• 한국방사선학회논문지
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• 제9권7호
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• pp.515-521
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• 2015

고정형 그리드(stationary grid)에서 그리드 아티팩트(grid artifacts)와 모아레 아티팩트($moir{\acute{e}}$ pattern artifacts)로 인한 영상의 질의 저하와 이동형 그리드(moving grid)에서의 컷 오프 아티팩트(cut off artifacts)로 인한 영상의 질의 저하를 정량적으로 비교 평가하였다. CDRAD 팬텀(Phantom)과 두께 24 cm의 acryl Phantom을 촬영조건(X-ray exposure conditions)을 100 cm, 80 kVp, 30 mA로 하여 고정형 그리드와 이동형그리드에서 영상(X-ray imaging)을 획득하였다. CDRAD Analyser을 이용한 영상(X-ray imaging) 인식률(observer's perception)은 고정그리드에서 평균(mean) 49.36, 표준편차(standard deviation) 3.76, 최대값(max) 55.56, 최소값 38.67이었고 이동형그리드에서 평균 47.04, 편차 12.69, 최대값 55.56, 최소값 20.89이었다. 이동형 그리드보다 고정형 그리드가 인식률의 평균과 표준편차에서 더 우수하게 나타났다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2000년도 전력전자학술대회 논문집
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• pp.628-631
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• 2000

A new control method for precision robust speed control of a PMSM(Permanent Magnet Synchronous Motor) using load torque observer is presented. With this system we can obtain more reliable eye moving singal(nystagmus) Until now rotating chair system which is called 2D-optokinetic stimulator is used to make dizzincess. However an inclined rotating chair system witch is 3D-optokinetic stimulator is needed to obtain the precise dizziness data. This 3D-optokinetic sitimulator include unbalanced load aused by unbalanced center of mass. For this case new compensation method is considered to obtain robust speed control using load torque observer. To reduce the effect of this disturbance we can use dead-beat observer which has high gain. The application of the load torque observer is published in [1] for position control. A problem of using speed information such as amplifying effect of noise is reduce by moving average process. The experimental results are depicted in this paper to show the effect of this proposed algorithm.

• 전기학회논문지
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• 제62권12호
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• pp.1737-1743
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• 2013

This paper proposes the range and velocity of the object estimation method using a moving camera. Structure and motion (SaM) estimation is to estimate the Euclidean geometry of the object as well as the relative motion between the camera and object. Unlike the previous works, the proposed estimation method can relax the camera and object motion constraints. To this end, we arrange the dynamics of moving camera-moving object relative motion model in an appropriate form such that the nonlinear observer can be employed for the SaM estimation. Through both simulations and experiments we have confirmed the validity of the proposed estimation algorithm.

• 전력전자학회논문지
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• 제5권5호
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• pp.459-466
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• 2000

전정기관 자극용 회전자극기에 있어서 외란 관측기를 이용한 PMSM(permanent Magnet Synchronous Motor)의 강인한 정밀 속도 제어 방법에 대해서 제안한다. 본 제어기는 더욱 정확한 전정기관 평가를 가능하게 한다. 현기증을 유발시키기 위해서 지면에 수직인 회전축을 갖는 2D 자극기가 사용되어져 왔다. 그러나 정확한 현기증의 원인 규명을 위해서 회전축을 기울인 3D 자극기가 필요하다. 3D 자극기와 같이 기울임을 갖는 회 전자극기의 경우, 회전축에 대한 무게중심의 이격은 불평형 부하를 유발하게 된다. 이러한 경우에 대하여 강인한 속도 제어를 위한 외란 관측기를 이용하는 보상방법을 연구하였다 정확한 전정기관 자극을 위해 정밀한 속도 제어가 필요하며, 이러한 정밀 속도 제어에 있어서 외란의 영향을 제거하기 위해 데드비트 관측기와 같은 높은 이득을 갖는 관측기가 필요하다. 외란 관측기의 위치 제어에 대한 응용이 연구되어 졌다. 그러나 속도와 같은 노이즈가 많은 신호를 이용한 속도 제어에 있어서 데드비트 관측기는 노이즈 증폭 효과를 가져와 적용이 어렵다는 문제를 가지고 있다. 따라서 MA(Moving Average)처리를 이용하여 노이즈 효과를 저감한다. 이상의 제안된 알고리즘의 효과를 실험으로 보였다.

