2,897 research outputs found
Automatic Bridge-based Interface for Differential Capacitive Full Sensing
Abstract The authors here propose, for the first time, an automatic analog interface for differential capacitance estimation, able to reveal and quantify both low and high (full-range) capacitive variations. The working principle is based on a modified De-Sauty AC bridge configuration where two differential capacitances and two resistances are employed, one of which is implemented by a Voltage Controlled Resistor (VCR). Through a suitable feedback loop, a very accurate estimation over the complete range of the differential capacitance variation is possible, while the bridge allows a continuous differential capacitance evaluation without the need of knowing the accurate value of the sensor baseline and/or its variation range. A general but very simple formula, considering both the "autobalancing" and the "out-of-equilibrium" ranges, is also given. Theoretical, experimental and simulated results are in a very good agreement. Sensitivity and resolution values, typical of sensors and their interfaces, have been determined in a practical case, showing satisfactory values
Piezo-electromechanical smart materials with distributed arrays of piezoelectric transducers: Current and upcoming applications
This review paper intends to gather and organize a series of works which discuss the possibility of exploiting the mechanical properties of distributed arrays of piezoelectric transducers. The concept can be described as follows: on every structural member one can uniformly distribute an array of piezoelectric transducers whose electric terminals are to be connected to a suitably optimized electric waveguide. If the aim of such a modification is identified to be the suppression of mechanical vibrations then the optimal electric waveguide is identified to be the 'electric analog' of the considered structural member. The obtained electromechanical systems were called PEM (PiezoElectroMechanical) structures. The authors especially focus on the role played by Lagrange methods in the design of these analog circuits and in the study of PEM structures and we suggest some possible research developments in the conception of new devices, in their study and in their technological application. Other potential uses of PEMs, such as Structural Health Monitoring and Energy Harvesting, are described as well. PEM structures can be regarded as a particular kind of smart materials, i.e. materials especially designed and engineered to show a specific andwell-defined response to external excitations: for this reason, the authors try to find connection between PEM beams and plates and some micromorphic materials whose properties as carriers of waves have been studied recently. Finally, this paper aims to establish some links among some concepts which are used in different cultural groups, as smart structure, metamaterial and functional structural modifications, showing how appropriate would be to avoid the use of different names for similar concepts. © 2015 - IOS Press and the authors
Electro-optomechanical equivalent circuits for quantum transduction
Using the techniques of optomechanics, a high- mechanical oscillator may
serve as a link between electromagnetic modes of vastly different frequencies.
This approach has successfully been exploited for the frequency conversion of
classical signals and has the potential of performing quantum state transfer
between superconducting circuitry and a traveling optical signal. Such
transducers are often operated in a linear regime, where the hybrid system can
be described using linear response theory based on the Heisenberg-Langevin
equations. While mathematically straightforward to solve, this approach yields
little intuition about the dynamics of the hybrid system to aid the
optimization of the transducer. As an analysis and design tool for such
electro-optomechanical transducers, we introduce an equivalent circuit
formalism, where the entire transducer is represented by an electrical circuit.
Thereby we integrate the transduction functionality of optomechanical systems
into the toolbox of electrical engineering allowing the use of its
well-established design techniques. This unifying impedance description can be
applied both for static (DC) and harmonically varying (AC) drive fields,
accommodates arbitrary linear circuits, and is not restricted to the
resolved-sideband regime. Furthermore, by establishing the quantized
input-output formalism for the equivalent circuit, we obtain the scattering
matrix for linear transducers using circuit analysis, and thereby have a
complete quantum mechanical characterization of the transducer. Hence, this
mapping of the entire transducer to the language of electrical engineering both
sheds light on how the transducer performs and can at the same time be used to
optimize its performance by aiding the design of a suitable electrical circuit.Comment: 30 pages, 9 figure
Development of limb volume measuring system
The mechanisms underlying the reductions in orthostatic tolerance associated with weightlessness are not well established. Contradictory results from measurements of leg volume changes suggest that altered venomotor tone and reduced blood flow may not be the only contributors to orthostatic intolerance. It is felt that a more accurate limb volume system which is insensitive to environmental factors will aid in better quantification of the hemodynamics of the leg. Of the varous limb volume techniques presently available, the ultrasonic limb volume system has proven to be the best choice. The system as described herein is free from environmental effects, safe, simple to operate and causes negligible radio frequency interference problems. The segmental ultrasonic ultrasonic plethysmograph is expected to provide a better measurement of limb volume change since it is based on cross-sectional area measurements
Integrated Electronics for Wireless Imaging Microsystems with CMUT Arrays
Integration of transducer arrays with interface electronics in the form of single-chip CMUT-on-CMOS has emerged into the field of medical ultrasound imaging
and is transforming this field. It has already been used in several commercial products such as handheld full-body imagers and it is being implemented by commercial and academic groups for Intravascular Ultrasound and Intracardiac Echocardiography. However, large attenuation of ultrasonic waves transmitted through
the skull has prevented ultrasound imaging of the brain. This research is a prime
step toward implantable wireless microsystems that use ultrasound to image the
brain by bypassing the skull. These microsystems offer autonomous scanning
(beam steering and focusing) of the brain and transferring data out of the brain for
further processing and image reconstruction.
The objective of the presented research is to develop building blocks of an integrated electronics architecture for CMUT based wireless ultrasound imaging systems while providing a fundamental study on interfacing CMUT arrays with their
associated integrated electronics in terms of electrical power transfer and acoustic
reflection which would potentially lead to more efficient and high-performance
systems.
A fully wireless architecture for ultrasound imaging is demonstrated for the
first time. An on-chip programmable transmit (TX) beamformer enables phased
array focusing and steering of ultrasound waves in the transmit mode while its
on-chip bandpass noise shaping digitizer followed by an ultra-wideband (UWB)
uplink transmitter minimizes the effect of path loss on the transmitted image data
out of the brain. A single-chip application-specific integrated circuit (ASIC) is de-
signed to realize the wireless architecture and interface with array elements, each
of which includes a transceiver (TRX) front-end with a high-voltage (HV) pulser,
a high-voltage T/R switch, and a low-noise amplifier (LNA). Novel design techniques are implemented in the system to enhance the performance of its building
blocks.
Apart from imaging capability, the implantable wireless microsystems can include a pressure sensing readout to measure intracranial pressure. To do so, a
power-efficient readout for pressure sensing is presented. It uses pseudo-pseudo
differential readout topology to cut down the static power consumption of the sensor for further power savings in wireless microsystems.
In addition, the effect of matching and electrical termination on CMUT array
elements is explored leading to new interface structures to improve bandwidth
and sensitivity of CMUT arrays in different operation regions. Comprehensive
analysis, modeling, and simulation methodologies are presented for further investigation.Ph.D
Advanced sensors technology survey
This project assesses the state-of-the-art in advanced or 'smart' sensors technology for NASA Life Sciences research applications with an emphasis on those sensors with potential applications on the space station freedom (SSF). The objectives are: (1) to conduct literature reviews on relevant advanced sensor technology; (2) to interview various scientists and engineers in industry, academia, and government who are knowledgeable on this topic; (3) to provide viewpoints and opinions regarding the potential applications of this technology on the SSF; and (4) to provide summary charts of relevant technologies and centers where these technologies are being developed
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