Transducer Layout Research Articles

Measured Regional Division Optimization for Acoustic Tomography Velocity Field Reconstruction in a Circular Area.

The acoustic tomography (AT) velocity field reconstruction technique has become a research hotspot in recent years due to its noninvasive nature, high accuracy, and real-time measurement advantages. However, most of the existing studies are limited to the reconstruction of the velocity field in a rectangular area, and there are very few studies on a circular area, mainly because the layout of acoustic transducers, selection of acoustic paths, and division of measured regions are more difficult in a circular area than in a rectangular area. Therefore, based on AT and using the reconstruction algorithm of the Markov function and singular value decomposition (MK-SVD), this paper proposes a measured regional division optimization algorithm for velocity field reconstruction in a circular area. First, an acoustic path distribution based on the multipath effect is designed to solve the problem of the limited emission angle of the acoustic transducer. On this basis, this paper proposes an adaptive optimization algorithm for measurement area division based on multiple sub-objectives. The steps are as follows: first, two optimization objectives, the condition number of coefficient matrix and the uniformity of acoustic path distribution, were designed. Then, the weights of each sub-objective are calculated using the coefficient of variation (CV). Finally, the measured regional division is optimized based on particle swarm optimization (PSO). The reconstruction effect of the algorithm and the anti-interference ability are verified through the reconstruction experiments of the model velocity field and the simulated velocity field.

A Lamb-wave based SHM for multi-damage localizations in large composite plates by using piezoelectric transducer array

In this paper, a Lamb-wave based structural health monitoring for multi-damage localizations in large composite plates is presented. The Lamb waves are generated and received by piezoelectric transducers, which are arranged in array on the composite plate. In the experiments, three composite plates with various laminate stacking sequences and taper designs were prepared. The damages were created on the specimens by impact testing. In each specimen, 24 piezoelectric transducers were utilized and mounted on the specimen surface. This study proposed an algorithm to identify the damage localizations. The transducer layout is classified by 10 subsets. In each subset, the wave propagation paths can be grouped into path groups pivoted by actuators and that by sensors. Based on the damage index, the mean angle line for each path group in a subset can be obtained. By assuming that the mean angle line passes through the actual damage, the damage localization can be achieved if there exist more than two mean angle lines in one subset. In this study, two exclusion rules are proposed to exclude a path group from the damage localization calculations. The damage localization results show that, for a composite plate with multiple damages, their locations can be identified by using multiple subsets. The damage localization results show that the damage location can be accurately predicted for the case that a damage exists in the interior of a subset. The experiment results also show that the Lamb wave characteristics and the localization results are not affected by the thickness variation of the plate, indicating that the proposed algorithm is available for tapered composite plate.

A Novel Airspace Planning Algorithm for Cooperative Target Localization

With the development of modern electromagnetic stealth technology and ARM, traditional active radar detection cannot accomplish its detection mission, limited by its ability. Relying on such superior advantages such as imperceptibility, anti-electromagnetic interference and electromagnetic stealth, passive transducers are playing an indispensable and significant role in situation awareness. While, in addition to different passive transducer localization modes and solutions of target’s location, the reasonable planning and optimal layout of passive transducers’ location are other major factors affecting the precision of localization. Planning an optimal airspace for passive transducers is the key problem to improve the monitoring efficiency. This paper proposes the optimal layout algorithm for the cooperative platform in the space based on the geometrical relationship of cooperative localization. For example, the principle of direction location in traditional methods is simple: only two passive sensors can work, but the location accuracy of long-distance targets is low. At the same time, TDOA (Time Difference Of Arrival) location has high accuracy and good stability, but it needs at least three passive sensors to work together, which requires the most resources. In this paper, a platform optimization layout algorithm based on direction and TDOA hybrid positioning is proposed. Compared with direction positioning, it improves the long-distance positioning accuracy, reduces the number of sensors required for TDOA positioning, and reduces the resource occupancy rate. However, the TDOA positioning data mixed with direction positioning data inevitably leads to the decline of overall accuracy. In order to solve these difficulties, the weighted least square method is used to optimize the accuracy. The simulation shows that, within the designated target airspace, the optimal action airspace can be generated automatically based on the platforms’ cooperation mode. If there is no resource limitation, the airspace planning based on TDOA positioning has the highest accuracy for the target. However, in practical application, considering the resource limitation, the hybrid positioning of direction and TDOA can also meet the requirements of high accuracy and high stability. The average error is reduced by more than 45% compared with direction positioning, and the airspace occupancy is reduced by more than 30% compared with TDOA positioning. The goal of minimizing the scope of platform airspace planning is realized.

