• 국제지역연구
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• 제15권3호
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• pp.175-188
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• 2011

본 논문은 미국의 경제변동이 일본경제에 어떻게 영향을 미쳤는가에 대한 연구를 수행한다. 미국경제가 일본경제에 다양한 영향을 미치고 있다는 것이 광범위하게 받아들여지고 있다. 실제로 미국은 일본의 수출입에 있어서 중요한 부분을 차지하고 있다. 미국에서 발생된 경제변동이 일본경제에 어떻게 전달되는가를 인지하는 것이 경제정책가들에게는 매우 중요하다고 할 수 있다. VAR모형이 경제변동의 국제전달경로를 분석하는데 활용된다. 미일경제의 상호작용은 분산분해(VDCs)를 이용하여 분석된다. 본 논문의 분석결과 몇가지 경제적 시사점을 도출할 수 있다. 첫째는, 미국의 경제변동에 대한 일본 통화정책의 일부 의존성을 지적할 수 있다.미국의 경제변동은 일본 통화량과 이자율에 어느정도의 영향성을 나타내는 것으로 조사되었다. 둘째는, 미국의 물가변동에 대한 일본 물가의 긍정적인 반응이다. 셋째는, 미국의 경제변동에 대한 엔/달러 환율의 반응성이다. 엔/달러 환율의 반응은 조사기간이 장기로 진행할수록 보다 강력하고 의미있게 나타났다. 결론적으로, 본 논문은 조사분석기간동안 미국의 경제변동이 일본경제에 중요한 영향을 미쳤음을 나타낸다. 본 연구는 상대적으로 규모가 큰 경제(미국)에 대한 규모가 작은 경제(일본)의 경제의존성에 대한 개념을 지지한다.

• 한국전자통신학회논문지
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• 제18권1호
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• pp.115-126
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• 2023

무작위 및 주기적인 변동하는 재생에너지 발전 전력 품질 교란으로 인해 발전 변환 송전 및 배전에서 더 자주 발생하게 된다. 전력 품질 교란은 장비 손상 또는 정전으로 이어질 수 있다. 따라서 서로 다른 전력 품질 외란을 실시간으로 자동감지하고 분류하는 것이 필요하다. 전통적인 PQD 식별 방법은 특징 추출 특징 선택 및 분류의 세 단계로 구성된다. 그러나 수동으로 생성한 특징은 선택 단계에서 정확성을 보장하기 힘들어서 분류 정확도를 향상하는 데에는 한계가 있다. 본 논문에서는 16가지 종류의 전력 품질 신호를 인식하기 위해 CNN(Convolution Neural Networ)과 LSTM(Long Short Term Memory)을 기반으로 시간 영역과 주파수 영역의 특징을 결합한 심층 신경망 구조를 제안하였다. 주파수 영역 데이터는 주파수 영역 특징을 효율적으로 추출할 수 있는 FFT(Fast Fourier Transform)로 얻었다. 합성 데이터와 실제 6kV 전력 시스템 데이터의 성능은 본 연구에서 제안한 방법이 다른 딥러닝 방법보다 일반화되었음을 보여주었다.

• 대한전기학회논문지:시스템및제어부문D
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• 제50권1호
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• pp.31-37
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• 2001

A robust adaptive technique for the longitudinal control of a platoon of automated vehicles is presented. A nonlinear model is used to represent the dynamics of each vehicle within the platoon. The external disturbances such as wind gust and a disturbance term due to engine transmission variations and so on are considered. The state observer is used to avoid direct measurement of the relative velocity or acceleration between the controlled and leading vehicles or the controlled vehicles's acceleration. The proposed controller guarantees to recover platoon stability in operation even if a speed dependent spacing policy is adopted, which incorporates a constant time headway in addition to the constant distance. It is shown that the proposed observer is exponentially stable, and the at the robust adaptive controller is stable. The simulation results demonstrate excellent tracking even in the presence of disturbances.

• 제어로봇시스템학회논문지
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• 제2권2호
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• pp.81-87
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• 1996

Time delay control(TDC) law has been recently suggested as an effective control technique for nonlinear time-varying systems with uncertain dynamics and/or unpredictable disturbances. This paper focuses on the applications of the TDC algorithm to torque control of an engine system and speed control of an engine/automatic transmission system. Through the stability analysis of the engien system based on TDC, determination of the appropriate time delay and control factor is investigated. It was revealed that the size of time delay of the TDC law should be greater than that of transport delay of the system for both stability and better control performance. Simulation and experimental results for the engine torque control and engine/automatic transmission speed control systems show both relatively good command following and disturbance rejection properties. However, TDC controller shows rather slow responses when applied to the system with large transport delay.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2000년도 제15차 학술회의논문집
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• pp.263-263
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• 2000

Electromagnetic Suspension(EMS) System produces no noise, friction and heat through non-contacting operation Therefore, the applicable device using EMS system has a lot of attraction in case of the high-speed and non-contacting transmission EMS with nonlinear properties requires a precise airgap position control and stable kinematics characteristics under the disturbances, In this study, the nonlinear system was linearized by a Nonlinear Feedback Lineariztion(NFL) method. The NFL method requires that the modelling should be exact, and the state variables should be measured and a rapidly operating controller be necessary on account of a heavy data calculating In the experiments. the ideal control characteristics of the NFL was acquired through simulation at first. then the characteristics of the actual system were compared with those of simulation. In addition, the results by NFL were examined and analysed considering the characteristics of the PID control. The Control by NFL shows much stable control characteristics than the PID control. Whereas, the steady state errors occur for various disturbances. hence a robust control design is remained for a further study.

