• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 심포지엄 논문집 정보 및 제어부문
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• pp.83-85
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• 2007

A new approach on identifying a first-order plus time-delay (FOPTD) model using finite--duration pulse inputs has been presented recently [1]. The identification methods are very simple because it is enough to observe only two extremes and the time when they occur in the transient response to pulse input. However, when there is mismatch between actual system and FOPTD model. how sensitive the methods are has not been studied. In this paper, we investigate robustness issue of those identification algorithms in the presence of the model structure mismatch and uncertainties. Through an example we will demonstrate it.

• Journal of Advanced Marine Engineering and Technology
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• 제37권1호
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• pp.85-90
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• 2013

시간지연을 갖는 불안정한 시스템의 PID 제어는 적용하기가 쉽지 않은데 이는 복소평면의 우반부에 존재하는 극점으로 인한 불안정성과 시간지연의 영향 때문이다. 본 연구에서는 설계자가 제어환경에 따라 오버슈트나 상승시간 등을 미리 정의한 경우의 PID 제어기 설계 기법에 대해 고려한다. 이와 같이 제약성을 갖는 최적화 문제를 해결하기 위해 본 연구에서는 벌점전략이 결합된 RCGA를 사용한다. 이는 제약조건을 위배하면 그 정도에 따라 벌점을 부가하도록 벌점함수를 정의하고, 평가함수에 합하여 비제약성 최적화 문제로 변환하는 방법이다. 제안하는 방법은 불안정 FOPTD 시스템에 적용하고 시뮬레이션을 실시하여 그 유효성을 검토한다.

• Journal of Advanced Marine Engineering and Technology
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• 제33권5호
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• pp.721-728
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• 2009

PID control is widely used to control stable processes, however, PID control for unstable processes is less common. In this paper, systematic tuning methods are derived to tune the PID controller for unstable FOPTD(Forst Order Plus Time Delay) processes. The proposed PID controllers for set-point tracking and disturbance rejection problem are tuned based on minimizing the performance indexes (IAE, ISE, ITAE) using a real-coded genetic algorithm. Simulation example is given to illustrate the set-point tracking and disturbance rejection performance of the proposed method.

• 수산해양기술연구
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• 제59권1호
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• pp.55-64
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• 2023

Gas turbine engines are widely used as prime movers of generator and propulsion system in warships. This study addresses the problem of designing a DS-based PID controller for speed control of the LM-2500 gas turbine engine used for propulsion in warships. To this end, we first derive a dynamic model of the LM-2500 using actual sea trail data. Next, the PRC (process reaction curve) method is used to approximate the first-order plus time delay (FOPTD) model, and the DS-based PID controller design technique is proposed according to approximation of the time delay term. The proposed controller conducts set-point tracking simulation using MATLAB (2016b), and evaluates and compares the performance index with the existing control methods. As a result of simulation at each operating point, the proposed controller showed the smallest in %OS, which means that the rpm does not change rapidly. In addition, IAE and IAC were also the smallest, showing the best result in error performance and controller effort.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 한국자동제어학술회의논문집(국내학술편); 포항공과대학교, 포항; 24-26 Oct. 1996
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• pp.1412-1415
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• 1996

In this paper, a new identification method of the cascade control system is proposed which can overcome the weak points of Krishnaswamy and Rangaiah(1987)'s method. This new method consists of two steps. One is on-line process identification using the numerical integration to approximate the two process dynamics with a high order linear transfer function. The other is a model reduction technique to derive out low order transfer function(FOPTD or SOPTD) from the obtained high order linear transfer function to tune the controller using usual tuning rules. While the proposed method preserves the advantages of the Krishnaswamy and Rangaiah(1987)'s method, it has such a simplicity that it requires only measured input and output data and simple least-squares technique. Simulation results show that the proposed method can be a promising alternative in the identification of cascade control systems.

• Korean Chemical Engineering Research
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• 제46권5호
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• pp.949-957
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• 2008

공정의 계단응답으로부터 일차시간지연모델을 구하고, 이로부터 PID(Proportional-Integral-Derivative) 제어기를 설계하는 방법은 공정제어 분야에서 널리 사용되는 오랜 것이다. 이를 위한 간단한 그래프에 근거한 방법에서 복잡한 수치적 최소자승법에 근거한 방법까지 다양한 방법들이 제안되어 있는데, 노이즈가 섞여 있는 계단응답에 대응하는 간단한 방법들은 의외로 잘 알려져 있지 못하다. 최근 계단응답 신호의 적분을 이용하는 방법들이 제안되어 있는데 이들을 비교 검토하여 실용적인 방법을 찾고자 한다. 계단응답의 적분 신호는 현 제어 계기에서 쉽게 얻어진다.

• 한국자동차공학회논문집
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• 제21권3호
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• pp.88-97
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• 2013

This paper presents a robust air-to-fuel ratio (AFR) control algorithm for managing exhaust gas recirculation (EGR) systems. In order to handle production tolerance, deterioration and parameter-varying characteristics of the EGR system, quantitative feedback theory (QFT) is applied for designing the robust AFR control algorithm. A plant model of EGR system is approximated by the first order transfer function plus time-delay (FOPTD) model. EGR valve position and AFR of exhaust gas are used as input/output variables of the plant model. Through engine experiments, parameter uncertainty of the plant model is identified in a fixed engine operating point. Requirement specifications of robust stability and reference tracking performance are defined and these are fulfilled by the following steps: during loop shaping process, a PID controller is designed by using a nominal loop transmission function represented on Nichols chart. Then, the frequency response of closed-loop transfer function is used for designing a prefilter. It is validated that the proposed QFT-based AFR control algorithm successfully satisfy the requirements through experiments of various engine operating points.