Behavior Of Transducer Research Articles

Wire bonding dynamics monitoring by wavelet analysis

Aluminum wire bonding was performed on a lab test-bed with PZT transducer device. Vibration behavior of bonder transducer was monitored, and the correlations between bonding pressure, high frequency tool vibrations, and average bond strength were then demonstrated to determine the statistically significant differences among them. Wavelet decomposing, combined with statistics-based data processing, was utilized to explore the details of bonding process and evade inherent bonding uncertainties. Experimental results show that the method is practical and effective even if the interactions between transducer and its bonding target are very small. The obtained time-frequency plots were depicted for identifying un-modeled wire bonding dynamics.

Construction and Experimental Implementation of a Model-Based Inverse Filter to Attenuate Hysteresis in Ferroelectric Transducers

Hysteresis and constitutive nonlinearities are inherent properties of ferroelectric transducer materials due to the noncentrosymmetric nature of the compounds. In certain regimes, these effects can be mitigated through restricted input fields, charge- or current-controlled amplifiers, or feedback designs. For general operating conditions, however, these properties must be accommodated in models, transducer designs, and model-based control algorithms to achieve the novel capabilities provided by the compounds. In this paper, we illustrate the construction of inverse filters, based on homogenized energy models, which can be used to approximately linearize the piezoceramic transducer behavior for linear design and control implementation. Attributes of the inverse filters are illustrated through numerical examples and experimental open loop control implementation for an atomic force microscope stage

Piezoelectric transducer design via multiobjective optimization

The design of piezoelectric transducers is usually based on single-objective optimization only. In most practical applications of piezoelectric transducers, however, there exist multiple design objectives that often are contradictory to each other by their very nature. It is impossible to find a solution at which each objective function gets its optimal value simultaneously. Our design approach is to first find a set of Pareto-optimal solutions, which can be considered to be best compromises among multiple design objectives. Among these Pareto-optimal solutions, the designer can then select the one solution which he considers to be the best one. In this paper we investigate the optimal design of a Langevin transducer. The design problem is formulated mathematically as a constrained multiobjective optimization problem. The maximum vibration amplitude and the minimum electrical input power are considered as optimization objectives. Design variables involve continuous variables (dimensions of the transducer) and discrete variables (the number of piezoelectric rings and material types). In order to formulate the optimization problem, the behavior of piezoelectric transducers is modeled using the transfer matrix method based on analytical models. Multiobjective evolutionary algorithms are applied in the optimization process and a set of Pareto-optimal designs is calculated. The optimized results are analyzed and the preferred design is determined.

Investigation of electrical transient behavior of an ultrasonic transducer under impulsive mechanical excitation

This paper investigates the electrical transient responses of a bolt-clamped ultrasonic transducer (BLT) subjected to an impulsive mechanical excitation under various load conditions. The theoretical analysis obtained with a second-order model of the BLT is checked experimentally. The responses include open-circuit voltages and short-circuit currents. These responses occur at open- or short-circuited terminals of the BLT immediately after impulsive forces excite the BLT. The study of the responses is focused on maximum strengths, time constants and energy losses. Equations of the responses and the energy losses are first obtained from a second-order model of a linear system, including the BLT and an oscilloscope. Then, a driving and measuring system is constructed to generate the forces and record the responses. Moreover, effects of the forces on the responses and the energy losses are measured. Finally, applying the impulse responses to estimate the model parameters of the BLT is discussed.

