• 대한토목학회논문집
• /
• 제28권2A호
• /
• pp.215-222
• /
• 2008

본 논문은 현수교 이중 행어 시스템에 대한 진동기반 SI 장력추정기법의 실험적 검증을 소개한다. 현수교 이중 행어 시스템을 모사한 실험 모델을 제작되었으며, 세가지 경우의 클램프 위치에 대한 세가지 경우의 행어장력에 대해서 총 9회의 진동실험이 반복 수행되었다. 각각의 계측된 가속도 응답 데이터에 대해서, 모달분석을 통한 고유진동수와 모드 형상이 추출되었다. 추출된 일련의 동특성치들에 대하여 기존의 장력추정 이론인 현이론과 선형회기법을 적용하여 장력을 추정하였다. 또한 진동기반 SI 장력추정기법을 적용하여 장력을 추정하였는데, 추정된 장력은 수치모델과 계측모델의 동적 특성치들이 동일하게 될 때, 수치모델의 케이블 장력을 인식함으로써 추정되었다. 추정결과, 클램프의 위치에 따라서 기존의 이론을 이용한 추정장력의 오차는 최대 53.1%까지 보이는 반면, 진동기반 SI기법을 이용한 추정장력기법의 장력추정 오차는 모든 경우에 대하여 3% 이내 이다.

• Geomechanics and Engineering
• /
• 제37권5호
• /
• pp.475-498
• /
• 2024

The prediction of the susceptibility of soil to liquefaction using a limited set of parameters, particularly when dealing with highly unbalanced databases is a challenging problem. The current study focuses on different ensemble learning classification algorithms using highly unbalanced databases of results from in-situ tests; standard penetration test (SPT), shear wave velocity (V_s) test, and cone penetration test (CPT). The input parameters for these datasets consist of earthquake intensity parameters, strong ground motion parameters, and in-situ soil testing parameters. liquefaction index serving as the binary output parameter. After a rigorous comparison with existing literature, extreme gradient boosting (XGBoost), bagging, and random forest (RF) emerge as the most efficient models for liquefaction instance classification across different datasets. Notably, for SPT and V_s-based models, XGBoost exhibits superior performance, followed by Light gradient boosting machine (LightGBM) and Bagging, while for CPT-based models, Bagging ranks highest, followed by Gradient boosting and random forest, with CPT-based models demonstrating lower G_mean(error), rendering them preferable for soil liquefaction susceptibility prediction. Key parameters influencing model performance include internal friction angle of soil (ϕ) and percentage of fines less than 75 µ (F₇₅) for SPT and V_s data and normalized average cone tip resistance (q_c) and peak horizontal ground acceleration (a_max) for CPT data. It was also observed that the addition of V_s measurement to SPT data increased the efficiency of the prediction in comparison to only SPT data. Furthermore, to enhance usability, a graphical user interface (GUI) for seamless classification operations based on provided input parameters was proposed.

• 한국구조물진단유지관리공학회 논문집
• /
• 제24권6호
• /
• pp.17-24
• /
• 2020

본 연구에서는 물로 둘러싸인 철근콘크리트 취수탑에 대한 비선형내진해석을 수행하였다. 구조물 주변의 유체를 고려하기 위하여 부가질량 및 CEL을 이용한 유체구조물 상호작용 모델을 구성하였다. 이 때 부가질량모델은 음해법을 사용하였고 유체구조물 상호작용 모델은 양해법을 사용하였다. 입력운동은 동일한 인공지진을 재현주기에 따라 500년, 1000년, 2400년에 해당하도록 크기를 조절하였다. 유체를 고려한 모델의 보수성을 평가하기 위하여 유체를 고려하지 않은 모델을 구성하여 참조해로 삼았다. 콘크리트와 철근의 재료모델은 항복후의 비선형 거동을 고려할 수 있도록 선정하였고 ABAQUS를 이용하여 해석을 수행하였다. 해석결과 얻어진 구조물의 가속도응답스펙트럼을 비교한 결과 주변 유체의 영향은 구조물의 기본 진동수에 해당하는 첨두의 진동수와 첨두값의 크기를 감소시키는 것으로 나타났다. 하지만 부가 질량 모델에서는 고차 진동수에 해당하는 첨두값에는 영향을 미치지 못하였다. 유체의 영향을 고려한 단면모멘트는 부가질량모델의 경우 참조 모델의 응답에 비하여 크게 증가하였다. 특히 선형거동이 지배적인 작은 크기의 지진응답에 대해서 이러한 증폭이 크게 발생하였다. 유체구조물 상호작용 모델의 경우 낮은 진동수성분을 가진 단면모멘트는 참조모델의 응답에 비하여 증폭이 발생하나, 높은 진동수 성분을 단면 모멘트는 증폭이 발생하지 않았다. 이러한 결과를 종합하여 볼 때 부가질량모델의 보수성이 유체구조물상호작용 모델이 비해 큰 것으로 평가되었다.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2011년도 정기총회 및 추계학술대회 논문집
• /
• pp.3079-3085
• /
• 2011

