• ETRI Journal
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• v.30 no.1
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• pp.59-67
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• 2008

The necessity for the precise time synchronization of measurement data from multiple sensors is widely recognized in the field of global positioning system/inertial navigation system (GPS/INS) integration. Having precise time synchronization is critical for achieving high data fusion performance. The limitations and advantages of various time synchronization scenarios and existing solutions are investigated in this paper. A criterion for evaluating synchronization accuracy requirements is derived on the basis of a comparison of the Kalman filter innovation series and the platform dynamics. An innovative time synchronization solution using a counter and two latching registers is proposed. The proposed solution has been implemented with off-the-shelf components and tested. The resolution and accuracy analysis shows that the proposed solution can achieve a time synchronization accuracy of 0.1 ms if INS can provide a hard-wired timing signal. A synchronization accuracy of 2 ms was achieved when the test system was used to synchronize a low-grade micro-electromechanical inertial measurement unit (IMU), which has only an RS-232 data output interface.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.2182-2186
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• 2003

This paper presents the differential type resonant accelerometer (DRXL) and its performance test results. The DRXL is the INS grade, surface micro-machined sensor. The proposed DRXL device produces a differential digital output upon an applied acceleration, and the principle is a gap-dependent electrical stiffness variation of the electrostatic resonator with torsion beam structures. Using this new operating concept, we designed, fabricated and tested the proposed device. The final device was fabricated by using the wafer level vacuum packaging process. To test the performance of the DRXL, a nonlinear self-oscillation loop is designed using describing function technique. The oscillation loop is implemented using discrete electronic elements. The performance test of the DRXL shows that the sensitivity of the accelerometer is 12 Hz/g and its long term bias stability is about $2mg(1{\sigma})$. The turn on repeatability, bandwidth, and dynamic range are 4.38 mg, 100 Hz, and ${\pm}\;70g$, respectively.

• Transactions on Electrical and Electronic Materials
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• v.10 no.4
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• pp.135-139
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• 2009

$H_2S$ micro-gas sensors have been developed employing $SnO_2$:CuO composite thin films. The films were prepared by e-beam evaporation of Sn and Cu metals on silicon substrates, followed by oxidation at high temperatures. Results of various studies, such as scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) reveal that $SnO_2$ and CuO are mutually non-reactive. The CuO grains, which in turn reside in the inter-granular regions of $SnO_2$, inhibit grain growth of $SnO_2$ as well as forming a network of p-n junctions. The film showed more than a 90% relative resistance change when exposed to $H_2S$ gas at 1 ppm in air at an operating temperature of $350^{\circ}C$ and had a short response time of 8 sec.

• Journal of the Korean Ceramic Society
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• v.40 no.4
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• pp.385-392
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• 2003

Sol-gel preparation technique using a chemical reaction of metal alkoxides has been widely used for the fabrication of various materials including ceramics. However, its mechanism has been studied till now because a number of chemical ways are possible from various alkoxides and additives. In this study, the mechanism of hydrolysis, condensation, and polymerization of alkoxides were investigated from the fabrication of lead-zirconate-titanate (PbZr$\_$x/Ti$\_$l-x/O$_3$; PZT) thin film that is used as various micro-actuator, transducer, and sensor because of its high electro-mechanical coupling factors and thermal stability. Furthermore, the fabrication process and characteristics of self-patternable PZT film using photosensitive stabilizer were studied in order to resolve the problem of physical damage and properties degradation during dry etching for device fabrication. Using an optimum condition to prepare the self-patternable PZT film, more than 5000 ${\AA}$ thick self-patternable PZT film could be fabricated by three times coating. The PZT film showed 28.4 ${\mu}$c/cm$^2$ of remnant polarization (Pr) and 37.0 kV/cm of coercive field (E$\_$c/).

• Journal of Sensor Science and Technology
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• v.21 no.4
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• pp.249-255
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• 2012

Among the human senses, olfactory information still does not have a proper data presentation method unlike that regarding vision and auditory information. It makes presenting the sense of smell into multimedia information impossible, which may be an exploratory field in human computer interaction. In this paper, we propose an olfactory information presentation method, which is a way to use smell as multimedia information, and show an application for scent generation and odor display using a web service. The olfactory information can present smell characteristics such as intensity, persistence, hedonic tone, and odor description. The structure of data format based on olfactory information can also be organized according to data types such as integer, float, char, string, and bitmap. Furthermore, it can be used for data transmitting via a web service and for odor display using a scent generator. The scent generator, which can display information of smell, is developed to generate 6 odors using 6 aroma solutions and a diluted solution with 14 micro-valves and a micropump. Throughout the experiment, we confirm that the remote user can grasp information of smell transmitted by messenger service and request odor display to the computer controlled scent generator. It contributes to enlarge existing virtual reality and to be proposed as a standard reference method regarding olfactory information presentation for future multimedia technology.

