Commercial Transducer Research Articles

Evaluation Methodology of a Smart Clothing Biomechanical Energy Harvesting System for Mountain Rescuers.

The article presents a methodology developed for the evaluation of biomechanical energy harvesting systems that permits avoiding long-duration outdoor tests while providing realistic input signals and preserving uniform conditions across repeated tests. It consists of two stages: transducer output signal recording and power conversion and storage system measurements. The proposed approach was applied to assess the usefulness of a commercial electromagnetic transducer for supplying a Global Positioning System (GPS) receiver used as an active component of a smart clothing dedicated for mountain rescuers. Electrical power yield measurements have been presented together with ergonomic tests results. They all involved diverse physical activities performed by mountain rescuers that simulated their true operations, but were conducted in a training room for the sake of standardization. By providing reliable data on the transducer’s performance under realistic use conditions, the proposed evaluation procedure revealed that the true energy yield was much smaller not only with respect to the manufacturer’s assertions, but also substantially lower than what was expected based on an independent review which used unrealistic and non-uniform excitations. On the other hand, ergonomics ratings given by potential end users were very high, which demonstrates that the evaluated transducer can still be useful for supplying active cloth components with a lower power demand. The study also revealed that transducer location and orientation strongly affect its performance, which must be taken into account at the first stage of the evaluation procedure. Moreover, physical activity type and conditions (such as motion speed and ground tilt) influence the output power and should be carefully considered when composing a typical case scenario for the second stage.

A Self-Powered and Area Efficient SSHI Rectifier for Piezoelectric Harvesters

This article presents an area efficient fully autonomous piezoelectric energy harvesting system to scavenge energy from periodic vibrations. Extraction rectifier utilized in the system is based on synchronized switch harvesting on inductor (SSHI) technique which enables system to outperform standard passive rectifiers. Compared to conventional SSHI circuits, enhanced SSHI (E-SSHI) system proposed in this paper uses a single low-profile external inductor in the range of $\mu \text{H}$ ’s to reduce overall system cost and volume, hence broadening application areas of such harvesting systems. Furthermore, E-SSHI does not include any negative voltage converter circuit and therefore, it offers area efficient AC/DC rectification. Detection of optimal voltage flipping times in E-SSHI technique is conducted autonomously without any external calibration. Energy transfer circuit provides control over how much energy is delivered from E-SSHI output to electronic load. The proposed system is fabricated in 180 nm CMOS process with 0.28 mm2 active area. It is tested using a commercial piezoelectric transducer MIDE V22BL with periodic excitation. Measured results reveal that E-SSHI circuit is capable of extracting up to 5.23 and 4.02 times more power compared with an ideal full-bridge rectifier at 0.87 V and 2.6 V piezoelectric open circuit voltage amplitudes (VOC, P), respectively. A maximum voltage flipping efficiency of 93% is observed at VOC,P = 3.6 V, owing to minimized losses on charge flipping path. Measured results are compared with state-of-the-art interface circuits. Comparison shows that E-SSHI design offers a huge step towards miniaturized harvesting systems thanks to its low-profile and fully autonomous design.

Sub-Nanowatt Ultrasonic Bio-Telemetry Using B-Scan Imaging.

Goal: The objective of this paper is to investigate if the use of a B-scan ultrasound imaging system can reduce the energy requirements, and hence the power-dissipation requirements to support wireless bio-telemetry at an implantable device. Methods: B-scan imaging data were acquired using a commercial 256-element linear ultrasound transducer array which was driven by a commercial echoscope. As a transmission medium, we used a water-bath and the operation of the implantable device was emulated using a commercial-off-the-shelf micro-controller board. The telemetry parameters (e.g. transmission rate and transmission power) were wirelessly controlled using a two-way radio-frequency transceiver. B-scan imaging data were post-processed using a maximum-threshold decoder and the quality of the ultrasonic telemetry link was quantified in terms of its bit-error-rate (BER). Results: Measured results show that a reliable B-scan communication link with an implantable device can be achieved at transmission power levels of 100 pW and for implantation depths greater than 10 cm. Conclusions: In this paper we demonstrated that a combination of B-scan imaging and a simple decoding algorithm can significantly reduce the energy-budget requirements for reliable ultrasonic telemetry.

