• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.11
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• pp.1697-1705
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• 2022

The safety of marine construction workers and marine pollution problems are occurring due to large-scale offshore construction. In particular, underwater construction work in the sea has a higher risk than other work, so it is necessary to apply an unmanned alternative system that considers the safety of the workers. In this paper, the ROV system for offshore construction has been developed for underwater unmanned work. A monitoring system was developed for position control through the control of underwater propellants, pneumatic gripper, and monitoring of underwater work. As a result of the performance evaluation, the underwater movement speed of the ROV was evaluated to be 0.89 m/s, and it was confirmed that the maximum load of the pneumatic gripper was 80 kg. In addition, the network bandwidth required for underwater ROV control and underwater video streaming was evaluated to be more than 300Mbps, wired communication at 92.7 ~ 95.0Mbit/s at 205m, and wireless communication at 78.3 ~ 84.8Mbit/s.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.1
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• pp.41-50
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• 2021

In this study, the flow path width (Gap Size), which is the flow path of fluid, was selected differently among various factors that determine the Ccontrol Force of MR damper, and the change of Control Force was confirmed accordingly. For this purpose, two MR dampers with a Gap Size of 1.0mm and 1.5mm were fabricated, respectively, and dynamic load experiments were conducted according to changes in applied current and vibration conditions The experimental results showed that the minimum Control Force was 3.2 times higher than 1.5mm in the case of 1.0mm Gap Size, and the maximum Control Force was 2.3 times higher than 1.5mm in the case of 1.0mm Gap Size. In addition, the increased width of the Control Force according to applied current was 34N for Gap Size 1.0mm, and 12.7N for Gap Size 1.5mm. As the gap Size increased, the overall Control Force and the increase in the Control Force by the applied current decreased. Next, the dynamic range, which is a performance evaluation index of the semi-active Control device, was 2.3 on average under 1.0mm condition and 2.8 on average under 1.5mm condition, confirming the possibility of utilization as a semi-active Control device.

• Journal of the Earthquake Engineering Society of Korea
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• v.2 no.4
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• pp.95-102
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• 1998

본 연구의 목적은 능동질량 장치를 이용하여 지진하중을 받는 건물모델의 응답을 제어하는 것으로서 실험에 사용된 능동질량 장치는 교류형 서보 모터에 의해 관성력이 건물모델의 응답에 반작용하여 제어를 하게 되는 원리를 이용한 것이다 소형 진동대에 의한 외부하중 묘사 신호처리와 제어력 발생을 위한 장비들이 구축된 실험 모델로써 능동 질량 추진기가 1층 전단형 건물모델 상부에 설치된 해석 모델을 실현하였으며 제어력 산정을 위한 선형 2차 제어 알고리듬은 LabVIEW 프로그램을 사용해서 구현하였다. 건물의 응답과 제어력을 고려해서 제어성능을 검증하였으며 능동 질량 장치를 설치함으러써 공진하중과 지진하중에 대한 건물의 응답이 감소하고 또한 속도피드백 알고리듬이 그 외의 피드백 알고리듬 보다 제어력이 가장 적게 소용되면서 건물의 응답을 감소시키는 것을 실험적으로 파악하였다.

• Transactions of The Korea Fluid Power Systems Society
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• v.3 no.2
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• pp.7-13
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• 2006

In this paper the noise source and the amplifying mechanism are analyzed to reduce the noise of the excavator return line using the experimental approach and the CFD simulation. The result says that the reason of noise generation is pipe vibration caused by the cavitation at the main control valve and the level of noise is proportional to the valve back pressure at the return line. The methodology to reduce this noise was proposed and verified by the vehicle test.

• Proceedings of the KSR Conference
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• 2011.05a
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• pp.1681-1688
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• 2011

The platform screen door open-close mechanisms at today's subway are divided by "Radio Frequency method" and "Method at entrance perception sensor". In the case of "method at entrance perception sensor", there happen a lot of occasions of malfunctioning that may cause problems in terms of timeliness, swiftness and reliability of train operation and even ends up to train operation stop since the perceiving process is complicated and it is prone to have dust on lenses, position alteration by train vibration, and less reflection light in the case of new train. In this study, we find how to minimize possible problems in terms of maintenance during train operation period, and seek its alternatives in order not only to have no malfunction in perception but also to cause no disturbance in train operation through dealing organically when perceiving door open-close to minimize delay time.

