• 전자공학회논문지S
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• 제34S권1호
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• pp.65-71
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• 1997

In this paper, we propose a new .mu.-controller design method using an equivalent weighting function $W_{\mu}$(s). The proposed mehtod is not guaranteed to converge to the minimum as D-K and .mu.-K iteration method. However, the robust performance problem can be converted into an equivalent $H^{\infty}$ optimization problem of unstructured uncertainty by using an equivalent weightng function $W_{\mu}$(s). Also we can find a .mu.-optimal controller iteratively using an error index $d_{\epsilon}$ of differnce between maximum singular value and .mu.-norm. And under the condition of the same order of scaling functions, the proposed method provides the .mu.-optimal controller with the degree less than that obtained by D-K iteration..

• 제어로봇시스템학회논문지
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• 제10권10호
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• pp.878-886
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• 2004

Uncertainties are inevitable in robotic assembly in unstructured environment since it is difficult to construct fixtures to guide motions of robots. This paper proposes an augmented Petri net and an algorithm to adapt the assembly model on-line during actual assembly process. The augmented Petri net identifies events using force and position information simultaneously. Unmodeled contact states are identified and incorporated into the model on-line. The proposed method increases the level of intelligence of the robot system by enhancing the autonomy. The proposed method is evaluated by simulation and experiments with L-type peg-in-hole assembly using a two-arm robot system.

• 한국정밀공학회지
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• 제20권10호
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• pp.130-140
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• 2003

This paper presents an $H_\infty$controller synthesis based on disturbance observer for the trajectory control of a hydraulic excavator. Compared to conventional robot manipulators driven by electrical motors, hydraulic excavator have more nonlinear and coupled dynamics. In particular, the interactions between an excavation tool and the materials being excavated are unstructured and complex. In addition, its operating modes depend on working conditions, which make it difficult to not only derive the exact mathematical model but also design a controller systematically. In this study, the approximated linear model obtained through off-line system identification is used as nominal plant model for a disturbance observer. A disturbance observer based tracking controller which considers the effect of disturbance and model uncertainty is synthesized in $H_\infty$frameworks. Simulation results are used to demonstrate the applicability of the proposed control scheme.

• 대한전기학회논문지
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• 제45권1호
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• pp.131-138
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• 1996

In this paper, we consider an iterative learning control system(ILCS) consisting of an iterative learning controller, a feedback controller and a controlled plant in the frequency domain. At first, we review the convergence of ILCS. And we give some design guidelines of the ILCS using a nominal model of the plant. Then we present the structured and the unstructured uncertainty bound which guarantees the convergence of the designed iterative learning controller. In particular, we analyze the relationship between the convergence and the magnitude and phase uncertainties. In order to show the usefulness of the proposed analysis and design guidelines, we present some simulation examples. (author). 13 refs., 5 figs.

• 수산해양기술연구
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• 제31권2호
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• pp.178-189
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• 1995

병렬형 도립진자를 수학적으로 모델링하고 주파수 응답법에 의해 파라미터를 동정하여, $H_\infty$제어이론 중 혼합감도문제에 의거하여 제어계를 설계한 후 응답 시뮬레이션을 한 결과그 응답으로부터 모델링의 불확실성에 대처할 수 있는 강인한 제어계를 구성할 수 있었다. 앞으로 실제 시스템에 대하 s제어들 과제로 남겨두고 있다. 시뮬레이션 응답과는 달리 실제 으답실험에서도 좋은 결과를 얻기 위해서는 여러 가지의 어려움이 있을 것으로 예상된다. 특히 응답 시뮬레이션에서도 나타난 바와 같이 전자가 미소각으로 기울어진 상태에서 제어를 할 경우에도 각 상태의 변동량이 크고, 또한 상당한 제어입력을 요한다. 따라서 센서 잡음에 대한 영향을 충분히 고려할 필요가 있으므로, 노이즈를 많이 발생시키는 PWM방식의 직류모터 구동 드라이버보다는 선형 드라이버를 이용하는 것이 적절할 것으로 예상된다

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.552-557
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• 2004

