Showing papers on "Piezoelectric sensor published in 2009"

Piezoelectric-Based Vibration Control: From Macro to Micro/Nano Scale Systems

Abstract: Piezoelectric-Based Vibration-control Systems: Applications in Micro/Nano Sensors and Actuators covers: Fundamental concepts in smart (active) materials including piezoelectric and piezoceramics, magnetostrictive, shape-memory materials, and electro/magneto-rheological fluids; Physical principles and constitutive models of piezoelectric materials; Piezoelectric sensors and actuators; Fundamental concepts in mechanical vibration analysis and control with emphasis on distributed-parameters and vibration-control systems; and Recent advances in piezoelectric-based microelectromechanical and nanoelectromechanical systems design and implementation.

A flexure-based mechanism and control methodology for ultra-precision turning operation

Abstract: This paper presents the methodology for modeling and control of a high precision flexure-based mechanism for ultra-precision turning operation. A high performance piezoelectric actuator is used to driven the flexure-based mechanism. A parallel flexure hinge mechanism is utilized to guide the moving platform and to preload the piezoelectric actuator. A high resolution capacitive sensor is used to measure the displacement of the flexure-based mechanism for closed-loop control. With consideration of the driving circuit, the dynamic model of the flexure-based mechanism has been established. The effect of the driving circuit on the dynamic response of the precision mechanism is investigated. Experimental tests have been carried out to verify the established model and the performance of the flexure-based mechanism.

A Lamb-wave-based technique for damage detection in composite laminates

Abstract: This paper presents the application of Lamb waves to inspect damage in composite laminates. The proposed methodology employs a network of transducers that are used to sequentially scan the structure before and after the presence of damage by transmitting and receiving Lamb wave pulses. A damage localization image is reconstructed by analyzing the cross-correlation of the scatter signal envelope with the excitation pulse envelope for each transducer pair. A potential damage area is then reconstructed by superimposing the image observed from each actuator and sensor signal path. Both numerical and experimental case studies are used to verify the proposed methodology for composite laminates. Three-dimensional finite element models with a transducer network consisting of four transducer elements are used in the numerical case studies. The experimental case studies employ a transducer network using four piezoelectric transducers as transmitter elements and a laser vibrometer to measure the response signals at four locations close to the transducers. The results show that the method enables the reliable detection of structural damage with locating inaccuracies of the order of a few millimeters inside as well as outside of an inspection area of 100 x 100 mm(2).

Vibrations of an elastic structure with shunted piezoelectric patches: efficient finite element formulation and electromechanical coupling coefficients

Abstract: This article is devoted to the numerical simulation of the vibrations of an elastic mechanical structure equipped with several piezoelectric patches, with applications for the control, sensing and reduction of vibrations. At first, a finite element formulation of the coupled electromechanical problem is introduced, whose originality is that provided a set of non-restrictive assumptions, the system's electrical state is fully described by very few global discrete unknowns: only a couple of variables per piezoelectric patches, namely (1) the electric charge contained in the electrodes and (2) the voltage between the electrodes. The main advantages are (1) since the electrical state is fully discretized at the weak formulation step, any standard (elastic only) finite element formulation can be easily modified to include the piezoelectric patches (2) realistic electrical boundary conditions such that equipotentiality on the electrodes and prescribed global charges naturally appear (3) the global charge/voltage variables are intrinsically adapted to include any external electrical circuit into the electromechanical problem and to simulate shunted piezoelectric patches. The second part of the article is devoted to the introduction of a reduced-order model (ROM) of the problem, by means of a modal expansion. This leads to show that the classical efficient electromechanical coupling factors (EEMCF) naturally appear as the main parameters that master the electromechanical coupling in the ROM. Finally, all the above results are applied in the case of a cantilever beam whose vibrations are reduced by means of a resonant shunt. A finite element formulation of this problem is described. It enables to compute the system EEMCF as well as its frequency response, which are compared with experimental results, showing an excellent agreement.