Behavior of Piezoelectric Transducer on Energy-Recycling Semiactive Vibration Suppression

Behavior of Piezoelectric Transducer on Energy-Recycling Semiactive Vibration Suppression

Behavior of a Self-Sustained Electromechanical Transducer and Routes to Chaos

This paper studies the dynamics of a self-sustained electromechanical transducer. The stability of fixed points in the linear response is examined. Their local bifurcations are investigated and different types of bifurcation likely to occur are found. Conditions for the occurrence of Hopf bifurcations are derived. Harmonic oscillatory solutions are obtained in both nonresonant and resonant cases. Their stability is analyzed in the resonant case. Various bifurcation diagrams associated to the largest one-dimensional (1-D) numerical Lyapunov exponent are obtained, and it is found that chaos can appear suddenly, through period doubling, period adding, or torus breakdown. The extreme sensitivity of the electromechanical system to both initial conditions and tiny variations of the coupling coefficients is also outlined. The experimental study of̱the electromechanical system is carried out. An appropriate electronic circuit (analog simulator) is proposed for the investigation of the dynamical behavior of the electromechanical system. Correspondences are established between the coefficients of the electromechanical system model and the components of the electronic circuit. Harmonic oscillatory solutions and phase portraits are obtained experimentally. One of the most important contributions of this work is to provide a set of reliable analytical expressions (formulas) describing the electromechanical system behavior. These formulas are of great importance for design engineers as they can be used to predict the states of the electromechanical systems and respectively to avoid their destruction. The reliability of the analytical formulas is demonstrated by the very good agreement with the results obtained by both the numeric and the experimental analysis.

Steady-state 1D electrothermal modeling of an electrothermal transducer

Electrothermal models that describe the steady-state electrothermal behavior of a general electrothermal transducer have been developed using the one-dimensional heat transport equation. Compared to previously reported electrothermal transducer models, these models produce simpler equations for the temperature change versus an electrical input. Models of the transducer temperature distribution are derived using various thermal conditions such as surface convection and temperature-dependent electrical resistivity. The models are made for a general electrothermal transducer by assuming that the transducer is attached to arbitrary thermal resistances at its boundaries. Critical thermal parameters of the transducer—such as the position of maximum temperature, maximum temperature change and average temperature change—are derived from the models. It is shown that the average temperature change versus applied power and voltage relationships of the simpler models always agree with the more accurate model within factors of 12/π2 and respectively. It is also shown that the temperature change of an electrothermal transducer is approximately linear with respect to applied voltage when actuated in a certain voltage range. The models are compared to FEM simulations and experimental results of an electrothermal micromirror.

Extended Frequency Bandwidth and Electrical Resonance Tuning in Hybrid Terfenol-D/PMN-PT Transducers in Mechanical Series Configuration

This article addresses the modeling and characterization of hybrid transducers incorporating both ferroelectric and ferromagnetic elements. The complementary electrical and mechanical properties of the two classes of materials can yield transducers with higher performance or enhanced functionality relative to single-element devices. As a template for studying the properties of hybrid architectures, a transducer is considered which consists of a mechanical series arrangement of a PMN-PT stack and a Terfenol-D rod. This configuration exhibits a double resonant frequency response that can be tuned for a variety of applications. We are specifically interested in the development of models and design criteria for achieving broadband electromechanical transduction over the range from 500 Hz to over 6 kHz. To that end, a model is presented which is constructed from three classical, widely available theories: (i) linear mechanical vibrations, (ii) classical electroacoustics, and (iii) linear piezoelectricity and piezomagnetism. Despite the general limitations of linear models when applied to nonlinear materials, the linear formulation is justified in this article by the consideration of biased, low signal regimes in which transducer behavior is quasilinear. The model is applicable to the design and control of high-performance devices, while being mathematically tractable and accurate over the regimes considered. The model also provides a framework which permits extraction of material property information from dynamic impedance measurements – as opposed to quasistatic measurements – that is under conditions similar to those found in transducer operation. The study also shows that it is possible to tune the electrical resonance frequency without fundamentally altering the transducer bandwidth. This result has practical implications in that it allows matching of the transducer response to individual drivers. This could allow for retrofit of an existing hybrid device with a newer, more advanced ferroelectric stack without compromising the device bandwidth.

