Showing papers on "Transducer published in 2014"

Combination touch and transducer input system and method

Abstract: A combination touch and transducer input system is provided, which facilitates user input into an electronic system with a finger and/or a transducer (e.g., a stylus). The system includes a transducer configured to generate an electric field, and a sensor including an array of electrodes and a controller. The transducer is configured to transmit digital data, such as pen pressure data and switch status data, to the sensor. For example, the transducer comprises electronic circuitry configured to encode the digital data in a signal for transmission to the sensor. The sensor controller is configured to operate both in a touch sensing mode and in a transducer sensing mode. During the touch sensing mode, the controller determines a position of a proximate object (e.g., a finger) by capacitively sensing the object with the array of electrodes. During the transducer sensing mode, the controller determines a position of the transducer based on a signal received by the array of electrodes from the transducer, and also receives and decodes the digital data encoded in the received signal. Digital data can be encoded in a signal using any suitable digital modulation techniques, such as a Frequency-Shift Keying (FSK) technique.

Transducer sound arrangement for pocket-forming

Abstract: The present disclosure describes a plurality of transducer arrangements that may be suitable for wireless power transmission based on single or multiple pocket-forming. Single or multiple pocket-forming may include one transmitter and at least one or more receivers, being the transmitter the source of energy and the receiver the device that is desired to charge or power. The transducer arrangements may vary in size and geometry, and may operate as a single array, pair array, quad arrays or any other suitable arrangement, which may be designed in accordance with the desired application.

High temperature, high power piezoelectric composite transducers

Abstract: Piezoelectric composites are a class of functional materials consisting of piezoelectric active materials and non-piezoelectric passive polymers, mechanically attached together to form different connectivities. These composites have several advantages compared to conventional piezoelectric ceramics and polymers, including improved electromechanical properties, mechanical flexibility and the ability to tailor properties by using several different connectivity patterns. These advantages have led to the improvement of overall transducer performance, such as transducer sensitivity and bandwidth, resulting in rapid implementation of piezoelectric composites in medical imaging ultrasounds and other acoustic transducers. Recently, new piezoelectric composite transducers have been developed with optimized composite components that have improved thermal stability and mechanical quality factors, making them promising candidates for high temperature, high power transducer applications, such as therapeutic ultrasound, high power ultrasonic wirebonding, high temperature non-destructive testing, and downhole energy harvesting. This paper will present recent developments of piezoelectric composite technology for high temperature and high power applications. The concerns and limitations of using piezoelectric composites will also be discussed, and the expected future research directions will be outlined.

An effective energy harvesting method from a natural water motion active transducer

Abstract: We demonstrated a new water motion active transducer (WMAT) without any external bias-voltage sources or additional processes, which critically limit the use of conventional passive capacitive transducers that convert mechanical motion into electric energy. From a simple structure, we successfully turned on an LED using various kinds of natural water motion. The WMAT, which has wide applicability, has good potential to be a candidate for generating sustainable electric energy.

Electrostatic vibration energy harvester with combined effect of electrical nonlinearities and mechanical impact

Abstract: This paper presents an advanced study including the design, characterization and theoretical analysis of a capacitive vibration energy harvester. Although based on a resonant electromechanical device, it is intended for operation in a wide frequency band due to the combination of stop-end effects and a strong biasing electrical field. The electrostatic transducer has an interdigited comb geometry with in-plane motion, and is obtained through a simple batch process using two masks. A continuous conditioning circuit is used for the characterization of the transducer. A nonlinear model of the coupled system ‘transduce-conditioning circuit’ is presented and analyzed employing two different semi-analytical techniques together with precise numerical modelling. Experimental results are in good agreement with results obtained from numerical modelling. With the 1 g amplitude of harmonic external acceleration at atmospheric pressure, the system transducer-conditioning circuit has a half-power bandwidth of more than 30% and converts more than 2 μ Wo f the power of input mechanical vibrations over the range of 140 and 160 Hz. The harvester has also been characterized under stochastic noise-like input vibrations.

