Showing papers on "Piezoelectric sensor published in 2007"
TL;DR: In this article, an ultrasonic guided wave structural health monitoring (SHM) system was developed for aircraft wing inspection, where small, low-cost and light-weight piezoelectric (PZT) discs were bonded to various parts of the aircraft wing, in a form of relatively sparse arrays, for simulated cracks and corrosion monitoring.
Abstract: This work focuses on an ultrasonic guided wave structural health monitoring (SHM) system development for aircraft wing inspection. In part I of the study, a detailed description of a real aluminum wing specimen and some preliminary wave propagation tests on the wing panel are presented. Unfortunately, strong attenuation and scattering impede guided waves for large-area inspection. Nevertheless, small, low-cost and light-weight piezoelectric (PZT) discs were bonded to various parts of the aircraft wing, in a form of relatively sparse arrays, for simulated cracks and corrosion monitoring. The PZT discs take turns generating and receiving ultrasonic guided waves. Pair-wise through-transmission waveforms collected at normal conditions served as baselines, and subsequent signals collected at defected conditions such as rivet cracks or corrosion detected the presence of a defect and its location with a novel correlation analysis based technique called RAPID (reconstruction algorithm for probabilistic inspection of defects). The effectiveness of the algorithm was tested with several case studies in a laboratory environment. It showed good performance for defect detection, size estimation and localization in complex aircraft wing structures.
670 citations
TL;DR: In this article, the dispersive and anisotropic behavior of Lamb waves in a two different types of symmetric laminates is studied theoretically and experimentally, with emphasis on group velocity and characteristic wave curves.
280 citations
TL;DR: In this paper, the authors evaluated the performance of different damage detection techniques for composite laminated plates using smart piezoelectric materials and modern instrumentation like scanning laser vibrometer (SLV).
212 citations
TL;DR: In this article, piezoelectric ceramics patches are used as sensors and actuators to suppress the vibration of the smart flexible clamped plate, and an efficient control method by combining positive position feedback and proportional-derivative control is proposed for vibration reduction.
207 citations
TL;DR: High-amplitude actuation of a piezoelectric tube is achieved using a charge amplifier using a positive velocity and position feedback (PVPF) controller.
Abstract: In this paper, a piezoelectric tube of the type typically used in scanning tunneling microscopes (STMs) and atomic force microscopes (AFMs) is considered. Actuation of this piezoelectric tube is hampered by the presence of a lightly damped low-frequency resonant mode. The resonant mode is identified and damped using a positive velocity and position feedback (PVPF) controller, a control technique proposed in this paper. Input signals are then shaped such that the closed-loop system tracks a raster pattern. Normally, piezoelectric tubes are actuated using voltage amplifiers. Nonlinearity in the form of hysteresis is observed when actuating the piezoelectric tubes at high amplitudes using voltage amplifiers. It has been known for some time that hysteresis in piezoelectric actuators can be largely compensated by actuating them using charge amplifiers. In this paper, high-amplitude actuation of a piezoelectric tube is achieved using a charge amplifier.
177 citations
TL;DR: An approach based upon the employment of piezoelectric transducer rosettes is proposed for passive damage or impact location in anisotropic or geometrically complex structures as discussed by the authors.
Abstract: An approach based upon the employment of piezoelectric transducer rosettes is proposed for passive damage or impact location in anisotropic or geometrically complex structures. The rosettes are comprised of rectangular macro-fiber composite (MFC) transducers which exhibit a highly directive response to ultrasonic guided waves. The MFC response to flexural (A0) motion is decomposed into axial and transverse sensitivity factors, which allow extraction of the direction of an incoming wave using rosette principles. The wave source location in a plane is then simply determined by intersecting the wave directions detected by two rosettes. The rosette approach is applicable to anisotropic or geometrically complex structures where the conventional time-of-flight source location is challenging due to the direction-dependent wave velocity. The performance of the rosettes for source location is validated through pencil-lead breaks performed on an aluminum plate, an anisotropic CFRP laminate and a complex CFRP-honeycomb sandwich panel.
