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6자유도 정밀 스테이지의 추종제어를 위한 슬라이딩 모드 제어기 설계
문준희(Jun-Hee Moon),이봉구(Bong-Gu Lee) 한국생산제조학회 2011 한국생산제조학회지 Vol.20 No.2
As high precision industries such as semiconductor, TFT-LCD manufacturing and MEMS continue to grow, the demand for higher DOF precision stages has been increasing. In general, the stages should accommodate a prescribed range of payloads in order to position various precision manufacturing/inspection instruments. Therefore a nonlinear controller using sliding motion is developed, which bears mass perturbation and makes the upper plate of the stage move in 6 DOF. For the application of the nonlinear control, an observer is also developed based on expected noise covariance. To eliminate the steady state error of step response, integral terms are inserted into the state-space model. The linear term of the controller is designed using optimization scheme in which parameters can be weighted according to their physical significance, whereas the nonlinear term of the controller is designed using trial and error method. A comprehensive simulation study proves that the designed controller is robust against mass perturbation and completely eliminates steady state errors.
회전체의 진동 측정과 분석을 통한 이상 진단 시스템 개발
문준희(Jun Hee Moon),강성범(Sung Bum Kang),박희재(Heui Jae Park) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5
Rotating machinery's faults such as unbalanced mass, eccentricity, and bearing fracture make the characteristic features of vibration different from that of normal operating condition. Fault diagnosis of the rotating machinery is achieved by the following ways: Firstly, identify the system in normal condition with a linear model. Secondly, assess the stochastic characteristic of the system in order to define the threshold of abnormal condition and to design a digital filter appropriate for the system. Finally, diagnose the system fault by error difference evaluation and by STFT analysis. The developed algorithm is experimentally verified for a CD-ROM drive.
문준희(Jun Hee Moon),박종호(Jong Ho Park),박희재(Heui Jae Pahk) Korean Society for Precision Engineering 2009 한국정밀공학회지 Vol.26 No.6
A 6-DOF precision stage was developed based on parallel kinematics structure with flexure hinges to eliminate backlash, stick-slip and friction and to minimize parasitic motion coupled with motions in the other-axis directions. For the stage, lever linkage mechanism was devised to reduce the height of system for the enhancement of horizontal stiffness. Frequency response comparison between experimental results and mathematical model extracted from dynamics of the stage was performed to identify the system parameters such as spring constants and damping coefficients of actuation modules, which cannot be calculated accurately by analytic methods owing to their complicated structures. This newly developed precision stage and its identified model will be very useful for precision positioning and control because of its high accuracy and non-coupled movement.
문준희(Jun Hee Moon),이봉구(Bong Gu Lee) Korean Society for Precision Engineering 2009 한국정밀공학회지 Vol.26 No.11
Spin coaters are the essential instruments in micro-fabrication processes, which apply uniform thin films to flat substrates. In this research, a spin coater diagnosis system is developed to detect the abnormal operation of TFT-LCD process in real time. To facilitate the real-time data acquisition and analysis, the circular-buffered continuous data transfer and the short-time Fourier transform are applied to the fault diagnosis system. To determine whether the system condition is normal or not, a steady-state detection algorithm and a frequency spectrum comparison algorithm using confidence interval are newly devised. Since abnormal condition of a spin coater is rarely encountered, algorithm is tested on a CD-ROM drive and the developed program is verified by a function generator. Actual threshold values for the fault detection are tuned in a spin coater in process.
문준희(Jun Hee Moon),김화수(Hwa Soo Kim),박희재(Heui Jae Pahk) Korean Society for Precision Engineering 2007 한국정밀공학회지 Vol.24 No.3
Active vibration isolation systems need the following performance specifications which are different from those of existing positioning systems: usage of seismic sensors, strict suppression of phase lead/lag in signal processing for sensors and actuators, excellent control in low frequency range and so on. In consideration of such specifications, a 3-DOF precision stage for vibration isolation is designed and modeled based on the physical characteristics. Then the major parameters such as spring constants and damping coefficients are valued by the system identification method using empirical transfer function. Finite element analysis is used as a verification and simulation tool throughout this research. This paper lays the foundation for the future research on the control of the active vibration isolation system.
