• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1993년도 봄 학술발표회논문집
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• pp.53-60
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• 1993

Nonlinear equation of motion due to material nonlinearity of structure is transformed to linear equation of motion by treating the nonlinear elastic force term as an applied force. The solution in a time step is carried out by iterative linear dynamic analysis. The present simple algorithm is varidated by several examples .The results show that this algorithm is and efficient.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1997년도 한국자동제어학술회의논문집; 한국전력공사 서울연수원; 17-18 Oct. 1997
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• pp.167-174
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• 1997

In this paper, the mathematical model of the hydraulic control valve is formulated, that is, this dynamic modeling which includes the motion equations and continuity equations can analyze the dynamic characteristics of the hydraulic control valve. The control valve for the transmission has the Over Speed Protection to protect a hydraulic travel motor. Therefore, this simulation shows the over speed protection and researches the main design parameters. The results of the computer simulation were assured through the experiment. From the comparison between both results, it is shown that this simulation program is useful and effective.

• Journal of Mechanical Science and Technology
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• 제16권1호
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• pp.83-93
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• 2002

This paper presents a motion control method and its simulation results of a mobile robot for a lattice type welding. Its dynamic equation and motion control methods for welding speed and seam tracking are described. The motion control is realized in the view of keeping constant welding speed and precise target line even though the robot is driven for following straight line or curve. The mobile robot is modeled based on Lagrange equation under nonholonomic constraints and the model is represented in state space form. The motion control of the mobile robot is separated into three driving motions of straight locomotion, turning locomotion and torch slider control. For the torch slider control, the proportional-integral-derivative (PID) control method is used. For the straight locomotion, a concept of decoupling method between input and output is adopted and for the turning locomotion, the turning speed is controlled according to the angular velocity value at each point of the corner with range of 90$^{\circ}$ constrained to the welding speed. The proposed control methods are proved through simulation results and these results have proved that the mobile robot has enough ability to apply the lattice type welding line.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2002년도 추계학술대회 논문집
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• pp.161-166
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• 2002

As offshore oil fields move towards the deep ocean, the oil production systems such as FPSO are being built these days. Generally, the FPSO is moored by turret mooring lines to keep the position of FPSO. Thus nonlinear motion analysis of moored FPSO must be carried out in the initial design stage because sea environments affect motion of it. In this paper the mathematical model is based on the slow motion maneuvering equations in the horizontal plane considering wave, current and wind forces. The direct integration method is employed to estimate wave loads. The current forces are calculated by using mathematical model of MMG. The turret mooring forces are quasi-statically evaluated by using the catenary equation. The coefficients of a model for wind forces are calculated from Isherwood's experimental data and the variation of wind speed is estimated by wind spectrum according to the guidelines of API-RP2A. The nonlinear motions of FPSO are simulated under external forces due to wave, current, wind including mooring forces in time domain.

• 한국지반공학회논문집
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• 제19권4호
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• pp.145-153
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• 2003

공진주 실험은 탄성파 이론을 이용하여 흙의 동적 물성, 즉 전단변형률의 크기에 따른 전단탄성계수와 재료감쇠비를 측정하는 실험이다. 공진주 실험에 의한 시료의 동적물성의 측정은 공진주 실험 시스템의 동적 거동에 대한 이해를 전제로 한다. 공진주 실험의 시료 및 실험장치의 구성은 고정단-자유단 경계조건을 가지고 있는 연속보로 단순화할 수 있어서, Richart, Hall and Woods는 공진주 실험 시스템에 대한 파동방정식을 유도하였으나, 시료를 단순히 탄성으로 가정하였고 시료의 점성을 고려하지는 않았다. 그리고, Hardin은 파동방정식의 유도에서 시료의 점탄성을 고려하였으나, 시료의 전단탄성계수를 결정하기 위하여 시료의 점탄성을 가정하여야 하는 문제점을 가지고 있었다. 본 연구에서는 기존의 연구자들이 시도했던 공진주 실험 시스템에 대한 파동방정식을 새로운 측면에서 유도하였으며, 새로이 유도된 파동방정식의 해법을 제안하였다. 한편, 일반적으로 시스템에 대한 동적 거동을 이해하는 방법으로, 시스템의 운동방정식을 이용하는 방법이 있으나, 공진주 실험 시스템에 대한 동적 거동의 해석방법으로 이와 같은 운동방정식을 이용하는 해석방법을 연구한 경우는 거의 없었다. 운동방정식에 의한 해법은 시스템의 동적 증폭계수와 동적 응답에 대한 위상각을 구할수 있기 때문에 파동방정식에 대한 해법보다 더 많은 정보를 활용할 수 있는 장점이 있다. 따라서, 본 연구에서는 공진주 실험 시스템에 대한 보다 기본적이고 많은 정보를 도출하기 위하여, 공진주 실험 시스템에 대한 운동방정식을 유도하였으며, 이를 이용하여 공진주 실험자료를 해석하는 새로운 해석기법의 제안을 위한 근간을 마련하였다. 그리고, 공진주 실험 시스템에 대한 유한요소 해석을 수행하여, 본 연구에서 제안한 공진주 실험시스템의 이론적 모델링의 타당성과 합리성을 검증하였다.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제13권4호
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• pp.247-256
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• 2009

In this paper, a motion detection algorithm which works well in low illumination environment is proposed. By using the level set based bimodal motion segmentation, the algorithm obtains an automatic segmentation of the motion region and the spurious regions due to the large CCD noise in low illumination environment are removed effectively.

