Piezoelectric Ceramic Transducers Research Articles

Research on the Characteristics of High-Performance Textured Ceramic Materials and Their Application in Composite Rod Transducers

Recently, textured piezoelectric ceramics have become a hot topic in the field of piezoelectric materials. Due to their high cost-effectiveness, textured ceramics are expected to be the material of choice for the next generation of acoustic transducers. In this study, we investigated the coercive field (Ec), piezoelectric constant (d33), and dielectric constant (ε33) of textured PIN-PSN-PT ceramics under different torques, in response to the demand for the development of composite rod transducer technology for transmitting and receiving. Based on the obtained data, a wideband composite rod transducer was designed and fabricated using textured PIN-PSN-PT ceramics with high performance. Compared with conventional PZT piezoelectric ceramic transducers of the same size, the wideband composite rod transducer made with textured ceramics extends the frequency band to a lower frequency of 6.5 kHz, improves the emission performance by 2 dB, and enhances the reception performance by 2 dB. Compared with conventional PZT piezoelectric ceramics in the same frequency band, the acoustic performance is comparable, but there is a volume reduction of 59.23% and a weight reduction of 49.7%, solving the technical bottleneck of developing composite rod transducers that are miniaturized and lightweight. The research results of this study have important reference value for the engineering application of textured ceramic materials in acoustic transducers.

Multi-frequency instantaneous wavenumber damage imaging method based on ultrasonic guided waves induced by laser point-by-point excitation

ABSTRACT A multi-frequency instantaneous wavenumber damage imaging method based on ultrasonic guided waves induced by laser point-by-point excitation is proposed in this paper. The experiment involved using the Nd:YAG pulsed laser is used as the excitation source to excite ultrasonic guided waves point-by-point in the detection area, and the piezoelectric ceramic transducer is used to receive ultrasonic guided wavefield at a fixed position. The wavefield information at different frequencies is extracted by a three-dimensional Fourier transform. The spatial phase distribution of the extracted guided wavefield with different frequencies is obtained by the Hilbert transform and phase unwrapping method. Then, the wavenumber of each detection point and the dispersion relations of the test piece with different thicknesses are calculated. Based on the calculated dispersion relation, the mapping relationship between the wavenumber and the thickness of the test piece is obtained. Furthermore, based on the obtained wavenumber information and wavenumber thickness mapping relationship, the thickness reduction depth of the defect can be calculated. Finally, the quantitative detection of defects is achieved through data fusion. The proposed method is verified through quantitative detection of the rectangular groove defects and the flat bottom defects with variable thickness and complex contour in the aluminium plate. At the same time, the detection results of the proposed method are compared with those of the single-frequency instantaneous wavenumber imaging method, single-frequency local wavenumber imaging method, and multi-frequency local wavenumber imaging method. In the detection results, the method proposed in this paper presents a better defect detection effect.

Analysis of electromechanical equivalent circuit model for the functionally graded tubular piezoelectric transducer

Abstract In this paper, a functionally graded tubular piezoelectric transducer (FG-tPET) is proposed. Based on the constitutive equation and wave equation, the electromechanical equivalent circuit model (EECM) of FG-tPET is obtained. When the non-uniformity coefficient tends to zero, the EECM can be simplified as the EECM of the traditional single-tube piezoelectric ceramic transducer. The correctness of the theoretical model is verified in comparison with the experimental results in the literature. Based on the theoretical model, the influence of the geometric size and the non-uniform coefficient of the transducer on the resonance/anti-resonance frequency is analyzed. The results show that the geometric size and the non-uniform coefficient can realize the coordinated adjustment of the resonance/anti-resonance frequency.