Microelectronics mounted on a piezoelectric transducer: Method, simulations, and measurements

This paper describes the design of a highly integrated ultrasound sensor where the piezoelectric ceramic transducer is used as the carrier for the driver electronics. Intended as one part in a complete portable, battery operated ultrasound sensor system, focus has been to achieve small size and low power consumption. An optimized ASIC driver stage is mounted directly on the piezoelectric transducer and connected using wire bond technology. The absence of wiring between driver and transducer provides excellent pulse control possibilities and eliminates the need for broad band matching networks. Estimates of the sensor power consumption are made based on the capacitive behavior of the piezoelectric transducer. System behavior and power consumption are simulated using SPICE models of the ultrasound transducer together with transistor level modelling of the driver stage. Measurements and simulations are presented of system power consumption and echo energy in a pulse echo setup. It is shown that the power consumption varies with the excitation pulse width, which also affects the received ultrasound energy in a pulse echo setup. The measured power consumption for a 16 mm diameter 4.4 MHz piezoelectric transducer varies between 95 μW and 130 μW at a repetition frequency of 1 kHz. As a lower repetition frequency gives a linearly lower power consumption, very long battery operating times can be achieved. The measured results come very close to simulations as well as estimated ideal minimum power consumption.

Response evaluation of TiO 2 sensor to flue gas on spark ignition engine and in controlled environment

Increasingly strict emissions regulations and heightened environmental awareness on the part of users around the world have led to energetic research into emissions reduction by various automobile manufacturers and research institutes. In this paper we tested sol–gel TiO 2 sensor in order to evaluate the reliability and combustion sensor properties in controlled environment and on spark ignition engine. Experiments were carried out for understanding influence of single gas component of flue gas on the response of TiO 2 sensor and evaluate transducer behaviour on real spark ignition engine. Higher responses were obtained for oxygen and nitrogen oxide, rather than CO 2 and CH 4. So TiO 2 sensor was more sensitive towards the first components of mixture, and good response times were observed on engine bench.

A fast compensation algorithm for real-time control of magnetostrictive actuators

Applications of magnetostrictive materials in smart devices spread from micro-positioning to active compensation of mechanical vibrations. In non-static conditions, several dynamic phenomena affects the transducer's behavior. Therefore, the design of the control system requires accurate modelling of either the static magneto-elastic constitutive relationship and rate-dependent behavior. Also when dynamic effects are not negligible, compensation of rate-independent (hysteresis) phenomena plays a key role when real-time control task are of concern. In the paper a new approach to hysteresis compensation is described. The basic properties, either in terms of accuracy and computational efficiency, are analyzed and compared to other approaches.

Intraluminal ultrasound intensity distribution and backscattered Doppler power

Ultrasound (US) incident obliquely on a cylindrical vessel is redistributed in space when the propagation path includes walls with acoustic impedance different from that of the surrounding media. We investigated this using low-density polyethylene (PE) as the vessel wall material. Both simulations and experiments were carried out. Direct hydrophone measurements of the acoustic field were made within a half section of the PE tube, and the distribution of backscattered Doppler power along a scan line was obtained using a range-Doppler instrument. Both simulation and hydrophone results demonstrate lateral shadow regions within the lumen. In every one of various Doppler flow experiments conducted, the backscattered Doppler power, compensated for on-axis transducer behaviour, increased with depth. Simulation results for an incident continuous-wave (CW) plane wave show that it tends to be focused by the curvature of the PE tube walls. The wall interactions are, however, angle-dependent and so the behaviour of a focused US beam depends on the beam as well as the walls. This study demonstrates alterations in the spatial distribution of US within a cylindrical vessel as a result of known vessel wall properties. It also provides evidence that local intensity variations within the lumen affect the relative Doppler power backscattered from small sample volumes. (E-mail: roset@maths.usyd.edu.au)

Characterization of matched piezoelectric transducer bars

To aid the design of linear arrays, it is quite important to have a detailed understanding of the elementary transducer behavior. These transducer bars must be backed and matched. The aim of this work is to characterize and to optimize layers that are used to match such transducer bars. In order to show the influence of these layers, the acoustical (acoustical power, far-field directivity pattern), electrical (electrical impedance) and mechanical (displacement field) parameters of the transducer are computed using the finite element method. Numerical studies of several transducers with different ideal matching layers which satisfy the one-dimensional criterion are presented and carefully analyzed. These studies show the existence of parasitic modes in the desired operating band of the transducer, due to shear wave propagation in the matching layer. A simple choice criterion of the matching material suggesting no parasitic mode in the desired operating band of the transducer bar has been defined. This criterion is given by W<λS/2, where W is the width of the transducer and λS is the shear wavelength of the matching layer at the working frequency. Finally, experimental results of a matched transducer bar are successfully compared with numerical ones.