• Journal of Astronomy and Space Sciences
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• 제15권1호
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• pp.209-220
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• 1998

The stability problem of steady motion of a rigid body with multi-elastic appendages and multi-liquid-filled cavities, in the presence of no external forces or torque, is considered in this paper. The flexible appendages are modeled as the clamped -free-free-free rectangular plates, or/and as the discrete mass- spring sub-system. The motion of liquid in every single ellipsoidal cavity is modeled as the uniform vortex motion with a finite number of degrees of freedom. Assuming that stationary holonomic constraints imposed on the body allow its rotation about a spatially fixed axis, the equation of motion for such a systematic configuration can be very complex. It consists of a set of ordinary differential equations for the motion of the rigid body, the uniform rotation of the contained liquids, the motion of discrete elastic parts, and a set of partial differential equations for the elastic appendages supplemented by appropriate initial and boundary conditions. In addition, for such a hybrid system, under suitable assumptions, their equations of motion have four types of first integrals, i.e., energy and area, Helmholtz' constancy of liquid - vortexes, and the constant of the Poisson equation of motion. Chetaev's effective method for constructing Liapunov functions in the form of a set of first integrals of the equations of the perturbed motion is employed to investigate the sufficient stability conditions of steady motions of the complete system in the sense of Liapunov, i.e., with respect to the variables determining the motion of the solid body and to some quantities which define integrally the motion of flexible appendages. These sufficient conditions take into account the vortexes of the contained liquids, the vibration of the flexible components, and coupling among the liquid-elasticity solid.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.709-714
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• 2000

A splitting method for the direct numerical simulation of solid-liquid mixtures is presented, where a symmetric pressure equation is newly proposed. Through numerical experiment, it is found that the newly proposed splitting method works well with a matrix-free formulation fer some bench mark problems avoiding an erroneous pressure field which appears when using the conventional pressure equation of a splitting method. When deriving a typical pressure equation of a splitting method, the motion of a solid particle has to be approximated by the 'intermediate velocity' instead of treating it as unknowns since it is necessary as a boundary condition. Therefore, the motion of a solid particle is treated in such an explicit way that a particle moves by the known form drag (pressure drag) that is calculated from the pressure equation in the previous step. From the numerical experiment, it was shown that this method gives an erroneous pressure field even for the very small time step size as a particle velocity increases. In this paper, coupling the unknowns of particle velocities in the pressure equation is proposed, where the resulting matrix is reduced to the symmetric one by applying the projector of the combined formulation. It has been tested over some bench mark problems and gives reasonable pressure fields.

• 한국해안해양공학회지
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• 제7권2호
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• pp.156-162
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• 1995

스커트의 유연성을 고려한 2차원 오일붐 모델에 대한 수치해법을 개발하였다. 본 수치모델에서는 부체를 강체로, 스커트를 장력이 걸려 있는 막으로, 스커트의 아래끝엔 집중질량이 놓여 있다고 가정하였다. 유동은 포텐셜이라고 가정하였으며 부체와 스커트의 연결부에서는 변위가 연속이라는 운동학적 조건을 그리고 스커트의 아래끝에는 집중질량에 대한 동력학적인 조건을 부가하였다. 수치해법은 선형포텐셜유동 이론에 근거한 Green 함수방법에 기초를 두고 있다. 스커트의 변형을 미리 알 수 없으므로 방사 포텐셜(radiation potential)과 부체의 변위 그러고 스커트의 변형을 동시에 구하는 방식을 택하였다. Green 정리를 적용하여 얻은 적분방정식과 부체의 운동방정식 그리고 스커트의 변형 관계식을 이산화하여 방사포텐셜과 부체의 변위 그리고 스커트의 변위에 대한 선형대수 방정식을 얻었다. 수치계산결과에 의하면 스커트의 유연성이 부체의 운동응답을 다소 줄일 수 있으며 부체의 공진체계를 바꿀 수 있음을 확인하였다. 그리고 오일붐의 운동응답특성에 영향을 주는 인자들 중에서 스커트의 길이와 집중질량을 파라미터로 하여 오일붐 모델의 운동응답특성을 비교해 보았다. 스커트가 유연한 경우와 스커트가 강체인 경우의 저주파수 극한해는 거의 일치하고 있어 수치해의 타당성을 간접적으로 확인할 수 있었다.

• Earthquakes and Structures
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• 제23권2호
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• pp.169-181
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• 2022

To research the dynamic response of the high-rise structure under the rocking ground motion, which we believed that the effect cannot be ignored, especially accompanied by vertical ground motion. Theoretical analysis and shaking table seismic simulation tests were used to study the response of a high-rise structure to excitation of a H-V-R ground motion that included horizontal, vertical, and rocking components. The use of a wavelet analysis filtering technique to extract the rocking component from data for the primary horizontal component in the first part, based on the principle of horizontal pendulum seismogram and the use of a wavelet analysis filtering technique. The dynamic equation of motion for a high-rise structure under H-V-R ground motion was developed in the second part, with extra P-△ effect due to ground rocking displacement was included in the external load excitation terms of the equation of motion, and the influence of the vertical component on the high-rise structure P-△ effect was also included. Shaking table tests were performed for H-V-R ground motion using a scale model of a high-rise TV tower structure in the third part, while the results of the shaking table tests and theoretical calculation were compared in the last part, and the following conclusions were made. The results of the shaking table test were consistent with the theoretical calculation results, which verified the accuracy of the theoretical analysis. The rocking component of ground motion significantly increased the displacement of the structure and caused an asymmetric displacement of the structure. Thus, the seismic design of an engineering structure should consider the additional P-△ effect due to the rocking component. Moreover, introducing the vertical component caused the geometric stiffness of the structure to change with time, and the influence of the rocking component on the structure was amplified due to this effect.