• 제어로봇시스템학회논문지
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• 제11권6호
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• pp.496-501
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• 2005

This paper presents experimental results of the frequency offset locking of He-Ne lasers and the stability analysis. The master laser is free running, and the slave laser is a single-mode operating laser. The frequency difference of two lasers is stabilized to 200 MHz which can be synchronized using PLL servo. The measured beat frequency between two lasers was 200.004 MHz ${\pm}$ 0.15 MHz. The square root of Allan variance as a measure of stability in time domain is also measured. The long-term stability of the beat was worse than sort-term stability. With a gate time $\tau=1000\;s$, the square root of Allan variance was about 1 GHz. The results of the square root of Allan variance of the stabilized beat signal was a gate time of $\tau=1000\;s$, the square root of Allan variance was about 1.5 kHz. The long-term stability was improved by more than several hundred times compared with that without the stabilization.

• 제어로봇시스템학회논문지
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• 제14권7호
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• pp.663-671
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• 2008

This paper presents a real-time haptic rendering method for multi-contact interaction with virtual environments. Haptic systems often employ physics-based deformation models such as finite-element models and mass-spring models which demand heavy computational overhead. The haptic system can be designed to have two sampling times, T and JT, for the haptic loop and the graphic loop, respectively. A multi-rate output-estimation with an exponential forgetting factor is proposed to implement real-time haptic rendering for the haptic systems with two sampling rates. The computational burden of the output-estimation increases rapidly as the number of contact points increases. To reduce the computation of the estimation, the multi-rate output-estimation with reduced parameters is developed in this paper. Performance of the new output-estimation with reduced parameters is compared with the original output-estimation with full parameters and an exponential forgetting factor. Estimated outputs are computed from the estimated input-output model at a high rate, and trace the analytical outputs computed from the deformation model. The performance is demonstrated by simulation with a linear tensor-mass model.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2018년도 전력전자학술대회
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• pp.192-194
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• 2018

In this paper a new single-stage ac-dc converter with high frequency isolation and low components count is introduced. The proposed converter is constructed using two interleaved boost circuits in the grid side and non-regulating full bridge in the DC side. An optimized switching is implemented on the two interleaved boost circuits resulting in a ripple-free grid current without a ripple cancellation network; hence very small filter inductors are used. A simple and reliable closed-loop control system is easily implemented, since the phase-shift angle is the only independent variable. Moreover, current imbalance is avoided in the presented topology without current control loop in each phase. The proposed charger charges the battery with a sinusoidal-like current instead of a constant direct current. ZVS turn on of all switches is achieved throughout the operation in both directions of power flow without any additional components.

• 한국정보통신학회논문지
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• 제21권5호
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• pp.899-905
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• 2017

본 논문은 2.496Gb/s 데이터 레이트를 갖는 mobile industry processor interface (MIPI) M-PHY를 위한 기준 클록이 없는 이중 루프 클록 데이터 복원 회로(CDR : Clock and Data Recovery Circuit)를 제안한다. 제안하는 클록 데이터 복원회로는 적응형 루프 대역폭 조절 기법을 사용하여 적은 타임 지터를 가지면서 빠른 고정 시간을 가질 수 있다. 클록 데이터 복원회로는 주파수 고정 루프와 위상 고정 루프로 이루어진다. 제안하는 2.496Gb/s 기준 클록이 없는 이중 루프 클록 데이터 복원 회로는 1.2V 공급 전압을 갖는 65nm CMOS 공정을 이용하여 설계되었다. 2.496Gb/s pseudo-random binary sequence (PRBS)15 입력에서 시뮬레이션 된 출력 클록의 타임 지터는 $9.26ps_{p-p}$이다. 클록 데이터 복원 회로의 면적과 전력 소모는 각각 $400{\times}470{\mu}m^2$와 6.49mW이다.

• 융합신호처리학회논문지
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• 제11권1호
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• pp.74-79
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• 2010

많은 제어기법들이 제어계의 제어성능을 개선하기 위해 제안되고 있다. 제어계에서 제어에 대한 자유도는 독립적으로 조정할 수 있는 폐루프 전달함수의 수로 결정된다. 목표치 추종 및 외란억제에 대해 2자유도 제어기법이 많이 이용되고 있다. 본 논문에서는 외란을 제거하기 위해 외란관측기를 갖는 제어계를 2자유도 제어계로 변환시켰으며, 기동 및 부하변동 시 과도응답의 제거를 용이하게 하였다. 그리고 외란관측기의 설계법이 주파수 영역으로 제안하였으며, 이 방법으로 설계된 외란관측기를 이용하여 2자유도 제어계를 구성하였다. 시뮬레이션 결과를 통하여 제안한 알고리즘의 유효성을 확인 하였다.

