• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.4
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• pp.89-95
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• 2017

The improvement of a flow coefficient for the recirculation chill-down flow in a main oxidizer shut-off valve has been presented. The flow coefficient, which is mainly affected by the recirculation outlet port size and the configuration inside the valve, has been predicted with measured flow coefficient values. The comparison of experimentally measured flow coefficient with the predicted value shows the effect of valve inside configuration on the flow coefficient. Consequently, the flow coefficient is twice the previous value and about 75% of the pressure loss assigned to the main oxidizer shut-off valve can be used for additional pressure losses for other components in the recirculation chill-down system of a launch vehicle.

• 유체기계공업학회:학술대회논문집
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• 2005.12a
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• pp.448-453
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• 2005

Temperature Control Valve (TCV) is one of the useful temperature control devices, which is used to control constant temperature of working fluid in power and chemical plants and domestic water supply systems. TCV is composed of body, cylinder and piston, and the body shape has a symmetrical H-type. In general, it has several inlet and outlet holes, and its shape is like as tubular sleeve. The piston has three rings two rings of the end of piston have the function of controlling inlet flow rate with hot and cold working fluids, the center ring has the function of preventing hot and cold water from intermixing. Consequently, the shapes of piston and cylinder are the main design parameters in the performance of TCV. In this study, numerical analyses were carried out with two different piston and cylinder shapes to investigate the functions as a temperature control valve and the flow characteristics according to piston opening grade in TCV. Using a commercial code, FLUENT, velocity and pressure fields in TCV are obtained under steady, standard $k -{\epsilon}$ turbulence model and no-slip condition.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.419-422
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• 2003

The hydraulic excavator has been a popular research object for automation because of its multi-workings and economic efficiency. The objective of this paper is to design each components and to construct boom, arm, bucket circuit. These models modeled with AMESim show us change of variables and behavior of excavator. Simulation model will be used for simulator of excavator.

• The KSFM Journal of Fluid Machinery
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• v.3 no.4 s.9
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• pp.52-58
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• 2000

The numerical study on the waterhammer was carried out for the intake pumping station of the metropolitan water supply 6th stage project. Because the waterhammer problems as a result of the pump power failure were the most important, these situations were carefully investigated. The surge tank and the stand pipes effectively protected the tunnels md the downstream region of pipeline from the pressure surge. In case the moment of inertia of the pump and motor was above $5080\;kg{\cdot}m^2$, the column separation did not occur in the pipeline between the pumping station and the inlet of 1st tunnel. As the moment of inertia increased, the pressure surges decreased in the pipeline conveying raw water. The pump control valve was chosen as the main surge suppression device for the intake pumping station. After power failure, the valve disc should be rapidly closed in 2.5 seconds and controlled the final closure to 15 seconds by the oil dashpot. If the slamming happened to the pump control valve, there was some danger of this system damaging. As the reverse flow through the valve increased, the upsurge extremely increased.

• Journal of Drive and Control
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• v.13 no.3
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• pp.15-23
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• 2016

The direct-drive servo valve(DDV) is a kind of one-stage valve because the main spool valve is directly driven by the dc motor. Since the DDV structure is simple, it is less expensive, more reliable, and offers a reduced internal leakage and a reduced sensitivity to fluid contamination. The control system of the DDV is highly nonlinear due to a current limiter, a voltage limiter, and the flow-force effect on the spool motion. The shape of the step response of the DDV-control system varies considerably according to the magnitudes of the step input and the load pressure. The system-design requirements mean that the overshoots should be less than 20%, and the errors at 0.02s should be less than 2%, regardless of the reference-step input sizes of 1V and 5V and the load-pressure magnitudes of 0MPa and 20.7MPa. To satisfy the system-design requirements, the PID-controller parameters of $K_c$, $T_i$ and $T_d$, and the derivative-feedback gain of $K_{der}$ are designed using the root locus and manual tuning.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.51-52
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• 2006

Gabion can be used for the purpose of preventing overflow of river and side loss of road. However the manufacturing process of the gabion is manually controlled especially to the joining process at the terminal part of gabion with small diameter wire. In this paper automatic feeding guide system was designed and fabricated to make automation. The fabricated system was tested in the factory level. Pneumatic system was considered as the main idea of the feeding system. 3/2-way and 5/2-way manual control valve, eight double-acting cylinders were used. Based on the theoretical simulation and actual test the fabricated system was well controlled. The system was applied to the patent.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.12
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• pp.142-147
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• 1998

Developing robot hands with multi-degree-of-freedom is one of the topics that researchers have recently begun to improve the limitation by adding flexibility and dexterity. In this study, an articulated servo-pneumatic robot hand system with direct-drive joints has been developed whose main feature is the minimization of the dimension. The servo-pneumatic system is advantageous to fabricate a dexterous robot hand system due to the high torque-to-weight and torque-to-volume ratio. This enables the design of a finger joint with an integrated rotary vane type actuator which produces high output torque without reduction gears, being very robust. In order to control the servo-pneumatic finger joints, a miniature proportional valve that can be attached to the robot hand is required. In this paper, a flapper nozzle type 4/3-way proportional directional valve has been designed and tested. The experimental results show that the developed valve can control a finger joint satisfactorily without much vibratory joint movements and acoustic noises.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.243-247
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• 2004

The dynamometers which had made in a long time ago could not control the input/output quantity of water minutely and was sensitive to a noise since it was controlled by an analog control method. Therefore, a fully digital controlled system was urgently required to be robust against various noises. In this paper, the new system which can control the amount of circulated water in dynamometer was developed. This system is consisted of an industrial digital type controller and a servo motor. The industrial PLC was used as a main controller for the developed system, and the actuator and servo motor were used to control the inlet and outlet valve independently. The torque signal of load cell was fed back to the main controller to regulate the diesel engines load. Generally, an input/output valve position of the old dynamometer was fixed with a proper situation for an engine output test and the torque was changed according to the time interval. However, the torque value for the dynamometer could not be constantly kept because of the variation of the input water flow and fluid characteristic. Therefore, the automatic control of an inlet and outlet valve should be performed to keep the constant torque. So, the PID control method was applied to solve this problem. Also, the development of a web-based remote control system was described in this paper. This software will give us the convenience of operation, the more efficient operations, and the reduced operator workload for operation of the dynamometer. The application results of the system have been verified at actual diesel engine field.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.111-114
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• 2010

MOV(Main Oxidizer shut-off Valves) control the combustion of launch vehicle systems by the supply and the isolation of liquid oxygen to a main combustion chamber in launch vehicle systems. Moreover, the MOV should secure a constant flow rate of liquid oxygen for combustion instability in the steady operational state. To modify the middle flange and rip of inlet valve design by Computer Aided Structural Analysis for improvement of EM core functions. In result, it has been verified to improve performance of EM by tests.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.7
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• pp.40-45
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• 2001

This paper proposes a methodology for the small-displacement-movement of a piston and develops a hybrid control algorithm for the precision position control of a pneumatic rodless cylinder. The pneumatic system uses the voltage-proportional solenoid valves to minimum valve switching since the on/off type valves are create diffculties for accurate position control and induce a lot of valve switching. For the accurate position control a methodology for the small-displacement-movement of the piston is developed and identified experimentally. The main consideration on the development of the hybrid control law is to eliminate a stick-slip phenomenon in the pneumatic control system. This paper addresses these critical issues and presents experimental results for the pneumatic control system.