• Proceedings of the KSR Conference
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• 2011.05a
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• pp.824-829
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• 2011

EMS-type Maglev vehicle maintains constant levitation air-gap between electromagnet and guideway by using gap sensor. The other words, when Maglev vehicles levitating over the guideway, mass of the vehicle effects through 1st (electromagnetic air-gap control) and 2nd (air-spring) suspension to grider. Resonace between electromagnetic suspension and grider could be occurred, which causes instability and poor ridecomfort. This paper is to test the dymanic interaction between levitation air-gap and switching system grider that has less mass and high natural frequencies than other type of general girders.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.931-938
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• 2011

Nondestructive inspection(NDI) is a testing procedure used to easily inspect an object for internal defects, abnormalities, shape, and structure, etc. without destroying it. Typical candidates for NDI include buildings, railways, aircraft, bridges, underground pipelines and various types of factory equipment. Recent advances in nondestructive evaluation(NDE) technologies have led to improved methods for quality control and in-service inspection, and the development of new options for material diagnostics. Under frame side sill in rolling stocks is designed for preventing corrosion in order to meet mechanical requirements. However during long operation time, there are corrosion in the under frame side sill caused by environmental effect, vibration and etc. This paper introduces the methods of a survey and assessment on NDI applications in Electric Multiple Units(EMU). The main objective of this paper was to obtain information on various applications and evaluation of NDI technology in EMU.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.2115-2124
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• 2011

The rail surface defects which are generated on repeated rolling contact fatigue are getting increased according to high speed, high density, and minimum weight. In addition, Increasing noise and vibration are affected by these also impact load generated as well. Because of this phenomenon, more serious and critical damages were occurred. In fact, in order to control them, the rail grinding were conducted. However, there are not enough researches to make an criteria of generating optimal rail grinding amount in Korea. This study evaluated how depth of hardening on rail surface is formed and suggested optimal rail grinding amount by RCF(rolling contact fatigue) test with generated contact pressure between KTX wheel and UIC60 rail by applying FEM analysis. Therefore, the amount was generated approximately 0.2mm/20MGT to maintain integrity of rail surface by getting rid of depth of hardening on rail according to rail accumulated passing tonnage.

• Interaction and multiscale mechanics
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• v.6 no.4
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• pp.339-356
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• 2013

This paper investigates the optimized parameters of Tuned Mass Dampers (TMDs) for vibration control of high-rise structures including Soil Structure Interaction (SSI). The Artificial Bee Colony (ABC) method is employed for optimization. The TMD Mass, damping coefficient and spring stiffness are assumed as the design variables of the controller; and the objective is set as the reduction of both the maximum displacement and acceleration of the building. The time domain analysis based on Newmark method is employed to obtain the displacement, velocity and acceleration of different stories and TMD in response to 6 types of far field earthquakes. The optimized mass, frequency and damping ratio are then formulated for different soil types; and employed for the design of TMD for the 40 and 15 story buildings and 10 different earthquakes, and well results are achieved. This study leads the researchers to the better understanding and designing of TMDs as passive controllers for the mitigation of earthquake oscillations.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.1802-1807
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• 2004

When a construction company builds a high structure, many piles should be driven into the ground by a hammer whose weight is 7,000 Kg in order to make the ground under the structure safe and strong. So, it is essential to determine whether a pile is penetrated into the ground enough to support the weight of the structure since ground characteristics at different locations are different each other. This paper proposes a visual measurement system for pile rebound and penetration movement including vibration using a high-speed line-scan camera and a specially designed mark to recognize two-dimensional motion parameters of the mark using only a line-scan camera. A mark stacking white and black right-angled triangles is used for the measurement, and movement information for vertical distance, horizontal distance and rotational angle is determined simultaneously