• 국제학술발표논문집
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• The 9th International Conference on Construction Engineering and Project Management
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• pp.328-335
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• 2022

With the advance of robot capabilities and functionalities, construction robots assisting construction workers have been increasingly deployed on construction sites to improve safety, efficiency and productivity. For close-proximity human-robot collaboration in construction sites, robots need to be aware of the context, especially construction worker's behavior, in real-time to avoid collision with workers. To recognize human behavior, most previous studies obtained 3D human poses using a single camera or an RGB-depth (RGB-D) camera. However, single-camera detection has limitations such as occlusions, detection failure, and sensor malfunction, and an RGB-D camera may suffer from interference from lighting conditions and surface material. To address these issues, this study proposes a novel method of 3D human pose estimation by extracting 2D location of each joint from multiple images captured at the same time from different viewpoints, fusing each joint's 2D locations, and estimating the 3D joint location. For higher accuracy, the probabilistic representation is used to extract the 2D location of the joints, considering each joint location extracted from images as a noisy partial observation. Then, this study estimates the 3D human pose by fusing the probabilistic 2D joint locations to maximize the likelihood. The proposed method was evaluated in both simulation and laboratory settings, and the results demonstrated the accuracy of estimation and the feasibility in practice. This study contributes to ensuring human safety in close-proximity human-robot collaboration by providing a novel method of 3D human pose estimation.

• 한국정밀공학회지
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• 제13권9호
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• pp.114-129
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• 1996

This paper describes the whole development phase for the underwater vehicle actuating system with high hydroload torque disturbance. This includes requirement analysis, system modeling, control algorithm design, real time implementation, test and performance evaluations. As for driving control algorithms, fuzzy logic, variable structure and PD(Proportional-Differential) algorithm were designed and implemented on board controller using a single chip microprocessor. Intel 8797. And test and performance evaluation is carried out both single test and wystem integration test. We could confirm the basic performance of actuating system through the single test and gereral developing work of any actuating systems was finished with a single performance test of actuating system without system integration test. But, we suggested that system integration test be needed. System integration test is carried out using G/C HILS(Guidance and Control Hardware-In-the -Loop Simulation) which is constituted flight motion simulator, load simulator, real time host computer and the related subsystems such as inertial navigation system, power supply system and Guidance and Control Computer etc.. The most important practical contribution of this paper is that full system characteristics such as minimal control effort, enhancement of guidance and autopilot performance by the actuating system using G/C HILS technique are investigated. Through full running G/C HILS, in spite of the passing to single tests, some control algorithm resulted in failure as to stability of full system and system time frame.

• 한국지반공학회논문집
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• 제26권4호
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• pp.59-68
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• 2010

파이핑은 제체 내부 침식의 한 형태로서 토립자의 진행성 유출에 기인하며 균열이 발생한 댐 뿐만 아니라 용해성 재료로 인하여 수년 동안 만족스런 거동을 보인 댐들에서도 발생한다. 파이핑 현상은 필댐의 붕괴 원인의 약 50%를 차지하고 있으며 필댐 관리의 주요항목이나, 이에 대한 체계적인 평가에는 다소 어려움이 있다. 이에 본 연구에서는 파이핑 현상에 대한 비파괴 탐지를 위한 전기비저항 탐사기법의 적용성을 파악하기 위해 대청댐 비상여수로 건설을 위해 해체되는 부댐에 파이핑 모사시험과 전기비저항 모니터링을 수행하였다. 제체에 수평공을 천공하여 인공적인 유로를 만들고 저수지 물을 유입시켜 실규모 파이핑 현상을 모사하였으며, 파이핑 현상 모사 시험전과 시험 중 측정한 전기비저항값을 비교한 결과 파이핑 발생 시 측정한 전기비저항값이 조금 더 큰 변화를 보임으로써 전기비저항 모니터링 탐사는 실제 담수되어 있는 제체의 파이핑 현상을 효과적으로 탐지할 수 있을 것으로 판단된다.

