• Journal of Power Electronics
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• 제12권6호
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• pp.1003-1010
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• 2012

Recent power electronics and variable-frequency motor drive technologies have been applied to air conditioners to improve efficiency and power density. However, the mechanical vibrations and acoustic noise resulting from the compressor still remain as a serious problem. This paper presents the development and implementation of an online disturbance state-filter for the suppression of multiple unknown and time-varying vibrations of air conditioning systems. The proposed design has a form of the state-filter based on a Luenburger-style closed-loop speed observer. An active vibration decoupling strategy with an estimated disturbance is provided, which manipulates a motor torque command. Since the proposed estimation does not require any additional transducers or hardware for obtaining real-time information upon disturbances, it is suitable for retrofitting industrial air conditioners.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 추계학술대회논문집 II
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• pp.1126-1131
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• 2001

Excessive vibration in rotating machinery is a problem encountered in many different fields, causing such difficulties as fatigue of machinery components and failure of supporting bearings. Passive techniques, though sometimes limited in their capabilities, have been used in the past to attenuated vibrations. Recently active techniques have been developed to provide vibration control perform beyond that provided by their passive counters. Most often, the focus of active control methods has been to suppress rotating machinery displacements. In cases where vibration results in bearing failures, displacement suppression may not be the best choice of control approaches (it can, in fact, increase dynamic bearing loads which would be even more harmful to bearings). This paper presents two optimal control methods for attenuating steady state vibrations in rotating machinery. One method minimizes shaft displacements while the other minimizes dynamic bearing reaction forces. The two methods are applied to a model of a typical rotating machinery system and their results are compared. It is found that displacement minimization can increase bearing loads, while bearing load minimization, on the other hand, decreases bearing loads.

• 고전문학과교육
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• 제34호
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• pp.223-257
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• 2017

오랫동안 동양 문학에는 비극이 존재하지 않는다고 생각되어 왔는데, 이는 행동을 모방하고 극적 구조를 지닌 고대 그리스 비극을 비극의 유일한 기준으로 삼았기 때문이었다. 이 글은 이러한 고정된 기준에 대해 의문을 제기하면서 한국의 비극 작품들이 지니는 특징을 밝히고, 이를 통해 비극이라는 장르에 대한 새로운 이해를 도모하는 데 목적을 두었다. 2장에서는 극과 서정의 장르적 성격을 살펴 다음과 같은 가설을 수립하였다. 즉 어떤 작품이 고통을 당하고 있는 작중인물과, 그 작중인물을 바라보며 관찰하는 자가 분리되어 있는 극적인 구조를 가지고 있고, 작중인물에 대한 관찰자의 연민이 드러난다면 서정적인 담화양식을 가지고 있다 하더라도 '비극'이라고 불릴 수 있다는 것이다. 3장의 논의를 통해 한국의 서정시 중에는 시적자아가 고통스러운 교착상태에 빠진 작중인물과 관찰자의 역할을 동시에 수행하면서, 관찰자가 작중인물을 연민하는 구조로 되어 있는 비극 작품이 존재함을 확인할 수 있었다. 한국 비극의 특징들은 비극에 대한 새로운 기준을 제시하는 근거가 될 수 있으며, 서구의 비극 개념으로는 이해하기 어려웠던 현대 비극을 이해하는 데 유용한 실마리를 제공한다.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2022년도 춘계학술대회
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• pp.147-149
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• 2022

본 논문은 불연속 개별시도 훈련을 모방하는 상호작용 로봇이 자폐아동 대상의 사회적 상호작용 훈련에 지원 가능한 상태머신 설계 방법론을 제안한다. 사회적 상호작용 훈련에 적용되는 로봇은 아동의 행동반응을 측정하는 센서들로부터 수신된 데이터를 처리하여 제공되는 훈련자극에 대한 반응을 정량적인 지표로 사용하게 된다. 여기서, 상태머신은 취득된 데이터의 상태를 분류한 후 불연속 개별시도 훈련의 후속 자극을 제공하는 정보로 사용된다. 공동 주의 훈련을 통하여, 지속가능한 불연속 개별시도 훈련의 횟수와 아동반응에 대한 데이터를 정량적으로 분류함으로써 근거기반의 치료정보로 활용될 수 있을 뿐만 아니라 원격지 모니터링을 수행하는 관찰자에게 현재 아동의 반응 상태를 제공함과 동시에 오인식 상황에 적절히 대응 가능함을 확인하였다.

• 제어로봇시스템학회논문지
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• 제14권11호
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• pp.1094-1102
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• 2008

Through the motion control experiment using Industrial Emulator(Model 220 by ECP), the performance comparison of three kinds of controllers such as PID, RIC and LQR was carried out. It was shown that RIC has the best performance in the presence of disturbances such as step one, sinusoidal one and Coulomb friction for the rigid body. LQR using feedback state variables has the best tracking performance far the flexible body. The performance of PID controller is low compared to other controllers, but the design process is simple. The most advanced controller is LQR. In order to attenuate disturbance, an additional state observer should be used to estimate it, making more complex control system. RIC lies between PID and LQR in view of complexity of design. Even though RIC is not complicated, it has good disturbance rejection ability and less tracking error. By considering these aspects, the RIC is suggested as high precision controller to be used in motion control system.