• 한국소음진동공학회논문집
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• 제14권11호
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• pp.1182-1194
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• 2004

This paper addresses the application of an active magnetic bearing (AMB) system to levitate the elevation axis of an electro-optical sight mounted on a moving vehicle. In this type of system, it is desirable to retain the elevation axis in an air-gap between magnetic bearing stators while the vehicle is moving. To eliminate disturbance responses, a disturbance observer based sliding mode control is developed. This control can decouple disturbance observation dynamics from sliding mode dynamics and preserves the robustness of the sliding control. The sliding surfaces are designed in the consideration of scattering of received image. The proposed control is applied to a 2-DOF active magnetic bearing system subject to base motion. Along with experimental results, the feasibility of the proposed technique is illustrated.

• 제어로봇시스템학회논문지
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• 제22권8호
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• pp.650-655
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• 2016

In this paper, a novel RLS-based DOB (Recursive Least Squares Disturbance Observer) scheme is proposed to improve the performance of DOB for nominal model identification. A nominal model can be generally assumed to be a second order system in the form of a proper transfer function of an ARMA (Autoregressive Moving Average) model. The RLS algorithm for the model identification is proposed in association with DOB. Experimental studies of the balancing control of a one-wheel robot are conducted to demonstrate the feasibility of the proposed method. The performances between the conventional DOB scheme and the proposed scheme are compared.

• 한국공작기계학회논문집
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• 제14권3호
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• pp.23-31
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• 2005

The purpose of this study is to design a disturbance observer for a micro-stepping stage to eliminate the disturbances from cables, friction, mass unbalance of the moving part, etc. The disturbance observer is designed for air-floating X-Y precision micro-stepping X-Y stage which widely used in stepper machine or semiconductor manufacturing systems. The micro-stepping X-Y stage has a weak point of the variation of characteristics with position locations, which caused by various disturbances. In this study, it will be described that a simple and high throughput disturbance observer algorithm improves the dynamic error and settling time of the micro-stepping stage.

• Journal of Mechanical Science and Technology
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• 제19권2호
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• pp.540-548
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• 2005

This paper concerns the application and demonstration of sliding mode observer for aeroelastic system, which is robust to model uncertainty including mass and stiffness of the system and various disturbances. The performance of a sliding mode observer is compared with that of a conventional Kalman filter to demonstrate robustness and disturbance decoupling characteristics. Aeroelastic instability may occur when an elastic structure is moving even in subcritical flow speed region. Simulation results using sliding mode observer are presented to control aeroelastic response of flapped wing system due to various external excitations as well as model uncertainty and sinusoidal disturbances in subcritical incompressible flow region.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제53권3호
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• pp.188-195
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• 2004

This paper presents neural load torque observer that is used to deadbeat load torque observer and gain compensation by parameter estimator As a result, the response of the PMSM(permanent magnet synchronous motor) follows that nominal plant. The load torque compensation method is composed of a neural deadbeat observer To reduce the noise effect, the post-filter implemented by MA(moving average) process, is adopted. The parameter compensator with RLSM (recursive least square method) parameter estimator is adopted to increase the performance of the load torque observer and main controller The parameter estimator is combined with a high performance neural load torque observer to resolve the problems. The neural network is trained in on-line phases and it is composed by a feed forward recall and error back-propagation training. During the normal operation, the input-output response is sampled and the weighting value is trained multi-times by error back-propagation method at each sample period to accommodate the possible variations in the parameters or load torque. As a result, the proposed control system has a robust and precise system against the load torque and the Parameter variation. A stability and usefulness are verified by computer simulation and experiment.

• Smart Structures and Systems
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• 제20권1호
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• pp.1-10
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• 2017

Ionic Polymer Metal Composite (IPMC) is an electroactive polymer (EAP) and a promising candidate actuator for various potential applications mainly due to its flexible, low voltage/power requirements, small and compact design, and lack of moving parts. Although widely used in industry, this material requires accurate numerical models and knowledge of optimal control methods. This paper presents State-Dependent Riccati Equation (SDRE) approach as one of rapidly emerging methodologies for designing nonlinear controllers. Additionally, the present paper describes a novel method of Multi HGO Observer design. In the proposed design, the calculated position of the IPMC strip accurately tracks the target position, which is illustrated by the experiments. Numerical results and comparison with experimental data are presented and the effectiveness of the proposed control strategy is verified in experiments.