This paper presents a disturbance observer based on an $H_{\infty}$ controller synthesis for the trajectory control of a hydraulic excavator. Compared to conventional robot manipulators driven by electrical motors, the hydraulic excavator has more nonlinear and coupled dynamics. In particular, the interactions between an excavation tool and the materials being excavated are unstructured and complex. In addition, its operating modes depend on working conditions, which make it difficult to not only derive the exact mathematical model but also design a controller systematically. In this study, the approximated linear model obtained through off-line system identification is used as nominal plant model for a disturbance observer. A disturbance observer based tracking controller which considers the effect of disturbance and model uncertainty is synthesized in $H_{\infty}$ frameworks. Simulation results are used to demonstrate the applicability of the proposed control scheme.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.316-321
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• 2003

This paper presents a design method of the wavelet neural network based controller using direct adaptive control method to deal with a stable intelligent control of chaotic systems. The various uncertainties, such as mechanical parametric variation, external disturbance, and unstructured uncertainty influence the control performance. However, the conventional control methods such as optimal control, adaptive control and robust control may not be feasible when an explicit, faithful mathematical model cannot be constructed. Therefore, an intelligent control system that is an on-line trained WNN controller based on direct adaptive control method with adaptive learning rates is proposed to control chaotic nonlinear systems whose mathematical models are not available. The adaptive learning rates are derived in the sense of discrete-type Lyapunov stability theorem, so that the convergence of the tracking error can be guaranteed in the closed-loop system. In the whole design process, the strict constrained conditions and prior knowledge of the controlled plant are not necessary due to the powerful learning ability of the proposed intelligent control system. The gradient-descent method is used for training a wavelet neural network controller of chaotic systems. Finally, the effectiveness and feasibility of the proposed control method is demonstrated with application to the chaotic systems.

• 센서학회지
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• 제4권4호
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• pp.47-54
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• 1995

센서의 계측에는 필연적으로 불화실성이 내포되어 있으며 이는 센서궤환장치의 신뢰성을 저하시키는 요인이 된다. 본 논문에서는 다중센서를 사용하여 신뢰성 높은 계측을 행하기 위한 기법을 연구하였다. 동적인 환경에서 작동하는 미지의 특성을 가진 센서들을 가정하였으며, 센서출력은 군집화와 추정된 신뢰도를 이용하여 융합하였다. 제안된 기법은 논리적으로 정의된 센서를 사용한 실험에서 기존의 확률적 기법들이 적용되기 어려운 상황에서도 피계측치에 대한 적응적 추정을 행할 수 있었다. 센서 로보트의 지능작업과 같이 구조화되어 있지 않은 환경에서 동작하는 자동화 장치를 위해 제안된 기법은 유용하게 사용될 수 있을 것이다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 추계학술대회 논문집
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• pp.3-6
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• 2000

The magnetic bearing system are intrinsically unstable, and need the feedback control of electromagnetic forces with measured displacements. So the controller design plays an important role in constructing high performance magnetic bearing system. In case of magnetic bearing system, the order of identified model is high because of unknown dynamics included in closed loop systems - such as sensor dynamics, actuator dynamics - and non-linearity of magnetic bearings itself. In this paper the identification and robust control of flexible rotor supported by magnetic bearing are discussed. We measure and identify overall system that contains not only flexible rotor model but also magnetic bearing and time delay. The structured and unstructured uncertainties are modeled that cover variations of natural frequencies, uncertainties in sensor and actuator gains and unmodeled dynamics. And desired performances are specified with several weighting function. Using augmented system that includes identified model, uncertainties, and weighting functions, μ-synthesis is applied to flexible rotor supported with magnetic bearing. The flexible rotor was spin up over the first flexible critical speed.

• 한국공간구조학회논문집
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• 제15권1호
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• pp.75-84
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• 2015

This paper presents the dimensionless wall distance, y+ effect on SST turbulent model for wind turbine blade. The National Renewable Energy Laboratory (NREL) Phase VI wind turbine was used for the study, which the wind tunnel and structural test data has publicly available. The near wall treatment and turbulent characteristics have important role for proper CFD simulation. Most of the CFD development in this area is focused on advanced turbulence model closures including second moment closure models, and so called Low-Reynolds (low-Re) number and two-layer turbulence models. However, in many cases CFD aerodynamic predictions based on these standard models still show a large degree of uncertainty, which can be attributed to the use of the $\epsilon$-equation as the turbulence scale equation and the associated limitations of the near wall treatment. The present paper demonstrates the y+ definition effect on SST (Shear Stress Transport) turbulent model with advanced automatic near wall treatment model and Gamma theta transitional model for transition from lamina to turbulent flow using commercial ANSYS-CFX. In all cases the SST model shows to be superior, as it gives more accurate predictions and is less sensitive to grid variations.