Angular Displacement and Velocity Sensors Based on Electric-LC (ELC) Loaded Microstrip Lines

Abstract: Planar microwave angular displacement and angular velocity sensors implemented in microstrip technology are proposed. The transducer element is a circularly shaped divider/combiner, whereas the sensing element is an electric-LC resonator, attached to the rotating object and magnetically coupled to the circular (active) region of the transducer. The angular variables are measured by inspection of the transmission characteristics, which are modulated by the magnetic coupling between the resonator and the divider/combiner. The degree of coupling is hence sensitive to the angular position of the resonator. As compared with coplanar waveguide angular displacement and velocity sensors, the proposed microstrip sensors do not require air bridges, and the ground plane provides backside isolation.

Broadband Rydberg Atom-Based Electric-Field Probe: From Self-Calibrated Measurements to Sub-Wavelength Imaging

Abstract: We discuss a fundamentally new approach for the measurement of electric (E) fields that will lead to the development of a broadband, direct SI-traceable, compact, self-calibrating E-field probe (sensor). This approach is based on the interaction of radio frequency (RF) fields with alkali atoms excited to Rydberg states. The RF field causes an energy splitting of the Rydberg states via the Autler-Townes effect and we detect the splitting via electromagnetically induced transparency (EIT). In effect, alkali atoms placed in a vapor cell act like an RF-to-optical transducer, converting an RF E-field strength measurement to an optical frequency measurement. We demonstrate the broadband nature of this approach by showing that one small vapor cell can be used to measure E-field strengths over a wide range of frequencies: 1 GHz to 500 GHz. The technique is validated by comparing experimental data to both numerical simulations and far-field calculations for various frequencies. We also discuss various applications, including: a direct traceable measurement, the ability to measure both weak and strong field strengths, compact form factors of the probe, and sub-wavelength imaging and field mapping.

Micropower Design of a Fully Autonomous Energy Harvesting Circuit for Arrays of Piezoelectric Transducers

Abstract: This paper presents a self-powered energy harvesting circuit based on synchronous charge extraction with a single shared inductor for power conversion from arrays of independent piezoelectric transducers. The number of handled elements can be easily increased at the expense of few additional components and without affecting performance. The energy harvesting circuit was characterized with three 0.5 × 12.7 × 31.8 mm3 piezoelectric cantilevers subject to different types of vibrations. Throughout all operating conditions, the circuit was able to extract the maximum power independently from every transducer. Compared to passive energy harvesting interfaces, the output power is significantly higher, with worst-case increases ranging from +75% to +184%. The circuit starts up passively and is based on ultralow power active control, which consumes during operation at 3 V a fraction of the extra harvested power as low as 10 μW per source. As part of the best tradeoff between harvested and intrinsic power, an overall energy efficiency up to 74% was achieved.

Vibration energy harvesting system for railroad safety based on running vehicles

Abstract: This research is focused on energy harvesting from track vibration in order to provide power for the wireless sensors which monitor railroad health. Considering that track vibration has vibration energy, a new method is proposed in the paper to harvest energy based on the piezoelectric effect. The piezoelectric generator called drum transducer is the key part for track vibration energy harvesting. The model of drum transducer is established and the simulation results show that it can generate 100 mW in real track situation. In addition, an experiment rig is developed and its vibration model is also established. The simulation and experiment results show that peak open-circuit voltage of piezoelectric generator is about 50–70 V at the full load of the train. The whole track vibration energy harvesting system is analytically modeled, numerically simulated, and experimentally realized to demonstrate the feasibility and the reliability of the theoretical model. This paper is the theoretical basis of harvesting, recovering and recycling of the track vibration energy for track safety.

Embedded 3D electromechanical impedance model for strength monitoring of concrete using a PZT transducer

Abstract: The electromechanical (EM) impedance approach in which piezoelectric ceramics (PZT) simultaneously act as both a sensor and an actuator due to their direct and inverse piezoelectric effects has emerged as a powerful tool for structural health monitoring in recent years. This paper formulates a new 3D electromechanical impedance model that characterizes the interaction between an embedded square PZT transducer and the host structure based on the effective impedance. The proposed formulations can be conveniently used to extract the mechanical impedance of the host structure from the electromechanical admittance measurements of an embedded PZT patch. The proposed model is verified by experimental and numerical results from a smart concrete cube in which a square PZT transducer is embedded. Subsequently, this paper also presents a new methodology to monitor the compressive strength of concrete based on the effective mechanical impedance. By extracting the effective mechanical impedances from the electromechanical admittance signatures, measuring the compressive strength of the concrete cubes at different ages and combining these measurements with the index of the correlation coefficient (CC), a linear correlation between the concrete strength gain and the CC of the real mechanical admittances was found. The proposed approach is found to be feasible to monitor the compressive strength of concrete by age.

