• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.2
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• pp.627-633
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• 2020

Assembly process data can be gathered in real time in a manufacturing execution system (MES) server using proximity sensors, barcodes, RFID, ZigBee, Bluetooth, wireless sensor networks, etc. Although this is suitable for identifying process flow and checking production progress, it is difficult to trace the location of individual workers in real time for missing work or trajectories within the work area. To overcome this, the location and trajectory of the working tool can be analyzed in real time through a position tracking system of an operator's working tool. It can instruct the operator to perform a consistent working process. Productivity and quality improvement can be achieved by an alarming or blocking operator with possible assembly defects during the assembly process in real time. To this end, we developed a real-time tool position-tracking sensor system based on Ultra Wide Band (UWB) trilateration using a Kalman filter to eliminate mechanical vibration and radio communication noise.

• Korean Journal of Optics and Photonics
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• v.30 no.6
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• pp.249-254
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• 2019

An optical current sensor device that measures electric current by the principle of the Faraday effect was designed and fabricated. The polarization-rotated reflection interferometer and the quadrature phase interferometer were introduced so as to improve the operational stability. Complex structures containing diverse optical components were integrated in a polymeric optical integrated circuit and manufactured in a small size. This structure allows sensing operation without extra bias feedback control, and reduces the phase change due to environmental temperature changes and vibration. However, the Verdet constant, which determines the Faraday effect, still exhibits an inherent temperature dependence. In this work, we tried to eliminate the residual temperature dependence of the optical current sensor based on polarization-rotated reflection interferometry. By varying the length of the fiber-optic wave plate, which is one of the optical components of the interferometer, we could compensate for the temperature dependence of the Verdet constant. The proposed optical current sensor exhibited measurement errors maintained within 0.2% over a temperature range, from 25℃ to 85℃.

• Journal of Sensor Science and Technology
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• v.19 no.5
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• pp.361-368
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• 2010

ACROSS device, which is composed of an implantable microphone, a signal processor, and a vibrating transducer, is a fullyimplantable middle ear hearing device(F-IMEHD) for the recovery of patients with hearing loss. And since a microphone is implanted under skin and tissue at the temporal bones, the amplitude of the sound wave is attenuated by absorption and scattering. And the vibrating transducer attached to the ossicular chain caused also the different displacement from characteristic of the stapes. For the gain control of auditory signals, most of implantable hearing devices with the digital audio signal processor still apply to fitting rules of conventional hearing aid without regard to the effect of the implanted microphone and the vibrating transducer. So it should be taken into account the effect of the implantable microphone and the vibrating transducer to use the conventional audio fitting rule. The aim of this study was to measure gain characteristics caused by the implanted microphone and the vibrating transducer attached to the ossicle chains for the gain compensation of ACROSS device. Differential floating mass transducers (DFMT) of ACROSS device were clipped on four cadaver temporal bones. And after placing the DFMT on them, displacements of the ossicle chain with the DFMT operated by 1 $mA_{peak}$ current was measured using laser Doppler vibrometer. And the sensitivity of microphones under the sampled pig skin and the skin of 3 rat back were measured by stimulus of pure tones in frequency from 0.1 to 8.9 kHz. And we confirmed that the microphone implanted under skin showed poorer frequency response in the acoustic high-frequency band than it in the low- to mid- frequency band, and the resonant frequency of the stapes vibration was changed by attaching the DFMT on the incus, the displacement of the DFMT driven with 1 $mA_{rms}$ was higher by the amount of about 20 dB than that of cadaver's stapes driven by the sound presssure of 94 dB SPL in resonance frequency range.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.4
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• pp.295-311
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• 2021

