Showing papers on "Piezoelectric sensor published in 2003"

Overview of Piezoelectric Impedance-Based Health Monitoring and Path Forward

Abstract: In this paper we summarize the hardware and software issues of impedance-based structural health moni- toring based on piezoelectric materials. The basic concept of the method is to use high-frequency structural excitations to monitor the local area of a structure for changes in structural impedance that would indicate imminent damage. A brief overview of research work on experimental and theoretical stud- ies on various structures is considered and several research papers on these topics are cited. This paper concludes with a discussion of future research areas and path forward. Piezoelectric materials acting in the "direct" manner pro- duce an electrical charge when stressed mechanically. Con- versely, a mechanical strain is produced when an electrical field is applied. The direct piezoelectric effect has often been used in sensors such as piezoelectric accelerometers. With the converse effect, piezoelectric materials apply local- ized strains and directly influence the dynamic response of the structural elements when either embedded or surface bonded into a structure. Piezoelectric materials have been widely used in structural dynamics applications because they are lightweight, robust, inexpensive, and come in a variety of forms ranging from thin rectangular patches to complex shapes being used in microelectromechanical systems (MEMS) fabrications. The applications of piezoelectric mate- rials in structural dynamics are too numerous to mention and are detailed in the literature (Niezrecki et al., 2001; Chopra, 2002). The purpose of this paper is to explore the importance and effectiveness of impedance-based structural health mon- itoring from both hardware and software standpoints. Imped- ance-based structural health monitoring techniques have been developed as a promising tool for real-time structural dam- age assessment, and are considered as a new non-destructive evaluation (NDE) method. A key aspect of impedance-based structural health monitoring is the use of piezoceramic (PZT) materials as collocated sensors and actuators. The basis of this active sensing technology is the energy transfer between the actuator and its host mechanical system. It has been shown that the electrical impedance of the PZT material can be directly related to the mechanical impedance of a host structural component where the PZT patch is attached. Uti- lizing the same material for both actuation and sensing not only reduces the number of sensors and actuators, but also reduces the electrical wiring and associated hardware. Fur- thermore, the size and weight of the PZT patch are negligible compared to those of the host structures so that its attach- ment to the structure introduces no impact on dynamic char- acteristics of the structure. A typical deployment of a PZT on a structure being monitored is shown in Figure 1. The first part of this paper (Sections 2 and 3) deals with the theoretical background and design considerations of the impedance-based structural health monitoring. The signal processing of the impedance method is outlined in Section 4. In Section 5, experimental studies using the impedance approaches are summarized and related previous works are listed. Section 6 presents a brief comparison of the imped- ance method with other NDE approaches and, finally, sev- eral future issues are outlined in Section 7. 2. Theoretical Background

A survey of recent innovations in vibration damping and control using shunted piezoelectric transducers

Abstract: Research on shunted piezoelectric transducers, performed mainly over the past decade, has generated new opportunities for control of vibration and damping in flexible structures. This is made possible by the strong electromechanical coupling associated with modern piezoelectric transducers. In vibration control applications, a piezoelectric transducer is bonded to, or embedded in a base structure. As the structure deforms, the piezoelectric element strains and converts a portion of the structural vibration energy into electrical energy. By shunting the piezoelectric transducer to an electrical impedance, a part of the induced electrical energy can be dissipated. Hence, the impedance acts as a means of extracting mechanical energy from the base structure. This paper reviews recent research related to the use of shunted piezoelectric elements for vibration damping and control. In particular, the paper presents an overview of the literature on piezoelectric shunt damping and discusses recent observations on the feedback nature of piezoelectric shunt damping systems.

Lamb wave generation with piezoelectric wafer active sensors for structural health monitoring

Abstract: The capability of embedded piezoelectric wafer active sensors (PWAS) to perform in-situ nondestructive evaluation (NDE) is explored. Theoretical developments and laboratory tests are used to prove that PWAS transducers can satisfactorily perform Lamb wave transmission and reception, pulse-echo, pitch-catch, and phased array functions of conventional ultrasonics thus opening the road for embedded ultrasonics. Subsequently, crack detection in an aircraft panel with the pulse-echo method is illustrated. For large area scanning, a PWAS phased array is used to create the embedded ultrasonics structural radar (EUSR). For quality assurance, PWAS self-tests with the electromechanical impedance method are discussed.

A broadband controller for shunt piezoelectric damping of structural vibration

Abstract: In this paper a broadband active shunt technique for controlling vibration in piezoelectric laminated structures is proposed. The effect of the negative capacitance controller is studied theoretically and then validated experimentally on a piezoelectric laminated simply supported plate. The 'negative capacitance controller' is similar in nature to passive shunt damping techniques, as a single piezoelectric transducer is used to dampen multiple modes. While achieving comparable performance to that of the passive shunt schemes, the negative capacitance controller has a number of advantages. It is simpler to implement, less sensitive to environmental variations and can be considered as a broadband vibration absorber.

