close match between the reported and predicted performance, we emphasize that monitoring the proposed factors is sufficient to attain the best performance from a harvester.

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43

楊育彰. "Performance Evaluation of Piezoelectric Synthetic Jet Actuators Using Design Parameters Approach." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/75856843933873098897.

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Анотація:

碩士
大葉大學
機械工程研究所碩士班
92
The primary objective of active flow control research is to develop a cost-effective technology that has the potential for revolutionary advances in aerodynamic performance and maneuvering compared to conventional approaches. The development of such systems have many implications for aerospace vehicles including: reduced mechanical complexity and hydraulic failure, reduced noise and weight, lower energy and fuel consumption, lower downtime and maintenance, enhanced maneuvering and agility with enhanced aerodynamic performance and safety. Interest in active flow control for aerospace applications has stimulated the recent development of innovative actuator designs that create localized disturbances in a flow field. The primary objective of this thesis is to set up a finite element model of piezoelectric synthetic jet actuators and two experiment devices to research the optimization of designing parameters of influences in flow speed. The designing parameters are the area of piezoelectric synthetic jet, flow field volume, cavity depth and slot size. Characteristics of system (frequency, amplitude and flowing speed) will be measured experimentally when the designing parameters are changed. By system model, the designing parameters will be optimized and the performance of piezoelectric synthetic jet will be evaluated. Natural frequencies and parameters of equivalent circuit of piezoelectric actuator will be measured by impedance analyzer, to provide a useful tool to make studies of the relation of dimensions and flowing speed of piezoelectric synthetic jet.

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44

Chen, Chih-Yen, and 陳智彥. "Nanostructured Gold, Titanium Silicides and Piezoelectric Materials: Synthesis, Characterization, and Performance." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/06491659273559005133.

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Анотація:

博士
國立清華大學
材料科學工程學系
100
The central theme of this dissertation is mainly design and systematic exploration of advanced material performances including the following: (1) gold nanowire, (2) nickel silicide-titanium silicide (Ni2Si/TiSi2) core-shell nanowire, and (3) piezopotential nanowries. Basically, they possess two different kinds of properties, metallic and semiconducting properties, which can be applied in various applications. For metallic nanomaterials, we mainly focus on synthesis and characterization of the gold nanowires and Ni2Si/TiSi2 core-shell nanowires for applications including magnetic, electronic and field-emission properties. An innovative grow mechanism is discussed in detail based on the S-L-S process for both of metallic nanowires. Our gold nanowires exhibit outstanding properties with the lowest turn-on field of 3 V/μm and the maximum current density of 1.5 mA/cm2. Furthermore, Ni2Si/TiSi2 silicides nanowires have many interesting properties measured as well like high melting temperature, thermal stability and low resistivity. For piezopotential materials, we try to synthesize some wurtzite structure nanomaterials such as zinc oxide (ZnO) and gallium nitrite (GaN). The effect of piezopotential on the transport behavior of charge carriers is significant due to their multiple functionalities of piezoelectricity, semiconductor and photon excitation. Therefore, we also study for their various applications in energy science including self-powered LED devices, hybrid nanogenerators, and power generation from human daily activity. The results have shown the great potential of these nanomaterials in future applications. Efforts have been carried out to understand the underlying science and to enhance and glorify their possible engineering applications. The above outstanding results warrant several possible applications for (1) gold nanowires as the electron field emitters, (2) Ni2Si/TiSi2 core-shell nanowire as electronic interconnect or magneto-resistance devices, and (3) promising wurtzite structure ZnO and GaN nanowires for the energy harvester which coverts low frequency mechanical movements of human/animal into electricity in future microelectronics.

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45

Lin, Yi-chin, and 林宜瑾. "Carrier screening and piezoelectric effects on optical performance of GaN-based LED." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/p8cqyn.

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Анотація:

博士
國立中央大學
化學工程與材料工程學系
103
GaN crystal has the piezoelectric characteristic, the producing piezoelectric field would cause the energy level tilting in the InGaN MQWs, which is named as quantum-confinement Stark effect. Energy level tilting causes some disadvantages, i.e., the carrier confinement ability decay, the carrier spatial separation (reducing carrier recombination). The carrier spatial separation also causes a carrier screening effect with a direction opposite to the piezoelectric field, which could ease the quantum-confinement Stark effect. To explore the relationship between the piezoelectric field and the carrier screening effect, and their effects on the optical performance of the GaN-based LEDs. We adjust the process temperature of the die-attachment process, to vary the residual compressive stress in the GaN epilayer. We note that the higher temperature of the die-attachment process, the more compressive stress of the GaN LEDs can be released. By this concept, the residual compressive stress in the GaN epilayer could be controlled. In this Ph. D. study, we first propose that the CTE mismatch (between the GaN epilayer and the sapphire substrate) causes a CTE-induced piezoelectric field, which dominates the energy levels distortion in the InGaN MQWs of the GaN-based LEDs. However, the decreasing in the CTE-induced piezoelectric field does not have a significant effect on the optical performance of the GaN-based LEDs. One of the major reasons could be that the carrier screening effect could compensate the CTE-induced piezoelectric field. And, we realize that the magnitude of the carrier screening field depends on the piezoelectric field induced energy level tilting and the carrier concentration. Thus, the carrier screening field is a function of the CTE-induced piezoelectric field and applied electric field, which can be described as . Two major conclusions are: (1) the CTE-induced piezoelectric field dominates the initial energy level tilting in the InGaN MQWs; (2) the carrier screening effect is the major internal electric fields that influences the optical property of the GaN-based LEDs.

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46

Chiu, Cheng-Wei, and 邱政維. "Performance Evaluation of Piezoelectric Fiber Composite Transducers on Fiber-reinforced Composite Plates." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/23046553839257175135.

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Анотація:

碩士
國立交通大學
機械工程系所
104
This thesis evaluates the performance of two kinds of piezoelectric fiber composite (PFC) transducers, which are used to actuate and sense the Lamb waves and transverse horizontal waves in fiber-reinforced composite laminates. Composite specimens include single layer glass/epoxy plates, a balsa wood sandwiched between two skins of woven glass/epoxy; 4-ply glass/epoxy and graphite/epoxy specimens were also considered. A pulse Nd:YAG laser was used to generate thermo-elastic plate waves for experimental determination of the dispersion curves of plate wave propagation in composite specimens. The experimental results indicate that most energy carried by the plate wave localizes in the skin layer. The radiation patterns and mechanical response spectrum induced by both PFC transducers adhered on composite specimens were measured. The measured mechanical responses have been compared with the simulated results to assist explaining phenomena. Examination of defect detection using both PFC transducers has been carried out. Two artificial defects are considered. The first is an inclusion of release cloth in a composite laminate. The second is a coin attached on to the surface of a specimen. The signal amplitudes appear with significant differences, up to 14%. It has been shown that the PFC transducers have a capability to detect the embedded and surface defects in composite laminates.

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47

Lin, Hsiu-fen, and 林秀芬. "The Study of Heat Transfer Performance of Piezoelectric Bimorphs in Electronic Cooling Application." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/2erh6k.

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Анотація:

碩士
國立臺灣科技大學
機械工程系
94
This study investigates the possibility of employing the piezoelectric material to build a flow driving device in order to enhance the cooling performance of electronic devices. Computer – Aided engineering (CAE) software was employed to study the structure dynamic characteristics of piezoelectric bimorphs. Both modal analysis and harmonic analysis are performed to investigate the influence of various design parameters on the natural frequency and vibration mode of the piezoelectric bimorphs. A performance merit parameter is defined as a guide to characterize the flow driving ability of the bimorph structure. Computational fluid dynamic (CFD) software is the employed to obtain the velocity and temperature distributions of the flow field drive by the piezoelectric bimorph. The effect of the vibration amplitude and vibration modes and the cooling performance are both investigated.

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48

Lin, Ting-Kai, and 林莛凱. "Performance improvement of PZT micro piezoelectric energy harvester fabricated by Aerosol deposition method." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/89adqr.

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Анотація:

碩士
國立臺灣大學
工程科學及海洋工程學研究所
105
For past years the idea of "Internet of Things(IoT)" has become more expanding, which makes the demand of low power consumption sensors increased rapidly. In generally we use power lines or battery to drive these sensors. However, powering the sensors in remote areas with power lines is costly no matter in installation or maintenance. On the other hand, using battery can solve the problems, but the maintenance issue and risk of environmental pollution will emerge. Summing up the above reasons, scavenging energy from varying ambient energy sources and transferring them into electricity to drive the end devices, or called "Self-powered technology", seems to be a better solution to completely solve the problems, maximize the application scope and lifetime for IoT sensors. This thesis is based on scavenging the environmental vibration energy. Comparing to solar power, vibration energy is capable to provide energy no matter indoor or not. The power density of ambient vibration is also high enough to be exploited due to the past researches. By utilizing the piezoelectric material PZT we successfully fabricated cantilever structure piezoelectric energy harvester. A static force analysis for cantilever structure to evaluate effective piezoelectric constant d31 of thin film piezoelectric material is also presented. Combining the study for improving Aerosol deposition method (ADM) efficiency, the optimization of annealing and poling process, and metal micro electro-mechanical system (MEMS) process, we accomplished the stainless-based cantilever structure piezoelectric energy harvesters. The output performance could reach more than 300μW at 0.5g resonant frequency. The power density was better than all studies made before. The results show that our device is very close to practical application. Keyword: PZT, piezoelectric material, aerosol deposition, energy harvester, MEMS