In this study, an experiment was carried out on the field applicability of tension measuring devices of the cables in cable-stayed bridges. The vibration method was used to estimate the tension of cables of cable-stayed bridge, and the mode characteristics of the cable were analyzed using a cable tension measuring device. GTDL360, NI Module, and 9 Axes Motion Sensorwere applied to estimate the cable tension of five target bridges. Numerical analysis of the five target bridges was conducted to analyze the natural frequency of the cable and cable tension. The estimated tension of the cable based on field measurements and estimated tension of cable by numerical analysis were compared with the estimated tension of the cable based on field measurements. The analysis showed that the measured tension of the cable based on field measurements was within the margin of error. Therefore, it is safe to apply these measuring devices to the site. As a result of comparing and analyzing the values of the acceleration-based cable estimation tension and numerical analysis of the field demonstration bridge, the acceleration-based cable estimation of tension is deemed appropriate within the allowable range. On-site applicability analysis revealed limitations of the measuring devices, such as the installation location of sensors and weather conditions, so continuous follow-up research on smart cable tension measuring systems is expected.

• Journal of Internet of Things and Convergence
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• v.8 no.6
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• pp.115-122
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• 2022

Recently, the importance of CPR training for the layperson has been emphasized to improve the survival rate of out-of-hospital cardiac arrest patients. An accurate and realistic training strategy is required for the CPR training effect for laypersons. In this study, we develop an extended reality (XR) based CPR training system and evaluate its usability. The XR based CPR training system consisted of three applications. First, a 3D heart anatomy image registered to the manikin is transmitted to the smart glasses to guide the chest compression point. The second application provides visual and auditory information about the CPR process through smart glasses. At the same time, the smartwatch sends a vibration notification to guide the compression rate. The 'Add-on-kit' is a device that detects the depth and speed of chest compression via sensors installed on the manikin and sends immediate feedback to the smartphone. One hundred laypersons who participated in this study agreed that the XR based CPR training system has realism and effectiveness. XR based registration technology will contribute to improving the efficiency of CPR training by enhancing realism, immersion, and self-directed learning.

• Journal of the Korean Geosynthetics Society
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• v.19 no.4
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• pp.41-50
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• 2020

Since cracks in concrete structures expedite corrosion of reinforced concrete over a long period of time, regular on-site inspections are essential to ensure structural usability and prevent degradation. Most of the safety inspections of facilities rely on visual inspection with naked eye, so cost and time consuming are severe, and the reliability of results differs depending on the inspector. In this study, a portable measuring device that can be used for safety diagnosis and maintenance was developed as a device that measures the width and length of concrete cracks through image analysis of cracks photographed with a camera. This device captures the cracks found within a close distance (3 m), and accurately calculates the unit pixel size by laser distance measurement, and automatically calculates the crack length and width with the image processing algorithm developed in this study. In measurement results using the crack image applied to the experiment, the measurement of the length of a 0.3 mm crack within a distance of 3 m was possible with a range of about 10% error. The crack width showed a tendency to be overestimated by detecting surrounding pixels due to vibration and blurring effect during the binarization process, but it could be effectively corrected by applying the crack width reduction function.

• Korean Chemical Engineering Research
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• v.60 no.2
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• pp.249-254
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• 2022

With the rapid advance of the semiconductor and Information and communication technologies, remote environment monitoring technology, which can detect and analyze surrounding environmental conditions with various types of sensors and wireless communication technologies, is also drawing attention. However, since the conventional remote environmental monitoring systems require external power supplies, it causes time and space limitations on comfortable usage. In this study, we proposed the concept of the self-powered remote environmental monitoring system by supplying the power with the levitation-electromagnetic generator (L-EMG), which is rationally designed to effectively harvest biomechanical energy in consideration of the mechanical characteristics of biomechanical energy. In this regard, the proposed L-EMG is designed to effectively respond to the external vibration with the movable center magnet considering the mechanical characteristics of the biomechanical energy, such as relatively low-frequency and high amplitude of vibration. Hence the L-EMG based on the fragile force equilibrium can generate high-quality electrical energy to supply power. Additionally, the environmental detective sensor and wireless transmission module are composed of the micro control unit (MCU) to minimize the required power for electronic device operation by applying the sleep mode, resulting in the extension of operation time. Finally, in order to maximize user convenience, a mobile phone application was built to enable easy monitoring of the surrounding environment. Thus, the proposed concept not only verifies the possibility of establishing the self-powered remote environmental monitoring system using biomechanical energy but further suggests a design guideline.