• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.11
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• pp.718-724
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• 2017

Considerable efforts have been made to expand the boundaries of domestic offshore plant industries, which have focused on the construction of the structures, to the engineering field. On the other hand, time domain analysis, which is one of the most important areas in designing floating offshore plants, relies mainly on the information given by foreign companies. As an early design of the Dynamic Positioning System (DPS) is mostly conducted by several specialized companies, domestic ship builders need to spend time and money to reflect the analysis into the hull shape design. This paper presents the framework required to analyze time domain performance of floating type offshore structures, which are equipped with DPS. To easily perform time domain analysis, framework generates the required input data for the solver, and is modularized to test the control algorithm and performance of a certain DPS. The effectiveness of the developed framework was verified by a simulation with a model ship and the total time for the entire analysis work was reduced by 50% or more.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.7
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• pp.953-959
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• 2018

This paper deals with controlling surge oscillations of a mooring vessel system under large external disturbances such as wind, waves and currents. A control synthesis based on Sliding Mode Control (SMC) with a Super-Twisting Algorithm (STA) has been applied to suppress nonlinear surge oscillations of a two-point mooring system. Despite the advantages of robustness against parameter uncertainties and disturbances for SMC, chattering is the main drawback for implementing sliding mode controllers. First-order SMC shows convergence within the desired level of accuracy, in which chattering is the main obstacle related to the destructive phenomenon. Alternatively, STA completely eliminates chattering phenomenon with high accuracy even for large disturbances. SMC based on STA is an effective tool for the motion control of a nonlinear mooring system because it avoids the chattering problems of a first-order sliding mode controller. In addition, the error trajectories of controlled mooring systems implemented by means of STA form in the bounded region. Finally, the control gain effect of STA can be observed in sliding surface and position trajectory errors.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.11a
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• pp.127-128
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• 2008

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.4D
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• pp.523-533
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• 2009

The purpose of the present study is to examine the dynamic interaction characteristics between moving maglev vehicle and guideway bridge system. For this purpose, the dynamic governing equation of 2-dof maglev vehicle using optimal feedback control scheme of LQG was derived with or without consideration of the dynamic interaction between vehicle and guideway bridge system. From the parametric study, it was found that the dynamic interaction effect between bridge and vehicle was large in case of neglecting the railway roughness effect. But if the railway roughness effect was considered, it was observed two analysis results with or without consideration of the dynamic interaction did not show big difference. As a conclusion, it is required to take into account the dynamic interaction effect of bridge and maglev vehicle and the railway roughness for precise evaluation of runnability of maglev vehicle and impact factor of guideway.

• Journal of the Society of Naval Architects of Korea
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• v.57 no.6
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• pp.345-352
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• 2020

This study aims to investigate the crabbing motion of the research vessel "NARA" by full-scale maneuvering trials. The crabbing test method refers to ITTC recommended procedures and guidelines. In order to minimize the fluctuation of the heading angle due to the external force acting on the hull during the pure lateral motion, the tests are conducted using the dynamic positioning system applied to the ship. The test results are analyzed by applying a low-pass filter to remove the noise included in the measurement data. Three conditions are set to define the steady state of crabbing motion. The index to be derived from the crabbing test is quantitatively presented. The ship is confirmed to be capable of the lateral motion of up to 0.844m/s in Beaufort 3.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.4
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• pp.328-341
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• 2017

In the control actuator system of a launch vehicle based on thrust vectoring, the interaction between electro-mechanical position servo and inertial load are combined with the dynamic characteristics of the flexible vehicle support to generate synthetic resonance. This occurred resonance is fed back to the attitude control system and can influence stability of launch vehicle. In this study, we proposed a simulation model to analyze synthetic resonance of electro-mechanical actuation system for thrust vector control and explained the results of simulation and test using dynamic force feedback control which improves dynamic characteristics of servo actuation system by reducing synthetic resonance.

• Proceedings of the Korea Information Processing Society Conference
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• 2002.11b
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• pp.1451-1454
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• 2002

