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슬롯 다이 코팅 균일도 평가를 위한 실용적인 중량계측 기반 유량 측정 방법
윤경택,배정현,최영만 한국정밀공학회 2023 한국정밀공학회지 Vol.40 No.2
Slot-die coating is a method of coating a wide layer of thin film on a substrate. It has the advantages of large-area coating with high reproducibility and uniform thickness. For this reason, it has been widely applied in various industrialmanufacturing fields. To secure higher coating uniformity under various coating conditions, estimating and controlling the flow rate of the coating solution discharged to the substrate is crucial. In this study, a practical gravimetric flow rate measurement method for slot-die coating uniformity evaluation has been introduced. The gravimetric method is a technique for accurately and quickly estimating the flow rate through the mass change over time using a precision weighing balance. We analyzed the measurement principle and errors caused by fluid mechanics such as hydrodynamic force or capillary force. The dynamic properties based on fluid viscosity were also evaluated for flow rates from 5 to 50 μL/s. The repeatability of the fabricated measurement system was ~1.5 μL/s. Finally, it was confirmed that the settling time for highviscosity fluid could be advanced by 56.4% through multi-step feedforward control.
K. T. Yoon(윤경택),Y. M. Choi(최영만) Korean Society for Precision Engineering 2021 한국정밀공학회 학술발표대회 논문집 Vol.2021 No.11월
In the wearable exoskeletons for assisting lower limbs during human walking, strategy for assisting eccentric muscle contractions can effectively save human metabolic energy by replacing the negative joint biological power used for braking body. This technique provides deceleration torque to the lower limb joint in the negative work phase during gait cycle, removing portion of kinetic energy that is naturally dissipated by the muscle. The braking torque is provided from the back-electromotive force of an electromagnetic generator, which is amplified through a gear transmission. This configuration has the advantage that Watts of power are generated while providing deceleration assistance simultaneously. In this study, experimental evaluation of the wearable knee exoskeleton for assisting eccentric muscle contraction is introduced. Our knee exoskeleton prototype provides 8 Nm of braking torque while generating 3 W of electrical power within a gait cycle with a device efficiency of 66%. In the treadmill-walking test, kinematics and muscle activities of lower limbs were observed according to the assist torque level change. In addition, we confirmed that the exoskeleton provides accurate assistance even when the kinetics of the lower limb joints change according to the slope of the ground.
가변형 슬롯 다이 코팅의 균일도 확보를 위한 토출 유량 정밀 측정 및 제어
배예은,윤경택,이현호,이문구,김현정,최영만 한국생산제조학회 2023 한국생산제조학회지 Vol.32 No.5
Slot die coating is a pre-metered coating process commonly used for manufacturing thin and wide films with high production speed and good uniformity. Recently, there has been an increasing demand for variable-width coating by changing the slot width. In this case, the discharged flow rate per unit width must be continuous for optimal uniformity thickness. This study assesses the flow rate from the variable width slot die nozzle by adapting a gravimetric method using a precision weighing balance. Changing slot width alters internal flow dynamics. Therefore, through the fluid simulation, we gauged any flow rate change caused by the hydrodynamic force from the width change. For uniform coating thickness, we controlled the pump with the feedforward method from the baseline obtained by the simulation. Experimental results demonstrate that the flow rate error was enhanced by 81% and 14% for opening and closing slot cases, respectively.