Showing papers on "Piezoelectric sensor published in 2022"

Piezoelectric Dynamics of Arterial Pulse for Wearable Continuous Blood Pressure Monitoring

Abstract: Piezoelectric arterial pulse wave dynamics are traditionally considered to be similar to those of typical blood pressure waves. However, achieving accurate continuous blood pressure wave monitoring based on arterial pulse waves remains challenging, because the correlation between piezoelectric pulse waves and their related blood pressure waves is unclear. To address this, the correlation between piezoelectric pulse waves and blood pressure waves is first elucidated via theoretical, simulation, and experimental analysis of these dynamics. Based on this correlation, the authors develop a wireless wearable continuous blood pressure monitoring system, with better portability than conventional systems that are based on the pulse wave velocity between multiple sensors. They explore the feasibility of achieving wearable continuous blood pressure monitoring without motion artifacts, using a single piezoelectric sensor. These findings eliminate the controversy over the arterial pulse wave piezoelectric response, and can potentially be used to develop a portable wearable continuous blood pressure monitoring device for the early prevention and daily control of hypertension.

A method for quantitatively separating the piezoelectric component from the as-received “Piezoelectric” signal

Abstract: Polymer-based piezoelectric devices are promising for developing future wearable force sensors, nanogenerators, and implantable electronics, etc. The electric signals generated by them are often assumed as solely coming from the piezoelectric effect. However, triboelectric signals originated from contact electrification between the piezoelectric devices and the contacted objects can produce non-negligible interfacial electron transfer, which is often combined with the piezoelectric signal to give a triboelectric-piezoelectric hybrid output, leading to an exaggerated measured "piezoelectric" signal. Herein, a simple and effective method is proposed for quantitatively identifying and extracting the piezoelectric charge from the hybrid signal. The triboelectric and piezoelectric parts in the hybrid signal generated by a poly(vinylidene fluoride)-based device are clearly differentiated, and their force and charge characteristics in the time domain are identified. This work presents an effective method to elucidate the true piezoelectric performance in practical measurement, which is crucial for evaluating piezoelectric materials fairly and correctly.

Polyvinylidene fluoride piezoelectric yarn for real-time damage monitoring of advanced 3D textile composites

Abstract: Real-time online damage monitoring is essential and critical to the safe service of the advanced fibers reinforced composites. This paper firstly reports a piezoelectric yarn sensor based on electrospinning and 2D braiding technology, to monitor advanced 3D textile composites, which can generate a voltage of about 1 V and sustain long-term cycles at high frequency of 4 Hz. The polyvinylidene fluoride (PVDF) piezoelectric yarn is embedded into 3D orthogonal composites to realize the online health monitoring of advanced 3D textile composites through the three-point bending test. Following the bending fatigue and modal tests, the PVDF piezoelectric yarn sensor proposed in this work enables long-term, low-frequency, high-frequency, and stable monitoring, thus showing good potential and wide application in damage monitoring as a piezoelectric sensor in composites.

Looseness monitoring of multiple M1 bolt joints using multivariate intrinsic multiscale entropy analysis and Lorentz signal-enhanced piezoelectric active sensing

Abstract: Bolts are widely used in the fields of mechanical, civil, and aerospace engineering. The condition of bolt joints has a significant impact on the safe and reliable operation of the whole equipment. The failure of bolt joints monitoring leads to severe accidents or even casualties. This paper proposes a novel bolt joints monitoring method using multivariate intrinsic multiscale entropy (MIME) analysis and Lorentz signal-enhanced piezoelectric active sensing. Lorentz signal is used as excitation signal in piezoelectric active sensing to expose nonlinear dynamical characteristics of the bolt joints. Multivariate variational mode decomposition (MVMD) is employed to decompose multiple components of the collected Lorentz signal into multivariate band-limited intrinsic mode functions (BLIMFs). Afterward, improved multiscale sample entropy (IMSE) values of each channel’s BLIMFs are computed to measure its irregularity and complexity. IMSE values are taken as quantitative features, reflecting dynamical characteristics of bolt joints. Further, the constructed 3-layer feature matrices are adopted as the input of the convolutional neural network (CNN) to achieve accurate bolt joint monitoring. The multiple M1 bolt joints are used during the experiment to verify the effectiveness and superiority of the proposed approach. The results demonstrate the proposed novel approach is promising in bolt joints monitoring.