165 citations
TL;DR: In this article, a new methodology of guided-wave-based nondestructive testing (NDT) is developed to detect crack damage in a thin metal structure without using prior baseline data or a predetermined decision boundary.
Abstract: A new methodology of guided-wave-based nondestructive testing (NDT) is developed to detect crack damage in a thin metal structure without using prior baseline data or a predetermined decision boundary. In conventional guided-wave-based techniques, damage is often identified by comparing the 'current' data obtained from a potentially damaged condition of a structure with the 'past' baseline data collected at the pristine condition of the structure. However, it has been reported that this type of pattern comparison with the baseline data can lead to increased false alarms due to its susceptibility to varying operational and environmental conditions of the structure. To develop a more robust damage diagnosis technique, a new concept of NDT is conceived so that cracks can be detected even when the system being monitored is subjected to changing operational and environmental conditions. The proposed NDT technique utilizes the polarization characteristics of the piezoelectric wafers attached on both sides of the thin metal structure. Crack formation creates Lamb wave mode conversion due to a sudden change in the thickness of the structure. Then, the proposed technique instantly detects the appearance of the crack by extracting this mode conversion from the measured Lamb waves, and the threshold value from damage classification is also obtained only from the current dataset. Numerical and experimental results are presented to demonstrate the applicability of the proposed technique to instantaneous crack detection.
151 citations
TL;DR: In this article, the static bending, free vibration, and dynamic response of monomorph, bimorph, and multimorph actuators made of functionally graded piezoelectric materials (FGPMs) under a combined thermal-electro-mechanical load by using the Timoshenko beam theory was investigated.
Abstract: This paper investigates the static bending, free vibration, and dynamic response of monomorph, bimorph, and multimorph actuators made of functionally graded piezoelectric materials (FGPMs) under a combined thermal-electro-mechanical load by using the Timoshenko beam theory. It is assumed that all of the material properties of the actuator, except for Poisson's ratio, are position dependent due to a continuous variation in material composition through the thickness direction. Theoretical formulations are derived by employing Hamilton's principle and include the effect of transverse shear deformation and axial and rotary inertias. The governing differential equations are then solved using the differential quadrature method to determine the important performance indices, such as deflection, reaction force, natural frequencies, and dynamic response of various FGPM actuators. A comprehensive parametric study is conducted to show the influence of shear deformation, temperature rise, material composition, slenderness ratio, end support, and total number of layers on the thermo-electro-mechanical characteristics. It is found that FGPM monomorph actuators exhibit the so-called 'non-intermediate' behavior under an applied electric field.
151 citations
TL;DR: Zhao et al. as discussed by the authors developed a wireless ultrasonic structural health monitoring (SHM) system for aircraft wing inspection, which can effectively deliver at least 100?mW of DC power continuously from a transmitter at a range of 1?m.
Abstract: The objective of this study is to develop a wireless ultrasonic structural health monitoring (SHM) system for aircraft wing inspection. In part I of the study (Zhao et al 2007 Smart?Mater.?Struct. 16 1208?17), small, low cost and light weight piezoelectric (PZT) disc transducers were bonded to various parts of an aircraft wing for detection, localization and growth monitoring of defects. In this part, two approaches for wirelessly interrogating the sensor/actuator network were developed and tested. The first one utilizes a pair of reactive coupling monopoles to deliver 350?kHz RF tone-burst interrogation pulses directly to the PZT transducers for generating ultrasonic guided waves and to receive the response signals from the PZTs. It couples enough energy to and from the PZT transducers for the wing panel inspection, but the signal is quite noisy and the monopoles need to be in close proximity to each other for efficient coupling. In the second approach, a small local diagnostic device was developed that can be embedded into the wing and transmit the digital signals FM-modulated on a 915?MHz carrier. The device has an ultrasonic pulser that can generate 350?kHz, 70?V tone-burst signals, a multiplexed A/D board with a programmable gain amplifier for multi-channel data acquisition, a microprocessor for circuit control and data processing, and a wireless module for data transmission. Power to the electronics is delivered wirelessly at X-band with an antenna?rectifier (rectenna) array conformed to the aircraft body, eliminating the need for batteries and their replacement. It can effectively deliver at least 100?mW of DC power continuously from a transmitter at a range of 1?m. The wireless system was tested with the PZT sensor array on the wing panel and compared well with the wire connection case.
