• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.1
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• pp.85-94
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• 2011

This paper is concerned to constitute a semi-active realtime feedback vibration control system and evaluate it through experiments in order to control in realtime the vibration externally generated, specially on the bridges which is structurally flexible. For the experiment of vibration control, we built a model bridge structure of Seohae Grand Bridge in a 1/200 reduced form and inflicted El-centro wave on the model structure also in a reduced force considering the lab condition. The externally excited vibration was to be controled by placing a shear type MR damper vertically on the center of bridge span, and the response (displacement and acceleration) of structure was to be acquired by placing LVDT and Accelerometer at the same time. As for the experiment concerning controlling vibration, a realtime feedback vibration control experiments were performed under each different condition largely such as un-control, passive on/off control, Lyapunov stability theory control, and Clipped-optimal control. Its control performance under different condition was quantitatively evaluated in terms of the peak absolute displacements, the peak absolute accelerations and the power required for control on the center of span. The results of experiments proved that the Lyapunov control and clipped-iptimal control were effective to decrease the displacement and acceleration of the structure, and also to decrease the power consumption to a great extent. Finally, the semi-active realtime feedback vibration control system constituted in this research was proven to be an effective way to control and manage the vibration generated on bridge structure.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.42 no.3
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• pp.409-415
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• 2022

The length of the acceleration lane in the area of entrance terminals is calculated based on 13 PS/ton horsepower of a cargo truck in Korea, so it is generally overestimated compared with the capacity of most vehicles traveling on an entrance ramp. Most drivers have, therefore, an indiscreet tendency to enter the main lane in all sections of an acceleration lane, which affects the traffic flow of the main lane. Because of this tendency, measures are required to minimize the impact on traffic flow of the main lane. The operating speed, rate of entrance, and traffic volume for each vehicle were investigated at the entrance terminals of the interchanges (ICs) of Yangji IC, Suseok IC, Yongin IC, and Osan IC, and the level of improvement in traffic flow was analyzed via VISSIM simulation. From the VISSIM simulation analysis, 74.0 % of the total vehicles traveled over the specified speed from the nose point where drivers would be able to recognize the traffic condition of the main carriageway, or the point at which there is a simplification of the curve section. In addition, 88.6 % of the vehicles entered the main carriageway up to 0.8 points compared with the entire length of the acceleration lane. It was subsequently found that an improvement of average speed in the main carriageway and at the entrance ramp can be achieved from 60.1 km/h to 68.5 km/h by intentionally limiting the entrance point onto the main carriageway up to 0.265 points of the entrance ramp.

• The Journal of the Acoustical Society of Korea
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• v.23 no.4
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• pp.309-315
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• 2004

To estimate the rate of noise contribution caused in each part of a vehicle in the course of a pass-by noise test. researches precedent have been made to study characteristics of nearby radiation noise measured on both sides of cars in a stationary state. With different revolutions per minute of engine. 2.800rpm and 3.200rpm respectively, in the measurement area of pass-by noise, the experiments have been conducted 7.5 meters away from the central axis of the test vehicle to study direction radiation according to frequencies. The results can be applied to reduce vehicle noise.

• Proceedings of the KIEE Conference
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• 2007.10a
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• pp.217-218
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• 2007

최근 개발된 비선형 자동조종 제어기를 사용하면 비행 환경에 무관하게 BTT 미사일의 입출력 동특성이 일정한 선형 시스템의 형대로 표현될 수 있다. 본 논문에서는 이와 같은 특성을 바탕으로 BTT 미사일이 목표물의 취약 지점을 정밀하게 요격할 수 있도록 자동조종장치 동역학의 시간 지연 효과를 고려하여 표적 충돌각을 최소화하는 최적 종말 유도 법칙을 설계하였다. 제안된 최적 종말 유도 법칙은 극좌표 변환을 사용하지 않기 때문에 가제어성을 보장하며, 가속도 편향값을 사용하지 않기 때문에 기존의 유도 법칙에 비하여 미사일의 기동성을 향상시킬 수 있는 장점을 갖는다.

• Proceedings of the Korea Water Resources Association Conference
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• 2018.05a
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• pp.324-324
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• 2018

지구 온난화로 인한 기후변화로 점차 가속됨에 따라 이로 인한 수자원 관리의 취약성이 증가되고 있는 전망이다. 물수지 순환에서 지하수와 증발산은 수자원 총량에서 많은 부분을 차지하고 있는 인자로써, 두 인자의 정량적인 분석은 지표와 대기 시스템의 분석에서 필수적이라고 할 수 있다. 지구의 담수 중 약 30%를 차지하고 있는 것이 지하수로써 이는 토양의 수원으로도 작용할 수 있으며, 특히 지하수면이 토양과 가까울수록 토양수분에 상당한 영향을 미칠 뿐만 아니라 증발산의 변동성과도 밀접하게 연결되어 있다. 지하수위 및 수문인자의 변화는 지하수를 활용하는 농업 및 수자원 관리와도 연계되어 있으므로 지하수와 증발산의 연관성에 대한 정량적인 변화의 비교/분석이 필수적이다. 또한 식생의 종류에 따른 지하수 및 증발산의 거동이 달라지게 됨으로 이에 대한 영향 또한 고려해야 한다. 그러나 지하수와 증발산의 직접적인 관계를 규명하는 선행연구가 아직 미흡하며, 국내 수자원분야에서의 두 인자간의 직접적인 연관성에 대하여 밝힌 연구는 거의 전무한 실정이다. 따라서 본 연구에서는 국내 플럭스 타워 관측 지점 중 다른 지표 특성 및 식생 조건을 가진 지역을 선정하여 각 다른 특성의 관측 지점에서의 분석을 실시하고자 한다. 관측된 수문기상인자인 증발산, 강수량과 관측 지점에서 가장 가까운 지하수 측정망으로부터 획득된 지하수 자료를 활용하여 각 인자들 사이의 연관성을 비교/분석을 실시하여 수문순환에서의 이들 간의 영향 정도를 파악할 예정이다.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.23 no.1
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• pp.82-96
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• 2024