Laser-scanning vibrometry for ultrasonic transducer development

Abstract A laser-scanning vibrometer can be used for measuring even the smallest motions of the active area of ultrasonic transducers. Additionally, a new method for measuring and visualising the acoustic sound waves, emitted from such transducers, is developed. The new method, too, is based on laser-scanning vibrometry and allows the contact-less measurement of ultrasound fields with high spatial resolution. The combination of both techniques permits to analyse and optimise the acoustic behaviour of ultrasonic transducers. Moreover, the method is qualified for investigating and presenting numerous acoustic phenomena.

MEMS Devices and Applications in Aerospace and Civil Engineering

J ‘‘Examination of Bulge Test for Determining Residual Stress, Young’s Modulus, and Poisson’s Ratio of 3C-SiC Thin Films,’’ describe their study of a test that is based on plate mechanics, and illustrate its capabilities within their work on silicon carbide fabrication. Another important topic within MEMS ~and its nanoscale counterpart, NEMS! research is biochemical sensing, for which dissolvable hydrogels can serve as indicators. Aluru and his colleagues from the University of Illinois, in a paper entitled ‘‘Mathematical Modeling and Simulation of Dissolvable Hydrogels,’’ present a mathematical model for hydrogel behavior with comparisons between model and experimental results. Three papers are contributed by researchers in the MEMS community describing the development of devices that can revolutionize aerospace and civil engineering practice. My colleagues from Carnegie Mellon, Xie ~now at the University of Florida! and Fedder, report on the development of vibratory gyroscopes in a paper entitled ‘‘Integrated MEMS Gyroscopes.’’ In a paper entitled ‘‘Capacitive Micromachined Ultrasonic Transducers: Theory and Technology,’’ Khuri-Yakub and his coworkers from Stanford give the reader comprehensive insight into the design, behavior, and performance of ultrasonic transducers. Liu and his coworkers, from the University of Illinois, contribute a paper entitled ‘‘Two-Dimensional Micromachined Flow-Sensor Array for Fluid Mechanics Studies’’ in which they describe the development of two novel sensors for use in fluid mechanics; they start with the physical concepts, show the development of the MEMS process and the device design, and then illustrate the results with experimental studies. I wish to thank the authors of these papers, as well as others who responded with interest and whose papers may appear in future issues of this Journal. The ideas they describe are stimulating, their research practices are exemplary, and their writing is excellent. They set a high standard and we are the beneficiaries. Irving J. Oppenheim Carnegie Mellon University

Chemical Gas Sensors Based on Organic Semiconductor Polypyrrole

Polypyrrole (PPy) is one of the most studied conducting polymers. It is well known that the mechanical, physical, and chemical properties of PPy strongly depend on the nature of the dopant anion. In this context, on overwiev of the influence of small anions and metallomacrocycles, for example, metallophthalocy anines (MPcTS), on the chemical transducer behavior of the doped PPy layer studied by the Kelvin Probe method is given. The gas-polymer interaction changes the work function of the polymer, which can be explained by a secondary doping of the polymer by the adsorbed gas molecule. Studies have revealed that the central metal ion in MPcTS plays an important role in the chemical sensing properties toward NO2, chlorinated hydrocarbons, and organophosphorous compounds in the low ppm concentration range. Furthermore, the competitive doping method of PPy with a mixture of small anions and MPcTS strongly enhances the selectivity and reduces the response time of the conducting polymer, which are general problems in the use of conducting organic polymers for gas and vapor detection.Chemical sensitive PPy layers have been used to build chemical sensors in which the organic semiconductor works both as the active component in the electronic device structure and as the chemical sensing transducer element, for example, polymer field-effect transistors, PPy/Au-Schottky, and PPy/Si-heterojunction diodes. The junction parameters of the polymer-based diodes, as the ideality and the rectification factor, are strongly influenced by the dopant of the conducting polymer. In both forward bias and reverse bias, these junctions exhibit a significant, fast, and reversible response to NO2 gas, which can be explained by changes in the barrier height and in the charge carrier concentration of the PPy layer due to NO2 interaction.