Piezoelectric-Wafer Active-Sensor Embedded Ultrasonics in Beams and Plates

Abstract: In this paper we present the results of a systematic theoretical and experimental investigation of the fundamental aspects of using piezoelectric wafe active sensors (PWASs) to achieve embedded ultrasonics in thin-gage beam and plate structures. This investigation opens the path for systematic application of PWASs forin situ health monitoring. After a comprehensive review of the literature, we present the principles of embedded PWASs and their interaction with the host structure. We give a brief review of the Lamb wave principles with emphasis on the understanding the particle motion wave speed/group velocity dispersion. Finite element modeling and experiments on thin-gage beam and plate specimens are presented and analyzed. The axial (S 0) and flexural (A 0) wave propagation patterns are simulated and experimentally measured. The group-velocity dispersion curves are validated. The use of the pulse-echo ultrasonic technique with embedded PWASs is illustrated using both finite element simulation and experiments. The importance of using high-frequency waves optimally tuned to the sensor-structure interaction is demonstrated. In conclusion, we discuss the extension of these results toin situ structural health monitoring using embedded ultrasonics.

A Novel Semi-Active Multi-Modal Vibration Control Law for a Piezoceramic Actuator

Abstract: In this paper, a novel semi-active energy rate multi-modal vibration control technique is developed for a piezoceramic actuator coupled to a switching resistor/inductor shunt. The technique works by briefly connecting a resistor/inductor shunt to a piezoceramic actuator in order to apply the necessary signed charge to allow energy dissipation. The switch timing is determined by a control scheme that observes the rate of energy change in controlled modes. The control scheme is developed in the paper, and is simplified to enable practical implementation. This new multi-modal control law is applied to both a simple numerical and an experimental test structure. The results from the numerical and experimental tests show that the energy rate multi-mode control law is able to dissipate energy from one, two and three modes of the flexible structures using a single actuator.

System for generating electric power from a rotating tire's mechanical energy using reinforced piezoelectric materials

Abstract: A system for generating electric power from a rotating tire's mechanical energy concerns a power generation device with a piezoelectric structure and an energy storage device. The piezoelectric structure preferably comprises a plurality of piezoelectric fibers embedded in a generally unidirectional fashion within an epoxy matrix. The piezoelectric structure may be mounted on a support substrate that helps distribute mechanical strain to which the piezoelectric fibers are subjected in a substantially uniform fashion. The piezoelectric structure is preferably mounted within a tire structure such that electric charge is generated therein as the wheel assembly moves along a ground surface. Electrode layers within the piezoelectric structure are coupled to a power conditioning module that rectifies the resultant electric current from the piezoelectric structure and stores it in an energy storage device, preferably an electrolytic capacitor. A rechargeable battery may also be provided for storing additional charge generated within the piezoelectric structure. A regulated voltage source is provided from the energy stored in the power generation device and can be used to power various electronics systems integrated within a tire or wheel assembly. An example of an integrated tire electronics system for use with the disclosed power generation device corresponds to a tire monitoring system that wirelessly transmits such information as tire pressure, temperature and identification variables to a remote receiver location.

Polyimide membrane with ZnO piezoelectric thin film pressure transducers as a differential pressure liquid flow sensor

Abstract: Fabrication and characterization of ZnO thin film piezoelectric sensors on a polyimide membrane is presented in this paper. As a test device a differential pressure liquid flow sensor has been fabricated. We discuss new material combinations for the fabrication of the test devices. The pressure sensor membrane is a thin polyimide sheet bonded to a silicon wafer and the sensing material is sputtered ZnO piezoelectric thin film. The fabricated liquid flow sensor has been tested with a piezoelectric micropump for flow rates from 30 µl h−1 to 300 µl h−1. Stroke volumes of 1 to 10 nl have been measured. The strain in the sensing layer has been modeled and a transverse piezoelectric coefficient of e31,f = −0.294 C m−2 has been extracted.

Adaptive piezoelectric shunt damping

Abstract: Piezoelectric shunt damping systems reduce structural vibration by shunting an attached piezoelectric transducer with an electrical impedance. Current impedance designs result in a coupled electrical resonance at the target modal frequencies. In practical situations, variation in structural load or environmental conditions can result in significant changes in the structural resonance frequencies. This variation can severely reduce shunt damping performance as the electrical impedance remains tuned to the nominal resonance frequencies. This paper introduces a method for online adaptation of the shunting impedance. A reconstructed estimate of the RMS strain is minimized by varying the component values of a synthetic shunt damping circuit. The techniques presented are applied in real time to tune the component values of a randomly excited beam.