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49

LAI, CHUN-CHUN, and 賴俊俊. "Design, fabrication and performance evaluation for the elastic elements coupled multi-frequency piezoelectric harvester." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/w44x3m.

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Анотація:

碩士
國立中央大學
機械工程學系在職專班
103
In this study, three models of elastic elements coupled multi-frequency piezoelectric harvester have been designed and developed as the application of vibration-based energy harvester. Through electrical tuning of the characteristic frequency and impedance matching, the output power of the three models of the harvester has been evaluated. The Type A model, a new piezoelectric cantilever generator using elastic spiral springs as a supporting mechanism, was fabricated for vibration-based energy harvester application to replace the basic of single-degree-of-freedom (DOF) cantilever generator system supported by a rigid metal bar. Under a base acceleration magnitude of approximately 1.5g, the strongest output power 10.7W was obtained at an optimum load resistance of 9.1kΩ. Under a base acceleration magnitude of approximately 0.5g, the strongest output power 0.01mW was obtained at a optimum load resistance of 8.2kΩ. The Type B model, a new piezoelectric cantilever generator using elastic metal sheet, was fabricated with multiple flexible materials to provide elastic elements coupled multi-frequency piezoelectric harvester. Under a base acceleration magnitude of approximately 1.5g, the strongest output power 0.54W was obtained at an optimum load resistance of 68kΩ. Under a base acceleration magnitude of approximately 0.5g, the strongest output power 116.8mW was obtained at an optimum load resistance of 91kΩ. The Type C model, a new piezoelectric cantilever generator using 3D printing to produce a cylinder where the circle cantilever beam is mounted in, was fabricated with elastic spiral spring to provide multi-frequency piezoelectric harvester. Under a base acceleration magnitude of approximately 1.5g, the strongest output power 0.41mW was obtained at an optimum load resistance of 68kΩ. Under a base acceleration magnitude of approximately 0.5g, the strongest output power 1.40mW was obtained at an optimum load resistance of 100kΩ. The generator could be a 2-DOF vibrating body, which can offer a wide resonance frequency bandwidth. Therefore, it is considered that the elastic spring enhanced the performance and frequency flexibility of the piezoelectric cantilever generator for broadband energy harvesting.

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50

Nagarajan, Bhuvana. "Development and Performance Evaluation of the Flapping Wing with In-situ Piezoceramic Actuator." Thesis, 2023. https://etd.iisc.ac.in/handle/2005/6156.

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Анотація:

Unmanned Aerial Vehicles (UAV) are essentially automatic flight vehicles having dimensions, wingspan and airspeed, smaller than the conventional aerial vehicles. UAVs are employed widely in applications such as surveillance over a short distance, acquisition of a local target, detection of hazardous chemicals / biological agent, exploration of a harmful environment, search operations, etc. UAV can be classified into three main types depending on their method of propulsion and lift. These are fixed wing, rotary wing, and flapping wing. Flapping wing UAVs are more suitable for insect scale flights. Flapping mechanism requires actuators with large stroke periodic (reciprocal) motion at high speed (10-100s of Hz) with large output forces for overcoming the aerodynamic damping. There are several actuation mechanisms applicable to flapping-wing UAVs. The emphasis is on linear actuators, which simplify the mechanical transmission for flapping motions. Most of the prototypes developed so far have employed motor-driven mechanisms to achieve the flapping wing. Unconventional methods such as piezoelectric, thermal, electromagnetic, shape memory, electrostatic, etc. for actuation of flapping wings have also been used. Among the unconventional actuation methods, piezoelectric actuation is the most used mechanism because of its compact size and high-power density. However, the deflection generated by the piezoelectric actuator is intrinsically very small. Therefore, it is necessary to employ numerous types of motion amplification mechanisms to achieve large deflection. The development of an amplification mechanism is a complex procedure. Hence, several efforts have been made to evaluate different forms of piezoelectric actuators for flapping vehicle application. The in-situ piezoelectric actuator, employing piezoceramic coating directly on the structure by a simple method, looks promising for flapping wing application as it generates large displacement compared to the displacement produced by the bulk piezoelectric actuators. Piezoceramic coating is light in weight compared to the bulk piezoelectric actuator, as it is a composite material of highly dense piezoceramic material and less dense polymeric material. The current study evaluates the basic characteristics, performance and the aerodynamic behavior of the in-situ piezoceramic actuator for flapping wing applications. Initially, the basic characteristics of the in-situ piezoceramic actuator were evaluated. Its properties like density, elastic modulus and the transverse piezoelectric coefficient, d31, were evaluated. The density was measured to be 2300 kg/m3. Elastic modulus was measured as 3 GPa. The piezoelectric coefficient, d31 was measured by applying the coating on various substrates such as stainless steel, brass and polymer. Also, the in-situ piezoceramic actuator was applied with different thicknesses 30, 40 and 50 µm on the polymer substrate. The mean value of the measured d31 was found to be -26 pm/V. The performance of the piezoceramic coating (coated on a flexible substrate) was evaluated for flapping wing application using performance metrics from aerodynamic studies. The performance metrics are the tip velocity,, the dynamic electromechanical coupling factor (EMCF), k12, and the elastic energy per unit mass, . These metrics were obtained and verified using an analytical model. Based on these metrics, the performance of the developed flexible actuator was compared with conventional flexible piezoelectric polyvinylidene difluoride (PVDF) actuator. These metrics were found to be better for the developed actuators than PVDF. The best suitable wing configuration was selected using FE modelling based on the tip velocity ( ). It was found that the tip velocity depends on the thickness, length and shape of the flapping wing. Wing shapes of the dragonfly’s, tobacco hawkmoth’s and cicada’s forewings were considered. The thickness and length of the in-situ piezoceramic actuator were also varied. The results obtained through FE modelling were verified experimentally. Dragonfly wing was found to give maximum tip velocity ( ). The maximum value for υ of 114.7 mm/s was obtained for a dragonfly wing having in-situ piezoceramic actuator of 30 mm length from the root of the wing and a thickness of 30 µm. The lift force was measured using a load cell measurement set up in the clamped condition for the dragonfly wing. Insects use a variety of wingbeat kinematics to produce and control aerodynamic forces for their flight. For mimicking an insect flight, the selected actuator needs to be capable of producing insect flight kinematics. Therefore, twisting along with flapping motions of the wings by the in-situ piezoceramic actuators were attempted. Twisting motion of the wing was achieved by actuating two piezoceramic cantilevers type in-situ actuators applied over a wing with sinusoidal signals out of phase with each other by 180°. The fore wing and the hind wing were actuated by sinusoidal signals with a phase difference of 0°, 90°, 180° and 270°. Tip displacements of 4 mm for the fore wing and 3 mm for hind wing were measured. The kinematics of the flapping wing, which has been achieved by other actuators with complex mechanisms can thus be achieved by the simple in-situ piezoceramic actuators. The experiments on the measurement of the lift and kinematics of the flapping wing establishes that the in-situ piezoceramic actuator is a suitable candidate for flapping wing application. The improvement studies on tip velocity were carried out by implementing in-situ bimorph piezoceramic actuators. Dragonfly wings with the piezoceramic layer of thickness 30 µm were considered. As there was a implication of increase in the mass of the wing, selection of length of piezoceramic layers were carried out using FE modelling. The results obtained through FE modelling were verified experimentally. The maximum tip velocity of 245.1 mm/s is obtained for 25 mm length of both piezoceramic coating layers. Modified strip theory based on the blade elemental analysis has been used to study the aerodynamic performance of the three types of wing planforms. Lift, thrust and drag forces generated by the three wing forms have been calculated analytically by the model. As flapping wings are operated at the first mode resonance, the first mode resonant frequency, and the tip displacement at resonance from the experimental results were given as input to the aerodynamic model. The effect of variations in aerodynamic parameters such as incident angle, pitching angle and forward speed on the relevant forces were studied for the in-situ piezoceramic actuator actuated wings of three different wing planforms. For all the three wing planforms, it was observed that the lift increased with incident angle and forward speed and it was less affected by increasing the pitching angle. For the increasing forward speed, incident angle and pitching angle, thrust and drag also increased. The modelling results show that the wings produce positive mean lift and condition where the thrust is more than the drag for all the wing planforms. The overall results show that the in-situ piezoceramic actuator can be employed for flapping wing applications with further efforts.

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