• The Transactions of the Korean Institute of Electrical Engineers A
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• v.48 no.6
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• pp.671-677
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• 1999

In this paper, we have designed power system stabilizer (PSS) using object-oriented method. There are several types of power system stabilizer. A proportional-integral(PI) controller is very simple for practical implementation. Therefore it has been widely employed by the industry. The methods of obtaining the gains(Ki,Kp) of PI controller are root-locus method and sub-optimal regulator approach. But these methods are cannot be applicable to nonlinear system and faulted power system. So we proposed a new method which can be applied to nonlinear system by numerical analysis method. The method of dynamic system simulation by numerical method is very difficult and complex. We proposed flexible simultaion method for complex power system analysis using object-oriented programming(OOP) and applied to PI controller design.

• Journal of Power Electronics
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• v.11 no.4
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• pp.393-400
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• 2011

The main objective of this paper is to control the speed of Nonlinear Hybrid Electric Vehicle (HEV) by controlling the throttle position. Various control techniques such as well known Proportional-Integral-Derivative (PID) controller in conjunction with state feedback controller (SFC) such as Pole Placement Technique (PPT), Observer Based Controller (OBC) and Linear Quadratic Regulator (LQR) Controller are designed. Some Intelligent control techniques e.g. fuzzy logic PD, Fuzzy logic PI along with Adaptive Controller such as Self Organizing Controller (SOC) is also designed. The design objective in this research paper is to provide smooth throttle movement, zero steady-state speed error, and to maintain a Selected Vehicle (SV) speed. A comparative study is carried out in order to identify the superiority of optimal control technique so as to get improved fuel economy, reduced pollution, improved driving safety and reduced manufacturing costs.

• Journal of Korean Society of Transportation
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• v.20 no.7
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• pp.177-183
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• 2002

Current state-of-the-art of VMS control is based upon simple knowledge-based inference engine with message set and each message's priority. And R&Ds of the VMS control are focused on the accurate detection and estimation of traffic condition of the subject roadways. However VMS display itself cannot achieve a desirable traffic allocation among alternative routes in the network In this context, VMS display strategy is the most crucial part in the VMS control. VMS itself has several limitations in its nature. It is generally known that VMS causes overreaction and concentration problems, which may be more serious in urban network than highway network because diversion should be more easily made in urban network. A feedback control algorithm is proposed in this paper to address the above-mentioned issues. It is generally true that feedback control approach requires low computational effort and is less sensitive to models inaccuracy and disturbance uncertainties. Major features of the proposed algorithm are as follows: Firstly, a regulator is designed to attain system optimal traffic allocation among alternative routes for each VMS in the network. Secondly, strategic messages should be prepared to realize the desirable traffic allocation, that is, output of the above regulator. VMS display strategy module is designed in this context. To evaluate Probable control benefit and to detect logical errors of the Proposed feedback algorithm, a offline simulation test is performed using real network in Daejon, Korea.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.1
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• pp.41-52
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• 1992

An algorithm of transforming continuous-time state feedback gains into equivalent discrete-time feedback gains or vice versa is proposed using bilinear transformation. The proposed method is evaluated experimentally by an application control of a mobile crane system which is implemented by 16bits micro computer with A/D and D/A converters. It has been shown from the experimental result that the transformed feedback gains are virtually identical to the optimal discrete gain over range of significant sampling time. Since the transformed matrix is composed by a distinct relationship between continuous-time gain and discrete-time gain, it is noted that the proposed method can be regarded as an explicit gain transformation method compared to the other methods using series expansion.

• Journal of Power Electronics
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• v.13 no.6
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• pp.975-984
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• 2013

This paper proposes a robust optimal nonlinear control with an observer to reject the offset errors of position tracking for surface mounted permanent magnet synchronous motors. We provide the control method to reject offset errors and load torque for designing field oriented control (FOC) based the alternating current (AC) frame. The proposed method consists of a torque generator, a commutation scheme, an electrical controller, and a load torque observer. The mechanical controller is designed to compensate for load torque and the offset error and generate the desired torque. The commutation scheme is proposed to create the desired currents for the desired torque. The electrical controller is developed to guarantee the desired currents. The observer is designed to estimate both the velocity and the load torque. In order to obtain the robustness to parameter uncertainties and a gain tuning guide, the linear quadratic regulator method is applied to the proposed method. The closed-loop stability is proven. A detailed process for the FOC design and an analysis of the control methods based on the AC frame are presented. The performance of the proposed method was validated via experiments. The proposed method obtains the FOC based on the AC frame. Furthermore, the position tracking performance of the proposed method is superior to that of the conventional method.