136 citations
TL;DR: In this paper, a thin-film piezoelectric sensor was used to mimic the tactile feedback exhibited by the human hand in an artificial limb to detect object slip and provide information to a controller, which automatically adjusts the grip force applied to a held object to prevent it from falling.
Abstract: The ability to mimic the tactile feedback exhibited by the human hand in an artificial limb is considered advantageous in the automatic control of new multifunctional prosthetic hands. The role of a slip sensor in this tactile feedback is to detect object slip and thus provide information to a controller, which automatically adjusts the grip force applied to a held object to prevent it from falling. This system reduces the cognitive load experienced by the user by not having to visually assess the stability of an object, as well as giving them the confidence not to apply unnecessarily excessive grip forces. A candidate for such a sensor is a thick-film piezoelectric sensor. The method of fabricating a thick-film piezoelectric slip sensor on a prototype fingertip is described. The construction of experimental apparatus to mimic slip has been designed and analyzed to allow the coefficient of friction between the fingertip and the material in contact with the fingertip to be calculated. Finally, results show that for a coefficient of friction between the fingertip and grade P100 sandpaper of approximately 0.3, an object velocity of 0.025plusmn0.008 ms-1 was reached before a slip signal from the piezoelectric sensor was able to be used to detect slip. It is anticipated that this limiting velocity will be lowered (improved) in the intended application where the sensor electronics will be powered from a battery, connections will be appropriately screened, and if necessary a filter employed. This will remove mains interference and reduce other extraneous noise sources with the consequence of an improved signal-to-noise ratio, allowing lower threshold values to be used in the detection software
123 citations
TL;DR: In this paper, a method for integrating piezoelectric sensor networks into a composite structure during different fabrication processes, including the resin transfer molding (RTM) and filament winding processes, is examined.
Abstract: By implementing a built-in sensor network on a composite structure, crucial information regarding the condition, damage state, and service environment of the structure can be obtained. In this study, methods for integrating piezoelectric sensor networks into a composite structure during different fabrication processes, including the resin transfer molding (RTM) and filament winding processes, are examined. To integrate sensor networks with different contours of structures, the method to fabricate a three-dimensional (3-D) diagnostic layer is developed. It is demonstrated that a large number of sensors supported on a thin flexible dielectric film, called a SMART Layer, offers a simple and efficient way to integrate a large sensor network onto a complex 3-D structure. The sensor network permanently embedded inside the composite structures can be used with either active sensing or passive sensing to monitor the health condition of a structure throughout its lifetime.
TL;DR: In this paper, the optimal placement of collocated piezoelectric actuator-sensor pairs on a thin plate using a model-based linear quadratic regulator (LQR) controller is taken as objective for finding the optimal location of sensor-actuator pairs.
Abstract: This paper considers the optimal placement of collocated piezoelectric actuator–sensor pairs on a thin plate using a model-based linear quadratic regulator (LQR) controller. LQR performance is taken as objective for finding the optimal location of sensor–actuator pairs. The problem is formulated using the finite element method (FEM) as multi-input–multi-output (MIMO) model control. The discrete optimal sensor and actuator location problem is formulated in the framework of a zero–one optimization problem. A genetic algorithm (GA) is used to solve the zero–one optimization problem. Different classical control strategies like direct proportional feedback, constant-gain negative velocity feedback and the LQR optimal control scheme are applied to study the control effectiveness.
TL;DR: In this paper, an experimental and statistical investigation was conducted to show the influence of external loading on EM admittance signatures of PZT transducers, and it was observed that the susceptance signature is a better indicator than conductance signature for detecting in situ stress in the host structure.