Canola Oil로부터 코코아버터와 유사한 Triacylglycerol 조성을 가진 재구성지질의 효소적 합성 최적화 연구
문준희(Jun-Hee Moon),이정희(Jeung-Hee Lee),신정아(Jung-Ah Shin),홍순택(Soon-Taek Hong),이기택(Ki-Teak Lee) 한국식품영양과학회 2011 한국식품영양과학회지 Vol.40 No.10
본 연구에서는 카놀라유(canola oil)를 이용하여 코코아버터 유사 재구성지질 합성의 최적조건을 연구하였다. 반응기질로는 카놀라유와 palmitic ethyl ester와 stearic ethyl ester를 이용하였으며, 효소는 Lipozyme TLIM을 사용하여 반응기질의 몰비율과 반응효소의 양, 반응시간을 독립변수로 하고, D-optimal 계획에 의한 반응표면분석에 따라 합성을 실시하였다. 반응을 통해 acyl-migration은 최소로 일어나며, POS 및 SOS, POP의 함량은 최대로 합성되는 조건을 최적화 조건으로 결정하였다. D-optimal 계획에 의한 반응 표면분석을 실행한 결과, sn-2 위치 지방산 조성의 변화를 일으키는 acyl-migration(Y<sub>1</sub>)은 최소로 일어나고 POS(Y<sub>2</sub>)와 SOS(Y<sub>3</sub>), POP(Y<sub>4</sub>)는 최대로 일어나는 조건은 기질의 몰 비율은 canola oil : palmitic ethyl ester : stearic ethyl ester=1:3:9이며, 반응효소의 양은 6%이고, 반응시간은 40 min이었다. 이와 같은 반응조건으로 합성된 재구성지질의 acylmigration(% of palmitic acid+rstearic acid, Y<sub>1</sub>)은 10.43%, POS(Y<sub>2</sub>)의 함량은 25.31%, SOS(Y<sub>3</sub>)는 19.79%, 그리고 POP(Y<sub>4</sub>)는 11.22%로 측정되었다. Synthesis conditions of cocoa butter equivalents were optimized using the response surface method (RSM) by interesterification of canola oil (Ca), palmitic ethyl ester (PEE), and stearic ethyl ester (StEE). The reaction was catalyzed by immobilized lipase (Lipozyme TLIM) from Thermomyces lanuginosa to produce structured lipids containing a composition of triacylglycerols similar to cocoa butter. Reaction conditions were optimized using D-optimal design with the three reaction factors of the substrate molar ratio of canola oil to palmitic ethyl ester and stearic ethyl ester (Ca : PEE : StEE=1:1:3, 1:1.66:5, 1:2:6, 1:2.33:7, 1:3:9, X<sub>1</sub>), enzyme ratio (2∼6%, X<sub>2</sub>), and reaction time (30∼270 min, X<sub>3</sub>). The optimal conditions that minimized acyl-migration while maximizing 1-palmitoyl-2-oleoyl-3-stearoyl glycerol (POS), 1,3-distearoyl-2-oleoyl glycerol (SOS), and 1,3-dipalmitoyl-2-oleoyl glycerol (POP) were predicted, resulting in Ca : PEE : StEE=1:3:9, 6% of enzyme ratio, and 40 min of reaction time. The reaction product of structured lipids was synthesized again under the same conditions, showing 10.43 area% of acyl-migration, 25.31 area% of POS/PSO, 19.79 area% of SOS, and 11.22 area% of POP.
문준희(Jun Hee Moon),박회재(Heui Jae Pahk) Korean Society for Precision Engineering 2004 한국정밀공학회지 Vol.21 No.10
This paper is the first of two companion papers concerning the analysis and design of a pneumatic vibration isolation system. The design optimization of the pneumatic vibration isolation system is required for the reduction of cost, endeavor and time, and it needs modeling and calculation algorithm. The nonlinear models are devised from the fluid mechanical expression for components of the system and the calculation algorithm is derived from the mathematical relationship between the models. It is shown that the orifice makes the nonlinear property of the transmissibility curve that the resonant frequency changes by the amplitude of excited vibration. Linearization of the nonlinear models is tried to reduce elapsed time and truncation error accumulation and to enable the transmissibility calculation of the system with multi damping chambers. The equivalent mechanical models generated by linearization clarify the function of each component of the system and lead to the linearized transfer function that can give forth to the transmissibility exactly close to that of nonlinear models. The modified successive under-relaxation method is developed to calculate the linearized transfer function.
H<SUB>∞</SUB> norm 을 이용한 6 자유도 정밀스테이지의 모델기반 제어기 설계
문준희(Jun-Hee Moon),이봉구(Bong-Gu Lee) Korean Society for Precision Engineering 2010 한국정밀공학회지 Vol.27 No.12
We developed a model-based controller for 6-DOF micropositioning of a precision stage using H<SUB>∞</SUB> norm. For the design, a state-space system of the mathematical model of the stage is derived. In developing the controller, weighting functions are effectively designed in consideration of upper bounds of the sensitivity of the control loop and control input. Step responses in open and closed loop control are provided to verify the micropositioning performance of the stage. By applying the developed controller we prove that the inverse of the weighting function forms the upper bound of the control loop. It is also found that the controller makes the same sensitivity shape with all the DOFs due to the use of H<SUB>∞</SUB> norm. The developed controller is expected to be applied successfully for industrial use.