While analyzing traffic flow, speed, traffic volume, and density are important macroscopic indicators, and acceleration and spacing are the important microscopic indicators. The speed and traffic volume can be collected with the currently installed traffic information collection devices. However, acceleration and spacing data are necessary for safety and autonomous driving but cannot be collected using the current traffic information collection devices. 'You Look Only Once'(YOLO), an object recognition technique, has excellent accuracy and real-time performance and is used in various fields, including the transportation field. In this study, to measure acceleration and spacing using YOLO, we developed a model that measures acceleration and spacing through changes in vehicle speed at each interval and the differences in the travel time between vehicles by setting the measurement intervals closely. It was confirmed that the range of acceleration and spacing is different depending on the traffic characteristics of each point, and a comparative analysis was performed according to the reference distance and screen angle to secure the measurement rate. The measurement interval was 20m, and the closer the angle was to a right angle, the higher the measurement rate. These results will contribute to the analysis of safety by intersection and the domestic vehicle behavior model.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.1
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• pp.709-714
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• 2017

Structures like bridges or buildings need to be checked continuously to diagnose their safety. However, it is extremely difficult for the people who access such structures to check all areas directly. To overcome this problem, there is a lot of active research into structural health monitoring (SHM) with wireless sensor nodes (WSNs). In this paper, for more accurate checking of SHM with WSNs, we experimentally compare and evaluate the performance of Xenomai, which provides real-time processing under the traditional Linux kernel. For this purpose, we patch Xenomai into the traditional Linux kernel of a commercial embedded board, Raspberry Pi, and implement a task that periodically reads vibration data of the z-axis from an accelerometer in order to analyze the natural frequency of cantilever beams. Reading the data from the traditional Linux kernel with the same method, we analyze the natural frequency of the cantilever beams using Smart Office Analyzer. Finally, to review the validity of Xenomai for WSNs, we obtain vibration data on the z-axis from the accelerometer via wired network and compared and analyzed them the same way.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.14 no.3
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• pp.9-23
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• 2015

A lane change maneuver which has a high driver cognitive workload and skills sometimes leads to severe traffic accidents. In this study, the Advanced Lane Change Assist System (ALCAS) was developed to assist with the automatic lane changes in merging sections which is mainly based on an automatic control algorithm for detecting an available gap, determining the Optimal Lane Change Start Point (OLCSP) in various traffic conditions, and positioning the merging vehicle at the OLCSP safely by longitudinal automatic controlling. The analysis of lane change behavior and modeling of fundamental lane change feature were performed for determining the default parameters and the boundary conditions of the algorithm. The algorithm was composed of six steps with closed-loop. In order to confirm the algorithm performance, numerical scenario tests were performed in various surrounding vehicles conditions. Moreover, feasibility of the developed system was verified in microscopic traffic simulation(VISSIM 5.3 version). The results showed that merging vehicles using the system had a tendency to find the OLCSP readily and precisely, so improved merging performance was observed when the system was applied. The system is also effective even during increases in vehicle volume of the mainline.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.3
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• pp.770-776
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• 2021

Positioning systems have been actively researched and developed over the past few years and have been used in many applications. This paper presents a method to determine a location in a large space using a sensor system consisting of an accelerometer and a single-axis gyroscope. In particular, to consider usability, a sensor device was loosely worn on the waist so that the experimental data could be used in practical applications. Based on the experimental results of circular tracks with radiuses of 1m and 3m, in this paper, an algorithm using the threshold of rotation angle was proposed and applied to the experimental results. A tracking experiment was performed on the grid-pattern track model. For raw sensor data, the average deviation between the final tracking point and the target point was approximately 15.2 m, which could be reduced to approximately 4.0 m using an algorithm applying the rotation angle threshold.

• Journal of the Korean Geotechnical Society
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• v.37 no.11
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• pp.51-60
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• 2021

River scour erodes the soil around the pier, reducing the lateral bearing capacity of the pier and lowering the stability of the structure. In this study, in order to examine the effect of scouring on the stability of the structure, an experiment was performed to measure the natural frequency of the pier according to the excavation of the surrounding ground. Impact vibration test was conducted on the pier with the caisson foundation of the Mangyeonggang Bridge, which is scheduled to be demolished. Accelerometers were attached to the top, center, and bottom of the pier and the acceleration responses were measured by hitting those three points. The experimental results showed that the top hit showed consistent and reasonable results of the acceleration responses according to the hitting position. The measured accelerations were converted to the frequency domain through Fast Fourier Transform (FFT), and then the natural frequency was determined. In addition, to analyze the scour effect on the natural frequency of the pier, the ground around the pier was excavated and the natural frequency change was analyzed. As a result, the natural frequency showed the decreasing tendency according to the excavation depth, but the decrease was small due to the large stiffness of the caisson foundation.