Piezoelectric strain sensor with high sensitivity and high stretchability based on kirigami design cutting

Abstract: Abstract Wearable technology requires high-performance sensors with properties such as small size, flexibility, and wireless communication. Stretchability, sensitivity, and tunability are crucial sensor properties; stretchability and sensitivity ensure user comfort and accurate sensing performance, while tunability is essential for implementing sensors in diverse applications with different ranges of motion. In this study, we developed a high performance kirigami piezoelectric strain sensor. Using finite element analysis, the sensing performance was evaluated, and the kirigami patterns were optimized. The electromechanical properties of sensors with four different kirigami patterns were analyzed. A sensor voltage measurement circuit was also designed, amplifying the output voltage 86.5 times by improving measurement accuracy. A piezoelectric kirigami sensor was constructed with a sensitivity of 9.86 V/cm 2 and a stretchability of 320.8%, higher than those of previously reported kirigami piezoelectric strain sensors. Finally, the fabricated sensor was successfully applied in a haptic glove for playing musical instruments.

Highly sensitive and wearable bionic piezoelectric sensor for human respiratory monitoring

Abstract: Flexible piezoelectric sensors hold great promising for applications in electronic skin (E-skin), wearable devices, and biomedical devices. However, it is still challenging to apply flexible piezoelectric sensors to respiratory health monitoring which requires an extremely low detection limit. To address this challenge, a flexible bionic piezoelectric sensor inspired by the lateral line structure of fish is proposed in this study. Benefited from the excellent piezoelectric effect of polyvinylidene fluoride (PVDF) and the bionic structural design, the proposed sensor has a low detection limit of 0.0005 N and can be conformal with a cylindrical surface. In addition, the sensor can accurately sense the pressure at a high sensitivity of 0.24 V N−1 with a fast response time of 4 ms and long-term repeatability of 4000 cycles. Through the design of back-end circuitry, the bionic sensor is capable of accurately monitoring of various respiratory states, such as apnea, coughing, and deep breathing. These results show that our sensor has great potential as a wearable device in the field of respiratory health monitoring, and is also highly inspiring for designing other types of flexible sensors.

Active Vibration Control of Piezoelectric Sandwich Plates

Abstract: This paper deals with the active vibration control of piezoelectric sandwich plate. The structure consists of a substrate plate layer sandwiched between two layers of piezoelectric sensor and actuator. Based on laminate theory and constitutive equation of piezoelectric material, the vibration active control dynamic equation of the sandwich structure is established by using hypothetical mode method and Hamilton principle. The Rayleigh-Ritz method is used to solve it. The form of hypothetical solution is used for approximate solution, which is simple and accurate. The method of this paper is verified by several examples. The parametric studies of the sandwich plate structures are carried out. The results show that applying different boundary conditions and piezoelectric patch positions to the structures have a great influence on the natural frequency. When the driving voltage increases, the deflection of the plate structures increase approximately linearly. The active vibration control studies are investigated as well. The results show that within a certain range, the larger the value of the speed feedback coefficient, the better the active control effect. The positions of the piezoelectric patches affect the effectiveness and cost of active control. When the piezoelectric plate is located at the fixed end, the effect and cost of active control are better than that at the midpoint and free end of the plate.

Process Control Monitor (PCM) for Simultaneous Determination of the Piezoelectric Coefficients d31 and d33 of AlN and AlScN Thin Films

Abstract: Accurate and efficient measurements of the piezoelectric properties of AlN and AlScN films are very important for the design and simulation of micro-electro-mechanical system (MEMS) sensors and actuator devices. In this study, a process control monitor (PCM) structure compatible with the device manufacturing process is designed to achieve accurate determination of the piezoelectric coefficients of MEMS devices. Double-beam laser interferometry (DBLI) and laser Doppler vibrometry (LDV) measurements are applied and combined with finite element method (FEM) simulations, and values of the piezoelectric parameters d33 and d31 are simultaneously extracted. The accuracy of d31 is verified directly by using a cantilever structure, and the accuracy of d33 is verified by in situ synchrotron radiation X-ray diffraction; the comparisons confirm the viability of the results obtained by the novel combination of LDV, DBLI and FEM techniques in this study.