Deformation Method of Self-Mixing Laser Sensor’s Feedback Phase for Estimation of Optical Feedback Coupling Factor and Displacement

This paper, while focusing on post-perturbed phase processing of optical feedback based self-mixing laser displacement sensor, rigorously derives a general strategy to achieve the particular task of retrieving displacement from perturbed (feedback based) phase based on a proposition, which has been proved separately. From this, a new algorithm has been derived for estimation of optical feedback coupling factor and corresponding displacement over weak-, moderate-, and strong-optical feedback regimes, by using the concept of deformation. This method can work on all displacements so long as these are sufficiently smooth, i.e, have enough continuous derivatives. The algorithm’s steps are shown to be mathematically consistent. Furthermore, its performance has also been verified, and compared with a previous method, by using simulated and experimental signals for an SM sensor with emission wavelength of 785 nm. Displacement measurement precision has also been quantified by using a commercial transducer with 2 nm resolution showing that the proposed method provides comparable displacement precision even for fringe-loss affected, strong-feedback regime signals.

Fuzzy Logic Control-Based HIFU System Integrated with Photoacoustic Imaging Module for Ex Vivo Artificial Tumor Treatment

The objective of this study is to design a therapeutic method combining a portable high intensity focused ultrasound (HIFU) design which is suitable for the laboratory environment and a tailored integrated photo-acoustic imaging (PAI) system for monitoring thermal treatment. The electrical HIFU design is fabricated with changeable operating frequency and justified output power for resonating with different kinds of commercial transducers. The system’s control interface is built based on a touch screen to create a companionable interaction for users. The embedded fuzzy logic controller using the thermal input from the thermocouple sensor precisely drives the target temperature during HIFU exposure to achieve the expectedly coagulating results. The PAI system with 532-nm laser excitation is also integrated to define the affected region before and after HIFU treatment. The proposed fuzzy controller-integrated HIFU setup compatible with the PAI system is a feasible instrument in thermal therapy for ex vivo artificial tumors management.

Unsupervised anomaly detection in peripheral venous pressure signals with hidden Markov models

This paper proposes an automatic anomaly detection and removal algorithm for peripheral venous pressure (PVP) signals, which can be used to predict intravascular volume loss in humans. PVP signal collection is a minimally invasive procedure that can be performed by using a standard peripheral intravenous (PIV) catheter and a commercial pressure-monitoring transducer. PVP signals are highly susceptible to motion and noise artifacts such as patient movements or unintended manipulation of PIV lines. Anomalies in PVP signals can corrupt useful information and seriously affect the integrity of PVP signal analysis. We propose to detect and remove such anomalies by exploiting the properties of PVP signals. Specifically, a dynamic linear model (DLM) with a Kalman filter is used to track and predict the time-domain evolution of PVP signals. The prediction residuals of the Kalman filter are then modeled with a hidden Markov model (HMM), with the normal and anomalous status of the signal modeled by using binary states of a hidden Markov chain. The HMM parameters along with the hidden states are iteratively estimated by using an unsupervised learning algorithm with a modified Baum–Welch method. The anomaly detection algorithm is applied to clinical data from a cohort of 24 pediatric patients with hypertrophic pyloric stenosis. Experimental results demonstrate that the proposed unsupervised anomaly detection algorithm can efficiently remove anomalies in PVP signals without the need of a training phase. The algorithm can also be applied to other time series signals, such as Electrocardiography (ECG) and Photoplethysmogram (PPG) signals.

Development and characterization of a volume flow measurement system for low-pressure gases

This paper presents the design and validation of a volume flow measurement system developed to measure volume flowrate of gas at pressures below 1 kPa. The system had to be developed because a suitable commercial transducer was not available for the unusual working environment, where outgassing and sublimation phenomena become relevant for many materials and the rarefied atmosphere changes dramatically its heat and mass exchange parameters. The development of a low-pressure compatible measurement system comes from the need of measuring the flow rate of a rotary vane pump working under an environmental absolute pressure in the range between 600 and 1000 Pa, mostly composed by CO2 i.e. the average condition of the Martian atmosphere at the surface. The pump will be a key component of the MicroMED particle analyzer, an instrument of the ExoMars 2020 ESA-Roscosmos mission payload. The measurement system is based on a control volume, made by a stainless-steel bellow, which has been designed accounting for the environmental requirements and the expected flow rate. The measurement system has been calibrated at ambient condition and tests in low-pressure have been performed to validate the measurement system and to derive the flow rate characteristics of a pump mock-up at different environmental pressures.