Fundamentals of Ultrasonic Phased Arrays

Abstract: It is shown that the wave field of an ultrasonic linear array is closely related to that of an equivalent single element transducer. Using this relationship, it is demonstrated how one can construct a simple and efficient ultrasonic beam model for the wave field of a steered linear array.

Interface Design and Control Strategies for a Robot Assisted Ultrasonic Examination System

Abstract: This paper presents a new robotic system designed to assist sonographers in performing ultrasound examinations by addressing common limitations of sonography, namely the physical fatigue that can result from performing the examination, and the difficulty in interpreting ultrasound data. The proposed system comprises a robot manipulator that operates the transducer, and an integrated user interface that offers 3D visualization and a haptic device as the main user interaction tool. The sonographer controls the slave robot movements either haptically (collaborative tele-operation mode), or by prior programming of a desired path (semi-automatic mode). A force controller maintains a constant contact force between the transducer and the patient’s skin while the robot drives the transducer to the desired anatomical locations. The ultrasound imaging system is connected to a 3D visualization application which registers in real time the streaming 2D images generated by the transducer and displays the resulting data as 3D volumetric representation which can be further examined off-line.

Micro Blood Pressure Energy Harvester for Intracardiac Pacemaker

Abstract: This paper presents the design, fabrication, and tests of a microspiral-shaped piezoelectric energy harvester and its associated microfabricated packaging that collects energy from ordinary blood pressure variations in the cardiac environment. This device could become a life-lasting, miniaturized energy source for active implantable medical devices such as leadless pacemakers. We present the concept and tested prototypes of 10 $\mu{\rm m}$ thin and ultra-flexible electrodeposited microbellows (6 mm diameter, 21 ${\rm mm}^{3}$ volume) as a new type of implant packaging. It enables direct blood pressure harvesting and permits a high efficiency of energy transfer to a transducer operating in quasi-static mode and hence adaptable and unaffected by frequent heartbeat frequency changes. Spiral-shaped piezoelectric transducers are introduced for their flexibility and large incoming mechanical energy. Non-trivial optimal electrodes placement and best spiral design parameters are studied and discussed. Three types of spiral prototypes (11 ${\rm mm}^{3}$ volume each) with doubled-sided microstructured electrode patterns are presented and characterized. A power of 3 $\mu J/{\rm cm}^{3}$ /heartbeat and a transduction efficiency of $5.7\times 10^{-3}$ have been obtained for the best designs at 1.5 Hz and we predict that twice as much could be obtained using similar design process and material. Through implementing smart adapted electronic circuits, a potential additional tenfold increase in power output could be achieved, which would be sufficient to power a leadless pacemaker. $\hfill{[2013\hbox{-}0090]}$

Transducer features for ultrasonic surgical instrument

Abstract: An apparatus for operating on tissue includes a body, a shaft, an ultrasonic blade, and an acoustic assembly. The shaft extends distally from the body. The blade is disposed at the distal end of the shaft. The acoustic assembly comprises an acoustic waveguide coupled with the blade, a piezoelectric transducer element, a fastener, and a coupling member. The transducer element defines an inner diameter surface and an outer diameter surface. The fastener is configured to secure the transducer element relative to the waveguide. The coupling member is configured to provide electrical continuity between the fastener and the inner diameter surface of the transducer element. The outer diameter surface of the transducer element includes an annular recess. Another coupling member is configured to provide electrical continuity between the annular recess of the piezoelectric transducer element and a power source while permitting the piezoelectric transducer element to rotate relative to the body.