Finite element model updating of smart structures with direct updating algorithm

Abstract: In this paper, a finite element model updating algorithm is proposed to enhance the accuracy of the simulated finite element model of a smart structure (collocated piezoelectric patches embedded on a cantilever beam). Piezoelectric patches are used to sense and control the excessive vibrations of the structures. Mostly, they are mounted on flexible structures to measure their response at different excitations. The finite element method can be used to model the beam embedded with collocated piezoelectric patches. The complete finite element formulation of the smart structure is briefly described in this paper. There are different types of uncertainties that may be present in the simulated finite element model of a smart structure such as uncertainty in the structural boundary conditions, in the material elastic properties, the dimensions of the structure, piezoelectric elastic and electric properties, and the location of the piezoelectric patches mounted on the structure. In the present analytical study, the above uncertainties present in the smart structure are reduced by using the direct updating algorithm. It is found that the direct updating method through updating the mass and the stiffness matrices of the smart structure successfully enhance the accuracy of the simulated finite element model of the beam embedded with PZT patches. The state-space method is used to predict the response in the frequency domain. The maximum percentage error in the simulated finite element model of the piezoelectric embedded beam structure due to its structural and the electrical property uncertainty is 10.36% and 23.52% respectively and that was completely removed by using the direct updating algorithm. The optimal location of the piezoelectric patches is also taken as uncertainty which is successfully updated by using the proposed direct updating algorithm. The maximum percentage error in the natural frequencies of the smart structure due to location uncertainty is 18.39% which was also completely removed. To validate the outcomes, a frequency response function (FRF) is plotted.

Virtual Sensor Array Based on Piezoelectric Cantilever Resonator for Identification of Volatile Organic Compounds.

Abstract: Piezoelectric cantilever resonator is one of the most promising platforms for real-time sensing of volatile organic compounds (VOCs). However, it has been a great challenge to eliminate the cross-sensitivity of various VOCs for these cantilever-based VOC sensors. Herein, a virtual sensor array (VSA) is proposed on the basis of a sensing layer of GO film deposited onto an AlN piezoelectric cantilever with five groups of top electrodes for identification of various VOCs. Different groups of top electrodes are applied to obtain high amplitudes of multiple resonance peaks for the cantilever, thus achieving low limits of detection (LODs) to VOCs. Frequency shifts of multiple resonant modes and changes of impedance values are taken as the responses of the proposed VSA to VOCs, and these multidimensional responses generate a unique fingerprint for each VOC. On the basis of machine learning algorithms, the proposed VSA can accurately identify different types of VOCs and mixtures with accuracies of 95.8 and 87.5%, respectively. Furthermore, the VSA has successfully been applied to identify the emissions from healthy plants and "plants with late blight" with an accuracy of 89%. The high levels of identifications show great potentials of the VSA for diagnosis of infectious plant diseases by detecting VOC biomarkers.

New insights on piezoelectric thermoelastic coupling and transient thermo-electromechanical responses of multi-layered piezoelectric laminated composite structure

Abstract: In recent years there have been many papers that considered the pyroelectric effect in the investigations of thermo-mechanical coupling of piezoelectric ceramics serving in non-uniform thermal environment , particularly with extensive applications of ultrafast heating technologies (e.g., laser burst, laser ablation , etc.) in micro-machining of piezoelectric structures (e.g., piezoelectric sensor/actuator/generator/energy harvester , etc.). However, in such conditions, the existing piezoelectric thermoelasticity theories will not be applicable due to the lack of consideration of the memory-dependence feature in the constitutive relations and heat transport equation. To further refine the piezoelectric thermoelasticity models, present study develops a new theoretical model of generalized piezoelectric thermoelasticity which fully account for fractional order strain and heat conduction . By establishing constitutive equations within the extended thermodynamic framework , the governing equations are derived. In the aspect of application, the transient thermo-electromechanical responses of multi-layered piezoelectric laminated composite structure with non-idealized interfacial conditions is investigated. The effects of material constants ratio and fractional order parameters of each layer on structural responses are evaluated and summarized to offer some new insights and guidelines on the strength design, thermal protection , and vibration control of multi-layered piezoelectric laminated composite structure under ultrafast heating condition.

