• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.831-836
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• 2006

In the process of accurate manufacture and measurement, it is necessarily required to isolate external or internal vibration due to external disturbance and internal actuators. The higher vibration isolation system gets damping around resonance, the better it is generally. This paper analyzes the performance of an existing passive air-spring for vibration isolation table by using experiment and simulation. Optimal design for a passive air spring can be obtained by tuning the size of the orifice. Also design for an active isolation system is carried out by applying PID controller and considering non-linearity of pneumatic characteristics with help of look-up table. We have developed the active vibration isolation table with the better isolation performance.

• Journal of Biosystems Engineering
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• v.13 no.2
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• pp.9-17
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• 1988

This study was carried out to develop an agricultural robot for fruit harvesting. As the first step an experimental manipulator and its control system were constructed. The articulated manipulator driven by DC motors has 3 degrees-of-freedom. The manipulator has a gripper adequate for fruit harvesting and an upper arm which forms a kind of guiding channel so thai harvested fruit can pass through. Point-to-point control of joints are accomplished by a digital control system with a PID controller which consists of optical shaft encoders, power amplifiers using PWM, a microcomputer and a software. The microcomputer also computes the positions of manipulator and sequence of motions. The motion of the manipulator was to slow and rough that it would need further improvement.

• Proceedings of the KIEE Conference
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• 2001.04a
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• pp.311-313
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• 2001

This paper deals with a precise position synchronous control of two axes rotating systems by a cooperative control method. The system's dynamics including motor drives described by a motor circuit equation and Newton's kinetic formulation about rotating system. Current and speed controllers are designed very simply by conventional PID control law. Also, position synchronous controller designed to minimize position errors according to integration of speed errors between two motors. Then, the proposed control enables the distributed drives by a software control algorithm to behave in a way as if they are mechanically hard coupled in axes. Finally, the validity of the proposed system is confirmed through some simulations and experiments.

• Proceedings of the KIEE Conference
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• 2002.07d
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• pp.2055-2057
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• 2002

본 논문에서는 외란 및 파라미터 변동에 강건한 시간지연 제어 알고리즘을 전기식 구동장치의 위치 제어기에 적용하여 설계한 내용을 기술하였다. 시간지연 제어기는 일정하게 경과된 시간에서의 외란 및 동특성 변동의 양을 현재의 것으로 가정하여 전체 제어 시스템의 특성이 기준모델의 특성을 따르게 하는 제어기이다. 파라미터 변동 및 외란에 대해 시간지연 제어기의 강건성을 시뮬레이션을 통해 입증하였으며 PID 제어기와도 비교하였다. 또한 포화요소에 대한 와인드업 방지보상기와 모델링되지 않는 동특성에 대한 대향필터링 보상기를 설계하여 시스템의 안정성을 향상시켰다.

• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.980-981
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• 2006

전력변환 장치에서 기존의 PID 제어기의 해석적인 해를 얻는 것은 매우 어려운 일이다. 최근에 단상 UPS용 인버터 시스템에서 CRA 기법을 이용한 새로운 제어알고리즘을 바탕으로 시스템의 제어기의 제어상수를 해석적으로 접근하여 좋은 성능을 얻은 바 있다. CRA 기법은 해석적으로 시스템의 응답속도 및 오버슈트를 임의의 제한범위 내로 설계할 수 있도록 하는 장점이 있다. 이러한 CRA 기법을 사용하여 컨버터 제어기 설계부분에 적응하여 해석적인 해를 얻고 PSiM 시뮬레이션을 통해 오버슈트와 빠른 응답을 확인한다.

• Proceedings of the KIEE Conference
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• 1997.07b
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• pp.441-445
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• 1997

In this paper, we suggest a design scheme of receding horizon predictive control(RHPC) for boiler-turbine systems whose dynamics are given in nonlinear equations. RHPC is designed for linear state space models which are obtained at a nominal operating point of the boiler-turbine system. In this consideration, the boiler is operated in a sliding pressure mode, in which the reference value of drum pressure is changing according to the electrical power generation. The reference values of the system outputs are prefiltered before they are fed to the RHPC in order to compensate the linearization errors. Simulation results show that the proposed controller provides acceptable performances in both of the cases of 'steep and small changes' and 'slow and large changes' of power demand and yields the effect of modest coordination of conventional PID schemes such as boiler-following and turbine-following control.

