Multiple Piezoelectric Elements Research Articles

A Precise Rotary Piezoelectric Actuator Based on the Spatial Screw Compliant Mechanism

Rotary piezoelectric actuators (RPAs) are widely used in various precise applications. But given the rotary axis offset caused by the single off-center driving force or the discrepancy of multiple piezoelectric elements, most previous works present rotary roundness loss. Besides, there is a contradiction between the motion range of RPA and its response speed. For solving these problems, an RPA based on the spatial screw compliant mechanism (SSCM) is hereby proposed; a theoretical model and an finite element (FE) model are built to verify the actuation principle and guide the structural design; and a prototype is fabricated and tested. The experimental results indicate that the static rotary angle changes from 0 to 4.935 mrad as the voltage changes from 0 to 100 V with a high resolution of 45.53 nrad. The first resonant and –3 dB cutoff frequencies are measured as 1361.5 and 2040.1 Hz, respectively. With the application of the SSCM, the RPA is proven capable of avoiding the rotary roundness loss in theory, and it can balance the milliradian-level rotary range with millisecond-level response speed driving by one lead zirconium titanate (PZT) stack under a small size of Φ32 × 68 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> .

Energy harvesting array materials with thin piezoelectric plates for traffic data monitoring

This study developed energy harvesting arrays (EHA) composed of multiple piezoelectric elements for traffic monitoring and energy harvesting. The developed EHA was investigated through compression tests to simulate the effects of different vehicle axle loads and speeds. The effect of the number and configuration of piezoelectric elements on piezoelectric response was explored. To quantify the sensitivity of EHA under different loads, the concept of loading utilization efficiency was proposed. The influence of temperature and surface layer type on the output signal of EHA covered with asphalt surface layer was investigated using wheel rolling test. The compression test showed that the response of EHA was affected by both axle load and vehicle speed. The output voltage and loading utilization efficiency increased gradually with the increase of load and load frequency. The response law of EHA provided ideas for monitoring vehicle axle load and speed information. The open-circuit voltage signal decreased as the number of piezoelectric elements in parallel increased. The recommended number of piezoelectric elements was identified. To reduce the impact of temperature and surface covering material on the perceived traffic information, EHA was recommended to be encapsulated with thermal insulation materials for embedment. The open circuit voltage of EHA in the wheel rolling test was found higher than that in the compression test. This difference was further explained by finite element modeling results showing that the polyurethane plate increased the deformation of thin piezoelectric plates. Considering the strength of the piezoelectric response signal, the recommended thickness of polyurethane underlayment was determined.

Analysis according to the change in structure of ultrasonic sensors and the change in pressure inside the tank for measurement of fuel amounts in compressed natural gas (CNG) tank

AbstractThe present study is a fundamental research for precise measurement of fuel amounts in a compressed natural gas (CNG) tank where an analysis of receiving sensitivity was conducted as a result of changes in the contact surface shape in the number of piezoelectric element of the ultrasonic sensor as well as in the internal pressure of the tank. Experiments were conducted as a function of changes in the contact surface shape between the ultrasonic sensor and outside of the aluminum tank and in the number of piezoelectric element as well as in the internal pressure of the tank. According to the experimental results, it could be confirmed that the maximum receiving sensitivity value was increased by about 60 % when the contact surface shape of the transmission and receiving ultrasonic sensors compared with the ultrasonic sensor in the Line‐Line shape selected as the reference model was changed to the surface. As a whole, the highest receiving sensitivity values were observed when the transmission sensor of surface shape produced as multiple piezoelectric elements and the receiving sensor of surface shape produced as a single piezoelectric element were used. It could be confirmed that receiving sensitivities were improved at the same voltage value as a result of changes in the contact surface shape of the ultrasonic sensor and in the number of piezoelectric elements.

Селективное возбуждение упругих волн в композитах

This study analyzes the effect of various parameters of the piezoelectric transducer on the wave fields generated in the composite plate. A semi-analytical approach based on the application of the Fourier transform, integration by residues and the stationary phase method is used to calculate dispersion curves and wave fields in a wide frequency range. This model allowed us to calculate the displacement fields excited in the anisotropic plate, as well as to distinguish and analyze the contribution of each wave mode to the resulting wave field. The excited fields were calculated and analyzed over a wide frequency range. Another objective of the study was to obtain the information about the shapes and positioning of multiple piezoelectric elements, which facilitate the excitation of directed waves and individual Lamb wave modes. A technique for the selection of parameters and the positioning of piezoelectric actuators required for the wave excitation was developed. It was applied and successfully tested for a combination of several ring-shaped actuators. The relations between the stress amplitudes specified on the surfaces of all actuators from the combination were determined and allowed to suppress certain waves in a multi-layered composite host-structure. It was shown that by varying the voltage applied to the piezoelectric rings, it is possible to suppress or amplify individual waves without changing their size.