The High Frequency Flexural Ultrasonic Transducer for Transmitting and Receiving Ultrasound in Air

Flexural ultrasonic transducers are robust and low cost sensors that are typically used in industry for distance ranging, proximity sensing and flow measurement. The operating frequencies of currently available commercial flexural ultrasonic transducers are usually below 50 kHz. Higher operating frequencies would be particularly beneficial for measurement accuracy and detection sensitivity. In this paper, design principles of High Frequency Flexural Ultrasonic Transducers (HiFFUTs), guided by the classical plate theory and finite element analysis, are reported. The results show that the diameter of the piezoelectric disc element attached to the flexing plate of the HiFFUT has a significant influence on the transducer's resonant frequency, and that an optimal diameter for a HiFFUT transmitter alone is different from that for a pitch-catch ultrasonic system consisting of both a HiFFUT transmitter and a receiver. By adopting an optimal piezoelectric diameter, the HiFFUT pitch-catch system can produce an ultrasonic signal amplitude greater than that of a non-optimised system by an order of magnitude. The performance of a prototype HiFFUT is characterised through electrical impedance analysis, laser Doppler vibrometry, and pressure-field microphone measurement, before the performance of two new HiFFUTs in a pitch-catch configuration is compared with that of commercial transducers. The prototype HiFFUT can operate efficiently at a frequency of 102.1 kHz as either a transmitter or a receiver, with comparable output amplitude, wider bandwidth, and higher directivity than commercially available transducers of similar construction.

Kalman filter-based loading rate-dependent hysteresis compensation of flexoelectric torsional responses in polyvinylidene fluoride films for shaft torque sensors

This paper presents a new method of dynamic shaft torque measurement using polyvinylidene fluoride (PVDF) films, one of the new polymer type piezoelectric conversion materials. The measurement method is based on the shear strain gradient and the flexoelectric torsional response of the PVDF films. The loading rate-dependent hysteresis associated with viscoelastic behavior of PVDF film was modeled to estimate the torque input. The torque estimated by the proposed hysteresis model and optimization algorithm (genetic algorithm) can be implemented by the discrete Kalman filter. Because the torque estimated by the real-time Kalman filtering matches well with the actual torque input measured by the commercial in-line torque transducer, a new method of sensing the dynamic shaft torque using the PVDF output signal has been experimentally validated. This study offers potential applications for the development of new torque sensing technology to be widely used in a variety of mechanical engineering areas such as turbines, rotors, automobiles, and robotics.

Nonlinear Ultrasonic Second Harmonic Assessment of Concrete Defects Based on Embedded Piezoelectric Sensors

ABSTRACT In this work, the second harmonic generation (SHG) technique based on embedded piezoelectric (PZT) sensors is developed for the defect assessment of concrete samples. Three different imperfection forms of concrete including internal capillary void during the curing process, cracking damage due to compression, and bending loads are examined and analyzed. Clear second harmonics are observed by Fourier transform of time domain signal, and the square of fundamental signal amplitude shows a linear relation with the second harmonic amplitude as theoretically expected. The nonlinear parameter presents a good distinction for samples in different states of three cases, indicating the well-round feasibility of SHG technique based on embedded sensors. In addition, the nonlinear parameter presents an excellent correlation with the variation of internal capillary void and cracks in concrete. The high sensitivity of the developed SHG technique is further validated through a comparison between the nonlinear parameter and two traditional linear parameters, namely the phase velocity of Rayleigh wave and the resonance frequency of vibrations. Experimental results in this study demonstrate that the embedded sensors are promising for the nonlinear ultrasonic nondestructive evaluation of concrete structures, particularly as a low-cost alternative of commercial ultrasonic transducers.

Evaluation of adhesive-free focused high-frequency PVDF copolymer transducers fabricated on spherical cavities

A layer-by-layer deposition method for fabricating a focused ultrasonic transducer from piezoelectric copolymers has been developed. The fabrication process involves engraving a spherical cavity of 2 mm diameter on polyethyleneimines (PEI) polymer substrate. Surface roughness of the engraved spherical cavity is measured and compared with simulated line scan. Then, the transducer response was investigated by observing the acoustic pulse reflection from the glass plate used as reflector in a focal point. The average central frequency responses were measured to be 48.5 MHz, with a lower and upper −6 dB frequencies of approximately 25 and 76.5 MHz, yielding a bandwidth of 94.2%. A scanning hydrophone system has been employed to determine the focal zone of the transducer and compared with simulation using COMSOL Multiphysics. Two-dimensional surface scanning was performed on the test sample to provide the ultrasonic imaging of the transducer prototype and compare the image with commercial PVDF transducer with a center frequency of (48.5 ± 1) MHz.

Use of PVDF Wire Sensors for Leakage Localization in a Fluid-Filled Pipe.