Improving tangential resolution with a modified delay-and-sum reconstruction algorithm in photoacoustic and thermoacoustic tomography

Abstract: Spatial resolution in photoacoustic and thermoacoustic tomography is ultrasound transducer (detector) bandwidth limited. For a circular scanning geometry the axial (radial) resolution is not affected by the detector aperture, but the tangential (lateral) resolution is highly dependent on the aperture size, and it is also spatially varying (depending on the location relative to the scanning center). Several approaches have been reported to counter this problem by physically attaching a negative acoustic lens in front of the nonfocused transducer or by using virtual point detectors. Here, we have implemented a modified delay-and-sum reconstruction method, which takes into account the large aperture of the detector, leading to more than fivefold improvement in the tangential resolution in photoacoustic (and thermoacoustic) tomography. Three different types of numerical phantoms were used to validate our reconstruction method. It is also shown that we were able to preserve the shape of the reconstructed objects with the modified algorithm.

Distributed Strain Behavior of a Reinforced Concrete Bridge: Case Study

Abstract: To effectively assess and manage aging infrastructure, sensing technologies that produce accurate and useful quantitative data are required. Distributed fiber optic strain measurement systems are one potential technology that could fulfill this requirement. This case study investigates the performance of a distributed fiber optic strain measurement technology with high accuracy and spatial resolution during a load test on a RC bridge. The measurements from the fiber optic system are compared with conventional strain gauges and linear transducers, and good agreement between the sensors was found. The fiber optic measurements are also used to examine the bridge support conditions as well as the load distribution between beams. The results show that assumptions made about the support conditions during design do not match the actual bridge behavior, although the load distribution between beams is as expected.

Fabrication and performance of a miniaturized 64-element high-frequency endoscopic phased array

Abstract: We have developed a 40-MHz, 64-element phased-array transducer packaged in a 2.5 × 3.1 mm endoscopic form factor. The array is a forward-looking semi-kerfed design based on a 0.68Pb(Mg1/3Nb2/3)O3-0.32PbTiO3 (PMN-32%PT) single-crystal wafer with an element-to-element pitch of 38 μm. To achieve a miniaturized form factor, a novel technique of wire bonding the array elements to a polyimide flexible circuit board oriented parallel to the forwardlooking ultrasound beam and perpendicular to the array was developed. A technique of partially dicing into the back of the array was also implemented to improve the directivity of the array elements. The array was fabricated with a single-layer P(VDF-TrFE)-copolymer matching layer and a polymethylpentene (TPX) lens for passive elevation focusing to a depth of 7 mm. The two-way-6-dB pulse bandwidth was measured to be 55% and the average electromechanical coupling (keff) for the individual elements was measured to be 0.62. The one-way -6-dB directivities from several array elements were measured to be ±20°, which was shown to be an improvement over an identical kerfless array. The -3-dB elevation focus resulting from the TPX lens was measured to be 152 μm at the focal depth, and the focused lateral resolution was measured to be 80 μm at a steering angle of 0°. To generate beam profiles and images, the probe was connected to a commercial ultrasound imaging platform which was reprogrammed to allow for phased array transmit beamforming and receive data collection. The collected RF data were then processed offline using a numerical computing script to generate sector images. The radiation pattern for the beamformed transmit pulse was collected along with images of wire phantoms in water and tissue-equivalent medium with a dynamic range of 60 dB. Finally, ex vivo tissue images were generated of porcine brain tissue.

Spatial coherence in human tissue: implications for imaging and measurement.

Abstract: The spatial coherence properties of the signal backscattered by human tissue and measured by an ultrasound transducer array are investigated. Fourier acoustics are used to describe the propagation of ultrasound through a model of tissue that includes reverberation and random scattering in the imaging plane. The theoretical development describes how the near-field tissue layer, transducer aperture properties, and reflectivity function at the focus reduce the spatial coherence of the imaging wave measured at the transducer surface. Simulations are used to propagate the acoustic field through a histologically characterized sample of the human abdomen and to validate the theoretical predictions. In vivo measurements performed with a diagnostic ultrasound scanner demonstrate that simulations and theory closely match the measured spatial coherence characteristics in the human body across the transducer array's entire spatial extent. The theoretical framework and simulations are then used to describe the physics of spatial coherence imaging, a type of ultrasound imaging that measures coherence properties instead of echo brightness. The same echo data from an F/2 transducer was used to generate B-mode and short lag spatial coherence images. For an anechoic lesion at the focus, the contrast-to-noise ratio is 1.21 for conventional B-mode imaging and 1.95 for spatial coherence imaging. It is shown that the contrast in spatial coherence imaging depends on the properties of the near-field tissue layer and the backscattering function in the focal plane.