Vibration and Wave Propagation Control of Plates with Periodic Arrays of Shunted Piezoelectric Patches

Abstract: Periodic arrays of shunted, piezoelectric patches are employed to control waves propagating over the surface of plate structures, and corresponding vibrations. The shunted, piezoelectric patches act as sources of impedance mismatch, which gives rise to interference phenomena resulting from the interaction between incident, reflected and transmitted waves. Periodically distributed mismatch zones, i.e., the piezo patches, produce frequency dependent, wave-dynamic characteristics, which include the generation of band gaps, or stop bands in the frequency domain. The extent of induced band gaps depends on the mismatch in impedance generated by each patch. The total impedance mismatch, in turn, is determined by the added mass and stiffness of each patch as well as the shunting electrical impedance. Proper selection of the shunting electric-circuit thus provides control over the attenuation capabilities of the piezo-plate structure, as well as the ability to adapt to changing excitation conditions. Control of wave-propagation attenuation and vibration reduction for plates with periodic, shunted, piezoelectric patches is demonstrated numerically, employing finite-element models of the considered structures.

Mixing Rules for the Piezoelectric Properties of Macro Fiber Composites

Abstract: This article focuses on the modeling of structures equipped with Macro Fiber Composite (MFC) transducers. Based on the uniform field method under the plane stress assumption, we derive analytical mixing rules in order to evaluate equivalent properties for d31 and d33 MFC transducers. In particular, mixing rules are derived for the longitudinal and transverse piezoelectric coefficients of MFCs. These mixing rules are validated using finite element computations and experimental results available from the literature.

Connected Vibrating Piezoelectric Bimorph Beams as a Wide-band Piezoelectric Power Harvester

Abstract: We analyze coupled flexural vibration of two elastically and electrically connected piezoelectric beams near resonance for converting mechanical vibration energy to electrical energy. Each beam is a so-called piezoelectric bimorph with two layers of piezoelectrics. The 1D equations for bending of piezoelectric beams are used for a theoretical analysis. An exact analytical solution to the beam equations is obtained. Numerical results based on the solution show that the two resonances of individual beams can be tuned as close as desired by design when they are connected to yield a wide-band electrical output. Therefore, the structure can be used as a wide-band piezoelectric power harvester.

On development of a multi-channel PZT array scanning system and its evaluating application on UAV wing box

Abstract: Piezoelectric sensor (PZT) based structural health monitoring (SHM) methods can efficiently estimate the health condition of aircraft structures. To monitor large-scale structures, dense PZT arrays are usually needed. How to scan different PZT actuator–sensor channels in the PZT array to achieve a real time and stable SHM task is an important issue in the application of these methods. In this paper, an integrated multi-channel PZT array scanning system (ISS) is developed for the purpose of SHM. A type of gain programmable charge amplifier and a low crosstalk scanning module are discussed. An integrated software system which is based on the LabVIEW software platform is developed to manage the hardware, and perform signal processing and damage estimation. To validate the functions of this system, an evaluation is performed on a carbon fiber composite wing box of an unmanned aerial vehicle (UAV). The application results show the promising performance of this system.

Method for operating a piezoelectric element

Abstract: The invention relates to a method for operating a piezoelectric element, wherein a first voltage (1) is applied to a piezoelectric element, said voltage effecting a first deflection by a travel (w) of the piezoelectric element, and an electric discharge of the piezoelectric element after application of the first voltage effecting a first contraction of the piezoelectric element by a first compression (x). After the first contraction, a second voltage (2) is applied to the piezoelectric element, said voltage having an opposite polarity relative to the first voltage (1) and effecting a further contraction of the piezoelectric element by a second compression (y). A repeated application of the first voltage (1) after the electric discharge of the applied second voltage (2) effects a deflection of the piezoelectric element by the same travel (w).

