• 한국전자파학회논문지
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• 제12권7호
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• pp.1086-1093
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• 2001

본 논문에서는 n차 오차신호발생기(error signal generator)를 이용한 postdistortion 방식의 RF 전력증폭기의 선형화 기법을 제안하였다. n차 ESG(error signal generator)는 전력증폭기의 기저대역 등가 복소 전달함수를 바탕으로 오차신호를 발생시켜, 이를 전력증폭기의 출력 단에서 n차 이하의 비선형성만을 제거한다. 따라서, 출력 단의 n차 이상의 혼변조 왜곡(intermodulation distortion) 성분에 영향을 미치지 않으며, 개루프(open-loop) 형태이므로 시스템의 안정성을 보장할 수 있다. 또한, 전력증폭기의 입력 신호를 이용하여 오차신호를 발생시키므로 feedforward 방식에서와 같이 오차신호 발생에 따른 주신호 경로(main signal path)의 시간지연 회로가 불필요하다. 실험 결과로 7차 ESG를 이용한 postdistorter를 최대 출력이 5 W인 셀룰러 대역 A급 증폭기에 적용한 경우의 혼변조 왜곡 개선도와 3-carrier CDMA 신호를 이용한 측정 결과를 제시하여 본 방법의 타당성을 검증하였다.

• International Journal of Automotive Technology
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• 제5권2호
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• pp.135-144
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• 2004

In this paper, the model-matching control in the longitudinal autonomous driving system is investigated by vehicle dynamics simulation, which contains nonlinear subcomponents and simplified subcomponents. The design of the robust model-matching controller is performed by the characteristics of the 2 degrees of freedom controller, which is composed of the feedforward compensator and the feedback compensator. It makes the characteristics of tractive and brake force to be equivalent to the specific transfer function, which is suggested as the reference model. Mathematical models of vehicle dynamic analysis including the model-matching control are constructed for computer simulation. Then, simple examples on open-loop simulation without any controller and closed loop simulation with the model-matching controller are applied to check the validity of the robust controller. As the practical example, the autonomous driving system in the longitudinal direction is adopted. It is proved that the model-matching control is effective and adequate to the disturbances and the perturbations, which are shown in the responses of the change of a vehicle mass and a road gradient.

• 항공우주기술
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• 제11권1호
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• pp.158-168
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• 2012

본 논문에서는 나로호 2단 킥모터 TVC 노즐에 대한 행정확인시험 방법과 행정확인시험 데이터로부터 TVC 운용 특성을 분석하는 과정 및 결과에 대해 다루었다. 개루프 행정확인 시험을 통해 TVC 스트로크와 포텐셔미터 전압 간의 관계를 분석하고, 폐루프 행정확인시험을 통해 노즐정렬오차, TVC 구동오차, TVC 중립위치, 플렉스씰 노즐의 회전중심위치, 비행시험후 분석에 사용할 노즐각 환산계수 등을 분석할 수 있음을 보였다. 아울러, 나로호 1호기 및 2호기 TVC 시스템에 대해 행정확인시험을 수행한 결과 TVC 운용 관련 모든 파라미터가 정상 범위 내에서 설정되었음을 정량적인 수치로써 제시하였다.

• 전기학회논문지P
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• 제66권2호
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• pp.63-68
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• 2017

This paper proposes a new non-isolated DC conversion circuit topology of the voltage source coupled inductor series resonant high-frequency PFM controlled boost chopper type DC-DC power converter using two in one IGBT power module, which can efficiently operate under a principle of zero current soft switching for wide output regulation voltage setting ranges and wide fluctuation of the input DC side voltage as well as the load variation ranges. Its steady state operating principle and the output voltage regulation characteristics in the open-loop-based output voltage control scheme without PI controller loop are described and evaluated from theoretical and experimented viewpoints. Finally, in this paper the computer-aided simulation steady-state analysis and the experimental results are presented in order to prove the effectiveness and the validity of voltage regulation characteristics of the proposed series resonant zero current soft switching boost chopper type DC-DC power converter circuit using IGBTs which is based on simple pulse frequency modulation strategy more than, 20kHz.