Conformable Shear Mode Transducers from Lead‐Free Piezoelectric Ceramic Coatings: An Innovative Ultrasonic Solution for Submerged Structural Health Monitoring

AbstractShear mode‐guided ultrasonic waves are highly regarded for submerged or subterranean structural health monitoring (SHM), owing to their non‐dispersive feature and minimized acoustic energy loss when in contact with liquid or solid. High‐performance shear mode ceramic ultrasonic transducers with robustness and cost‐effectiveness are highly demanded for underwater or underground SHM applications, especially in harsh environments. However, the implementation of discrete shear mode piezoelectric ceramic ultrasonic transducers is hindered by the inconsistency with manual installation, lack of conformability on curved surfaces, and unreliable acoustic coupling between the transducers and the structure. Here, direct‐write conformable shear mode ultrasonic transducers made from piezoelectric lead‐free ceramic coatings, which are in situ produced on steel structures by a scalable thermal spray process, are proposed. The obtained lead‐free lithium‐doped potassium sodium niobate (KNN‐LN) ceramic coatings exhibit a high effective shear piezoelectric strain coefficient (d24, f) above 60 pm V−1 in a broad frequency range from 100 Hz to 200 kHz. The resulting conformable shear mode KNN‐LN ceramic coating transducers successfully showcase the functions of exciting and detecting stable shear mode ultrasonic wave signals with operation temperature exceeding 200 °C and demonstrate reliable capability in defect detection in both air and liquid environments.

Empirical models for the error induced in piezoelectric ceramic transducer-based acoustic ranging instrumentation and measurement

This article presents experimental methods and analytics for developing statistical models for ultrasonic sensors to improve reliability, repeatability, and signal-to-noise ratio (SNR) in static environments. The experiments use commercial piezoelectric ceramic transducers and over 4100 calibrated readings for three specimens of different materials. Using commercial piezoelectric ceramic transducers, the spatial-temporal approach considers range, environmental factors, material characteristics, and their interactions. A true value approach is used to formulate the error as a function of the distance measured in the time-of-flight (ToF) method at zero azimuth angular directivity. The three statistical models, linear temperature, averaged linear regression, and averaged cubic regression models, are formulated and validated. The most influential parameters in the calibrating distance with an acoustic sensor are the range, coupled effect of temperature, and material characteristics, followed by temperature. The linear model increases the SNR within 0–40 cm from ±20 dB to ≈80 dB, and the cubic model increases the repeatability of the measurement by reducing the absolute error for the entire range of sensors from ±3 cm to less than −1 cm.

Wavefront Reconstruction Using Two-Frame Random Interferometry Based on Swin-Unet

Due to its high precision, phase-shifting interferometry (PSI) is a commonly used optical component detection method in interferometers. However, traditional PSI, which is susceptible to environmental factors, is costly, with piezoelectric ceramic transducer (PZT) being a major contributor to the high cost of interferometers. In contrast, two-frame random interferometry does not require precise multiple phase shifts, which only needs one random phase shift, reducing control costs and time requirements, as well as mitigating the impact of environmental factors (mechanical vibrations and air turbulence) when acquiring multiple interferograms. A novel method for wavefront reconstruction using two-frame random interferometry based on Swin-Unet is proposed. Besides, improvements have been made on the basis of the established algorithm to develop a new wavefront reconstruction method named Phase U-Net plus (PUN+). According to training the Swin-Unet and PUN+ with a large amount of simulated data generated by physical models, both of the methods accurately compute the wrapped phase from two frames of interferograms with an unknown phase step (except for multiples of π). The superior performance of both methods is effectively showcased by reconstructing phases from both simulated and real interferograms, in comprehensive comparisons with several classical algorithms. The proposed Swin-Unet outperforms PUN+ in reconstructing the wrapped phase and unwrapped phase.