신뢰성을 갖는 멀티캐스트 전송 프로토콜에 확장성을 부여하기 위해 많은 연구들이 계층구조의 제어트리를 사용한다. 제어트리는 하부계층의 멀티캐스트 트리와 가급적 일치할수록 좋은 성능을 보이게 된다. 하지만 네트워크 계층의 멀티캐스트 트리와 완벽히 일치하는 제어트리의 구성은 매우 많은 계산량을 소비하게 되어 동적으로 멤버쉽이 변하는 형태의 멀티캐스트에는 적용하기 쉽지 않다. 따라서 성능에 가장 중요한 영향을 미치는 요소를 우선 고려하여 제어트리를 구성하는 것이 바람직하다. 기존 연구를 통해 우선적으로 고려되어야할 사항이 하부 멀티캐스트 트리와 제어트리간, 부모-자식 위상 일치성임을 알 수 있다. 본 연구는 성능에 영향을 미치는 또 다른 요소로 라우터의 혼잡을 제시한다. 결론적으로, ns-2를 이용한 시뮬레이션을 통해서 제어트리상의 부모와 자식이 서로 다른 라우터에 위치하였을 경우에 더 좋은 성능을 나타냄을 보인다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.7
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• pp.797-803
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• 2012

Proportional solenoid valves are a modulating type that can control the displacement of valves continuously by means of electromagnetic forces proportional to the solenoid coil current. Because the solenoid-type modulating valves have the advantages of fast response and compact design over air-operated or motor-operated valves, they have been gaining acceptance in chemical and power plants to control the flow of fluids such as water, steam, and gas. This paper deals with the auto tuning of the position controller that can provide the proportional and integral gain automatically based on the dynamic system identification. The process characteristics of the solenoid valve are estimated with critical gain and critical period at a stability limit based on implemented relay feedback, and the controller parameters are determined by the classical Ziegler-Nichols design method. The auto-tuning algorithm was verified with experiments, and the effects of the operating point at which the relay control is activated as well as the relay amplitude were investigated.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1990.10a
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• pp.157-162
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• 1990

기계의 정밀도 향상을 위하여는 기계에 대한 보다 정확한 해석을 요구한다. 그러나 실제 기계 시스템은 마찰, Backlash, Saturation등과 같은 비서형 특 성을 가지고 있어 시스템의 해석 및 제어가 어렵게 된다. 특히, 축, 링크, 기 어, 풀리, 베어링등의 기계요소에서는 마찰로 인해 정밀도가 크게 덜어지고 있어, 마찰에 의한 동특성 및 제어는 많은 연구자들에 의해 관심의 대상이 되어 왔다. 마찰력을 고려한 기계시스템의 운동은 정지상태 근처에서 마찰력 의 변화가 심한 비선형 동특성을 보이고 있어 그 해석에 어려움을 겪고 있 다. 실제 마찰이 저속에서 고급 비선형임에도 불구하고 가장 널리 사용되는 형태의 모델로서 쿨통 마찰을 고려한 운동방정식 조차 비선형성으로 인하여 해석에 어려움이 따르고 있다. 마찰은 오랜동안 연구되어 오면서 Fig.1, Fig2 와 같이 등가선형점성 감쇠, 쿨통마찰, 정적마찰로 모델화되거나 이들의 조 합으로 나타내었다[1-5]. 마찰력은 시간영역에서도 연구되어 Walrath[7]는 Fig.3-a의 속도가 역전되는 지점에서 마찰토오크가 .+-.Tf를 공유하는 문제 를 고려하기 위해, Fig.3-b와 같이 동적마찰모델을 사용하였다. 최근의 연구 로서 Armstrong[7]은 마찰의 위치의존성을 고려한 정확한 마찰모델을 설정 하여 개루프제어에 적용, 좋은 제어특성을 확인하였고, Canudas[8]는 저속영 역에서 overcompensation시 limit cycle과 gain의 관계를 해석하였다.

• Journal of the Society of Naval Architects of Korea
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• v.54 no.2
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• pp.102-112
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• 2017

Many studies on dynamic positioning control algorithms using fixed feedback gains have been carried out to improve station keeping performance of dynamically positioned vessels. However, the control algorithms have disadvantages in that it can not cope with changes in environmental disturbances and response characteristics of vessels motion in real time. In this paper, the Fuzzy Gain Scheduling - PID(FGS - PID) control algorithm that can tune PID gains in real time was proposed. The FGS - PID controller that consists of fuzzy system and a PID controller uses weighted values of PID gains from fuzzy system and fixed PID gains from Ziegler - Nichols method to tune final PID gains in real time. Firstly, FGS - PID controller, control allocation algorithm, FPSO and environmental disturbances were modeled using Matlab/Simulink to evaluate station keeping performance of the proposed control algorithm. In addition, simulations that keep positions and a heading angle of vessel with wind, wave, current disturbances were carried out. From simulation results, the FGS - PID controller was confirmed to have better performances of keeping positions and a heading angle and consuming power than those of the PID controller. As a consequence, the proposed FGS - PID controller in this paper was validated to have more effectiveness to keep position and heading angle than that of PID controller.