The detection and location of pipeline leakage can be deduced from the time difference between the arrival leak signals measured by sensors placed at the pipe access points on either side of a suspected leak. Progress has been made in this area to offer a potential improvement over the conventional cross-correlation method for time delay estimation. This paper is concerned with identifying suitable sensors that can be easily deployed to monitor the pipe vibration due to the propagation of leak noise along the pipeline. In response to this, based on the low-frequency propagation characteristics of leak noise in our previous study, polyvinylidene fluoride (PVDF) wire sensors are proposed as a potential solution to detect the pipeline leak signals. Experimental investigations were carried out at a leak detection pipe rig built in the Chinese Academy of Sciences. Their performances for leak detection were shown in comparison with hydrophones. It is suggested that with special considerations given to aspects pertaining to non-intrusive deployment and low cost, the PVDF wire sensors are of particular interest and may lead to a promising replacement for commercial leak noise transducers.

Measurement of local pulse wave velocity for carotid artery by using an ultrasound-based method

Currently, pulse wave velocity (PWV) is an important physical index for characterizing the mechanical properties of arteries. Carotid-femoral PWV (cfPWV) is a clinically-approved parameter for evaluating the cardiovascular risk and therapeutic efficacy. However, cfPWV only provides global information about vessel properties. Many recent studies have indicated that local PWV measurements provide precise evaluation of artery conditions. Here, an ultrasound (US) method based on a novel vessel displacement waveform correction, is proposed for improving the accuracy of local carotid PWV measurement. A programmable US device and a commercial array transducer were used, which allow a user to excite transducer and receive US signals arbitrarily with different beam settings. The local PWV measurement accuracy was verified using a phantom. The number of US beams used for PWV measurements was also considered, which indicates that eight elements is the acceptable setting. Subsequently, local carotid PWV and cfPWV were measured in 35 healthy human subjects (age: 21.9 ± 2.4 years) by using the US method and SphygmoCor device, respectively. The cfPWV and local carotid PWV were 6.65 ± 0.74 and 4.63 ± 0.57 m/s, respectively. A good linear correlation was observed between the two aforementioned methods (r = 0.8) for the subjects. All the results indicated that when few US beams were used, the proposed method exhibited a reliable measurement of local PWV.

A Piezoelectric Bellows Round-Window Driver (PBRD) for Middle-Ear Implants

We describe a new implantable hearing-aid output device, a piezoelectric bellows round-window driver (PBRD), which is expected to be unaffected by external magnetic fields. The core elements of the PBRD are a piezoelectric element and a gold-coated copper bellows of low stiffness that transmits piezoelectric displacements, without significant attenuation, to the round window (RW). We analyzed structural and mechanical vibrations when confirming bellows transmission efficiency using a finite element model simulation. The PBRD was bench-tested under no-load conditions to determine its frequency response characteristics. We compared the outputs of the PBRD and a commercial floating-mass transducer in situ in human cadaveric temporal bones with responses measured using a laser Doppler vibrometer. PBRD outputs were excellent at both low (0.1–0.7 kHz) and high (2–16 kHz) frequencies; thus, the PBRD has the potential to compensate for conductive and/or sensorineural hearing loss. The frequency-response performance of the PBRD is better than that of conventional RW drivers (actuators or transducers).

Development and Metrological Evaluation of an Industrial Force Transducer

This work regarding the design and development of EN 24-grade steel-based force transducer has been reported along with its metrological features in line with ISO 376:2011 standard. The force transducer has been designed on the basis of analytical and computational methodology and validated through experimental observations. The force transducer presents ease of design-cum-manufacturing and practically viable alternative to the commercial force transducers with uncertainty of measurement up to 0.10% in its working range.

Single-Crystal High-Frequency Intravascular Ultrasound Transducer With 40-$\mu$ m Axial Resolution

Intravascular ultrasound (IVUS) is one of the most useful tools available today to assist intravascular stenting procedures. Having higher resolution is very important for helping doctors to evaluate the nature of atherosclerotic plaques. The current commercial IVUS systems have a spatial resolution of 70- [Formula: see text] in the axial direction and 200- [Formula: see text] in the lateral direction, which are insufficient for accurate diagnosis. We report here a three-matching-layer IVUS transducer design using a 0.72Pb(Mg1/3Nb2/3O3 - 0.28PbTiO3 single crystal, which can improve the axial resolution to [Formula: see text] without sacrificing the penetration depth. Wire phantom imaging and in vitro porcine coronary artery imaging show noticeably better axial resolution and similar penetration depth compared with a commercial IVUS transducer.