• Computers and Concrete
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• 제31권5호
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• pp.405-417
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• 2023

The submerged floating tunnel (SFT) is tethered by mooring lines anchored to the seabed, therefore, the structural integrity of the anchor should be sensitively managed. Despite their importance, reaction forces cannot be simply measured by attaching sensors or load cells because of the structural and environmental characteristics of the submerged structure. Therefore, we propose an effective method for estimating the reaction forces at the seabed anchor of a submerged floating tunnel using a structural pattern model. First, a structural pattern model is established to use the correlation between tunnel motion and anchor reactions via a deep learning algorithm. Once the pattern model is established, it is directly used to estimate the reaction forces by inputting the tunnel motion data, which can be directly measured inside the tunnel. Because the sequential characteristics of responses in the time domain should be considered, the long short-term memory (LSTM) algorithm is mainly used to recognize structural behavioral patterns. Using hydrodynamics-based simulations, big data on the structural behavior of the SFT under various waves were generated, and the prepared datasets were used to validate the proposed method. The simulation-based validation results clearly show that the proposed method can precisely estimate time-series reactions using only acceleration data. In addition to real-time structural health monitoring, the proposed method can be useful for forensics when an unexpected accident or failure is related to the seabed anchors of the SFT.

• Geomechanics and Engineering
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• 제34권5호
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• pp.577-595
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• 2023

A dynamic triaxial discrete element numerical model of lightweight soil was established using the discrete element method to study the microscopic mechanism of expanded polystyrene (EPS) particles in the soil under cyclic loading. The microscopic parameters of the discrete element model of the lightweight soil were calibrated depending on the dynamic triaxial test hysteresis curves. Based on the calibration results, the effects of the EPS particles volume ratio and amplitude on the contact force, displacement field, and velocity field of the lightweight soil under different accumulated strains were studied. The results showed that the hysteresis curves of lightweight soil exhibit nonlinearity, hysteresis, and strain accumulation. The strain accumulated in remolded soil is mainly tensile strain, and that in lightweight soil is mainly compressive strain. As the volume ratio of EPS particles increased, the contact force first increased and then decreased, and the displacement and velocity of the particles increased accordingly. With an increase in amplitude, the dynamic stress of the particle system increased, and the accumulation rate of the dynamic strain of the samples also increased. At 5% compressive strain, the contact force of the particles changed significantly and the number of particles deflected in the direction of velocity also increased considerably. These results indicated that the cemented structure of the lightweight soil began to fail at a compressive strain of 5%. Thus, a compressive strain of 5% is more reasonable than the dynamic strength failure standard of lightweight soil.

• 대한토목학회논문집
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• 제28권2A호
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• pp.207-214
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• 2008

본 논문에서는 연계논문에서 제안된 혼합구조 접합부의 개선정도를 확인하기 위하여 2개의 혼합구조 실험체에 대하여 4절점 휨시험을 수행하였다. 혼합구조 접합부의 거동 분석을 위하여 3차원 비선형해석 결과와 실재하 실험 결과를 하중-처짐 관계, 하중-변형률 관계, 접합부 개구폭, 균열과 파괴모드를 통하여 비교하였다. 3차원 비선형 해석을 위하여 접촉요소를 사용하였으며 해석프로그램은 범용 구조 해석프로그램인 아바쿠스를 이용하였다. 실험과 해석의 결과로부터 제안된 L 모양의 접합부가 휨하중에서 기존안보다 강성이 크게 나타났으며, 보다 나은 구조적 성능을 나타냄을 확인하였다.

• 대한토목학회논문집
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• 제30권3A호
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• pp.309-316
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• 2010

이 논문에서는 인장과 압축하중에 놓은 무근 콘크리트와 철근콘크리트 구조물의 거동을 모사하기 위해 비국소화 이방성 손상모델을 제안하였다. 손상변수로써 대칭형의 이차 텐서을 사용한 연속체 손상모델에 기초한다. 콘크리트와 같은 준-취성재료에 있어 손상양상은 인장부와 압축부에서 다른 양상을 나타낸다. 이러한 두 개의 손상영역은 전체 변형률 텐서의 주변형률 성분을 손상텐서 속도에 비례하는 손상진전 법칙을 이용하여 모델링하였다. 제안된 모델의 유효성을 검토하기 위해 nooru-mohamed에 의해 실시된 이중 노치가 있는 시험체와 철근콘크리트 휨 시험체를 대상으로 해석을 수행하였다. 해석결과, 비국소화 이방성 모델은 혼합모드 파괴에 대한 균열진전을 적절히 모사할 수 있었으며 철근콘크리트 휨 시험체의 구조적 파괴에 있어서도 높은 수준의 콘크리트 손상 및 철근의 항복까지를 해석할 수 있었다.