Energy output of piezoelectric transducers and pavements under simulated traffic load

Piezoelectric technology introduced to pavement structures can transform the potential renewable mechanical energy in the road into electrical energy, and this provides new ideas for solving the energy supply problem of green and intelligent transportation. The purpose of this study is to quantify the energy output of piezoelectric transducers under vehicle load and thereafter estimate the daily energy output of piezoelectric pavements. The loading process and the energy output model of piezoelectric transducers are analyzed and established, respectively. Through numerical analysis, the energy output variation laws of these transducers are evaluated in three aspects: load, speed, and resistance. The energy output is estimated based on the daily traffic volume statistics. The layout of piezoelectric transducers on the piezoelectric pavement is designed, and the economic benefit of piezoelectric pavements is preliminarily analyzed. Results show that the larger loads and the faster speeds of vehicles, the larger the energy power. One piezoelectric transducer can output 0.058-J energy in a single 0.7-MPa loading. However, higher output power does not guarantee a higher energy output. The maximum energy output occurs at the optimal vehicle speed which is influenced by resistance, but the maximum energy output remains the same at different optimal speeds. By increasing the resistance, the energy output of piezoelectric transducers can reach the maximum at a low speed. Under the daily traffic volume, the energy output of a single piezoelectric transducer can reach 963.99 J, and the daily energy output of a 100-m piezoelectric pavement is approximately equal to the total battery power of 35 mobile phones. Clean energy harvesting in the pavement has broad prospects by using piezoelectric technology, but the energy output of road piezoelectric transducers still needs to be further improved.

Topology optimization of piezoelectric sensor and actuator layers for active vibration control

In this work, the layout of piezoelectric transducers is designed using the Topology Optimization Method (TOM). Starting with a finite element model and its modal reduction, a state-space model for a control scheme is built. With this model, two objective functions are formulated, i.e. the maximization of the trace of the controllability gramian matrix and the maximization of the trace of the observability gramian matrix. Each objective function simultaneously seeks an optimized distribution of piezoelectric material over an elastic structure. A SIMP material interpolation model, a spatial filter, and the Sequential Linear Programming (SLP) method with moving limits are used to solve the optimization problem. Moreover, a linear-quadratic-Gaussian controller (LQG) is implemented to verify the structural performance of a cantilever beam exposed to vibration. Finally, numerical results are shown for the transducers’ topologies and their control performance.

3D Layout of Interdigital Transducers for High Frequency Surface Acoustic Wave Devices

The development of mobile communication sets higher demands on high frequency surface acoustic wave (SAW) devices. The layout of interdigital transducers (IDT) in SAW devices is in plane and the traditional methods of improving frequency for SAW devices are the increase of acoustic velocity and the reduction of wavelength. However, these methods have a limit due to the limited acoustic velocity and the photolithography limit. This work proposes a new way for the development of high frequency SAW devices by redesigning the layout of IDT in three dimensions (3D). The set of IDTs is split into two layers, i.e. the ground electrodes on one layer and the signal electrodes on the other layer. This 3D layout of IDTs dramatically narrows the horizontal gap between two adjacent electrodes, which can significantly increase the frequency. The frequency and the electromechanical coupling factor (K 2 ) of the four structures of SAW devices with the 3D layout of IDTs were studied by the finite element method (FEM). The results show that the frequency can be doubled under the same critical resolution of lithography due to the shortening of wavelength, and the 3D layout of IDTs is available for SAW devices based on piezoelectric thin film or piezoelectric single crystal. This work develops a new alternative to increase the working frequency of SAW devices.