Finite element three-dimensional analysis of the vibrational behaviour of the Langevin-type transducer

The vibrational behaviour of the Langevin transducer is usually analysed using 1D Mason model which is valid when the lateral dimensions of the transducer are smaller than a quarter wavelength at the fundamental longitudinal resonance. In this work a 3D finite element analysis of the Langevin transducer's behaviour operating in the underwater sonar range of frequencies (30–140 kHz) is presented. Several samples with total length greater, comparable to, and smaller than the diameter of the transducer are analysed. For each sample, the resonance frequencies in the observed frequency range are computed and compared with those obtained experimentally from the measurements carried out using several in-house built prototypes. For the most important aspect ratios the resonance displacement distributions are presented and discussed. The results obtained permit to gain insight into the coupling phenomenon between thickness-extensional and radial modes and suggest that in practical applications transducers with diameters comparable to or greater than total length of the active stack can also be used. The trade-off between the efficiency and power handling ability for different designs is also discussed.

Analysis of flexural waves excited by rectangular contact type transducers

In this paper, an attempt was made to investigate a fundamental problem related to the flexural waves excited by rectangular transducers. Due to the disadvantages of the Green's function approach for solving this problem, a direct and effective method is proposed using a multiple integral transform method and contour integration technique. The explicit frequency domain solutions obtained from this newly developed method are convenient for understanding transducer behavior and theoretical optimization and experimental calibration of rectangular transducers. The time domain solutions can then be easily obtained by using the fast Fourier transform technique.

The contact geometry in a 2D μc-Si:H p-i-n imager

A two-dimensional imager has been designed and produced based on μc-Si:H material. The basic building block for the sensor element is a TCO/μc-p-i-n Si:H photodiode with two front metal contacts and a back TCO transparent one. A scan-out process obtains the image. The effect of the contact geometry on the sensor output characteristics (linearity, distortion, sensitivity and signal-to-noise ratio) were studied by systematic variation of the metal contact pattern (rectangular, L-like). The highest sensitivity has been achieved with L-like contacts. The differential responsivity shows a 10% linearity increase and a 30% image distortion decrease when the contact shape changes from rectangular to L-like. By using L-like front contacts a full 2D imaging has been achieved with a dynamic range of about 32 dB and a signal-to-noise ratio of about 37 dB without significant image distortion. A basic model that takes into account the physics of the sensor element and the transducer behaviour is presented. Simulation results are analysed and compared with the experimental data. Basic image processing algorithms will be developed for image enhancement (contrast, edge, noise filtering, sharpening) and restoration (deblurring, geometric distortion, non-linearity).

Airborne ultrasonic electrostatic transducers with conductive grooved backplates: tailoring their centre frequency, sensitivity and bandwidth

Several electrostatic transducers with metallic backplates have been manufactured. Some backplates have been subjected to coarse polishing, whereas others were first polished and then rectangular grooves were machined. Experimental investigations have been performed in order to study the influence of the groove widths, their layout and the value of DC bias on the transducer behaviour. These results are compared with theoretical predictions using the Helmholtz resonator model. The equation of the vibration of a membrane submitted to a mechanical stress, but neglecting the effects of its elasticity, was also compared with experimental results. This shows that the Helmholtz resonator model is adapted to the behaviour of the polished backplates, whereas the membrane model explains the vibration over the grooves. By choosing the groove widths and layout (i.e. polished- to grooved-surface ratio), the centre frequency, the bandwidth and the sensitivity of the transducer can be optimised for a given application.