• Structural Engineering and Mechanics
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• 제87권2호
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• pp.137-149
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• 2023

In this study, to explore the working performance of the CFST split spherical node wind power tower, two groups of CFST split spherical joint plane towers with different web wall thicknesses and a set of space systems were analyzed. The tower was subjected to a low-cycle repeated load test, and the hysteresis and skeleton curves were analyzed. ABAQUS finite element simulation was used for verification and comparison, and on this basis parameter expansion analysis was carried out. The results show that the failure mode of the wind power tower was divided into weld tear damage between belly bar, high strength bolt thread damage and belly rod flexion damage. In addition, increasing the wall thickness of the web member could render the hysteresis curve fuller. Finally, the bearing capacity of the separated spherical node wind power tower was high, but its plastic deformation ability was poor. The ultimate bearing capacity and ductility coefficient of the simulated specimens are positively correlated with web diameter ratio and web column stiffness ratio. When the diameter ratio of the web member was greater than 0.13, or the stiffness ratio γ of the web member to the column was greater than 0.022, the increase of the ultimate bearing capacity and ductility coefficient decreased significantly. In order to maximize the overall mechanical performance of the tower and improve its economy, it was suggested that the diameter ratio of the ventral rod be 0.11-0.13, while the stiffness ratio γ should be 0.02-0.022.

• Structural Engineering and Mechanics
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• 제84권2호
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• pp.155-165
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• 2022

The use of electricity and communication between electronic devices is increasing daily, which makes the stability of electrical power supply vital. Since the 1990s, large earthquakes have occurred frequently causing considerable direct damage to electrical power facilities as well as secondary damage, such as difficulty in restoring functions due to the interruption of electric power supply. Therefore, it is very important to establish measures to protect electrical power facilities, such as transformers and switchboards, from earthquakes. In this study, a 154 kV transformer whose service life had expired was installed on the base fabricated by simulating the field conditions and conducting the shaking table tests. The dynamic characteristics and seismic behavior of the 154 kV transformer were analyzed through the resonance frequency search test and seismic simulation test that considers the front, rear, left, and right directions. Since the purpose of this study is to analyze the acceleration amplification in the bushing due to the acceleration amplification, the experimental results were analyzed focusing on the acceleration response and the converted acceleration amplification ratio rather than the failure due to the displacement response of the transformer. The seismic force amplification at the transformer bushing was evaluated by simulating the characteristics of electrical power facilities in South Korea, and compared with the IEC TS 61463 acceleration amplification factor. Finally, the amplification factor at zero period acceleration (ZPA) modified for each return period was summarized. The results of this study can be used as data to define the amplification factor at ZPA of the transformer bushing, simulating the characteristics of electrical power facilities in Korea.

• 항공우주시스템공학회지
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• 제17권6호
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• pp.144-148
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• 2023

항공기 배터리는 항공기의 엔진 시동 전원 및 비상 전원을 공급하는 역할을 하는 핵심 장비이다. 배터리는 안정적인 전원 공급을 위해 언제나 충분한 용량을 보장하도록 충전되어야 하며 높은 신뢰성을 유지해야 한다. T-50 계열 항공기 배터리는 -18 ℃ 이상의 낮은 온도에서 엔진을 최대 2회 시동할 수 있도록 설계하였으나, 겨울철에 엔진 시동에 실패하는 현상이 간헐적으로 발생하였다. 이에 본 논문에서는 배터리의 저온 충전 시 발생하는 실패 현상에 대하여 분석 및 시험을 수행하고 이를 바탕으로 충전 알고리즘을 개선하였다. 또한 저온시동 모사시험을 수행한 결과 저온에서의 배터리 충전 결함이 해결되었으며 충전 성능 향상이 확인되어 새로운 알고리즘의 개선을 확인하였다.