Multimodal atomic force microscopy with optimized higher eigenmode sensitivity using on-chip piezoelectric actuation and sensing

Atomic force microscope (AFM) cantilevers with integrated actuation and sensing provide several distinct advantages over conventional cantilever instrumentation. These include clean frequency responses, the possibility of down-scaling and parallelization to cantilever arrays as well as the absence of optical interference. While cantilever microfabrication technology has continuously advanced over the years, the overall design has remained largely unchanged; a passive rectangular shaped cantilever design has been adopted as the industry wide standard. In this article, we demonstrate multimode AFM imaging on higher eigenmodes as well as bimodal AFM imaging with cantilevers using fully integrated piezoelectric actuation and sensing. The cantilever design maximizes the higher eigenmode deflection sensitivity by optimizing the transducer layout according to the strain mode shape. Without the need for feedthrough cancellation, the read-out method achieves close to zero actuator/sensor feedthrough and the sensitivity is sufficient to resolve the cantilever Brownian motion.

Dynamic Response of Shallow-Buried Small Spacing Tunnel with Asymmetrical Pressure: Shaking Table Testing and Numerical Simulation

A series of shaking table tests were designed and carried out to study the seismic behaviors of a shallow-buried small spacing tunnel with asymmetrical pressure. The key details to shaking table model test, including test equipment, model similarity relation, similarity constant, model box, physical model, layout of transducers, seismic waves, and loading system were presented. The numerical simulation of the shaking table test was also carried out by using a finite element simulation software. The results show that: (1) the Fourier spectrums in the vertical direction and horizontal direction are different at the same measuring point. The structure of tunnel transforms the Fourier spectrum of horizontal direction. (2) The stability of middle rock pillar is poor under seismic wave action. The anchor plays an important role in strengthening the stability of middle rock pillar. The dynamic strain of anchor has accumulative effect. (3) The numerical simulation results are in significant agreement with the shaking table test results. (4) Compared with type of seismic wave, peak seismic wave has a significant effect on acceleration response of tunnel. The peak acceleration response of the tunnel is linear with the peak seismic wave, in the horizontal direction. The peak acceleration response is nonlinear in the vertical direction. (5) The axial force of cross section at arch foot is larger than other position. The shock absorption effect of 10 cm seismic isolation layer is better than 5 and 20 cm.

Multimodal cantilevers with novel piezoelectric layer topology for sensitivity enhancement.

Self-sensing techniques for atomic force microscope (AFM) cantilevers have several advantageous characteristics compared to the optical beam deflection method. The possibility of down scaling, parallelization of cantilever arrays and the absence of optical interference associated imaging artifacts have led to an increased research interest in these methods. However, for multifrequency AFM, the optimization of the transducer layout on the cantilever for higher order modes has not been addressed. To fully utilize an integrated piezoelectric transducer, this work alters the layout of the piezoelectric layer to maximize both the deflection of the cantilever and measured piezoelectric charge response for a given mode with respect to the spatial distribution of the strain. On a prototype cantilever design, significant increases in actuator and sensor sensitivities were achieved for the first four modes without any substantial increase in sensor noise. The transduction mechanism is specifically targeted at multifrequency AFM and has the potential to provide higher resolution imaging on higher order modes.

Research on the High-Power Directional Acoustic Transducer

Through studying how to affect acoustic directivity with MATLAB software, it show that selection of a relatively larger surface of the transducer and a relatively closer transducer interval will be more preferable for directivity. While an array which possess more array element number and whose frequency of the drive signal can be as large as possible in a range, directivity will be more preferable. On the other hand, when the structure of the sound radiating surface of the transducer or array layout is symmetrical, the corresponding directivity pattern will be symmetrical. At a frequency of 10kHz, the individual rare earth magnetostrictive transducers its first point of the simulation carried out before the test. Sounding board with aluminum by the method used to improve the sound source diameter. With the sound plate diameter incrementing, the smaller the angle of the directivity. The beam width of the 3×3 array is about at 23kHz, and the directivity acute angle is about 10°, with a sounding board by the method used to improve their the diameter of the sound source, so as to realize the sound has directivity is feasible.

