비구조적 불확실성이 존재하는 DC모터에 대한 외란관측기 기반 제어기의 강인성에 대한 연구

조남훈,Jo, Nam-Hoon 대한전기학회 2017 전기학회논문지 Vol.66 No.1

In this paper, we study the robustness of disturbance observer based controller for DC motor in the presence of unmodeled dynamics. It is well known that the robustness property usually becomes weaker as the control gain becomes larger. On the contrary to this expectation, it is shown that the phase margin of DOB controller remains quite a large value even though the time constant of Q-filter becomes smaller. The computer simulation results show that DOB controller is able to stabilize the motor system even in the presence of unmodeled dynamics. On the contrary, the unity-feedback system fails to maintain stability when a high gain feedback is employed for the purpose of achieving better disturbance attenuation performance.

결함 형태 분류 과정이 필요없는 SG 세관 결함 크기 추정 시스템의 성능 평가

조남훈(Nam-Hoon Jo) 한국비파괴검사학회 2010 한국비파괴검사학회지 Vol.30 No.1

본 논문에서는 원전SG세관 결함 크기 추정을 위한 새로운 구조의 추정시스템에 대한 연구를 수행한다. 기존의 연구에서는 결함 크기를 추정하기 위하여 각각의 결함 형태별로 결함크기추정시스템을 설계하였다. 이와 같은 경우, 추정시스템의 구조가 복잡해지고 결함 크기 추정 이전에 수행하는 결함형태분류기의 정확성이 떨어질 경우 결함 크기 추정 성능도 결과적으로 악화될 수밖에 없다. 이에 본 논문에서는 결함 형태분류 과정을 필요로 하지 않는 결함크기추정시스템의 성능을 분석하고 이를 향상시키기 위한 방안을 연구하였다. 기존의 추정시스템은 각각의 결함 형태별로 특화된 추정기를 사용하기 때문에 추정 성능이 훨씬 뛰어날 것으로 예상되었지만, 실험 결과 두 추정시스템의 성능 차이는 그리 크지 않다는 것을 알 수 있었다. 따라서 결함형태분류기의 정확성이 완벽하지 않을 경우, 본 논문에서 제안한 구조의 추정기가 효과적으로 사용될 수 있을 것으로 기대된다. In this paper, we study a new estimation system for the prediction of steam generator tube defects. In the previous research works, defect size estimators were independently designed for each defect types in order to estimate the defect size. As a result, the structure of estimation system is rather complex and the estimation performance gets worse if the classification performance is degraded for some reason. This paper studies a new estimation system that does not require the classification of defect types. Although the previous works are expected to achieve much better estimation performance than the proposed system since it uses the estimator specialized in each defect, the performance difference is not so large. Therefore, it is expected that the proposed estimator can be effectively used for the case where the defect type classification is imperfect.

비구조적 불확실성이 존재하는 DC모터에 대한 외란관측기 기반 제어기의 강인성에 대한 연구

조남훈(Nam-Hoon Jo) 대한전기학회 2017 전기학회논문지 Vol.66 No.2

In this paper, we study the robustness of disturbance observer based controller for DC motor in the presence of unmodeled dynamics. It is well known that the robustness property usually becomes weaker as the control gain becomes larger. On the contrary to this expectation, it is shown that the phase margin of DOB controller remains quite a large value even though the time constant of Q-filter becomes smaller. The computer simulation results show that DOB controller is able to stabilize the motor system even in the presence of unmodeled dynamics. On the contrary, the unity-feedback system fails to maintain stability when a high gain feedback is employed for the purpose of achieving better disturbance attenuation performance.

Decentralized Suboptimal H₂ Filtering : An Exact Model Matching Approach

趙南熏(Nam-Hoon Jo),孔在燮(Jae-Sop Kong),徐鎭憲(Jin-Heon Seo) 대한전기학회 1996 전기학회논문지 Vol.45 No.2

상태궤환 적분제어기법을 이용한 HIV 감염 환자에 대한 약물 치료기법

조남훈(Nam-Hoon Jo) 대한전기학회 2015 전기학회논문지 Vol.64 No.10

In this paper, a drug treatment protocol is proposed for an HIV infection model that explicitly includes the concentration of healthy T cells, infected T cells, and HIV. Since real parameters of HIV infection model differ from patient to patient, most drug treatment protocols are not able to achieve the treatment goal in the presence of modelling errors. Recently, based on the nonlinear robust control theory, a robust treatment protocol has been proposed that deals with parameter uncertainties. Although the developed scheme is inherently complex, it cannot be applied to the case where all parameters are unknown. In this paper, we propose a new drug treatment protocol that is much simpler than the previous one but can achieve the treatment goal even when all model parameters are unknown. The simulation results verify that the substantial improvement in the performance can be achieved by the proposed scheme.