The Demonstration of Additive Manufacture in Power Ultrasonic and Sonar Transducers

Additive manufacture (AM) has been heralded as a disruptive technology with the potential to revolutionize manufacturing and transform how products are consumed. Within the power ultrasonic and sonar transducer domains, the capability of AM technologies to generate highly complex geometries could facilitate a step change in device performance, yet the usage of metallic additive manufactured parts in power ultrasonic or sonar devices is currently limited. This article demonstrates that it is possible to accurately model, using finite element methods, the vibratory behavior of a power ultrasonic device containing a part fabricated via AM before showing that the vibratory behavior of this device does not significantly vary from an identical device manufactured by conventional methods. Finally, a commercial Tonpilz-like sonar transducer containing a part fabricated by an AM technology is shown to exhibit similar performance to an identical device which contains conventionally manufactured parts.

Truncated Conical PVDF Film Transducer for Air Ultrasound

In this paper, a truncated conical polyvinylidene fluoride (PVDF) film transducer for air ultrasound is investigated. The transducer was designed and fabricated using two identical pieces of fan-shaped PVDF film that makes the curve direction as consistent as possible with the molecular orientation direction of the film. The transducer has a truncated conical geometry, which provides a wide bandwidth with wide vertical beam angle. Measurements of the frequency response of transmitter output, angular performance, and pulse response are presented. The results show that the radiation directivity pattern of the transducer is in the axial direction of the conical film and the beam width is 140° at −6dB level, which is more than that of the commercial 40-kHz ceramic transducers and cylindrical PVDF transducers. Therefore, this ultrasonic transducer is well-suited for three-dimensional (3D) ultrasonic positioning systems, and in particular for mounting at the conical head of electronic pens as an ultrasonic position transmitter.

Test-Retest Reliability of a Commercial Linear Position Transducer (GymAware PowerTool) to Measure Velocity and Power in the Back Squat and Bench Press.

Orange, ST, Metcalfe, JW, Marshall, P, Vince, RV, Madden, LA, and Liefeith, A. Test-retest reliability of a commercial linear position transducer (GymAware PowerTool) to measure velocity and power in the back squat and bench press. J Strength Cond Res 34(3): 728-737, 2020-This study examined the test-retest reliability of the GymAware PowerTool (GYM) to measure velocity and power in the free-weight back squat and bench press. Twenty-nine academy rugby league players (age: 17.6 ± 1.0 years; body mass: 87.3 ± 20.8 kg) completed 2 test-retest sessions for the back squat followed by 2 test-retest sessions for the bench press. GYM measured mean velocity (MV), peak velocity (PV), mean power (MP), and peak power at 20, 40, 60, 80, and 90% of 1 repetition maximum (1RM). GYM showed good reliability (intraclass correlation coefficient [ICC] and standard error of measurement percentage, respectively) for the measurement of MV at loads of 40 (0.77, 3.9%), 60 (0.83, 4.8%), 80 (0.83, 5.8%), and 90% (0.79, 7.9%) of 1RM in the back squat. In the bench press, good reliability was evident for PV at 40 (0.82, 3.9%), 60 (0.81, 5.1%), and 80% (0.77, 8.4%) of 1RM, and for MV at 80 (0.78, 7.9%) and 90% (0.87, 9.9%) of 1RM. The measurement of MP showed good to excellent levels of reliability across all relative loads (ICC ≥0.75). In conclusion, GYM provides practitioners with reliable kinematic information in the back squat and bench press, at least with loads of 40-90% of 1RM. This suggests that strength and conditioning coaches can use the velocity data to regulate training load according to daily readiness and target specific components of the force-velocity curve. However, caution should be taken when measuring movement velocity at loads <40% of 1RM.

Fabrication of a (K,Na)NbO3-based lead-free 1-3 piezocomposite for high-sensitivity ultrasonic transducers application

Ultrasonic imaging is a well-established powerful medical diagnosis tool at present. However, commercial ultrasonic transducers are commonly made of toxic lead-based piezoelectric materials. Thus, it is vital to develop lead-free alternatives with satisfactory performance. This study presents the development of a phase boundary-engineered (K,Na)NbO3-based lead-free 1-3 piezocomposite and its application on high-sensitivity ultrasonic imaging transducers. A modified dice-and-fill technique was used to manufacture the microscale piezocomposite, by which the ceramic pillars were miniaturized to a width of 55 μm with a kerf of 15 μm. Improved acoustic and electrical properties were obtained in the new piezocomposite, and ultrasonic imaging transducers were further designed and fabricated based on the composite. The fabricated transducers exhibit enhanced performance with a high center frequency (16 MHz), a broad bandwidth (83%), and a very low insertion loss (9.8 dB), outperforming state-of-the-art transducers based on other lead-free materials. Imaging capability of the transducers was evaluated via ex vivo imaging of a porcine eyeball, indicating that this lead-free piezocomposite has many attractive properties in developing environment-friendly high-sensitivity ultrasonic devices for biomedical imaging applications.