Investigation of Interlaminar Shear Properties of CFRP Composites at Elevated Temperatures Using the Lempel-Ziv Complexity of Acoustic Emission Signals

Abstract: Three-point bending tests on Short Beam Shear (SBS) specimens are performed to investigate the interlaminar shear properties of plain weave fabric CFRP composites. The tests are performed in a controlled environmental chamber at two different elevated temperatures. The interlaminar shear properties of the specimens remain largely unaffected by the testing temperature. However, the SEM micrographs show different damage progressions between the specimens tested at 100 °C and 120 °C. Fibre ruptures and longer delamination between the plies, as a result of a high temperature, are observed in the specimens tested at 120 °C, which are not observed in the specimens tested at 100 °C. In addition, the acoustic emission activities during the tests are investigated by using piezoelectric sensors. The information-theoretic parameter, the Lempel-Ziv (LZ) complexity, is calculated for the recorded acoustic signals. The LZ Complexities are used for identifying the occurrence of the first delamination failure in the specimens. Additionally, the two features of the acoustic signals, LZ complexity and Weighted Peak Frequency (W.P-Freq), are used for distinguishing the different damage sources in the CFRP specimens. The results are well-supported by the time-frequency analysis of the acoustic signals using a Continuous Wavelet Transform (CWT).

Thin Piezoelectric Sheet Assisted PGC Demodulation of Fiber-Optic Integrated MZI and its Application in Under Mattress Vital Signs Monitoring

Abstract: A modified solid fiber-optic integrated Mach-Zehnder interferometer (IMZI) assisted with a thin piezoelectric sheet (TPS, ~130 $\mu {\mathrm{ m}}$ thickness) and phase generated carrier (PGC) demodulation is proposed and investigated theoretically and experimentally. The IMZI’s two arms are respectively molded with epoxy resin (EP) and silicone rubber (SI). These two materials are with distinctly different elastic modulus and Poisson ratios, which guarantees the high sensitivity of the IMZI. As for PGC, different modulation frequencies and amplitudes are generated and the corresponding modulation depths are calculated to obtain the optimal modulating parameters. Furthermore, a pair of complementary photodetectors are used to remove unwanted DC component and only the first harmonic is utilized to recover the phase, which can effectively avoid signal fading. In the experiments, where the IMZI is put under the mattress, activity monitoring is addressed and subjects are recruited to investigate the vital signs monitoring performance. The consistency check analysis results show the calculated heart rate variability (HRV) and breath rate variability (BRV) results are highly correlated with reference results, and the Pearson’s r reaches 0.99. Moreover, reliability, post-exercise, and Valsalva Maneuver test are further conducted to verify the repeatability and dynamic monitoring capability. In conclusion, the proposed system is unobtrusive, cost-effective, robust, and convenient, which has great potential in future homecare and hospitalization.

Active Ultrasonic Structural Health Monitoring Enabled by Piezoelectric Direct-Write Transducers and Edge Computing Process

Abstract: While the active ultrasonic method is an attractive structural health monitoring (SHM) technology, many practical issues such as weight of transducers and cables, energy consumption, reliability and cost of implementation are restraining its application. To overcome these challenges, an active ultrasonic SHM technology enabled by a direct-write transducer (DWT) array and edge computing process is proposed in this work. The operation feasibility of the monitoring function is demonstrated with Lamb wave excited and detected by a linear DWT array fabricated in situ from piezoelectric P(VDF-TrFE) polymer coating on an aluminum alloy plate with a simulated defect. The DWT array features lightweight, small profile, high conformability, and implementation scalability, whilst the edge-computing circuit dedicatedly designed for the active ultrasonic SHM is able to perform signal processing at the sensor nodes before wirelessly transmitting the data to a remote host device. The successful implementation of edge-computing processes is able to greatly decrease the amount of data to be transferred by 331 times and decrease the total energy consumption for the wireless module by 224 times. The results and analyses show that the combination of the piezoelectric DWT and edge-computing process provides a promising technical solution for realizing practical wireless active ultrasonic SHM system.