An investigation on stress distribution effect on multi- piezoelectric energy harvesters

With the fast development of piezoelectric materials and due to its green and renewable characteristics, the piezoelectric energy harvesting technology has been paid more and more attention by pavement engineers. The stress distribution will significantly affect the piezoelectric material performance. In this paper, the effects of multiple piezoelectric elements on the generation of electrical energy and output power are studied. In the case of constant external load, the number of the piezoelectric units does not necessarily produce more energy. When the same multi piezoelectric units work together, if the stress state of the piezoelectric units is different, the total output energy affected by the connection mode. For uneven stress distribution, the optimal output mode is that each of the piezoelectric units rectified before connected in parallel.

Design and experiment of piezoelectric multimodal energy harvester for low frequency vibration

Abstract Most piezoelectric vibration energy harvesters are conventional single-degree-of-freedom (SDOF) systems, and typically perform well at the single resonant mode - which makes the harvesters less efficient for low ambient vibration frequencies. In this work, we have proposed and experimentally validated a piezoelectric multimodal energy harvester having several mechanical degrees of freedom (DOFs). This multi-modal vibration energy harvester has a unique design that helps to obtain multiple resonant mode operation of the harvester at the lower frequency range. The finite element method (FEM) simulation model has been used to predict the mode shapes of the proposed energy harvester at different vibration modes. The experimental results imply that the proposed energy harvester can obtain four peak values in the range of 10–20 Hz, which are concentrated around 10, 14, 16, and 20 Hz respectively. In addition, the piezoceramic material lead zirconate titanate (PZT) has been used as a piezoelectric element that has excellent piezoelectric properties. A prototype multimodal energy harvester with four piezoelectric elements is fabricated, where a single piezoelectric element generated a peak power with a maximum of 249 µW delivered to an optimum load of 55 KΩ at 16 Hz resonant mode under 0.4 g base acceleration. In order to increase the output power and bandwidth, it is always a good idea to use multiple piezoelectric elements in one harvester structure; consequently, four piezoelectric elements of the fabricated prototype are connected in parallel. The device with parallel connected piezoelectric modules generates a peak output power of 740 µW across an equivalent optimum load resistance at 3rd resonant mode (16 Hz), while the device's base is excited at 0.4 g acceleration.

Rectification Methods to Increase Harvested Energy in Vibration Generation Using Piezoelectric Elements

SUMMARYWe studied vibration power generation using piezoelectric elements in order to determine effective rectification methods to increase harvested energy from vibration power generation systems. First, we experimentally clarified the output characteristics of two kinds of passive rectification methods for vibration power generation systems. Then, an appropriate rectification method for various kinds of loads was studied. In order to increase the harvested power from an integrated vibration power generation system with multiple piezoelectric elements, we considered an appropriate circuit structure for connecting multiple piezoelectric elements. The effectiveness was verified experimentally.

High precision ultrasonic guided wave technique for inspection of power transmission line

Due to the merits of high inspection speed and long detecting distance, Ultrasonic Guided Wave(UGW) method has been commonly applied to the on-line maintenance of power transmission line. However, the guided wave propagation in this structure is very complicated, leading to the unfavorable defect localization accuracy. Aiming at this situation, a high precision UGW technique for inspection of local surface defect in power transmission line is proposed. The technique is realized by adopting a novel segmental piezoelectric ring transducer and transducer mounting scheme, combining with the comprehensive characterization of wave propagation and circumferential defect positioning with multiple piezoelectric elements. Firstly, the propagation path of guided waves in the multi-wires of transmission line under the proposed technique condition is investigated experimentally. Next, the wave velocities are calculated by dispersion curves and experiment test respectively, and from comparing of the two results, the guided wave mode propagated in transmission line is confirmed to be F(1,1) mode. Finally, the axial and circumferential positioning of local defective wires in transmission line are both achieved, by using multiple piezoelectric elements to surround the stands and send elastic waves into every single wire. The proposed research can play a role of guiding the development of highly effective UGW method and detecting system for multi-wire transmission line.

Design and analysis of a scalable harvesting interface for multi-source piezoelectric energy harvesting

Harvested power and operating frequency bandwidth of a piezoelectric harvester can be improved significantly by using multi-source piezoelectric energy harvesting (M-PEH). However, this M-PEH approach makes it more difficult to design an effective harvesting interface circuit. In this paper, three scalable harvesting interfaces for M-PEH are proposed: the scalable standard interface for M-PEH, the scalable Series-SSHI interface for M-PEH and the scalable SECE interface for M-PEH. These proposed scalable M-PEH interfaces, take advantage of the basic techniques of standard AC-DC, series-SSHI and SECE, and are capable of harvesting energy from multiple piezoelectric elements simultaneously. The theoretical derivations are conducted, and the experiments are performed with a good agreement between theory and experiment. Experiments utilizing two piezoelectric elements confirm the effectiveness of the proposed interfaces; they can produce twice as much energy as the typical single source piezoelectric energy harvesting (S-PEH) techniques, no matter what the piezoelectric voltage phase difference is. Finally, M-PEH exhibits significant bandwidth improvement and excellent scalability versus S-PEH.