• Journal of Sensor Science and Technology
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• v.27 no.3
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• pp.170-174
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• 2018

In this paper, the $TiO_2$/glucose oxidase (GOD) mixture has synthesized through simple and low-cost fabrication methods. The physical properties of the mixture were proved using an FT-IR/NIR spectrometer, an X-Ray diffractometer, and a Raman spectrometer. GOD maintained its bioactivity during all fabrication process. The current characteristics of the glucose biosensor were proportional to the glucose concentration and effective surface area of square pyramid on a silicon substrate. The maximum current change was measured in a pH 7.0 buffer solution. The simple and low-cost fabrication process and surface treatment can be used widely in previous research for improvements in effective surface area.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2006.04a
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• pp.77-81
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• 2006

GPS cannot determine random errors such as multipath and signal cutoff caused by surrounding environment that determines the visibility of satellites and the speed of data creation and transmission is lower than the speed of vehicles, it is difficult to determine accurate dynamic positions. Thus this study purposed to implement a method of deciding the accurate dynamic position of vehicles by combining AHRS (Attitude Heading Reference System) IMU (Initial Measurement Unit) based on low-priced MEMS (Micro Electro Mechanical System) in order to provide the information of attitude, position and speed at a high transmission rate without external help. This study conducted an initialization test to decide dynamic position using AHRS IMU sensor, and derived attitude correction angles of vehicles against time through regression analysis. The roll angle was $y=(A{\times}10^{-6})x^2 -(B{\times}10^{-5})x+Cr{\times}10^{-2}$ and the pitch angle was $y=(A{\times}10^{-6})x^2-(B{\times}10^{-7})x+C{\times}10^{-2}$, each of which was derived from second-degree polynomial regression analysis. It was also found that the heading angle was stabilized with variation less than $1^{\circ}$ after 60 seconds.

• Journal of Korean Society for Atmospheric Environment
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• v.30 no.6
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• pp.600-618
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• 2014

The metadata for urban meteorological observation is standardized through comparison with those established at the World Meteorological Organization and the Korea Meteorological Administration to understand the surrounding environment around the sites exactly and maintain the networks and sites efficiently. It categorizes into metadata for an observational network and observational sites. The latter is again divided into the metadata for station general information, local scale information, micro scale information, and visual information in order to explain urban environment in detail. The metadata also contains the static information such as urban structure, surface cover, metabolism, communication, building density, roof type, moisture/heat sources, and traffic as well as the update information on the environment change, maintenance, replacement, and/or calibration of sensors. The standardized metadata for urban meteorological observation is applied to the Weather Information Service Engine (WISE) integrated meteorological sensor network and sites installed at Incheon area. It will be very useful for site manager as well as researchers in fields of urban meteorology, radiation, surface energy balance, anthropogenic heat, turbulence, heat storage, and boundary layer processes.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.12 s.243
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• pp.1615-1620
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• 2005

We present a novel flow-rate independent cell counter using a fixed control volume between double electrical sensing zones. The previous device based on the single electrical cell sensing in a given flow-rate requires an accurate fluid volume measurement or precision flow rate control. The present cell counter, however, offers the flow-rate independent method for the cell concentration measurement with counting cells in a fixed control volume of $22.9{\pm}0.98{\mu}{\ell}$. In the experimental study, using the RBC (Red Blood Cell), we have compared the measured RBC concentrations from the fabricated devices with those from Hemacytometer. The previous and present devices show the maximum errors of $20.3\%\;and\;16.1\%$, which are in the measurement error range of Hemacytometer (about $20\%$). The present device also shows the flow-rate independent performance at the constant flow-rates ($5{\mu}{\ell}/min$ and $10{\mu}{\ell}/min$) and the varying flow-rate (4, 2, and $4{\mu}{\ell}/min$). Therefore, we demonstrate that the present cell counter is a simple and automated method for the cell concentration measurement without requiring an accurate fluid measurement and precision flow-rate control.

• Proceedings of the KIPE Conference
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• 2011.07a
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• pp.179-180
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• 2011

This paper focuses on the Current-Voltage concurrent control method devoted to the multiple LED (light-emitting diode) string driver. Isolated DC to DC converter with cascaded chopping switch is proposed for smart lighting system such as light with sensor or back light unit of display, which need to control the current of parallel connected multiple LED stings and regulate DC voltage for micro controller for brightness control. The proposed circuit regulates the current of parallel connected multiple LED strings and additional DC voltage output simultaneously. To verify the performance, experimental results are presented based on the prototype board. 5V, 1A voltage mode electric load and two LED strings with different forward voltages are used for output loads. 23W output power is achieved and measured efficiency is in the range of 85%-87%