Abstract: Damage detection using electromechanical (EM) impedance in structural health monitoring (SHM) of engineering structures is rapidly emerging as a useful technique. In the EM impedance method, piezoceramic (PZT) transducers are either surface bonded to or embedded inside the host structure and are subjected to electric actuation. The EM admittance signatures of the PZT transducers, which consist of real and imaginary parts, serve as indicators to predict the health/integrity of the host structure. However, in real life, structural components such as slabs, beams and columns are constantly subjected to some form of external loading. The EM admittance signature obtained for such a constantly loaded structure is different from that obtained when damages are present in the structure. This paper presents an experimental and statistical investigation to show the influence of loading on EM admittance signatures. It is also observed that the susceptance signature is a better indicator than the conductance signature for detecting in situ stress in the host structure. This observation is further supported by a statistical analysis. This paper is expected to be useful for the non-destructive evaluation of engineering structures with external loading.
06 Apr 2007
TL;DR: In this article, the performance of two types of micro-scale strain gage for installation on stainless steel parts are compared. And the advantage and disadvantage of these piezoresistors are compared to those of piezoelectric sensors.
Abstract: Both piezoresistive and piezoelectric materials are commonly used to detect strain caused by structural vibrations in macro-scale structures. With the increasing complexity and miniaturization of modern mechanical systems such as hard disk drive suspensions, it is imperative to explore the performance of these strain sensors when their dimensions must shrink along with those of the host structures. The miniaturized strain sensors must remain as small as possible so as to minimum their effect on structure dynamics, yet still have acceptable sensing resolution. The performances of two types of novel micro-scale strain gage for installation on stainless steel parts are compared in this paper. Micro-fabrication processes have been developed to build polycrystalline silicon piezoresistive strain sensors on a silicon substrate, which are later bonded to a steel substrate for testing. Piezoresistor geometries are optimized to effectively increase the gage factor of piezoresistive sensors while reducing sensor size. The advantage and disadvantage of these piezoresistors are compared to those of piezoelectric sensors. Experimental results reveal that the MEMS piezoelectric sensors are able to achieve a better resolution than piezoresistors, while piezoresistors can be built in much smaller areas. Both types of the MEMS strain sensors are capable of high sensitivity measurements, subject to differing constraints.
TL;DR: In this paper, the fundamental response of surface-bonded piezoelectric sensors to ultrasonic waves is examined, starting with harmonic excitation fields and moving to broadband and narrowband excitation field.
Abstract: A fundamental understanding of the response of piezoelectric transducer patches to ultrasonic waves is of increasing interest to the field of structural health monitoring While analytical solutions exist on the interaction of a piezoelectric actuator with the generated Lamb waves, the behavior of a piezoelectric sensor has only been examined for the limited case of a piezo-actuated Lamb wave in a pitch-catch configuration This paper focuses on the fundamental response of surface-bonded piezoelectric sensors to ultrasonic waves The response to both Rayleigh waves and Lamb waves is examined, starting with harmonic excitation fields and moving to broadband and narrowband excitation fields General oblique incidence of the wave on rectangular sensors is treated first; parallel incidence is then derived as a particular case The solutions are developed analytically for the harmonic and the narrowband excitations, and semianalytically for the broadband excitation The results obtained can be used to design u
TL;DR: In this article, a scaled model of a vertical tail of F/A-18 is developed in which piezoelectric actuators are bounded to the surface, and the frequency response function (FRF) of the system is then recorded and maximization of the FRF peaks is considered as the objective function of the optimization algorithm to enhance the actuator authority on the mode.
TL;DR: In this paper, the effect of damage size on the propagation of Lamb waves is presented, and the technique is applied to a stiffened panel, where damage on the skin or flange is detectable while damage on a web or cap is not detected with the current experimental set up.