Transducers with Origin Information

Abstract: Call a string-to-string function regular if it can be realised by one of the following equivalent models: mso transductions, two-way deterministic automata with output, and streaming transducers with registers. This paper proposes to treat origin information as part of the semantics of a regular string-to-string function. With such semantics, the model admits a machine-independent characterisation, Angluin-style learning in polynomial time, as well as effective characterisations of natural subclasses such as one-way transducers or first-order definable transducers.

12.1 3D ultrasonic gesture recognition

Abstract: Optical 3D imagers for gesture recognition suffer from large size and high power consumption. Their performance depends on ambient illumination and they generally cannot operate in sunlight. These factors have prevented widespread adoption of gesture interfaces in energy- and volume-limited environments such as tablets and smartphones. Wearable mobile devices, too small to incorporate a touchscreen more than a few fingers wide, would benefit from a small, low-power gestural interface. Gesture recognition using sound is an attractive alternative to overcome these difficulties due to the potential for chip-scale size, low power consumption, and ambient light insensitivity. Using pulse-echo time-of-flight, MEMS ultrasonic rangers work over distances of up to a meter and achieve sub-mm ranging accuracy [1,2]. Using a 2-dimensional array of transducers, objects can be localized in 3 dimensions. This paper presents an ultrasonic 3D gesture-recognition system that uses a custom transducer chip and an ASIC to sense the location of targets such as hands. The system block diagram is shown in Fig. 12.1.1. Targets are localized using pulse-echo time-of-flight methods. Each of the 10 transceiver channels interfaces with a MEMS transducer, and each includes a transmitter and a readout circuit. Echoes from off-axis targets arrive with different phase shifts for each element in the array. The off-chip digital beamformer realigns the signal phase to maximize the SNR and determine target location.

Flexible Optical Fiber Bending Transducer for Application in Glove-Based Sensors

Abstract: The development of a low-cost and flexible optical fiber transducer for measurement of angular displacements is reported. The light intensity attenuation due to fiber microbending losses is correlated to the variations in flexing angle, yielding to a sensitivity of 1.80°. The device was also mounted in a fabric glove to the monitoring of flexion and abduction movements of index and thumb fingers. Once calibrated by a simple procedure, the glove-based system was capable to measure the angular positions with average errors <;5° and 7° for interphalangeal and metacarpophalangeal joints, respectively. Additionally, the repeatability analysis resulted in average range and standard deviations of 8.06° and 3.45°, respectively. The optical fiber sensor provides a low-cost alternative to the real-time monitoring of hand posture, and can be suitable for applications in human-robot and human-computer interactions.

Block-sparse reconstruction and imaging for lamb wave structural health monitoring

Abstract: A frequently investigated paradigm for monitoring the integrity of plate-like structures is a spatially-distributed array of piezoelectric transducers, with each array element capable of both transmitting and receiving ultrasonic guided waves. This configuration is relatively inexpensive and allows interrogation of defects from multiple directions over a relatively large area. Typically, full sets of pairwise transducer signals are acquired by exciting one transducer at a time in a round-robin fashion. Many algorithms that operate on such data use differential signals that are created by subtracting prerecorded baseline signals, leaving only signal differences introduced by scatterers. Analysis methods such as delay-and-sum imaging operate on these signals to detect and locate point-like defects, but such algorithms have limited performance and suffer when potential scatterers have high directionality or unknown phase-shifting behavior. Signal envelopes are commonly used to mitigate the effects of unknown phase shifts, but this further reduces performance. The blocksparse technique presented here uses a different principle to locate damage: each pixel is assumed to have a corresponding multidimensional linear scattering model, allowing any possible amplitude and phase shift for each transducer pair should a scatterer be present. By assuming that the differential signals are linear combinations of a sparse subset of these models, it is possible to split such signals into location-based components. Results are presented here for three experiments using aluminum and composite plates, each with a different type of scatterer. The scatterers in these images have smaller spot sizes than delay-and-sum imaging, and the images themselves have fewer artifacts. Although a propagation model is required, block-sparse imaging performs well even with a small number of transducers or without access to dispersion curves.