Self-heat generation in piezoelectric stack actuators used in fuel injectors

Abstract: Multilayer piezoelectric actuators are used in fuel injectors due to their quick response, high efficiency, accuracy, low power consumption, and excellent repeatability. Experimental results for soft lead zirconate titanate (PZT) stack actuators have shown that a significant amount of heat is generated when they are driven under high frequency and/or high electric-field magnitudes, both of which occur in fuel injectors. Self-heat generation in these actuators, mainly caused by losses, can significantly affect their reliability and piezoelectric properties, and may also limit their application. Other studies have demonstrated that at large unipolar electric-field magnitudes, displacement–electric-field loss (displacement hysteresis) shows a direct relation with polarization–electric-field loss (dielectric hysteresis). In this paper, a simplified analytical self-heating model is presented. The model directly relates self-heating in multilayer piezoelectric actuators to displacement–electric-field loss (displacement hysteresis). The model developed is based on the first law of thermodynamics, and accounts for different parameters such as geometry, magnitude and frequency of applied electric field, duty cycle percentage, fuel type, and environmental properties. The model shows reasonable agreement with experimental results at low and high electric-field magnitudes.

Acoustic emission measurement using a strain-insensitive fiber Bragg grating sensor under varying load conditions.

Abstract: Acoustic emission (AE) during a pressure test of a carbon fiber-reinforced plastic tank was measured using a fiber Bragg grating (FBG) sensor and, for comparison, using a conventional piezoelectric sensor. The FBG-inscribed optical fiber was used not only as an optical transmission line but also as an ultrasonic transmission line. The FBG sensor showed resonant characteristics and could detect AE continuously during the test. AE detected with the FBG sensor exhibited a cumulative behavior similar to that detected with the piezoelectric sensor. The FBG sensor was demonstrated to have comparable AE detection capability to piezoelectric sensors.

A theoretical analysis of smart moderately thick shear deformable annular functionally graded plate

Abstract: Based on Mindlin's plate theory, free vibration analysis of moderately thick shear deformable annular functionally graded plate coupled with piezoelectric layers is presented in this paper. A consistent formulation that satisfies the Maxwell static electricity equation is presented so that the full coupling effect of the piezoelectric layer on the dynamic characteristics of the annular FGM plate can be estimated based on the free vibration results. The differential equations of motion are solved analytically for various boundary conditions of the plate through the transformation of variable method. The applicability of the proposed model is analyzed by studying the effect of varying the gradient index of FGM plate on the free vibration characteristics of the structure. For some specific cases, obtained results were cross checked with those existing literatures and furthermore, verified by those obtained from three-dimensional finite element (3D FE) analyses.

Static analysis for functionally graded piezoelectric actuators or sensors under a combined electro-thermal load

Abstract: Based on the theory of piezoelasticity, a functionally graded piezoelectric sandwich cantilever under an applied electric field and/or a heat load is studied. All materials may be arbitrary functional gradients in the thickness direction. The static solution for the mentioned problems is presented by the Airy stress function method. As a special case, assuming that the material composition varies continuously in the direction of the thickness according to a power law distribution, a comprehensive parametric study is conducted to show the influence of electromechanical coupling (EMC), functionally graded index, temperature change and thickness ratio on the bending behavior of actuators or sensors. The distribution of electric field or normal stress in present FGPM actuators is continuous along the thickness, which overcomes the problem in traditional layered actuators. The solution facilitates the design optimization for different piezoelectric actuators and has another potential application for material parameter identification.

Damage Detection for Composite Laminate Plates with A Distributed Hybrid PZT/FBG Sensor Network:

Abstract: Debond detection is a critical technique to ensure composite structural safety. Although there are many novel sensors being developed in recent years, piezoelectric transducers (PZT) and fiber Brag...