Energy-Recycling Semi-Active Method for Vibration Suppression with Piezoelectric Transducers

Abstract: *A novel energy-recycling method is studied that enables effective semi-active vibration suppression with piezoelectric transducers embedded or bonded to a structure. In this method, the energy converted from the mechanical energy of a vibrating structure is collected in the capacitor of a piezoelectric transducer as an electric charge, and to suppress vibration, rather than dissipate the energy, the polarity of the charge is changed according to the state of vibration. With this method, no energy is supplied to the total system of the structure and transducers with shunt circuit, which means that the system is stable. A simple electric circuit and a control law for multiple-degree-offreedom systems with multiple piezoelectric transducers are proposed for this method based on energy recycling. Numerical simulation of vibration suppression of a truss structure shows that this method is more effective in suppressing vibration than both a semi-active method without energy-recycling and that based on the use of an optimally tuned passive system. A preliminary experiment with a truss structure also shows that this method can effectively suppress vibration in an actual structure. However, there was some discrepancy in the experimental results compared to the results of the numerical simulation performed assuming ideal linear characteristics of the piezoelectric transducers estimated from a static test. Nomenclature

Reducing the inductance requirements of piezoelectric shunt damping systems

Abstract: Structural vibration can be reduced by shunting an attached piezoelectric transducer (PZT) with an electrical impedance. Current shunt circuit designs, e.g. a single-mode inductor–resistor network, typically require large inductance values of up to thousands of henries. In practice, discrete inductors are limited in size to around 1 H. By placing an additional capacitance across the terminals of the PZT, shunt circuit inductances can be drastically reduced. To justify our claims, we present a theoretical analysis of the damped system and identify the influence of the additional capacitance. Two modes of a simply supported beam are successfully damped using a capacitance modified shunt circuit. A low inductance multi-mode circuit is also studied and experimentally verified.

Piezoelectric Materials at Elevated Temperature

Abstract: Piezoelectric ceramic patches are the mainstay for actuating and sensing in smart structures, but these patches are limited in the temperature range in which they can operate Operation at temperat

Piezoelectric thin-film resonator, piezoelectric filter, and electronic component including the piezoelectric filter

Abstract: A piezoelectric thin-film resonator includes a supporting substrate. A piezoelectric thin-film is formed on the supporting substrate. A lower electrode and an upper electrode are formed with the piezoelectric thin-film therebetween. The stiffness of at least one of the lower and upper electrodes is higher than that of the piezoelectric thin-film.

Ultrasonic imaging devices and methods of fabrication

Abstract: A sensor (16) for an ultrasound imaging catheter (12) and methods of fabrication are provided. The sensor (16) may be based on a flex circuit (32) on which a block of piezoelectric sensor array transducer material is mounted. The flex circuit may include electrical conductors (34) that are electrically connected to electrodes on the piezoelectric blocks. A matching layer may be formed on the piezoelectric blocks between the blocks and the flex circuit substrate. Individual transducer array elements may be formed by dividing a piezoelectric block into a plurality of individual transducer elements after the matching layer has been formed. Cuts may be formed in the flex circuit substrate between adjacent transducer array elements to acoustically decouple adjacent elements. The flex circuit substrate and matching layers may have relatively high impedance to facilitate acoustic impedance matching between the sensor and the imaging environment.

Piezoelectric filter, duplexer, composite piezoelectric resonator, communication device and method for adjusting frequency of piezoelectric filter

Abstract: A piezoelectric filter and other electronic components are constructed such that the accuracy of frequency adjustment can be increased and an improvement in efficiency of the adjustment operation can be achieved. The piezoelectric filter includes a plurality of piezoelectric resonators including a substrate and a vibration portion provided on the substrate, the vibration portion having a structure in which the top and bottom surfaces of a thin film portion including at least one piezoelectric thin film are sandwiched between at least a pair of an upper electrode and a lower electrode facing each other, wherein the upper electrode of a predetermined piezoelectric resonator is made of a material having susceptibility to etching that is different from that of the upper electrode of the other piezoelectric resonator.

Finite element piezothermoelasticity analysis and the active control of FGM plates with integrated piezoelectric sensors and actuators

Abstract: An efficient finite element model is presented for the static and dynamic piezothermoelastic analysis and control of FGM plates under temperature gradient environments using integrated piezoelectric sensor/actuator layers The properties of an FGM plate are functionally graded in the thickness direction according to a volume fraction power law distribution A constant displacement-cum-velocity feedback control algorithm that couples the direct and inverse piezoelectric effects is applied to provide active feedback control of the integrated FGM plate in a closed loop system Numerical results for the static and dynamic control are presented for the FGM plate, which consists of zirconia and aluminum The effects of the constituent volume fractions and the influence of feedback control gain on the static and dynamic responses of the FGM plates are examined

Optimal Control of Laminated Shells Using Piezoelectric Sensor and Actuator Layers

Abstract: A simple method for optimal control of vibrations of simply supported thin laminated shells integrated with piezoelectric layers is presented. The piezoelectric layers act as the distributed sensors and actuators. Coupled electromechanical governing equations of motion are derived using Hamilton's variational principle. The algorithm for a linear quadratic regulator with output feedback has been employed to formulate the optimal control problem. Controlled responses for various design parameters are illustrated, and a study of the effect of variation of the central angle subtended by the shell on the performance of the actuator is presented.