Single-process fused filament fabrication 3D-printed high-sensitivity dynamic piezoelectric sensor

Abstract: Piezoelectric sensors require electric poling to provide piezoelectric properties. Furthermore, for a functional sensor, electrodes need to be deposited on the sensing element, which makes manufacturing the sensor a multi-process. Multi-processing limits the sensor’s shape complexity and makes it harder to embed the piezoelectric sensing elements in various 3D-printed structures. Integrating electric poling into the fused-filament-fabrication (FFF) 3D-printing technique was already researched; however, the methods require an additional electrode-deposition process and the piezoelectric sensitivities of the fabricated films were not comparable to conventional methods. This research presents the design principles of a functional, single-process, dynamic piezoelectric sensor using the FFF technique, which includes electrode deposition and electrode poling. A PVDF filament is used to fabricate the active piezoelectric layer. An Electrifi conductive filament is used to fabricate the electrodes of the piezoelectric film and the wire-like traces connecting the electrodes to the high-voltage terminals. As a result, the sensor undergoes electrode poling in the process of 3D printing. In order to study the piezoelectric response in different directions, two different dynamic sensor designs are presented. The sensor’s response to in-plane and out-of-plane loading is measured in terms of the sensor’s sensitivity. In-plane and out-of-plane sensitivities were measured for the two presented sensor designs. The proposed design principles for the FFF of piezoelectric sensors enable the single-process manufacturing of geometrically complex sensors and offer the possibility to embed the piezoelectric sensing elements into various FFF structures without an additional process.

3D-Printable Piezoelectric Composite Sensors for Acoustically Adapted Guided Ultrasonic Wave Detection

Abstract: Commercially available photopolymer resins can be combined with lead zirconate titanate (PZT) micrometer size piezoelectric particles to form 3D-printable suspensions that solidify under UV light. This in turn makes it possible to realize various non-standard sensor geometries which might bring benefits, such as increased piezoelectric output in specific conditions and less interference with incoming waves due to better acoustical adaptation compared to solid PZT ceramics. However, it is unclear whether piezoelectric composite materials are suitable for guided ultrasonic wave (GUW) detection, which is crucial for structural health monitoring (SHM) in different applications. In this study, thin piezoelectric composite sensors are tape casted, solidified under UV light, covered with electrodes, polarized in a high electric field and adhesively bonded onto an isotropic aluminum waveguide. This approach helps to demonstrate the capabilities of tape casting’s freedom to manufacture geometrically differently shaped, thin piezoelectric composite sensors for GUW detection. In an experimental study, thin two-dimensional piezoelectric composite sensors demonstrate successful detection of GUW for frequency-thickness products of up to 0.5 MHz mm. An analytical calculation of the maximum and minimum amplitudes for the ratio of the wavelength and the sensor length in wave propagation direction shows good agreement with the sensor-recorded signals. The output of the piezoelectric composite sensors and occurring reflections as measure for wave interactions are compared to commercial piezoelectric discs to evaluate their performance.

Properties of novel 0–3 PZT/silicone resin flexible piezoelectric composites for ultrasonic guided wave sensor applications

Abstract: Ultrasonic guided wave (UGW) technology based on piezoelectric sensors is considered a very promising technology for aircraft structural damage detection. Traditional piezoelectric sensors are made of lead zirconate titanate (PZT) ceramics, but their brittleness and hardness make them difficult to apply to curved structure surfaces. In this study, a novel 0–3 flexible piezoelectric composite was fabricated by dispersing PZT particles in silicone resin, and its performance for potential applications in UGW sensors was studied. The effects of polarization conditions, PZT volume fraction, and PZT powder size on the performance of the composite were investigated. The influence of ambient temperature on composite performance was discussed, and temperature adaptability experiments were conducted. The results show that the optimal poling process of 0–3 PZT/silicone resin piezoelectric composite has a poling time of 25 min, a poling electric field of 4 kV/mm, and a poling temperature of 100°C. When the sensor is required to meet the test strain range of 8,000 με, the composite should be fabricated with a PZT volume fraction of 50% and a powder size of 170∼212 μm to obtain optimal sensing sensitivity. At an ambient temperature range of -55–75°C, the fabricated piezoelectric composite sensor has good flexibility and sensitivity in detecting the guide wave signals. These research results provide a new flexible piezoelectric sensing technology for aircraft structural damage detection.

