• Bulletin of the Korean Space Science Society
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• 2004.04a
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• pp.97-97
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• 2004

현재 KSLV-I에서 탑재부의 Pitch, Yaw, Roll의 3축 제어 및 2단부의 Roll 제어를 위해 사용되는 보조 추진 시스템은 구성이 단순하며, 신뢰성이 높은 것으로 알려져 있는 단일 추진제인 하이드라진을 이용하는 추진 시스템을 고려하고 있다. 이러한 하이드라진 추진 시스템은 추력실 전방에 설치되어 있는 추력기 밸브의 ON/OFF를 이용하여 추력을 조절하게 되는데, 이 때 추력기 밸브의 빠른 작동으로 인해 수격현상에 의한 급격한 압력 상승이 발생하게 되어 구조물의 손상을 발생하게 된다. (중략)

• Bulletin of the Korean Space Science Society
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• 2004.04a
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• pp.83-83
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• 2004

상용프로그램인 AMESim을 이용하여 제어밸브 성능시험설비에 대한 Transient 구간에서 문제점 발생 확인과 동시에 시스템에 최적화를 통한 비용 절감효과를 위해 본 Simulation을 수행하였다. 가압 자동 조절 시스템은 직렬식과 병렬식 두 가지에 대해 고려했을 경우 직렬식이 더 타당함을 확인하였고, 특히 Tank Ullage의 압력 분포를 보면 직렬식에서 Fluctuation이 약 $\pm$0.2%이고, 병렬식에서 약 $\pm$0.7%가 됨을 보았다. (중략)

• Journal of Drive and Control
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• v.9 no.4
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• pp.32-41
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• 2012

Most diagnosis methods for servo valves requires installing spool displacement sensor or flow sensor as well as pressure sensor. The measurement of flow is hard to implement and many kinds of servovalves or proportional direction valves do not have a built-in spool displacement sensor. In this study, static performances of servovalve or proportional-direction-valve are studied theoretically and a diagnosis technique, which uses only load pressure and input current signal, is assessed. An experimental setup was made based upon a personal computer and the LabVIEW graphical language. A series of diagnosis tests were performed and the analysis results showed it possible to measure the pressure gain, hysteresis and null bias in a relatively simple methodology.

• Journal of the Korean Society of Propulsion Engineers
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• v.15 no.2
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• pp.74-83
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• 2011

For launcher applications, different from other applications, very high flow rate is required which can lead to supply pressure drop against required setting pressure. The supply pressure decrease is closely related to regulator characteristics. In this paper, supply pressure offset is investigated considering regulators as kinds of control systems. Pressure offset of self-operated regulator is analyzed with sensitive parameter defined as the ratio of valve travel to pressure offset. It is shown that pressure offset of self-operating regulator can be improved by incorporating proportional and integral controls and they can be materialized with pilot regulator systems.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.10
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• pp.976-982
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• 2010

This paper proposes a novel type of pressure control mechanism which can apply to vehicle ABS (anti-lock braking system) utilizing the piezoactuator based valve system associated with the pressure modulator. As a first step, a flapper-nozzle of a pneumatic valve system is devised by integrating the piezoacuator to the flexible beam structure. The dynamic modeling of the valve system is then undertaken and subsequently the governing equation of pressure control is derived considering the pressure modulator. A sliding mode controller is designed in order to achieve accurate pressure tracking control in the presence of actuator uncertainty as well as input pressure variation. It is shown through computer simulation that an accurate pressure tracking for sinusoidal motion whose magnitude is 40 bar is achieved by utilizing the proposed pressure control mechanism.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.3
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• pp.51-56
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• 2020

Research into natural refrigerants that use CO₂, instead of chlorofluorocarbons and hydrofluorocarbons, has increased due to the environmental problems caused by ozone depletion. CO₂ refrigerants are more environmentally friendly than conventional refrigerants because they have better latent heat of evaporation and heat transfer efficiency properties. However, they have very low critical temperatures and require high design pressures; therefore, pressure control valves, which reduce the pressure of the CO₂ refrigerant to a safe level and apply it to the refrigerant air conditioning system, are necessary to secure stability against high pressure. In the present study, we evaluated the flow characteristics and valve performance of the pressure control valve using a CO₂ refrigerant by measuring the pressure, velocity, and flow coefficient. In addition, we examined the applied forces caused by the internal pressure from the highly pressurized CO₂ refrigerant and required thrust characteristics.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.7
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• pp.634-642
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• 2011

A numerical analysis of steady/unsteady flow applying cavitation model and moving mesh method was carried out in order to analyze flow and response characteristics inside the pilot valve which controls the flight actuator system. The flow of the valve was assessed according to operation temperature and time. This research has found that valve characteristics became stable at above a specific temperature and the cavitation affected valve's performance. Internal pressure and response characteristics of the valve were analyzed and flow characteristics of steady and developed unsteady flow were confirmed to be matched each other.

• Transactions of The Korea Fluid Power Systems Society
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• v.8 no.4
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• pp.9-16
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• 2011

Because of the increasing demand on the high precision and high response of a machinery, proportional control valves are widely adopted at various application fields. This paper studies on the static and dynamic characteristics of a pilot proportional pressure control valve. An experimental apparatus including hydraulic pump, variable speed inverter, pressure and flow sensors and data aquisition system was set up. And various experiments such as P-Q-V curves, step responses due to input voltage and flow rate, hysteresis, frequency response of the proportional valve was carried out and the results are discussed.

• Journal of Advanced Navigation Technology
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• v.14 no.5
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• pp.760-766
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• 2010

In this paper, The static friction torque and viscous friction torque including hydraulic motor-load system driven by hydraulic proportional control valve analysis. The basic experimental was performed toward characteristic in pressure and flow rate in hydraulic system energy. The variable of friction torque was experiment on brake pressure variable using pneumatic brake system. The analysis of nonlinear friction and linear friction was perform ed toward friction characteristic of hydraulic system.

• Journal of Advanced Marine Engineering and Technology
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• v.23 no.1
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• pp.69-78
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• 1999

In this study a new pattern of pressure control of hydraulic cylinder using high speed On-Off solenoid valve in the electro-hydraulic system has been suggested. The control valve is 3-way high speed On-Off solenoid valve which is operated by PWM(Pulse Width Modulation)control signal. The high speed On-Off solenoid valve has a tendency to induce severe pressure fluctuation in the hydraulic actuator so it has not been used for the purpose of closed loop control with direct pres-sure feedback. In this study closed loop control with direct pressure feedback is enabled by using a digital filter which has linear minimum mean square filter algorithm. Through some experiments it is confirmed that stable pressure control can be realized by the proposed control technique.