• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.9
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• pp.11-20
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• 2014

For Web-based applications in IoT environment, IETF CoRE WG has standardizing the CoAP. One of limitations of CoAP is that CoAP standard does not consider the mobility management of the CoAP sensor node. In this paper, we propose the mobility management protocol of CoAP sensor node by considering the characteristics of the constrained network. The proposed mobility management protocol supports for Web client to be transmitted the sensing data from CoAP node reliably while the CoAP sensor moves into different wireless networks. To do this, we designed the architecture with the separate IP address management of CoAP sensor node and presented the mobility management protocol, which includes the holding and binding mode, in order to provide the reliable transmission. Finally, the numerical analysis and simulation with NS2 tool have been done for the performance evaluation in terms of the handover latency and packet loss with comparing the proposed mobility management protocol with other the existing mobility management protocols. The performance result shows that the proposed mobility management can provide the transmission of sensing data without the packet loss comparing with the existing mobility management protocol reliably.

• Journal of Institute of Control, Robotics and Systems
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• v.20 no.2
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• pp.218-222
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• 2014

In this paper, we introduce an autonomous calibration method for a 2D laser displacement sensor (e.g. laser vision sensor and laser range finder) by matching a single point on a flat structure. Many arc welding robots install a 2D laser displacement sensor to expand their application by recognizing their environment (e.g. base metal and seam). In such systems, sensing data should be transformed to the robot's coordinates, and the geometric relation (i.e. rotation and translation) between the robot's coordinates and sensor coordinates should be known for the transformation. Calibration means the inference process of geometric relation between the sensor and robot. Generally, the matching of more than 3 points is required to infer the geometric relation. However, we introduce a novel method to calibrate using only 1 point matching and use a specific flat structure (i.e. circular hole) which enables us to find the geometric relation with a single point matching. We make the rotation component of the calibration results as a constant to use only a single point by moving a robot to a specific pose. The flat structure can be installed easily in a manufacturing site, because the structure does not have a volume (i.e. almost 2D structure). The calibration process is fully autonomous and does not need any manual operation. A robot which installed the sensor moves to the specific pose by sensing features of the circular hole such as length of chord and center position of the chord. We show the precision of the proposed method by performing repetitive experiments in various situations. Furthermore, we applied the result of the proposed method to sensor based seam tracking with a robot, and report the difference of the robot's TCP (Tool Center Point) trajectory. This experiment shows that the proposed method ensures precision.

• Journal of Sensor Science and Technology
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• v.8 no.3
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• pp.259-264
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• 1999

The $CO_2$ measuring system using infrared sensor has the variance according to the temperature change. Therefore, the temperature compensation should be needed to obtain a reliable measurement. In this study, the sensor module consist of infrared $CO_2$ Sensor, IR Source, pipe and the heater and measuring system has amplifier, A/D converter and microprocessor. And we suggest a method to reduce the error by using the PID temperature control. We use optimum parameters setting of Ziegler & Nichols as well as PID temperature control algorithm for the temperature compensation. In this method, PID optimum parameter is set from dummy time(L) and maximum slope(R). As a result of using this PID temperature control, it is founded that it has the fast response and low steady state error. Therefore, it is certainly proved that this is very suitable algorithm to correct the error on measurement.

• Korean Journal of Optics and Photonics
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• v.33 no.1
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• pp.22-27
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• 2022

We fabricate a polarization-independent dielectric multilayer thin-film diffraction grating for a spectral-beam-combining (SBC) system with a simple grating structure and low aspect ratio. Due to the refractive index and thickness error of the manufactured thin films, the diffraction efficiency of the fabricated diffraction grating was lower than that of the design. The causes of the errors were analyzed, and it was confirmed through simulation that diffraction efficiency could be compensated through an additional coating on the manufactured diffraction grating. As a result of sputtering an additional Ta₂O₅ layer on a fabricated diffraction grating, the diffraction efficiency was corrected and a maximum 91.7% of polarization-independent diffraction efficiency was obtained.

• International Journal of High-Rise Buildings
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• v.3 no.2
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• pp.155-165
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• 2014

This study measured and compared the variation of ventilation rate and fan energy consumption according to various control strategies after installing wireless sensor-based pilot ventilation system in order to verify the applicability of demand-controlled ventilation (DCV) strategy that was efficient ventilation control strategy for underground parking lot. The underground parking lot pilot ventilation system controlled the ventilation rate by directly or indirectly tracking the traffic load in real-time after sensing data, using vehicle detection sensors and carbon monoxide (CO) and carbon dioxide ($CO_2$) sensor. The ventilation system has operated for 9 hours per a day. It responded real-time data every 10 minutes, providing ventilation rate in conformance with the input traffic load or contaminant level at that time. A ventilation rate of pilot ventilation system can be controlled at 8 levels. The reason is that a ventilation unit consists of 8 high-speed nozzle jet fans. This study proposed vehicle detection sensor based demand-controlled ventilation (VDS-DCV) strategy that would accurately trace direct traffic load and CO sensor based demand-controlled ventilation (CO-DCV) strategy that would indirectly estimate traffic load through the concentration of contaminants. In order to apply DCV strategy based on real-time traffic load, the minimum required ventilation rate per a single vehicle was applied. It was derived through the design ventilation rate and total parking capacity in the underground parking lot. This is because current ventilation standard established per unit floor area or unit volume of the space made it difficult to apply DCV strategy according to the real-time variation of traffic load. According to the results in this study, two DCV strategies in the underground parking lot are considered to be a good alternative approach that satisfies both energy saving and healthy indoor environment in comparison with the conventional control strategies.