Multi‐actuated functionally graded piezoelectric micro‐tools design: A multiphysics topology optimization approach

Abstract: Micro-tools offer significant promise in a wide range of applications such as cell manipulation, micro-surgery, and micro/nanotechnology processes. Such special micro-tools consist of multi-flexible structures actuated by two or more piezoceramic devices that must generate output displacements and forces at different specified points of the domain and at different directions. The micro-tool structure acts as a mechanical transformer by amplifying and changing the direction of the piezoceramics output displacements. The design of these micro-tools involves minimization of the coupling among movements generated by various piezoceramics. To obtain enhanced micro-tool performance, the concept of multifunctional and functionally graded materials is extended by tailoring elastic and piezoelectric properties of the piezoceramics while simultaneously optimizing the multi-flexible structural configuration using multiphysics topology optimization. The design process considers the influence of piezoceramic property gradation and also its polarization sign. The method is implemented considering continuum material distribution with special interpolation of fictitious densities in the design domain. As examples, designs of a single piezoactuator, an XY nano-positioner actuated by two graded piezoceramics, and a micro-gripper actuated by three graded piezoceramics are considered. The results show that material gradation plays an important role to improve actuator performance, which may also lead to optimal displacements and coupling ratios with reduced amount of piezoelectric material. The present examples are limited to two-dimensional models because many of the applications for such micro-tools are planar devices. Copyright © 2008 John Wiley & Sons, Ltd.

Wave Motion Optimization in Periodically Distributed Shunted Piezocomposite Beam Structures

Abstract: This article proposes a new, simple, and efficient strategy, allowing one to optimize the diffusion operator between a passive beam coupled to a like beam equipped with a periodically distributed network of shunted piezoelectric patch actuators. A multimodal wave dispersion model is used to compute the diffusion operator and analyze the stability properties of the combined system. Based on this mathematical tool, specific optimization procedures are introduced to allow maximization or minimization of the wave transmissibility between the passive and the active distributed beam. A specific example is used to demonstrate the capability of the shunted piezoelectric system to induce total reflection through the total absorption of incoming propagating flexural waves while guaranteeing the stability, robustness, and realizability of such a system.

Thermo-electro-mechanical Performance of Piezoelectric Stack Actuators for Fuel Injector Applications

Abstract: Piezoelectric actuators are increasingly used in fuel injectors due to their quick response, high efficiency, accuracy, and excellent repeatability. Current understanding of their thermo-electro-mechanical performance under dynamic driving conditions appropriate for fuel injection is, however, limited. In this paper, the thermo-electro-mechanical performance of soft Lead Zirconate Titanate (PZT) stack actuators is experimentally investigated over a temperature range of -30°C to 80°C, under driving electric fields of up to 2.0 kV/mm (using an AC drive method and a biased DC offset), different frequencies, and a constant preload of about 5 MPa. Experimental results show that the dynamic stroke of the actuators increases with the magnitude and frequency of the applied electric field, as well as ambient temperature. The dynamic stroke was also found to increase with decreased driving field rise time, which is equivalent to increasing the driving field frequency. At driving frequencies lower than the resonance...

Multilayer piezoelectric energy scavenger for large current generation

Abstract: Piezoelectric energy harvesting system is promising to the energy source of wireless sensor nodes for ubiquitous sensor networks. The piezoelectric material has been usually considered as a high voltage and low current source. When charging current into the thin film battery or supercapacitor, a larger current is needed to shorten the charging time. In order to increase the current in the piezoelectric energy harvesting, multilayer ceramics were fabricated. N-layer multilayer ceramics decreased the voltage but increased the current N times. The impedance of the multilayer ceramics are matched to 1 kΩ which is similar to the impedance of general electrical devices. The multilayer piezoelectric generator could be directly employed for electrical device without the additional electrical circuit to improve efficiency.

Guided-wave Health Monitoring of Aircraft Composite Panels under Changing Temperature

Abstract: This study deals with the health monitoring of fiber-reinforced composite panels using ultrasonic guided waves and flexible piezocomposite transducer patches in a changing temperature environment c...