• International Journal of Control, Automation, and Systems
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• 제6권4호
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• pp.506-514
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• 2008

This paper presents an intelligent model; named as free model, approach for a closed-loop system identification using input and output data and its application to design a power system stabilizer (PSS). The free model concept is introduced as an alternative intelligent system technique to design a controller for such dynamic system, which is complex, difficult to know, or unknown, with input and output data only, and it does not require the detail knowledge of mathematical model for the system. In the free model, the data used has incremental forms using backward difference operators. The parameters of the free model can be obtained by simultaneous perturbation stochastic approximation (SPSA) method. A linear transformation is introduced to convert the free model into a linear model so that a conventional linear controller design method can be applied. In this paper, the feasibility of the proposed method is demonstrated in a one-machine infinite bus power system. The linear quadratic regulator (LQR) method is applied to the free model to design a PSS for the system, and compared with the conventional PSS. The proposed SPSA-based LQR controller is robust in different loading conditions and system failures such as the outage of a major transmission line or a three phase to ground fault which causes the change of the system structure.

• Bulletin of the Korean Chemical Society
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• 제24권3호
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• pp.279-284
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• 2003

The One Pass Method (OPM) previously presented for the identification of single input single output systems is used to estimate the parameters of a Decentralized Control System (DCS). The OPM is a linear and therefore a simple estimation method. All of the calculations are performed in one pass, and no initial parameter guess, iteration, or powerful search methods are required. These features are of interest especially when the parameters of multi input-output model are estimated. The benefits of the OPM are revealed by comparing its results against those of two recently published methods based on pulse testing. The comparison is performed using two databases from the literature. These databases include single and multi input-output process transfer functions and relevant disturbances. The closed loop responses of these processes are roughly captured by the previous methods, whereas the OPM gives much more accurate results. If the parameters of a DCS are estimated, the OPM yields the same results in multi or single structure implementation. This is a novel feature, which indicates that the OPM is a convenient and practice method for the parameter estimation of multivariable DCSs.

• Smart Structures and Systems
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• 제20권6호
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• pp.657-668
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• 2017

In this research, an active vibration suppression of a smart beam having piezoelectric sensor and actuators is investigated by designing separate controllers comprising a linear quadratic regulator and a neural network. Firstly, design of a smart beam which consists of a cantilever aluminum beam with surface bonded piezoelectric patches and a designed mechanism having a micro servomotor with a mass attached arm for obtaining variations in the frequency response function are presented. Secondly, the frequency response functions of the smart beam are investigated experimentally by using different piezoelectric patch combinations and the analytical models of the smart beam around its first resonance frequency region for various servomotor arm angle configurations are obtained. Then, a linear quadratic regulator controller is designed and used to simulate the suppression of free and forced vibrations which are performed both in time and frequency domain. In parallel to simulations, experiments are conducted to observe the closed loop behavior of the smart beam and the results are compared as well. Finally, active vibration suppression of the smart beam is investigated by using a linear controller with a neural network based adaptive element which is designed for the purpose of overcoming the undesired consequences due to variations in the real system.

• 한국펄프종이공학회:학술대회논문집
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• 한국펄프종이공학회 2003년도 추계학술발표논문집
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• pp.230-248
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• 2003

본 연구에서는 제지공정에서의 wet-end 와 dry section 부분을 통합한 모델을 구하고 이를 바탕으로 하여 지종교체 공정의 모델예측제어 방법을 제안하였다. 폐회로 공정 인식기법을 이용하여 state-space 모델을 구한 후 지종교체 제어를 모사한 결과와 실제 제지공장의 지종교체 운전데이터를 비교 분석하였다. 입력 변수로서 이전까지는 간과되어 왔던 4가지 변수(thick stock, filler flow, speed, steam pressure), 그리고 출력변수로서 3가지 변수(basis weight, ash content, moisture content)를 고려하였으며, output trajectory는 1차 전달함수 형식으로 하여 적용하였다. 모델예측제어 모사결과를 지종교체 운전데이터와 비교하여 본 결과 지종교체 시간이 짧아지고 보다 안정적으로 정상상태에 이르는 것을 확인할 수 있었다. 아울러 모델예측제어로 인하여 지종교체 이후 입력 변수들이 큰 진동이 없이 보다 신속하게 정상상태에 도달함을 확인하였다.