• Journal of Sensor Science and Technology
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• v.14 no.4
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• pp.237-243
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• 2005

Strain gauge type load cell is used widely as weight sensor. However, it has problems such as noise, power consumption, high cost and big size. Semiconductor type piezoresistive pressure sensor is practically used in recent for low hysteresis, good linearity, small size, light weight and strong on vibration. In this paper, we have fabricated the piezoresistive pressure sensor and packaged the miniature weight sensor. We packaged the miniature weight sensor by flip-chip bonding between die and PCB for durability, because the weight sensor is directly contacted on a physical solid distinct from air and oil pressure. We measured the characteristics of the weight sensor, which had the output of $10{\sim}80$ mV on the weight range of $0{\sim}2$ kg. In the result, we could fabricate the weight sensor with an accuracy of 3 %FSO linearity.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.132-135
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• 2002

MI(Magneto-Impedance) sensor which is made by thin films has significantly high detecting sensitivity in weak magnetic field. It also has a merit to be able to build in the low power system. Its structure is simple, which makes it easier to prepare a miniature. In this study, its magnetic permeability and anisotropy field($H_{k}$) as a function of a thickness of sputtered amorphous CoZrNb films with zero-magnetostriction and soft magnetic property are investigated. In order to make a uniaxial anisotropy, film was subjected to the post annealing in a static magnetic field with 1KOe intensity at 250, 300, and $320^{\circ}C$ respectively for 2 hours. Magnetic properties of film are measured by using a MH loop tracer. Its magnetic permeability of a film is measured over the frequency range 1 MHz to 750MHz. And, it was examined on the permeability and impedance to design the MI sensor which acts at 50MHz by thickening a CoZrNb film relatively, and fabricated the MI sensor which acts at the 50MHz.

• Journal of Sensor Science and Technology
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• v.29 no.2
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• pp.112-117
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• 2020

Xylene is a hazardous volatile organic compound that should be precisely measured to monitor indoor air quality. However, the selective and sensitive detection of ppm-level xylene using oxide-semiconductor gas sensors remains a challenge. In this study, pure and Cr-doped Co₃O₄ nanoparticles (NPs) were prepared using flame spray pyrolysis, and their gas-sensing characteristics to 5-ppm xylene at 250 ℃ were investigated. The 4 at% Cr-doped Co₃O₄ NPs exhibited a high gas response to 5-ppm xylene (resistance ratio to gas and air = 39.1) and negligible cross-responses to other representative and ubiquitous indoor pollutants such as ethanol, benzene, formaldehyde, carbon monoxide, and ammonia. In this paper, the enhancement of the gas response and selectivity of Co₃O₄ NPs to xylene by Cr doping was discussed in relation to the catalytic promotion of the gas-sensing reaction. This sensor can be used to monitor indoor xylene.

• Journal of the Korean Ceramic Society
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• v.36 no.5
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• pp.564-569
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• 1999

• Journal of Sensor Science and Technology
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• v.18 no.1
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• pp.48-53
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• 2009

$Eu^{2+}$-doped ${SrAl_2}{O_4}$ and $Eu^{2+}$, $Dy^{3+}$ co-doped ${SrAl_2}{O_4}$ phosphors have been synthesized by conventional solid state method. Photocurrent properties of $Eu^{2+}$ doped ${SrAl_2}{O_4}$ and $Eu^{2+}$, $Dy^{3+}$ co-doped ${SrAl_2}{O_4}$ phosphors, in order to elucidate $Dy^{3+}$ co-doping effect, during and after ceasing ultraviolet-ray (UV) irradiation have been investigated. The photocurrent of $Eu^{2+}$, $Dy^{3+}$ co-doped ${SrAl_2}{O_4}$ phosphors during UV irradiation was 4-times lower than that of $Eu^{2+}$-doped ${SrAl_2}{O_4}$ during UV irradiation, and 7-times higher than that of $Eu^{2+}$-doped ${SrAl_2}{O_4}$ after ceasing UV irradiation. The photocurrent results indicated that holes of charge carriers captured in hole trapping center during the UV irradiation and liberated after-glow process, and made clear that $Dy^{3+}$ of co-dopant acted as a hole trap. The photocurrent of ${SrAl_2}{O_4}$ showed a good proportional relationship to UV intensity in the range of $1{\sim}5mW/cm^2$, and $Eu^{2+}$-doped ${SrAl_2}{O_4}$ was confirmed to be a possible UV sensor.