• Molecules and Cells
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• v.27 no.5
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• pp.547-556
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• 2009

Parathyroid hormone is the most important endocrine regulator of calcium concentration. Its N-terminal fragment (1-34) has sufficient activity for biological function. Recently, site-directed mutagenesis studies demonstrated that substitutions at several positions within shorter analogues (1-14) can enhance the bioactivity to greater than that of PTH (1-34). However, designing the optimal sequence combination is not simple due to complex combinatorial problems. In this study, support vector machines were introduced to predict the biological activity of modified PTH (1-14) analogues using mono-substituted experimental data and to analyze the key physicochemical properties at each position that correlated with bioactivity. This systematic approach can reduce the time and effort needed to obtain desirable molecules by bench experiments and provide useful information in the design of simpler activating molecules.

• 한국기계연구소 소보
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• s.17
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• pp.157-165
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• 1987

The SWATH concept hull form which is capable of high speed navigation with small oscillatory motions in waves, was developed from the catamaran type hull forms. This paper describes how the motion of a SWATH ship in irregular waves can be reduced by regulating the stabilizing fins. The optimal regulator and LQG (Linear Quadratic Gaussian) controller for vertical plane motion have been applied for both platforming mode and contouring mode controls. The calculations of hydrodynamic coefficients and external forces are possible for defining the system equation for the design purpose of motion control. Performances of the controlled system are compared with those of original system.

• Proceedings of the KIPE Conference
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• 2014.11a
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• pp.152-154
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• 2014

본 논문에서는 단상 5kVA의 용량을 갖는 3-레그 방식의 고효율 자동전압조정기에 최적화된 방열설계가 제안된다. 3-레그 자동전압조정기의 경우 스위칭 알고리즘에 따라 스위칭 횟수가 줄어들어 효율이 좋은 장점이 있다. 스위칭 소자로 IGBT를 사용하여 열 분배가 중요함으로 전력변환 장치의 신뢰성과 안전성을 높일 수 있도록 최적화된 방열설계안을 제시하고 설계의 타당성을 위해 시뮬레이션을 통한 검증을 수행하였다.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.36S no.3
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• pp.47-56
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• 1999

제한된 출력 즉 오차 측정된 출력 값만을 사용하여 원하는 목표치에 도달하도록 하는 제어 문제를 푸는데 많은 연구가 진행되어 왔다. 종종 그러한 제어기를 설계할 때 해를 구하기 어려운 Non Linear Two Point Boundary Value Problem에 직면하게 된다. 특히 Reduced order 추정자 알고리즘은 백색 잡음에 의하여 영향을 받은 선형 시스템의 측정된 상태 뿐 만 아니라 보조 상태를 추정하기 위하여 개발되었다. 추정자를 설계할 때 상태는 무편향성이고 추정자의 편차는 추정자 및 추정상태와 공통되는 상태에 대한 모든 출력의 subspace에 수직이 된다. 특히 reduced order에서의 필터 성능은 full order에서의 필터 성능에 대해 suboptimal 이지만 상응한 Riccati equation을 푸는데 계산시간이 줄고 memory사용이 적은 이점이 있다. 본 논문에서는 Kronecker algebra와 선택행렬을 이용하여 Non Linear Two Point Boundary Value Problem을 Linear Two Point Boundary Value Problem으로 변환시켜 부수적으로 수반되는 대수적인 Riccati equation을 유도함으로써 문제를 쉽게 해결하는데 있다.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.8 s.173
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• pp.34-41
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• 2005

Generally, it is not easy to get a suitable controller for multi variable systems. If the modeling equation of the system can be found, it is possible to get LQR control as an optimal solution. This paper suggests an LQR learning method to design LQR controller without the modeling equation. The proposed algorithm uses the same cost function with error and input energy as LQR is used, and the LQR controller is trained to reduce the function. In this training process, the Jacobian matrix that informs the converging direction of the controller Is used. Jacobian means the relationship of output variations for input variations and can be approximately found by the simple experiments. In the simulations of a hydrofoil catamaran with multi variables, it can be confirmed that the training of LQR controller is possible by using the approximate Jacobian matrix instead of the modeling equation and this controller is not worse than the traditional LQR controller.