• Journal of the Optical Society of Korea
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• v.10 no.4
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• pp.174-177
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• 2006

We propose a new technique to minimize gain-transient time of wavelength-division-multiplexing (WDM) signals in erbium-doped fiber amplifiers (EDFA) in channel add/drop networks. We have dramatically reduced the gain-transient time to less than $3{\mu}sec$ by applying, for the first time to our knowledge, a disturbance observer with a proportional/integral/differential (PID) controller to the control of EDFA gain. The $3{\mu}sec$ gain-transient time is the fastest one ever reported and it is approximately less than 1.5% of $200{\mu}sec$ gain-transient time of commercially available EDFAs for WDM networks. We have demonstrated the superiority of the new technique by performing the simulation with a numerical modeling software package such as the $Optsim^{TM}$.

• International Journal of Naval Architecture and Ocean Engineering
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• v.11 no.2
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• pp.851-857
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• 2019

A new robust sliding mode control with disturbance and state observers has been proposed to control the nozzle angle of a water-jet system for a Unmanned Surface Vehicle (USV). As the water-jet system of a ship is subjected to direct disturbances owing to the exposure to the marine environment in water, it requires a robust control. A state observer and a disturbance observer are added to the water jet nozzle control system to achieve a robust control against disturbances. To verify the performance of the proposed algorithm, a test bed is constructed by a propulsion system used in the popular USV. This proposed algorithm has been evaluated by comparing to the existing algorithm through experiments. The results show that the performance of the proposed algorithm is better than that of the conventional PID or sliding mode controller when controlling the steering of the USV with disturbances.

• Proceedings of the Korea Crystallographic Association Conference
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• 2002.11a
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• pp.35-35
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• 2002

나노미터 표준을 확립하기 위하여 일체식 엑스선 간섭계에 광간섭계를 결합시킨 복합간섭계를 구성하였다. 복합간섭계는 광간섭계의 Zero crossing 지점부터 표준시편이 올려진 미소이동대의 이동거리를 변화된 위상값으로 읽고 그 변화량을 고분해능 변위 측정기인 엑스선 간섭계로 읽어들이는 구조로 구성된다. 본 연구에서는 미소이동대의 위치 변화와 관련된 광간섭계의 위상 안정도, 엑스선 간섭계 및 미소이동대의 위치 안정도 등이 나노미터 영역의 길이 측정에 매우 중요한 요인이 되므로, 미소이동대의 위치 변화시 정지상태에서의 위상 잠김 (phase locking) 안정도를 측정하였다. 마이켈슨 레이저간섭계의 한쪽 팔을 고정시키고 다른 한 팔은 미소이동대 위에 반사거울을 설치하여 미소이동대의 움직임을 측정하였다. 보다 안정된 위상잠김 상태를 확보하기 위하여 PID feedback loop controller를 사용하였다. 측정 결과 위상 변동폭이 0.022 degree 이하의 높은 위상잠김 안정도를 확보하였으며, 이를 길이단위로 환산하면 정지상태에서 약 0.02 nm 이하의 위치 안정도를 나타낸다.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.1
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• pp.69.1-69.1
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• 2013

We are developing Adaptive Optics (AO) system for 1m telescope at Gwacheon National Science Museum Observatory. The beam spot of the Gwacheon 1m telescope. The tip-tilt correction system consists of a CMOS sensor, a tip-tilt mirror and a feed back loop. The beam spot location at the CMOS sensor indicates the tip-tilt components of the incoming light. The tip-tilt mirror is controlled by DAC output voltage calculated by proportional-integral-derivative (PID) controller. This system successfully corrects the tip-tilt motion of the spot.