Two Methods to Test Transducer Array Directivity

An array which possess more array element number and whose frequency of the drive signal can be as large as possible in a range, directivity will be more preferable. On the other hand, when the structure of the sound radiating surface of the transducer or array layout is symmetrical, the corresponding directivity pattern will be symmetrical. In order to test transducer directivity, two methods are designed. The one is to measure the ultrasonic sound pressure level by instruments. The sound pressure level is measured at multiple points to deduce the directivity angle of the acoustic transducer array. The beam width of the 3×3 array is about at 23kHz, and the directivity acute angle is about 10°; higher frequencies will lead to the side lobes, but it can be negligible when compared to the main lobe. The other method is using the frequency analyzer to test transducer directivity in a silencer chamber. The sound pressure level can be read out from frequency response diagrams. The angle between the sound pressure value that decreasing 3db from the max value 111.7db and the max value is about 11°. So the directivity acute angle is about 11°. It should be noticed that, as the directivity diagram can not be directly attributed, there is some deviation in the conclusion.

Layout optimization methodology of piezoelectric transducers in energy-recycling semi-active vibration control systems

Abstract An optimization methodology is proposed for the piezoelectric transducer (PZT) layout of an energy-recycling semi-active vibration control (ERSAVC) system for a space structure composed of trusses. Based on numerical optimization techniques, we intend to generate optimal location of PZTs under the constraint for the total length of PZTs. The design variables are set as the length of the PZT on each truss based on the concept of the ground structure approach. The transient problems of the mechanical and electrical vibrations based on the ERSAVC theory are considered as the equations of state. The objective is to minimize the integration of the square of all displacement over the whole analysis time domain. The sensitivity of the objective function is derived based on the adjoint variable method. Based on these formulations, an optimization algorithm is constructed using the fourth-order Runge–Kutta method and the method of moving asymptotes. Numerical examples are provided to illustrate the validity and utility of the proposed methodology. Using the proposed methodology, the optimal location of PZTs for the vibration suppression for multi-modal vibration is studied, which can be benchmark results of further study in the context of ERSAVC systems.

Experimental Behavior of One-Way Concrete Slabs at Large Displacements

This paper presents the tensile membrane action on one-way reinforced concrete slabs, and two full-scale specimens with one edge clamped and one edge simply supported were tested at large displacements. The details of the two tests including support conditions, arrangement of reinforcements and layout of displacement transducers are described. The test results show that the load-carrying capacity of the two slabs is significantly improved due to the tensile membrane action, about 26.6% more than the predicted value using the well-established yield-line theory. Until maximum vertical displacement reached 1/15 of the span-length, the slab did not fail and carried the load steadily.

Use of Interwire Ultrasonic Leakage to Quantify Loss of Prestress in Multiwire Tendons

This paper presents a technique developed on the basis of ultrasonic guided waves to monitor prestress levels in multiwire prestressing strands. The transducer layout identified for stress measurement is composed of an ultrasound excitation provided by a piezoelectric element bonded on a peripheral wire. Ultrasound detection is performed on the central and peripheral wires at the strand’s end. The ultrasonic feature used for stress monitoring is the interwire leakage between the peripheral and the central wire, occurring across the strand anchorage. A semianalytical finite-element analysis is first used to predict modal and forced wave solutions in seven-wire strands as a function of the applied prestress level. The numerical analysis accounts for the changing interwire contact as a function of applied loads and predicts the attenuation occurring in loaded strand when the wave travels across the anchorage. Results of load monitoring in free strands during laboratory tests are then presented. Finally, a st...

New ideas for a transducer layout in a spherical GW antenna

We discuss a general procedure to find the coupled motion of a set of resonant transducers attached to a spherical GW detector, and present some preliminary results. A new specific proposal for a polyhedric, quasispherical antenna is also presented.

Vectorial measurement of blood velocity by means of ultrasound.

The complete determination of blood velocity as a vector can be achieved using ultrasound techniques, by correlating the echo signals provided by a sector transducer. Here the general problem is approached by suggesting the processing procedure which should be adopted, so that longitudinal and transverse velocity components can be separated. After this a specific transducer layout is considered, which is suitable for in-plane measurements, and possible performances are evaluated by means of simulation. Finally, an experimental facility, set up to demonstrate the validity of the theoretical lines developed in two-dimensional geometry, is described, together with the preliminary results obtained.

Electromagnetic leakage suppression by interdigital transducers

A simple interdigital transducer layout is used in conjunction with a differential amplifier to obtain a high degree of suppression of direct electromagnetic leakages in surface acoustic wave devices. The degree of suppression can be adjusted independently of the device design.