Abstract: The aim of the present work is to develop a system of smart devices that could be permanently attached on the surface of the composite structure and monitor the interaction of low-frequency Lamb waves with defects. A linear array of transmitters would generate a relatively uniform wavefront allowing the inspection of large areas with a limited number of sensors. The asymmetric A0 Lamb mode is generated in carbon fibre reinforced plastic (CFRP) quasi-isotropic laminates using an array of thin piezoceramic transmitters operating in-phase. In this paper, the effect of damage size on the propagation of Lamb waves is presented. Experimental verification is also presented in multidirectional CFRP composite panels. Critical size impact damage is detected. Finally, the technique is applied to a stiffened panel. Damage on the skin or flange is detectable while damage on the web or cap is not detected with the current experimental set up.
TL;DR: In this paper, an unsymmetrical carbon fiber/epoxy composites with bonded piezoelectric actuators are investigated as a means to shape or morph, the composite structures.
Abstract: Unsymmetrical carbon fiber/epoxy composites with bonded piezoelectric actuators are investigated as a means to shape or morph, the composite structures. Both a cantilever and unsupported laminate structure are examined along with their response to applied strains (from piezoelectric actuators) and applied mechanical load; with particular emphasis on the characterization of shape/deflection, the influence of externally applied mechanical loads and methods of reversing or promoting snap-through of these materials from one stable state to another. A variety of shape change/actuation modes for such structures have been identified namely, (i) reversible actuation by maintaining a constant stable state using piezoelectric actuation, (ii) an increased degree of shape change by irreversible snap-through using piezoelectric actuation and (iii) reversible snap-through using combined piezoelectric actuation and an externally applied load.
TL;DR: In this article, a method to design piezoelectric benders for impact or shock energy harvesting in terms of their geometry and material properties is proposed, where the rate of transfer of energy towards the electrical load is optimized by maximizing the figure of merit of the structure and by choosing an appropriate value of the load.
Abstract: Piezoelectric bending structures can be designed to act as an electrical generator for converting ambient mechanical energy into useful electrical energy. The produced electrical energy is stored or dissipated into an electrical load. Most of the analyses on piezoelectric generators proposed in the literature are limited to a steady-state approach to the problem. These analyses fail to give clear insights when the dynamical behaviour of the piezoelectric bender is governed by its transient characteristics, for example in the case of a shock or impact excitation, and we analyse such a situation in this paper. It is first pointed out that the rate of transfer of energy towards the electrical load is optimized by maximizing the figure of merit of the structure and by choosing an appropriate value of the load. According to this consideration, a method to design piezoelectric benders for impact or shock energy harvesting in terms of their geometry and material properties is then proposed.
TL;DR: A new measurement method to characterize piezoelectric thin films utilizing a four-point bending setup in combination with a single- or a double-beam laser interferometer, which allows the determination of the effective transverse and longitudinal piez Zoelectric coefficients e31,f and d33,f respectively.
Abstract: We present a new measurement method to characterize piezoelectric thin films utilizing a four-point bending setup. In combination with a single- or a double-beam laser interferometer, this setup allows the determination of the effective transverse and longitudinal piezoelectric coefficients e31,f and d33,f respectively. Additionally, the dielectric coefficient and the large signal electrical polarization are measured to add further important characteristics of the film. These data are essential for piezoelectric thin film process specification and the design and qualification of microelectromechanical systems devices.
TL;DR: In this article, the results obtained using guided Lamb waves to detect flaws in aluminum specimens with design features applicable to space applications were presented. And the results have demonstrated the ability of piezoelectric wafer active sensors working in conjunction with guided Lamb wave to detect various types of damages present in complex geometry structures typical of space applications.
Abstract: Ultrasonic guided waves inspection using Lamb waves is suitable for damage detection in metallic structures. This paper will present experimental results obtained using guided Lamb waves to detect flaws in aluminum specimens with design features applicable to space applications. Two aluminum panels were fabricated from a variable-thickness aluminum top plate, with two bolted I-beams edge stiffeners and four bonded angle stiffeners. Artificial damages were introduced in the two panels: cracks, corrosions, and disbonds. The proposed investigation methods used bonded piezoelectric wafer active sensors to excite and receive Lamb waves. Three wave propagation methods were used: pitch-catch, pulse-echo, and the embedded ultrasonic structural radar. In addition, we also used a standing-wave damage detection technique, the electromechanical impedance method. The paper will present in detail the salient results from using these methods for damage detection and structural health monitoring. Where appropriate, comparison between different methods in detecting the same damage will be performed. The results have demonstrated the ability of piezoelectric wafer active sensors working in conjunction with guided Lamb waves to detect various types of damages present in complex geometry structures typical of space applications.