• 융합신호처리학회논문지
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• 제12권1호
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• pp.56-61
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• 2011

많은 제어기법들이 제어계의 제어성능을 개선하기 위해 제안되고 있다. 제어계에서 제어에 대한 자유도는 독립적으로 조정할 수 있는 페루프 전달함수의 수로 결정된다. 목표치 추종 및 외란억제에 2자유도 제어기법이 많이 이용되고 있다. 본 논문에서는 PID 제어기를 2자유도 제어기법을 이용하여 제어계를 설계할 수 있는 정규화법을 제안하였다. 제안한 설계법은 제어대상의 전달함수의 계수값을 이용하여 계의 전달함수를 정규화 하고, 제어기의 계수들이 결정되도록 하였다. 이 방법으로 설계된 제어계를 이용하여 2자유도 제어계를 구성하였고, 시뮬레이션 결과를 통하여 제안한 알고리즘의 유효성을 확인 하였다.

• Journal of Power Electronics
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• 제14권5호
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• pp.1038-1046
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• 2014

Lithium-ion batteries are widely used in hybrid and pure electric vehicles. State-of-charge (SOC) estimation is a fundamental issue in vehicle power train control and battery management systems. This study proposes a novel model-based SOC estimation method that applies closed-loop state observer theory and a comprehensive battery model. The state-space model of lithium-ion battery is developed based on a three-order resistor-capacitor equivalent circuit model. The least square algorithm is used to identify model parameters. A multi-state closed-loop state observer is designed to predict the open-circuit voltage (OCV) of a battery based on the battery state-space model. Battery SOC can then be estimated based on the corresponding relationship between battery OCV and SOC. Finally, practical driving tests that use two types of typical driving cycle are performed to verify the proposed SOC estimation method. Test results prove that the proposed estimation method is reasonably accurate and exhibits accuracy in estimating SOC within 2% under different driving cycles.

• 대한기계학회논문집
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• 제18권3호
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• pp.738-750
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• 1994

The load-sensing hydraulic system which was developed to improve energy efficiency of conventional hydraulic systems has its own properties. The instability of system responses, linearity of a servo valve, robustness for variation of external load, and dynamic interference between hydraulic motors are such properties which have much to do with control properties of the system. The load-sensing hydraulic system has instability tendancy because the load-sensing mechanism makes a positive feedback loop between the motor part and the pump part. A flow property of the servo valve can be said to be linear because the flow through the valve has nothing to do with a load pressure and the flow is strictly proportional to a valve opening which is adjusted by a valve command signal. The resultant control property can be said to be robust because the steady-state control performance is independent to the load actuated on the motor shaft. In the case when one pump simultaneously drives more than two hydraulic motors, the pump outlet pressure is determined by a hydraulic motor of the largest load pressure among all of the hydraulic motors, and, thus, the other motors are dominated by the largest load pressure. That is, the other motors can be said to be interfered by the motor of the largest load pressure.

• 대한기계학회논문집A
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• 제24권9호
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• pp.2151-2158
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• 2000

This paper presents vibration control performance of a passenger vehicle installed with the mixed-mode type ER engine mounts. The performance is evaluated via hardware-in-the-loop-simulation(HILS) method. As a first step, a dynamic model of a vehicle featuring the ER engine mounts is formulated by taking into account the engine excitation forces. A new type of the fuzzy skyhook controller is then established in order to control both engine and body vibrations. This is accomplished by adopting a weighting parameter between two performance criteria which is to be determined from the fuzzy algorithm. Vertical displacement and acceleration of the engine mount obtained from the HILS method are provided in the frequency domain. In addition, vibration control performance between the conventional hydraulic engine mount and the proposed engine mount is compared in the time and frequency domains.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 B
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• pp.994-995
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• 2006

This paper presents a grid-connected photovoltaic (PV) system with direct coupled power quality control (PQC) algorithm, which uses an inner current control loop (PRT : polarized ramp time) and outer feedback control loop to improve grid power quality and maximum power point tracking (MPPT) of PV arrays. To reduce the complexity, cost and number of power conversions, which results in higher efficiency, single stage CCVSI (Current Controlled Voltage Source Inverter) is used. The proposed system operation has been divided into two modes (sunny and night). In night mode, the proposed system operates to compensate the reactive power demanded by nonlinear or variation in loads. in sunny mode, the proposed system performs PQC to reduce harmonic current and improve power factor as well as MPPT to supply active power from the PV arrays simultaneously. it is shown that the proposed system improves the system utilization factor to 100% which is generally low for PV system (20%). To verify the proposed system, a comprehensive evaluation with theoretical analysis and simulation results are presented.