Investigation of the Temperature Compensation of Piezoelectric Weigh-In-Motion Sensors Using a Machine Learning Approach

Abstract: Piezoelectric ceramics have good electromechanical coupling characteristics and a high sensitivity to load. One typical engineering application of piezoelectric ceramic is its use as a signal source for Weigh-In-Motion (WIM) systems in road traffic monitoring. However, piezoelectric ceramics are also sensitive to temperature, which affects their measurement accuracy. In this study, a new piezoelectric ceramic WIM sensor was developed. The output signals of sensors under different loads and temperatures were obtained. The results were corrected using polynomial regression and a Genetic Algorithm Back Propagation (GA-BP) neural network algorithm, respectively. The results show that the GA-BP neural network algorithm had a better effect on sensor temperature compensation. Before and after GA-BP compensation, the maximum relative error decreased from about 30% to less than 4%. The sensitivity coefficient of the sensor reduced from 1.0192 × 10−2/°C to 1.896 × 10−4/°C. The results show that the GA-BP algorithm greatly reduced the influence of temperature on the piezoelectric ceramic sensor and improved its temperature stability and accuracy, which helped improve the efficiency of clean-energy harvesting and conversion.

Lead Zirconate Titanate-based bolt looseness monitoring using multiscale singular spectrum entropy analysis and genetic algorithm-based support vector machine

Abstract: The looseness monitoring of bolted joints is a significant issue to ensure structural integrity and safety in the industrial field. This paper proposes a novel approach to monitor bolt looseness based on piezoelectric active sensing. During the research, piezoelectric material is acted as an exciter to generate ultrasonic signals and a transducer is used to receive ultrasonic signals. In the process of signal processing, singular spectrum analysis (SSA) including phase reconstruction and principal component analysis is adopted to decompose the signal. Multiscale sample entropy (MSE) is employed to map the dynamic characteristics and regularity of the decomposed signals on multiple scales. The proposed strategy, named multiscale singular spectrum entropy analysis, refers to use MSE values of the new time series decomposed and reconstructed by SSA, to extract signal characteristics. Such a strategy can explore the underlying dynamical characteristics of a signal quantitatively in the reconstructed phase space. In our research work, SSA is employed to decompose the signals acquired by Lead Zirconate Titanate (PZT) to matrices, arranged from high to low singular values, and reconstruct the new time series (principal components) by diagonal averaging on determined matrices to characterize the essential dynamic characteristics of signals. MSE values of the principal components are used as damage index and adopted as input of genetic algorithm-based SVM to train a classifier to fulfill accurate monitoring of bolt joints. The theoretical derivation, application researches and comparison analysis can validate the effectiveness and superiority of the proposed approach in the field of bolt looseness monitoring.

Active Vibration Control on a Smart Composite Structure Using Modal-Shaped Sliding Mode Control

Abstract: Abstract This article proposes an active modal vibration control method based on a modal sliding mode controller applied to a smart material composite structure with integrated piezoelectric transducers as actuators and sensors. First, the electromechanical coupled system is identified using a modal reduced-order model. The sliding surface is based on the modal-filtered states and designed using a general formulation allowing the control of multiple vibration modes with multiple piezoelectric sensors and actuators. The performance and stability of the nonlinear controller are addressed and confirmed with the experimental results on a composite smart spoiler-shaped structure. The nonlinear switching control signal based on the modal-shaped sliding surface improves performances of the linear part of the control while maintaining not only stability but also robustness. The attenuation level achieved on the target modes on all piezoelectric sensors starts from −14 dB up to −22 dB, illustrating the strong potential of nonlinear switching control methods in active vibration control.