TL;DR: In this article, the authors examined the feasibility of employing the new generation fibre optic and piezoelectric sensor systems for comprehensive monitoring of rocks, covering load history monitoring/retrieval as well as damage assessment.
Patent•
10 Oct 2007TL;DR: In this paper, a flexible tip device (10) is used for assessing tissue contact, e.g., for mapping, tissue ablation, or other procedures, and methods for assembling and using it are described.
Abstract: Systems and methods are disclosed for assessing tissue contact, e.g., for mapping, tissue ablation, or other procedures. An exemplary tissue contact sensing system comprises a flexible tip device (10). At least one piezoelectric sensor (20) is housed within the flexible tip device (10). The at least one piezoelectric sensor (20) is responsive to contact stress of the flexible tip device (10) by generating electrical signals corresponding to the amount of contact stress. An output device (10) is electrically connected to the at least one piezoelectric sensor (20). The output device (10) receives the electrical signals for assessing tissue contact by the flexible tip device (10). Methods for assembling and using the flexible tip device (10) are also disclosed.
TL;DR: Cell-based biosensor has potential for identification and screening of biologically active drugs and other biomolecules affecting cellular shape and attachment and is suitable for studies of the cell adhesion processes.
TL;DR: In this article, a three-dimensional interaction model of a PZT-structure was proposed for non-destructive evaluation (NDE) of structural health monitoring (SHM).
Abstract: In the past few decades, piezoceramic (PZT) transducers have been used extensively in the vibration and noise control of engineering structures. However, in the last decade, PZT transducers have also been used in electromechanical impedance (EMI) based methods of structural health monitoring (SHM). In the EMI methods, the PZT transducers are either surface bonded using adhesive or wrapped with a protective cover and then bonded or embedded inside the host structure. They are then subjected to excitation in the desired frequency ranges to predict the electromechanical (EM) admittance signatures. These EM signatures serve as an indicator of the health/integrity of the structure. The existing PZT-structure interaction methods consider both the PZT transducer and the adhesive layer to be negligible in mass and are thus ignored. However, for wrapped PZT, the presence of thick adhesive significantly reduces the magnitude of the EM signature. This paper presents the formulation of a three-dimensional (3D) interaction model of a PZT-structure which considers the mass of both the PZT transducers and the adhesive. The model is generic in nature compared to the existing interaction models. The model is verified experimentally and is expected to be applicable to the non-destructive evaluation (NDE) of most engineering structures.
Patent•
11 Dec 2007TL;DR: In this paper, a system and method for measuring absolute pressure applied to a piezoelectric element by measuring a transition time of a voltage pulse applied to the piezel is presented.
Abstract: A system and method for measuring absolute pressure applied to a piezoelectric element by measuring a transition time of a voltage pulse applied to a piezoelectric element. The transition time (such as the rise time and/or fall time of the voltage pulse) is affected by the capacitance of the piezoelectric element, which in turn is affected by the amount of pressure currently being applied to the piezoelectric element. The system may also provide haptic feedback via the same piezoelectric element.
17 Jan 2007-Microsystem Technologies-micro-and Nanosystems-information Storage and Processing Systems
TL;DR: In this paper, a micro-cantilever with a piezoelectric film was used to detect bio-materials in the quartz crystal microbalance (QCM).