Introduction to Piezoelectric Actuators and Transducers

Abstract: : Certain materials produce electric charges on their surfaces as a consequence of applying mechanical stress The induced charges are proportional to the mechanical stress This is called the direct piezoelectric effect and was discovered in quartz by Piere and Jacques Curie in 1880 Materials showing this phenomenon also conversely have a geometric strain proportional to an applied electric field This is the converse piezoelectric effect The root of the word "piezo" means "pressure"; hence the original meaning of the word piezoelectricity implied "pressure electricity" Piezoelectricity is extensively utilized in the fabrication of various devices such as transducers, actuators, surface acoustic wave devices, frequency control and so on In this chapter we describe the piezoelectric materials that are used, and various potential applications of piezoelectric materials

Vibration Control of Composite Plates via Optimal Placement of Piezoelectric Patches

Abstract: A simple optimal placement strategy of piezoelectric sensor/actuator (S/A) pairs for vibration control of laminated composite plate is presented, where the active damping effect under a classical control framework is maximized using the finite element approach. The classical direct pattern search method is employed to obtain the local optimum, where two optimization performance indices based on modal and system controllability are studied. The start point for the pattern search is selected based on the maxima of integrated normal strains consistent with the size of the collocated piezoelectric patches used. This would maximize the virtual work done by the equivalent actuation forces along the strain field of an initial state. Numerical simulation using a cantilevered and a clamped composite square plate illustrate the effectiveness of the proposed strategy, where the results coincide with the global optimal layout from exhaustive search for both modal and system controllability indices. The number of tria...

Force or pressure sensor and method for applying the same

Abstract: The invention relates to a force or pressure sensor and a method for applying the same. The pressure sensor includes a substantially rigid, mechanical-load resistant frame, a flexible diaphragm secured over its peripheral rim to the frame, and a piezoelectric sensor diaphragm applied to the surface of the flexible diaphragm. The sensor diaphragm loading element comprises a substantially rigid, mechanical-load resistant cover, having its protrusion or shoulder bearing against a middle section of the flexible diaphragm and thereby prestressing the flexible diaphragm and the piezoelectric sensor diaphragm attached thereto. The frame and the cover define therebetween a closed, hermetically sealed housing chamber, the flexible diaphragm and the piezoelectric sensor diaphragm located thereinside. The placement of one or more responsive, yet load-resistant sensors in contact with a bed enables measuring a sleeping or lying person for his or her heart rate and respiratory amplitude, as well as frequency.

Vibration control of structures with self-sensing piezoelectric actuators incorporating adaptive mechanisms

Abstract: In a piezo-based self-sensing actuation (SSA) configuration, the control signal is mixed with the signal due to mechanical response The success of SSA relies on the extraction of that mechanical response from the mixed signal Owing to the relatively high amplitudes of those two signals and the ambience varying property of the equivalent capacitance of the piezoelectric element, a fix designed bridge circuit in the SSA configuration would extract a corrupted mechanical response under the variation of the piezoelectric capacitance This would degrade the system performance or even destabilize the closed loop system In this paper, an adaptive compensation is proposed to combine with the SSA technique to develop a vibration controller that is capable of extracting the true sensing signal due to structural deformation The results of this study illustrate that the combined design can simultaneously suppress the structural vibration during the piezoelectric capacitance variation

Environmental effects on Lamb wave responses from piezoceramic sensors

Abstract: Structural Health Monitoring using Lamb waves is based on the theory of elastic waves propagating in plates. Signal attenuation and mode conversion are used for damage detection. It is well known that the voltage amplitude from low-profile piezoceramic sensors used for inspection may change not only due to damage but also due to an inappropriate transducer coupling and temperature effects. The paper studies the effect of temperature on Lamb wave responses. The work involves a simple experiment in which two piezoelectric ceramics are bonded on an aluminium plate. The plate is exposed to various levels of temperature. A couple of simple features extracted from the Lamb wave responses are analysed to show the effect of the temperature changes. The plate was later subjected to damage and the series of tests and analysis repeated in order to give some comparison between the effects of damage and temperature change upon the responses. Several ways of how this problem can be circumvented using appropriate signal processing techniques are discussed.