• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.4A
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• pp.507-515
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• 2008

In this study, a method predicting the displacement response of structures from the measured dynamic strain signal is proposed by using mode decomposition technique. Evaluation of bridge stability is normally focused on the bridge completed. However, dynamic loadings including wind and seismic loadings could be exerted to the bridge under construction. In order to examine the bridge stability against these dynamic loadings, the prediction of displacement response is very important to evaluate bridge stability. Because it may be not easy for the displacement response to be acquired directly on site, an indirect method to predict the displacement response is needed. Thus, as an alternative for predicting the displacement response indirectly, the conversion of the measured strain signal into the displacement response is suggested, while the measured strain signal can be obtained using fiber optic Bragg-grating (FBG) sensors. As previous studies on the prediction of displacement response by using the FBG sensors, the static displacement has been mainly predicted. For predicting the dynamic displacement, it has been known that the measured strain signal includes higher modes and then the predicted dynamic displacement can be inherently contaminated by broad-band noises. To overcome such problem, a mode decomposition technique was used. Mode decomposition technique estimates the displacement response of each mode with mode shape estimated to use POD from strain signal and with the measured strain signal decomposed into mode by EMD. This is a method estimating the total displacement response combined with the each displacement response about the major mode of the structure. In order to examine the mode decomposition technique suggested in this study model experiment was performed.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.31 no.5
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• pp.259-266
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• 2018

This is the study for developing the hetero-core optical fiber sensors which are purpose to measure the prestress of PSC bridges during the life cycle period. The goal of this study is to improve the resolution of hetero-core sensors. As a result of the test, it is possible to measure the displacement in $2{\mu}m$ increments. In other words, if the length of the sensor module is 30cm, it is possible to measure the prestress variations in 0.2MPa increments at specified compressive strength of concrete(fck) of 40MPa by Hook's Law. So it can be useful for development of a sensor module measuring internal prestress measurement.

• Tunnel and Underground Space
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• v.21 no.1
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• pp.1-10
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• 2011

In these days, the development of optical fiber sensor technology is so remarkable that it can measure various physical and chemical quantities ranging from a few millimeters to over several kilometers. In addition, it is attempted to assess the structural integrity of the state of the advanced technologies and existing structures such as ships, aircrafts, and bridges. This paper introduced the case histories of the measuring technology of optical fiber applied on structures such as roads and tunnels. The case history using OTDR (Optical Time Domain Reflectometery) was also introduced in this paper. Measurement of the pre-convergence of a tunnel is essential to assess the safety of a tunnel and understand the geological conditions ahead of an advancing tunnel. Therefore, the pre-convergence measuring technology using OTDR is expected to substitute conventional measuring techniques.

• Journal of the Institute of Convergence Signal Processing
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• v.11 no.4
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• pp.338-344
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• 2010

Both ends of welding line are often closed by wall in the welding of ship blocks. In this research, seam tracking sensing system for butt welding in the condition with wall was developed. Seam tracking sensing system measures position of carriage from wall and detects root-pass of welding line. The system consists of the laser displacement sensors and ultrasonic sensors. The laser displacement sensor reciprocal1y rotates by the motor and measures a distance from laser sensor to the welding material. The ultrasonic sensor measures a distance between welding system and walls. The distance measured by the ultrasonic sensor is used to get X(driving) position and to determine initial and end point of the weld line. Y(weaving) and Z(height) of the weld line are obtained by the distance measured by the laser displacement sensor and the orientation of the sensor. The sensing system includes the controller that is independent from the welding carriage. The seam tracking sensing system is attached to both side of welding carriage so that interference between welding torch and sensing system can be avoided during the welding. And both side sensing system minimize dead zone. Finally, developed sensing system was adhered to welding carriage and verified usefulness by experiments.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.291-295
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• 1996

This paper discusses several design factors of a capacitance displacement sensor with a numerical method and several experiments and describes guide lines of the design of this type sensor. We introduce the charge density method for the analysis of this type sensor, which has feasible accuracy and efficiency. The analysis of this type sensor with the charge density method agrees with displacement sensitivity experiments of a circular plate capacitance sensor with the sensor amp based In the charge transfer principle.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.30 no.3
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• pp.249-254
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• 2017

The paper presents a new short-term dynamic displacement estimation method based on an acceleration and a geophone sensor. The proposed method combines acceleration and velocity measurements through a real time data fusion algorithm based on Kalman filter. The proposed method can estimate the displacement of a structure without displacement sensors, which is typically difficult to be applied to earthquake or fire sites due to their requirement of a fixed rigid support. The proposed method double-integrates the acceleration measurement recursively, and corrects an accumulated integration error based on the velocity measurement, The performance of the proposed method was verified by a lab-scale test, in which displacement estimated by the proposed method are compared to a reference displacement measured by laser doppler vibrometer (LDV).

• Proceedings of the Korean Information Science Society Conference
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• 2002.10d
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• pp.223-225
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• 2002

MEMS 가속도센서 기술의 발전은 가속도센서를 이용한 사용자 인터페이스 구현에 대한 연구를 촉진시키고 있다. 본 논문에서는 가속도센서를 기반으로 한 휴대폰 단말기를 사용하여, HCI 관점에서 센싱 기술을 소개한다. 이러한 기술은 센서 신호로부터 컴퓨터의 변위량을 계산함으로써 Knock & Mute 와 Tilt & Scroll와 같은 인터페이스를 구현할 수 있다.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2004.04a
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• pp.387-393
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• 2004

General purpose of cylindrical capacitive displacement sensor(CCS) is measuring run-out motion and deflection of rotor. If CCS has narrow sensing range, its sensitivity coefficients must be calibrated precisely. And x, y component of CCS output can be coupled. In this research, CCS calibration procedure is automated with automatic calibration program and PC-controlled stage. And, coupled-terms of CCS signals were removed and the errors between measured position and mapped CCS signal were reduced obviously by sensitivity matrix that linearly.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.207-211
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• 2004

The performance of an inductive position sensor has approved by previous research papers. In this paper, magnetic circuit model of a ring-type multi-pole insuctive position sensor is described. The magnetic circuit model is required to design in ductive position sensor as well as draw a fault tolerance algorithm. Using the magnetic circuit theory, we derived the relationship between voltage applied and flux density in the normal air-gap. By idealizing the modulation/demodulation processes of signal processing circuit, sensor gain with respect to change of displacement is theoretically calculation using the magnetic circuit model, which validate the theoretical derivation.

• Journal of Welding and Joining
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• v.13 no.4
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• pp.65-74
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• 1995

The weld seam tracking sensor is indispensable to improve the flexibility of automatic arc welding systems. Among the position sensing methods available, a laser displacement sensor is one of the most prevailing methods. In this study, a laser displacement sensor was examined on detecting the weld seam of lap joints in sheet metal arc welding. The output signal of the laser displacement sensor may ontain severe fluctuation from the effect of arc light, spatters, fume, etc. So a variety of signal processing methods was applied to smooth the output signal of the sensor. And then the weld joint was determined by using the central difference method. It was revealed that the quadratic mean method plays an important role in detecting the weld seam during welding especially.