Response Analysis of a Piezoelectric Ceramic Transducer Pair Excited by Phase-Modulated Signals for Improved Echo Measurement

Response Analysis of a Piezoelectric Ceramic Transducer Pair Excited by Phase-Modulated Signals for Improved Echo Measurement

Designing an Automatic Frequency Stabilization System for an External Cavity Diode Laser Using a Data Acquisition Card in the LabVIEW Platform

The frequency stability of free-running lasers is susceptible to the influence of environmental factors, which cannot meet the long-term frequency stabilization requirements for atom interferometry precision measurements. To obtain a frequency-stabilized 780 nm laser beam, an automatic frequency stabilization system for an external cavity diode laser (ECDL) based on rubidium (Rb) atomic saturated absorption spectrum was designed using a commercial data acquisition (DAQ) card. The signals acquired by the A/D terminal are processed and analyzed by LabVIEW, which can automatically identify all the locking points and output the piezoelectric ceramic transducer (PZT) scan and digital feedback through the D/A terminal. The experimental results show that the system can lock to six different frequencies separately and realize automatic relocking within 3.5 s after unlocking. The system has a stability of 1.68 × 10−10@1 s and 4.77 × 10−12@1000 s, which meets the laboratory’s requirements for atomic interference experiments.

A Gas Flow Measurement System Based on Lead Zirconate Titanate Piezoelectric Micromachined Ultrasonic Transducer.

Ultrasonic flowmeter is one of the most widely used devices in flow measurement. Traditional bulk piezoelectric ceramic transducers restrict their application to small pipe diameters. In this paper, we propose an ultrasonic gas flowmeter based on a PZT piezoelectric micromachined ultrasonic transducer (PMUT) array. Two PMUT arrays with a resonant frequency of 125 kHz are used as the sensitive elements of the ultrasonic gas flowmeter to realize alternate transmission and reception of ultrasonic signals. The sensor contains 5 × 5 circular elements with a size of 3.7 × 3.7 mm2. An FPGA with a resolution of ns is used to process the received signal, and a flow system with overlapping acoustic paths and flow paths is designed. Compared with traditional measurement methods, the sensitivity is greatly improved. The flow system achieves high-precision measurement of gas flow in a 20 mm pipe diameter. The flow measurement range is 0.5-7 m/s and the relative error of correction is within 4%.

Research on low-frequency bender disk transducer driven by multiple relaxor ferroelectric single crystal disks

In this paper, we investigate the low-frequency bender disk transducer designed by the relaxor ferroelectric single crystal. First, we introduce the principle of the bender disk transducer, and use multiple single crystal disks as driving materials to excite the bending vibration mode of the metal plate, which reduces the operating frequency of the transducer. Then we establish the three-dimensional finite element model of the bender disk transducer driven by multiple single crystal disks, analyze the influence of the number and position distribution of single crystal disks on the transducer performance, and compare with that of the piezoelectric ceramic transducer with the same structure. Finally, we manufacture the proposed relaxor ferroelectric single crystal, piezoelectric ceramic transducers and the conventional piezoelectric ceramic bender disk transducer respectively, and carry out the experimental measurement in an anechoic water tank. The experimental results show that for the proposed single crystal transducer, its measured maximum transmitting voltage response (TVR) is 126.2 dB at 1.1 kHz, which is 13.4 dB higher than that of the proposed piezoelectric ceramic transducer, and its frequency corresponding to the maximum TVR is reduced by 700 Hz compared with the conventional piezoelectric ceramic bender disk transducer.

Design of a Wearable Real-Time Hand Motion Tracking System Using an Array of Soft Polymer Acoustic Waveguides.