Through Korean Urban Maglev Program started in 2006, an urban maglev train was developed and the demonstration line is under construction as of now in 2011. The target speed of the developed maglev train is 110km/h, and the core technologies for super speed maglev trains over 500km/h are being studied. The propulsion and levitation systems of the super speed maglev train under consideration consist of linear synchronous motors (LSM) and levitation electromagnets which also act as a mover of LSM. In addition, guidance electromagnets are used to ensure stable running on curved tracks during super speed operation. The levitation and guidance control is focused on in this paper. For experimental purpose, a small maglev train is being manufactured, and its levitation and guidance controller is studied. The main task of the controller is to maintain the gap between the corresponding electromagnet and the guideway constantly. In general, measurements of the gap, acceleration and current and so on are utilized, and the gap control is implemented independently for each electromagnet. In this paper, the levitation and guidance system is modelled considering mechanical interactions, and the levitation and guidance controller is proposed based on this model. The developed controller is verified by various simulations using MATLAB/Simulink.

• 제어로봇시스템학회논문지
• /
• 제19권8호
• /
• pp.718-724
• /
• 2013

In today's automotive industry, there exist several systems that help drivers reduce the possibility of accidents, such as the ADAS (Advanced Driver Assistance System). The ADAS helps drivers make correct and quick decisions during dangerous situations. This study analyzed the performance of the IMM (Interacting Multiple Model) method based on multiple Kalman filters using the data acquired from a driving simulator. An IMM algorithm is developed to identify the current discrete state of neighboring vehicles using the sensor data and the vehicle dynamics. In particular, the driving modes of the neighboring vehicles are classified by the cruising and maneuvering modes, and the transition between the states is modeled using a Markovian switching coefficient. The performance of the IMM algorithm is analyzed through realistic simulations where a target vehicle executes sudden lane change or acceleration maneuver.

• 제어로봇시스템학회논문지
• /
• 제13권10호
• /
• pp.962-969
• /
• 2007

In this paper, an approach is developed for relative state estimation of satellite formation flying. To estimate relative states of two satellites, the Extended Kalman Filter Algorithm is adopted with the relative distance and speed between two satellites and attitude of satellite for measurements. Numerical simulations are conducted under two circumstances. The first one presents both chief and deputy satellites are orbiting a circular reference orbit around a perfectly spherical Earth model with no disturbing acceleration, in which the elementary relative orbital motion is taken into account. In reality, however, the Earth is not a perfect sphere, but rather an oblate spheroid, and both satellites are under the effect of $J_2$ geopotential disturbance, which causes the relative distance between two satellites to be on the gradual increase. A near-Earth orbit decays as a result of atmospheric drag. In order to remove the modeling error, the second scenario incorporates the effect of the $J_2$ geopotential force, and the atmospheric drag, and the eccentricity in satellite orbit are also considered.