다중출력 관측불가능 비선형 시스템의 적응관측기 설계기법

조남훈(Nam-Hoon Jo) 제어로봇시스템학회 2005 제어·로봇·시스템학회 논문지 Vol.11 No.4

교차검증을 이용한 SVM 전력수요예측

趙南熏(Nam-Hoon Jo) 대한전기학회 2006 전기학회논문지A Vol.55 No.11

In this paper, we study the problem of model selection for Support Vector Machine(SVM) predictor for short-term load forecasting. The model selection amounts to tuning SVM parameters, such as the cost coefficient C and kernel parameters and so on, in order to maximize the prediction performance of SVM. We propose that Cross-Validation method can be used as a model selection algorithm for SVM-based load forecasting technique. Through the various experiments on several data sets, we found that the difference between the prediction error of SVM using Cross-Validation and that of ideal SVM is less than 5%. This shows that SVM parameters for load forecasting can be efficiently tuned by using Cross-Validation.

비최소위상 외란관측기 제어기의 도립진자 적용에 관한 연구

조남훈(Nam Hoon Jo) 제어로봇시스템학회 2018 제어·로봇·시스템학회 논문지 Vol.24 No.6

Due to powerful ability of disturbance attenuation and uncertainty compensation, the disturbance observer (DOB) controller has been widely employed in control industries. But, it is well known that it is not easy to design conventional DOB controllers for non-minimum phase systems. In this paper, we design a non-minimum DOB controller to achieve high performance control for inverted pendulum system. It is shown via simulation studies that disturbance attenuation performance can be substantially improved by the application of non-minimum phase DOB controller. Since the derived DOB controller may have very high order, it is suggested that model reduction technique can be used for the design of DOB controller. It is shown that the order of DOB controller can be decreased without degrading the system performance significantly.

개선된 특징 추출을 이용한 원전SG 세관 결함 패턴 분류에 관한 연구

조남훈(Nam-Hoon Jo),이향범(Hyang-Beom Lee) 한국비파괴검사학회 2009 한국비파괴검사학회지 Vol.29 No.1

본 논문에서는 개선된 특징추출을 이용한 원자력 발전소 증기발생기 세관의 결함 형태 분류에 대한 연구를 수행한다. 본 논문에서는 4가지 축대칭 결함, 즉 I-In 형태, I-Out 형태, V-In 형태, V-Out 형태 결함을 고려한다. 유한요소법에 기초한 수치해석 프로그램을 이용하여 결함의 폭과 깊이를 변화시켜가면서 400개의 와전류탐상시험(ECT) 신호를 생성하였다. 이와 같이 생성된 ECT 신호로부터 새로운 특징을 제안하였는데, 여기에는 최대 임피던스 값을 갖는 점과 최대 임피던스 값의 1/2의 값을 갖는 점 사이의 위상각과 최대임피던스 값을 갖는 점과 최대 임피던스 값의 10%, 20%, 30%, 40%를 갖는 점사이의 위상각들이 포함된다. 또한, 결함형태를 분류하기 위하여 은닉층이 하나인 다층퍼셉트론을 사용하였다. 컴퓨터 모의실험 연구를 통하여 제안된 방법이 최대오차와 평균제곱오차 측면에서 향상된 결함 분류 성능을 얻는다는 것을 보였다. In this paper, we study the classification of steam generator tube defects using an improved feature extraction. We consider 4 axisymmetric defect patterns of tube: I-In type, I-Out type, V-In type, and V-Out type. Through numerical analysis program based on finite element modeling, 400 ECT signals are generated by varying width and depth of each defect type. From those generated ECT signals, we propose new feature vectors that include an angle between the two points where the Maximum impedance and half the Maximum impedance, and angles between Maximum impedance point and 10%, 20%, 30%, 40% of Maximum impedance points. Also, multi-layer perceptron with one hidden layer is used to classify the defect patterns. Through the computer simulation study, it is shown that the proposed method achieves an improved defect classification performance in terms of Maximum Error and mean square Error.

고속 팬터그래프의 새로운 동적 모형 및 외란관측기를 이용한 제어기 설계

趙南熏(Nam-Hoon Jo),李鋼泫(Kang-Hyun Lee) 대한전기학회 2007 전기학회논문지 Vol.56 No.12

The pantograph-catenary system is one of important components for high-speed rail system that are powered electrically. Electrical power is delivered from a catenary structure to the train via a pantograph and thus it is very important to regulate the contact force between catenary and pantograph. Although a lot of research results for active pantograph have been reported, most of them have made an unrealistic assumption that the catenary displacement is constant with respect to the time. In this paper, we present a new pantograph model that regards the catenary displacement as an unknown disturbance input. Moreover, a disturbance observer based controller is proposed to remove the effect of disturbance, i.e., the catenary displacement variation. The computer simulation result shows that the substantial improvement in regulating the contact force can be achieved by the proposed controller.