Robust hand motion tracking holds promise for improved human-machine interaction in diverse fields, including virtual reality, and automated sign language translation. However, current wearable hand motion tracking approaches are typically limited in detection performance, wearability, and durability. This article presents a hand motion tracking system using multiple soft polymer acoustic waveguides (SPAWs). The innovative use of SPAWs as strain sensors offers several advantages that address the limitations. SPAWs are easily manufactured by casting a soft polymer shaped as a soft acoustic waveguide and containing a commercially available small ceramic piezoelectric transducer. When used as strain sensors, SPAWs demonstrate high stretchability (up to 100%), high linearity (R2 > 0.996 in all quasi-static, dynamic, and durability tensile tests), negligible hysteresis (<0.7410% under strain of up to 100%), excellent repeatability, and outstanding durability (up to 100,000 cycles). SPAWs also show high accuracy for continuous finger angle estimation (average root-mean-square errors [RMSE] <2.00°) at various flexion-extension speeds. Finally, a hand-tracking system is designed based on a SPAW array. An example application is developed to demonstrate the performance of SPAWs in real-time hand motion tracking in a three-dimensional (3D) virtual environment. To our knowledge, the system detailed in this article is the first to use soft acoustic waveguides to capture human motion. This work is part of an ongoing effort to develop soft sensors using both time and frequency domains, with the goal of extracting decoupled signals from simple sensing structures. As such, it represents a novel and promising path toward soft, simple, and wearable multimodal sensors.

Finite element-based diffraction correction for piezoelectric transducers accounting for diffraction at transmission, propagation, and reception.

Existing diffraction correction models for ultrasonic transmit-receive measurement systems rely on simplifying assumptions with respect to the boundary conditions at the transmitter or receiver. Common simplifications include approximating the sound field radiated by a piezoelectric transducer using a baffled piston model and assuming that the receiver's electrical response is proportional to the spatially averaged free-field pressure over its front surface. In many applications, such simplifications may be adequate, but their validity and accuracy need to be evaluated and quantified. Here, a diffraction correction model utilizing the full set of electrical and mechanical boundary conditions at the transmitter and receiver is presented, avoiding these simplifications. The model is based on finite element modeling of coaxially aligned piezoelectric transducers in a fluid medium. Comparison is made with existing models for an example case of cylindrical piezoelectric ceramic disk transducers operating in air at 50-300 kHz and 0.03-2 m apart, relevant for, e.g., sound velocity and absorption measurements in fluids and ultrasonic gas flow metering. In the near-field, errors introduced by the simplifications are up to 3 dB and 47° for the first radial resonance. Generally, such errors are application-specific and depend on distance, frequency, transducer construction, vibration pattern, and medium properties.

Field experiments of watt-level piezoelectric energy harvester for different embedded depths

Road piezoelectric energy-harvesting technology uses the positive piezoelectric effect to convert vibrational energy produced by vehicular load to electrical energy. Road piezoelectric energy harvesters (RPEHs) are the core elements behind this technology. A new disc-type metal–piezoelectric ceramic transducer structure was developed to promote road piezoelectric energy collection and increase power generation from RPEHs. Finite element analyses and field tests were then conducted. The experimental results show that the disc transducers have excellent road compatibility. The greater the embedded depth of the transducer, the smaller is the output power of the RPEH; hence, an embedded depth of 2 cm was selected as the optimal value for comprehensive durability and electrical performance. When a small car travelling at a speed of 60 km/h passed over the RPEH embedded at a depth of 2 cm, a maximum voltage of 62 V, maximum current of 62 mA, and maximum utput power of 3844 mW (power density: 43 W/m2) were observed. The influence of the vehicle weight on the RPEH output power decreased with increase in speed. Therefore, this study confirms that the new disc-type RPEH is less costly, has excellent power generation, and requires less piezoelectric transducer material.

Accurate damage localization and enhanced mechanical performance of self‐sensing epoxy nanocomposites using graphene platelets

AbstractRecently, there has been growing interest in the use of composites structure with self‐sensing functionalities in the aerospace, automotive, and renewable energy industries. However, the integration of sensors such as Fiber Bragg Grating or piezoelectric ceramic transducers into the composite structure can significantly reduce the structure's inherent strength. To address this issue, we present a novel approach for developing self‐sensing composites by incorporating graphene platelets (GnPs) as an electric filler into an epoxy matrix. Our method involves the uniform dispersion of GnPs in epoxy, with some GnPs connected to each other to achieve a low electrical threshold of 0.61 vol% in the resulting nanocomposites. The resulting composite film exhibits high sensitivity to tensile strains ranging from 0% to 1.8%, with gauge factors (GFs) ranging from 19 to 172. This variation in GF is due to the calibration process, which relies on the relationship between input and output data and does not require a constant factor. In addition to its high sensitivity to tensile strains, the composite film also demonstrates excellent self‐sensing performance for bending deformation. Moreover, the composite film effectively responds to impact damage evolution, making it a promising candidate for practical applications. This work represents an advancement in the development of self‐sensing nanocomposites using two‐dimensional materials, offering exceptional sensitivity and adaptability for potential future use.