• 한국정밀공학회지
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• 제21권8호
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• pp.143-151
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• 2004

This paper deals with the precision NURBS interpolator for wire-EDM. Previous research about OAC (Open Architecture Controller) is mostly aimed at NC cutting machines such as milling or lathes, and hence these results are inadequate to apply to wire-EDM. In contradiction to NC machines, wire-EDM operates relatively slow feed rates and based on a feedback control loop to the machining process. The 2-stage interpolation method which reflects wire-EDM specific characteristics was proposed. The constant interpolation error could be acquired through 1 st stage interpolation. Feed rate regulation was performed through 2nd stage interpolation. The suggested algorithm was implemented to test-bed PC-NC system. Computer simulations and the experimental machining were conducted.

• 한국공작기계학회논문집
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• 제10권1호
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• pp.120-126
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• 2001

This study deals with a flow and pressure ripple characteristics for a hydrostatic transmission(HST) consisting of a vari-able axial piston pump connected in an open loop to a fixed displacement axial piston motor. These flow ripples produced by pump and motor in HST interacts with the source impedances of the pump or motor and dynamic characteristics of the connected pipeline, and results in a pressure ripples, Pressure ripples. Pressure ripples in HSP is major source of vibration, which can lead to fatigue failure of components and cause noise. In this paper, the flow ripples generated by a swash plate type axial piston pump or motor in HST are measured by making use of hydraulic pipeline dynamics and the measured pressure data at two points along the pipeline. By using the self-checking functions, the validity of the method us investigated by comparison with the measured and estimated pressure ripples at the halfway section of the pipeline, and good agreement is achieved.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 추계학술대회 논문집 학회본부
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• pp.52-54
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• 1995

When LIM is drived by the general purpose inverter, there is no food-back of speed and thrust, etc. Therefore, through analysis of LIM by the simulation, the prediction of operating characteristics and patterns of LIM is necessary. But, the open-loop control system is used widely, because it can consist of simple and cheap. In this paper, we foaled with the dynamic characteristics of LIM drived by V/f constant during acceleration, cruising speed deceleration. And, we compared the simulation value with actual measurement value.

• 한국자동차공학회논문집
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• 제5권3호
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• pp.27-34
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• 1997

The effects of the intake and exhaust valve timing to improve the engine performance in a spark ignition 3-cylinder LPG engine with a closed loop fuel supply system were studied. The engine torque and power have been measured using the 75kW EC-dynamometer while adjusting the optimal fuel consumption ratio with a solen- oid driver. As the results from this experiment, when intake valve opening is $12^{\circ}$ BTDC, intake valve closing is $36^{\circ}$ ABDC, exhaust valve opening is $12^{\circ}$ ATDC, and exhaust valve closing is $36^{\circ}$ BBDC respectively, the best torque characteristics in low and high speeds for a gives engine were obtained. And also we could find that the torque characteristics in low speeds were affected by the timing of exhaust valve open. An increased valve overlap by the EVC delay was ineffectual to the torque characte- ristics improvement in high speeds.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 추계학술대회 논문집 학회본부
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• pp.19-21
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• 1996

In this paper, the experiment on the dynamic characteristics of LIM for the propulsion system UTM(Urban Transit Maglev) is threated. Untill now LIM has been mainly experimented by using the rotational arch type system, but this system compose of the test vehicle mounted LIM, which driven by PWM inverter. And the anlysis of the performance and the steady-state characteristics of the LIM is treated under various operation patterns. This paper may be available to compose the operating system of LIM driven by the open or closed loop control.

• 한국전자파학회논문지
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• 제17권2호
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• pp.171-177
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• 2006

클락 유지 기능을 가지는 저가의 고성능 40 Gb/s 클락 복원기를 위상 고정 루프를 적용하여 설계 및 제작하였다. 클락 복원기는 클락 추출기, RF 믹서, 주파수 판별기, 위상 변환기, 클락 유지 회로로 구성되어 있다. 추출된 40 GHz 클락은 10 GHz 유전체 공진 발진기와 위상이 동기된다. 위상 고정 루프를 사용한 클락 복원기는 기존의 유전체 공진 필터를 사용한 개방형 클락 복원기에 비해 클락의 안정성과 지터 특성이 크게 향상되었다. 측정된 지터의 실효치는 230 fs였다. 또한 입력 신호가 끊어질 경우, 유지 회로에 의해 연속적인 클락 유지가 가능하였다.