• 한국자동차공학회논문집
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• 제10권4호
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• pp.114-121
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• 2002

This paper describes the control system of the toroidal traction driver continuously variable-speed transmission(CVT) fur a tractor. The instrumentation system, the hydraulic power control system and the principle control scheme were introduced. Experimental tests in the bench and the tractor were conducted to validate the performance of the CVT utilizing the proposed controller. The speed of the vehicle was continuously changed to follow the speed set by driver under various operating conditions. Given the reduction ratio of the variator from 2.0 to 1.0, the settling time was about just 0.52 seconds which was satisfactory value for working with the tractor. It was also proved that the tractor could work with continuously variable speed under heavy load disturbances.

• 대한기계학회논문집
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• 제18권6호
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• pp.1374-1381
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• 1994

This study suggests a new type shaft generating system driven by hydrostatic transmission suitable for small size vessels. In this system, the hydraulic motor speed is controlled by displacement adjustment using a 3-way high speed on/off valve. The 3-way high speed valve is operated by PWM control signal. In this study, a digital robust servo control algorithm is applied to the controller design of the system. By experiments and numerical computations, the frequency variation characteristics of the generating system under various disturbances are investigated. Conclusively, it is said that the shaft generating system proposed in this study shows excellent control performances.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1991년도 한국자동제어학술회의논문집(국제학술편); KOEX, Seoul; 22-24 Oct. 1991
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• pp.1659-1663
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• 1991

A new control design methodology is presented here which is based on a nonlinear time-series reference model. It is indicated by highly nonlinear simulations that such designs successfully stabilize troublesome aircraft maneuvers undergoing large changes in angle of attack as well as large electric power transients due to line faults. In both applications, the nonlinear controller was significantly better than the corresponding linear adaptive controller. For the electric power network, a flexible a.c. transmission system (FACTS) with series capacitor power feedback control is studied. A bilinear auto-regressive moving average (BARMA) reference model is identified from system data and the feedback control manipulated according to a desired reference state. The control is optimized according to a predictive one-step quadratic performance index (J). A similar algorithm is derived for control of rapid changes in aircraft angle of attack over a normally unstable flight regime. In the latter case, however, a generalization of a bilinear time-series model reference includes quadratic and cubic terms in angle of attack. These applications are typical of the numerous plants for which nonlinear adaptive control has the potential to provide significant performance improvements. For aircraft control, significant maneuverability gains can provide safer transportation under large windshear disturbances as well as tactical advantages. For FACTS, there is the potential for significant increase in admissible electric power transmission over available transmission lines along with energy conservation. Electric power systems are inherently nonlinear for significant transient variations from synchronism such as may result for large fault disturbances. In such cases, traditional linear controllers may not stabilize the swing (in rotor angle) without inefficient energy wasting strategies to shed loads, etc. Fortunately, the advent of power electronics (e.g., high-speed thyristors) admits the possibility of adaptive control by means of FACTS. Line admittance manipulation seems to be an effective means to achieve stabilization and high efficiency for such FACTS. This results in parametric (or multiplicative) control of a highly nonlinear plant.

• 대한기계학회논문집A
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• 제38권4호
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• pp.393-400
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• 2014

본 논문에서는 실제 자전거 주행에 적용 가능한 자동변속장치를 개발하기 위하여 자전거용 변속장치 중 내장기어허브를 이용하여 자전거 자동변속장치를 개발하였다. 개발된 자동변속장치는 주행 중 페달rpm과 주행속도를 측정하여 자동변속을 수행하며, 최대심박수의 ~80% 부근에서 ~150W정도의 주행출력을 낼 수 있는 일반적인 이용자가 사용가능하도록 개발되었다. 서울시 한강변 자전거 주행로의 경사를 구현한 실내주행 실험결과 자동변속장치는 자전거 주행시 이용자의 페달rpm을 적정한 수준에서 유지하도록 변속을 수행하였으며, 자전거 이용이 서투른 이용자도 적정한 페달rpm을 유지하며 주행할 수 있었다.

• Journal of Electrical Engineering and Technology
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• 제12권2호
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• pp.586-593
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• 2017

Modeling busbar distribution system as a transmission line is an important subject of power line communication in the smart grid concept. This requires extraction of busbar RLGC parameters, accurately. In this study, a comparison is made between conventional and modified method for the aspect of optimum RLGC parameters extraction in the 1 MHz to 50 MHz frequency band. The usefulness of these methods is shown both in time and frequency-domain analysis. The frequency-domain analyzes show that the inherent power of modified method can eliminate the errors especially due to the discontinuities arise in conventional method. This makes the modeling approach of modified method more advantageous for the busbars due to its robustness against disturbances in the S-parameters measurements which cannot be eliminated with the calibration procedure. On the other hand, time-domain simulations show that the transmission line representation of the modified method is closer to physical reality by handling causality issues.