Ultrasonic characterization of multi-layered porous lithium-ion battery structure for state of charge

A multi-layered porous finite element model of lithium-ion battery is proposed by using Voronoi polygons. The time domain simulation of ultrasonic transmission characteristics with different state of charge (SOC) are carried out, and the variation of acoustic parameters versus SOCs is explored. Then, in the experiment research, the ultrasonic transmission signals are obtained by employing piezoelectric ceramic transducers during the discharging step. By extracting the time domain characteristic parameters, it is discovered that the amplitude and time-of-flight (TOF) have a strong correlation with SOC, the slow pressure-wave (SPW) velocities of the experiments correspond well with the simulation results. In addition, the frequency domain analysis shows a linear link between the amplitude of the frequency spectrum and SOC. Moreover, via repeated experiments, it is found that the ultrasonic transmission method has good repeatability in probing the SOC, and the SPW velocities acquired by experiments can almost be covered by 95% confidence interval formed based on the results of the simulation. Furthermore, according to the results of the experiments, a gray model based on the particle swarm optimization-based-simulated annealing (GM-PSO-SA) is established, which realized the prediction of the SOC under the condition of small sample data. The research results can serve as a reference for creating a comprehensive finite element model of the multi-layered porous structure of lithium-ion battery. Meanwhile, it also provides a detection and evaluation tool for the monitoring of the SOC.

Performance Analysis and Prospect of Piezoelectric Ultrasonic Transducers Based on Vibration Modes

With the maturity of ultrasonic transducer technology, as a traditional ultrasonic transducer, piezoelectric ultrasonic transducer has leaped into the public view. This article briefly summarizes the development of ultrasonic transducers and the classification of piezoelectric ultrasonic transducers. In practical applications, different piezoelectric ultrasonic transducers are mostly selected based on the different sound source vibrations in the application scenarios. The principle analysis and structure introduction of longitudinal vibration type ultrasonic transducers, longitudinal bending vibration mode conversion type ultrasonic transducers, and torsional vibration piezoelectric ceramic ultrasonic transducers are conducted respectively, and the application fields are pointed out. Besides, heat dissipation is an important link that affects the energy transfer efficiency of piezoelectric ultrasonic transducers. For traditional air-cooled heat dissipation and phase change heat dissipation, the heat dissipation ability is investigated and analyzed separately, and the advantages and disadvantages of the two are compared. It is concluded that phase change heat dissipation can effectively solve the impact caused by excessive temperature difference inside the transducer, while traditional heat dissipation methods cannot solve this problem.

A floating piezoelectric electromagnetic hybrid wave vibration energy harvester actuated by a rotating wobble ball

This paper presents a floating piezoelectric electromagnetic hybrid wave vibration energy harvester actuated by a rotating wobble ball. The kinematic equation of the rotating wobble ball under the influence of the wave is established by simplifying the ocean wave model. One merit of the proposed harvester is that it can harvest wave vibration energy via a frequency up-conversion mechanism. The vibration energy of a wave is converted into electrical energy by the electromagnetic generator (EMG) and the piezoelectric ceramic transducer (PZT). Low-frequency vibration energy is converted into the high frequency vibration of the PZTs using frequency up-conversion mechanism. The results show that the maximum power generated by the proposed hybrid energy harvester is 21.95 mW when the external frequency of the wave is 1.4 Hz. Additionally, two PZTs and the EMG successfully output about 11.26 mW of power to light up LEDs throughout a test of low-power electronics. The results demonstrate that low-frequency wave vibrations can be efficiently harvested using the proposed hybrid vibration energy harvester.