• 대한전기학회논문지:시스템및제어부문D
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• 제54권12호
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• pp.689-697
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• 2005

In this paper, an application of a decentralized $H_{\infty}$ controller(DHC) to multiple controlled-permanent magnet(CMAG) magnetic levitation(Maglev) systems is presented. The designed DHC using two Riccati equations iteratively has simpler structure and needs less computational loads than conventional centralized $H_{\infty}$ controller. A target plant is a hybrid-type CMAG system with permanent magnet and coil, and its mathematical model is firstly derived to design the DHC. To implement the designed algorithm, a real Maglev vehicle system including digital controller, chopper, sensor, etc., is manufactured. To compare the performances of the DHC method with an observer-based state feedback control(OSFC), the input tracking and disturbance rejection characteristics are experimentally tested. As performance indices(PI), integral of squared error(ISE), integral of absolute error(IAE), integral of time multiplied by absolute error(ITAE) and integral of time multiplied by squared error(ITSE) are used. From the experimental results, it can be seen that the input tracking and disturbance rejection performances of the DHC are better than those of the conventional controller.

• 한국산업정보학회논문지
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• 제5권1호
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• pp.31-36
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• 2000

본 논문에서는 적분제어기와 전차수 상태관측기로 구성되는 데드비트제어기의 설계방법을 제안하고, 기어를 포함한 직류전동기로 가동되는 회전계통 플랜트에 적용하였다. 샘플링된 연속 데이터 프로세스의 제어시스템은 샘플링사이에 리플이 없음을 보장하지 않지만, 제안된 데드비트제어시스템의 응답은 MATLAB시뮬레이션을 통한 사례연구의 결과, 상태귀환형 최적제어나 출력귀환형 제어시스템응답 등에 비하여 정정시간이 훨씬 빠름을 나타내었다. 또한 플랜트가 연속시스템이므로 시뮬레이션의 정확도를 기하기 위하여 영차홀드를 제어입력측에 삽입하여 실행하였고, 그 결과 주어진 샘플링주기 후에 오차와 리플이 없는 안정상태에 이르는 것을 보여 주었다.

• Journal of Power Electronics
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• 제16권2호
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• pp.542-552
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• 2016

Central 60° synchronous modulation is an easy pulse-width modulation (PWM) method to implement for the traction inverters of urban rail trains at a very low switching frequency. Unfortunately, its switching patterns are determined by a Fourier analysis of assumed steady-state voltages. As a result, its transient responses are not very good with over-currents and high instantaneous torque pulses. In the proposed solution, the switching patterns of the conventional central 60° modulation are modified according to the dynamic error between the target and actual stator flux. Then, the specific trajectory of the stator flux and current vector can be guaranteed, which leads to better system transients. In addition, stator flux control is introduced to get smooth mode switching between the central 60° modulation and the other PWMs in this paper. A detailed flow chart of the control signal transmission is given. The target flux is obtained by an integral of the target voltage. The actual PMSM flux is estimated by a minimum order flux state observer based on the extended flux model. Based on a two-level inverter model, improved rules in the α-β stationary coordinate system and equations of the switching patterns amendment are proposed. The proposed method is verified by simulation and experimental results.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제5B권4호
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• pp.350-357
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• 2005

This paper presents a mechanical sensorless vector-controlled system with parameter identification by the aid of image processor. Based on the flux observer and the model reference adaptive system method, the proposed sensorless system includes rotor speed estimation and stator resistance identification using flux errors. Since the mathematical model of this system is constructed in a synchronously rotating reference frame, a linear model is easily derived for analyzing the system stability, including motor operating state and parameter variations. Because it is difficult to identify rotor resistance simultaneously while estimating rotor speed, a low-accuracy image processor is used to measure the mechanical axis position for calculating the rotor speed at a steady-state operation. The rotor resistance is identified by the error between the estimated speed using the estimated flux and the calculated speed using the image processor. Finally, the validity of this proposed system has been proven through experimentation.

• 제어로봇시스템학회논문지
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• 제4권1호
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• pp.45-55
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• 1998

In this paper, a robust path tracker and depth controller of Autonomous Underwater Vehicle based on sliding mode control is presented. We have also designed augmented equivalent control inputs by analyzing the sliding mode with the reaching mode. This can enhance the reaching rate, and improve chattering problems, that is, noise caused by the control plane actuator of the vehicle, which is one of the problems that occur when sliding mode control is used. Also to resolve the steady state error generated in the path tracker under current effect, a modified sliding plane is constructed. Also a redesigned sliding plane and control input using transformation matrix is proposed to do easy design of MIMO depth controller. For state variables that cannot be measured directly, reduced order sliding mode control is used to design an observer. The performance of designed path tracker and depth controller is investigated by computer simulation. The results show that the proposed control system has robust performance to parameter variation, modelling error and disturbance.