Abstract: A biosensor was developed for using in a Lab-On-a-Chip (LOC). The sensor detects the change in the resonance frequency of a micro-cantilever with a piezoelectric film. This is the mass micro-balancing technique, which has been successfully used for detecting bio-materials in the quartz crystal microbalance (QCM). The PZT film, a piezoelectric film, is designed to act as both sensor and actuator. The geometry of the micro cantilever is optimized to maximize the sensitivity and minimize the environmental effects such as viscous damping and added mass effect in liquid. The fabricated sensor is composed of a 100 μm long, 30 μm wide, and 5 μm thick cantilever with a 2.5 μm thick piezoelectric (PZT) layer on it. The ratio of thickness to length of the micro cantilever is very high compared to others in micro cantilever-based studies. This high aspect ratio is the key to maximize the sensitivity and minimize the environmental effects. The fabricated micro sensor was tested by detecting the mussel gluing protein, the insulin-anti insulin binding protein and the poly T-sequence DNA.
TL;DR: In this article, the authors compared the performance of two sensor systems, i.e., a surface-bonded piezoelectric sensor system and a noncontact scanning laser vibrometer (SLV) system, and their effectiveness in damage identification of composite laminated beams is compared.
Abstract: A reliable and effective damage detection technique is one of the significant tools to maintain the safety and integrity of structures. A dynamic response offers viable information for the identification of damage in the structures. However, the performance of such dynamics-based damage detection depends on the quality of measured data and the effectiveness of data processing algorithms. In this article, the experimentally measured data of two sensor systems, i.e., a surface-bonded piezoelectric sensor system and a noncontact scanning laser vibrometer (SLV) system, are studied, and their effectiveness in damage identification of composite laminated beams is compared. Three dynamics-based damage detection algorithms are evaluated using the data acquired from these two measurement systems. The curvature mode shape is selected as a parameter to locate damage due to its sensitivity. The piezoelectric sensors directly acquire the curvature mode shapes of the structures, while the SLV measures the displacement ...
TL;DR: By using the proposed control method to trajectory tracking of the two-axis piezopositioning stage, the dynamic performance, robustness to parameter variations, and trajectory tracking error can be improved.
Abstract: In this paper, an integrator-backstepping-based dynamic surface control method for a two-axis piezoelectric micropositioning stage is proposed. First, according to the dynamics of motion of a mechanical mass-spring system, mathematical equations that contain a linear viscous friction, a varied elasticity with cross-coupling effect due to mechanical bending, and dynamics of a hysteresis variable is proposed to describe the motion dynamics of the two-axis piezopositioning stage. Next, from the equations, a state-space model in which the applied voltage to the stage is defined as an output of an integrator is derived. On the basis of this state-space model, the integrator-backstepping-based dynamic surface control is proposed. By using the proposed control method to trajectory tracking of the two-axis piezopositioning stage, the dynamic performance, robustness to parameter variations, and trajectory tracking error can be improved. Experimental results of the time responses from the computer-controlled two-axis piezopositioning stage illustrate the validity of the proposed control method for practical applications in trajectory tracking.
TL;DR: High-frequency ultrasound array transducers using piezoelectric thin films on larger structures are being developed for high-resolution imaging systems, with increase in resolution achieved by a simultaneous increase in operating frequency and close coupling of the electronic circuitry.
Abstract: High-frequency ultrasound array transducers using piezoelectric thin films on larger structures are being developed for high-resolution imaging systems. The increase in resolution is achieved by a simultaneous increase in operating frequency (30 MHz to about 1 GHz) and close coupling of the electronic circuitry. Two different processing methods were explored to fabricate array transducers. In one implementation, a xylophone bar transducer was prototyped, using thin film PbZr0.52Ti0.48O3 (PZT) as the active piezoelectric layer. In the other, the piezoelectric transducer was prepared by mist deposition of PZT films over electroplated Ni posts. Because the PZT films are excited through the film thickness, the drive voltages of these transducers are low, and close coupling of the electronic circuitry is possible. A complementary metal-oxide-semiconductor (CMOS) transceiver chip for a 16-element array was fabricated in 0.35-mum process technology. The ultrasound front-end chip contains beam-forming electronics, receiver circuitry, and analog-to-digital converters with 3-Kbyte on-chip buffer memory.