EWOD (electrowetting on dielectric) digital microfluidics powered by finger actuation

We report finger-actuated digital microfluidics (F-DMF) based on the manipulation of discrete droplets via the electrowetting on dielectric (EWOD) phenomenon. Instead of requiring an external power supply, our F-DMF uses piezoelectric elements to convert mechanical energy produced by human fingers to electric voltage pulses for droplet actuation. Voltage outputs of over 40 V are provided by single piezoelectric elements, which is necessary for oil-free EWOD devices with thin (typically <1 μm) dielectric layers. Higher actuation voltages can be provided using multiple piezoelectric elements connected in series when needed. Using this energy conversion scheme, we confirmed basic modes of EWOD droplet operation, such as droplet transport, splitting and merging. Using two piezoelectric elements in series, we also successfully demonstrated applications of F-DMF for glucose detection and immunoassay. Not requiring power sources, F-DMF offers intriguing paths for various portable and other microfluidic applications.

Enhanced energy harvesting using multiple piezoelectric elements: Theory and experiments

Power and bandwidth of piezoelectric harvesters can be increased by using multiple piezoelectric elements in one harvester. In this contribution, a novel energy harvesting cantilever array with magnetic tuning including three piezoelectric bimorphs is investigated theoretically and experimentally, with a good agreement between model and experiment. Other than harvester designs proposed before, this array is easy to manufacture and insensitive to manufacturing tolerances because its optimum operation frequency can be re-adjusted after fabrication. Using the superposition principle, the Butterworth-Van Dyke model and a mechanical lumped parameters model, the generated voltage and current are determined analytically. Formulas for calculating the power generated by array harvesters with an arbitrary number of piezoelectric elements connected in series or in parallel are derived. It is shown that optimum harvester design must take both the connected load and the operating frequency into account. Strategies for connecting multiple bimorphs to increase the maximum generated power and/or enhance the bandwidth compared to a single bimorph harvester are investigated. For bandwidth enhancement it is essential that individual rectifiers are used for the bimorphs. An example with three bimorphs shows that, depending on the chosen tuning strategy, the power is increased by about 340% or the bandwidth is increased by about 500%, compared to one single bimorph.

Piezoelectric Fiber Composite Strip Transducer Design Considerations for Generating Lamb Waves

Lamb waves have great promise among the various active monitoring schemes being researched for Structural Health Monitoring. Planar Lamb wave excitation using surface-bonded piezoelectric strips to function as comb transducers is investigated numerically for both the fundamental symmetric S0 and the antisymmetric A0 wave modes. This comb-type transducer is comprised of multiple piezoelectric elements, which are piezoelectric fiber composites sandwiched between electrodes. These transducer strips reduce the wiring requirements, can conform to curved surfaces, and the properties can be tailored to suit the application. Transducer variables are many; here fiber orientation, volume fraction, poling directions, and electrode locations are investigated. Specifically, piezocomposite properties are estimated through micromechanical modeling for input to finite element analysis of Lamb wave generation and propagation. For this multiphysics problem, the finite element analysis employs co-simulation using ABAQUS Standard and ABAQUS Explicit to simulate transient wave propagation from a strip transducer on a plate. In the finite element results, the amplitude of the Lamb wave at a prescribed distance from the transducer is evaluated to characterize the effectiveness of the composite comb transducer. Furthermore, results show that there are a number of cases where composite actuators provide a large amplitude response. After considering piezoelectric fiber direction, poling direction, and electric field direction, it appears that fiber, polarization, and activation electric fields through the thickness of the transducer represent the optimal design.

Laboratory evaluation of the hybrid fiber-optic current sensor

This paper gives details of the design, construction and laboratory evaluation of the pre-prototype optical current sensor developed specifically to prove the concept of the possibility of monitoring remotely operated electrical plant. The proposed sensor is of a hybrid construction, and uses an optical voltage-to-strain transducer to monitor a specially designed current transformer. In this application, the voltage-to-strain transducer is realized using a novel approach: it employs a fiber Bragg grating (FBG) bonded to a stack of multiple piezoelectric elements, with their respective electrodes connected in parallel. This approach greatly increases the measurement sensitivity; thus, the FBG can be interrogated using a classic scanning filter configuration rather than the interferometric technique. Moreover, since the absolute wavelength information is preserved, this brings the advantage of the simultaneous temperature measurement capability and enables the straightforward multiplexing of several sensors on one optical fiber.

Active control of sound arounda fluid-loaded plate using multiple piezoelectric elements

This paper presents a method of using a least-squaresapproach and tabu search technique together with the commerciallyavailable FEA code, ANSYS, for active sound control around afluid-loaded plate by multiple piezoelectric elements.A numerical model of FEA is used to construct the transferfunction matrices, which relate the primary (an acousticsource) and the secondary (piezoelectric elements) sources tothe acoustic pressures in the field of interest withconsideration of environmental effects. With the transfer function matrices, the least-squares algorithm and tabu searchtechnique are applied for subsequent active sound control. Thispaper shows how to implement the local and global active soundcontrol in the upper and lower half-spaces of the plate by the useof multiple piezoelectric elements through some case studies.