• Smart Structures and Systems
• /
• 제16권6호
• /
• pp.1003-1021
• /
• 2015

MR dampers have been proposed for the control of cable vibration of cable-stayed bridge in recent years due to their high performance and low energy consumption. However, the highly nonlinear feature of MR dampers makes them difficult to be designed with efficient semi-active control algorithms. Simulation study has previously been carried out on the cable-MR damper system using a semi-active control algorithm derived based on the universal design curve of dampers and a bilinear mechanical model of the MR damper. This paper aims to verify the effectiveness of the MR damper for mitigating cable vibration through a full-scale experimental test, using the same semi-active control strategy as in the simulation study. A long stay cable fabricated for a real bridge was set-up with the MR damper installed. The cable was excited under both free and forced vibrations. Different test scenarios were considered where the MR damper was tuned as passive damper with minimum or maximum input current, or the input current of the damper was changed according to the proposed semi-active control algorithm. The effectiveness of the MR damper for controlling the cable vibration was assessed through computing the damping ratio of the cable for free vibration and the root mean square value of acceleration of the cable for forced vibration.

• 대한기계학회논문집
• /
• 제17권9호
• /
• pp.2294-2303
• /
• 1993

This paper investigated the characteristics of the turbulent incompressible flow past the orifice ring in an axi-symmetric pipe. The flow field was the turbulent pulsatile flow for Reynolds number of $2{\times}10^{5}$ which was defined based on the maximum velocity and the pipe diameter at the inlet, with oscillating frequence $(f_{os})=1/4{\pi}$ which was considered as quasi-steady state frequence. In the present investigation, finite analytic method was used to solve the governing equations in Navier Stokes and turbulent transport formulations. Particularly at high Reynolds number and low oscillation frequency, the effects of orifice ring on the flow were numerically investigated. The separation zone behind the orifice ring during the acceleration phase was found to be decreased. However, during the deceleration phase, the separation behind the orifice ring for pulsatile flow continuously grow to a size even larger than that in steady flow. The pressure drop in steady flow was found to be constant and always positive while for pulsatile flow the pressure drop change with time. And large turbulent kinetic energy, dissipation rate were found to be located in the region where the flow passes through the orifics ring. The maximum turbulent kinetic energy, generally occurs along the shear layer where the velocity gradient is large.

• 한국정밀공학회지
• /
• 제21권1호
• /
• pp.101-108
• /
• 2004

An electro-hydraulic manipulator using hydraulic actuators has many nonlinear elements, and its parameter fluctuations are greater than those of an electrically driven manipulator. So it is relatively difficult to obtain stable control performance. In this report, we applied disturbance estimation and compensation type robust control to all axes in a 3-link electro-hydraulic manipulator. From the results of experiment, it was confirmed that the performance of trajectory tracking and attitude regulating is greatly improved by the disturbance observer, which model is the same for each axis. On the other hand, for the autonomous assembly tasks, it is said that compliance control is one of the most available methods. Therefore we proposed compliance control which is based on the position control by disturbance observer for our manipulator system. To realize more stable contact work, the states in the compliance loop are feedback, where not only displacement but also velocity and acceleration are considered. And we applied this compliance control to Peg-in-Hole insertion task and analyzed mechanical relation between peg and hole. Also we proposed new method of shifting the position of end-effector periodically for the purpose of smooth insertion. As a result of using this method, it is experimentally confirmed that Peg-in-Hole insertion task with a clearance of 0.05［mm］can be achieved.

• 전산구조공학
• /
• 제5권3호
• /
• pp.127-137
• /
• 1992

해양 가이드 타워를 대상으로 하여 지진하중에 대한 심해용 구조물의 비정상 거동해법에 대하여 연구하였다. 지반운동의 비정상 특성을 정상과정 성분에 시간포락함수가 곱해진 형태로 모형화하였으며, 구조물의 비정상 거동은 시간종속 분산함수로 구하였다. 지진의 시간포락함수와 정상과정 성분의 자기상관함수를 지수함수로 수식화하여 나타냄으로써, 구조물 거동의 시간종속 분산값을 해석적인 방법으로 구할 수 있는 기법을 개발하였다. 시간에 따른 거동의 분산값을 기본자료로 하여 지진의 발생기간 동안 예상되는 최대거동을 구하였으며, 이 값을 구조물 거동을 정상과정으로 가정하여 산정한 결과와 비교 분석하였다.