Vibration monitoring of optical fiber composited in overhead transmission line using φ-OTDR

In order to evaluate the vibration state of the overhead line, the φ-OTDR (phase-sensitive optical time-domain reflectometry) is applied to the vibration monitoring for the optical fiber composited in overhead transmission line. The principle of φ-OTDR and the IQ demodulation algorithm is introduced. Common mono-mode dark optical fiber simulates the optical fiber composited in an overhead line. The sinusoidal vibration is applied to the optical fiber using an arbitrary waveform generator and piezoelectric ceramic transducer (PZT). The vibration status in the optical fiber is measured by optical fiber vibration monitoring system using φ-OTDR. The result reveals that this system can demodulate the vibration applied to the optical fiber. This paper provides a reference for vibration monitoring optical fiber composite overhead lines.

Energy harvesting and storage with ceramic piezoelectric transducers coupled with an ionic liquid-based supercapacitor

One of the main issues of wearable electronic devices regards their power supply and autonomy. The exploitation of mechanical energy from body motion and vibrations can be realized by using piezoelectric materials coupled with a proper energy storage device. To this aim, Self-Powered Supercapacitors (SPSCs) have been investigated over the last decades, either as internally integrated SPSC (iSPSC), where the piezoelectric element of the device is used as Super Capacitor (SC) separator, or via an external integration (eSPSC), where the piezoelectric unit and the SC are connected by a bridge rectifier. In this paper, an eSPSC power supply is developed by integrating a stuck of commercial ceramic piezoelectric disks and an ionic liquid-based micro-SC. In detail, a stack of 15 commercial lead zirconate titanate (PZT) disks is used as the energy harvesting unit and mechanically stressed by a compressive force of 85 N at 2 Hz. The piezoelectric output successfully charged the 22 mF supercapacitor up to 3.1 V after 2 h of test, achieving a stored energy value equal to 110 mJ. The proposed integrated system outperforms the state-of-the-art SPSC assembled with micro-SC (both iSPSC and eSPSC). The use of the two different units (piezo-energy harvesting unit and micro-SC energy storage unit) allows an independent sizing and tuning of the supercapacitor according to the output current of the piezoelectric unit.

An Impact Localization Solution Using Embedded Intelligence-Methodology and Experimental Verification via a Resource-Constrained IoT Device.

Recent advances both in hardware and software have facilitated the embedded intelligence (EI) research field, and enabled machine learning and decision-making integration in resource-scarce IoT devices and systems, realizing "conscious" and self-explanatory objects (smart objects). In the context of the broad use of WSNs in advanced IoT applications, this is the first work to provide an extreme-edge system, to address structural health monitoring (SHM) on polymethyl methacrylate (PPMA) thin-plate. To the best of our knowledge, state-of-the-art solutions primarily utilize impact positioning methods based on the time of arrival of the stress wave, while in the last decade machine learning data analysis has been performed, by more expensive and resource-abundant equipment than general/development purpose IoT devices, both for the collection and the inference stages of the monitoring system. In contrast to the existing systems, we propose a methodology and a system, implemented by a low-cost device, with the benefit of performing an online and on-device impact localization service from an agnostic perspective, regarding the material and the sensors' location (as none of those attributes are used). Thus, a design of experiments and the corresponding methodology to build an experimental time-series dataset for impact detection and localization is proposed, using ceramic piezoelectric transducers (PZTs). The system is excited with a steel ball, varying the height from which it is released. Based on TinyML technology for embedding intelligence in low-power devices, we implement and validate random forest and shallow neural network models to localize in real-time (less than 400 ms latency) any occurring impacts on the structure, achieving higher than 90% accuracy.