• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.6
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• pp.24-30
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• 2013

This paper studies the comparative analysis on two different internal cushion devices (the types of needle and relief valve) used to absorb the energy which is generated when the pneumatic cylinder moves with the load at meter-out speed control system. The effect at varying the piston velocity under same driving condition is mainly investigated. The simulation results on pressure in the cushion chamber and the dynamic behavior of the relief valve type cushion device are compared with the needle valve type. Design and performance are improved with the cushion configuration of better quality at high-speed pneumatic cylinder. Based on the relation between absorbed energy and impact energy at cushion process, cushion performance at pneumatic cylinder is evaluated.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.671-674
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• 2002

Pressure compensating temperature control valve(TCV) is one of the important control devices, which is used to maintain the constant temperature of working fluid in power and chemical plants. The ratio of cylinder hole diameters of inlet and outlet is the main design parameters of TCV. So this needs to be investigated to improve the function of control of temperature and void fraction. In this study, numerical analysis is carried out with various ratios of cylinder hole diameters of the inlet and outlet in the TCV. Especial1y, the distribution of the static pressure Is investigated to calculate the new coefficient($C_{\upsilon}$) and resistance coefficient(K). The governing equations are derived from making using of three-dimensional Naver-Stokes equations with standard $k-{\varepsilon}$ turbulence model and SIMPLE algorithm. Using a commercial code, PHOENICS, pressure and flow fields in TCV are calculated with different inlet and outlet diameters of the cylinder hole for cold and hot water passages.

• Transactions of The Korea Fluid Power Systems Society
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• v.6 no.3
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• pp.16-22
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• 2009

This paper deals with the issue of robust position tracking control and energy-saving control for a valve-controlled cylinder system using speed-controlled fixed displacement pump. The whole feedback control system is composed of a pair of interconnected subsystems, that is, valve-controlled cylinder system and load-sensing control system. From experiments it is shown that position tracking control in the load sensing control system can accomplish significant reduction in input energy to pump comparing to a conventional valve-controlled cylinder system, while exhibiting the same position tracking control accuracy.

• Journal of Advanced Marine Engineering and Technology
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• v.15 no.4
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• pp.54-69
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• 1991

This study deals with the position control of a hydraulic cylinder system operated by two port 3-way high speed solenoid valve in Pulse-Width-Modulation mode, instead of using conventional electro-hydraulic servovalve. Due to the complexity and the relatively poor reliability of the servovalve, an actuator using simpler and more study high speed solenoid valve will be presented. The high speed solenoid valve acts as converters of electronic pulse signal to hydraulic ones. It has been pointed out that there are practical problems to be solved in the PWM system, that is (1) accuracy of positioning control becomes considerably insufficient because the system is affected by on/off action of the solenoid valves, and (2) serious nonlinerality appears in the valve characteristics as a result of the switching behavior of the valves. As a method to overcome these defects, the differential PWM driving method of a hydraulic cylinder that improved the steady-state-error, flow rate nonlinearity in simple PWM, and the hydraulic hunting of dead time compensated-PWM driving is proposed in this study.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.565-568
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• 1995

This paper presents the position control of a closed-loop cylinder system using ER(electro-rheological)valve actuators. Following the field-dependent pressure analysis of the ER valve actuators on the basis of Bingham model of ER fluids, a 3 d.o.f. close-loop sylinder system having the heave, roll and pitch motions is proposed. The governing equations of motion are derived using Lagrange's equation, and a control model is established by considering system uncertain parameters such as load conditions. A sliding mode controller which has inherent robustness to system uncertainties is adopted to achieve robust tracking control performance. Tracking control results for sinusoidal trajectory were presented in order to demonstrate the effectiveness of the proposed control system.

• Journal of Aerospace System Engineering
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• v.8 no.1
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• pp.1-6
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• 2014

The conventional hydraulic circuits for electro-hydrostatic actuators equipped with a single-rod cylinder can oscillate under overrunning load conditions. In this paper the oscillation problem encountered in the conventional hydraulic circuits for EHAs is analyzed and it is shown by simulation results that this problem can be solved by employing a counter balance valve instead of a pilot-operated check valve generally used in the conventional hydraulic circuits.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.636-639
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• 1996

We have developed a part of hydraulic stroke sensing cylinder using magnetic sensor that can detect each position under severe construction fields. In this paper, for evaluating the developed cylinder under various environment condition, thermal control systems and two hydraulic systems to be coupled consist of. The former is composed of an heater case, temperature sensor, and interface circuits which include SCR(silicon controlled rectifier) for the control of the voltage's phase. The latter is composed of an hydraulic cylinder for position control with solenoid valve (ON/OFF motion) and a load cylinder with proportional reducing valve. To obtain the various performance evaluation, it is carried out under high temperature condition in thermal system controlled by using Ziegler-Nichols PID tuning method and artificial disturbances such as impulse or constant force. The results show that the developed cylinder has good performance under the various environment condition.

• Journal of Mechanical Science and Technology
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• v.15 no.1
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• pp.108-116
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• 2001

The in-cylinder flow field of gasoline engine comprises unsteady compressible turbulent flows caused by the intake port, combustion chamber geometry. Thus, the quantitative analysis of the in-cylinder flow characteristics plays an important role in the improvement of engine performances and the reduction of exhaust emission. In order to obtain the quantitative analysis of the in-cylinder gas flows for a gasoline engine, the single-frame particle tracking velocimetry was developed, which is designed to measure 2-dimensional gas flow field. In this paper, influences of the swirl and tumble intensifying valves on the in-cylinder flow characteristics under the various intake flow conditions were investigated by using this PTV method. Based on the results of experiment, the generation process of swirl and tumble flow in a cylinder during intake stroke was clarified. Its effect on the tumble ratio at the end of compression stroke was also investigated.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2000.11a
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• pp.221-227
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• 2000

The design of the valve plate is most important to increase efficiency in the oil hydraulic axial piston pump. A theoretical study was carried out to clarify the pressure characteristics at the land of the valve plate in the oil hydraulic axial piston pump. Dynamic pressure acts on the land of the valve plate was computed numerically with discharge pressure, rotational speed and swash plate angle. Pressure distribution between the valve plate and the cylinder block also was obtained with dynamic pressure. The results are applicable to improve the design technique of the valve plate in the oil hydraulic axial piston pump.

• Journal of Mechanical Science and Technology
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• v.19 no.2
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• pp.704-715
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• 2005

In this study, to investigate in-cylinder tumble or swirl intake flow of a gasoline engine, the flow characteristics were examined with opening control valve (OCV) and several swirl control valves (SCV) which intensify intake flow through steady flow experiment, and also turbulent characteristics of in-cylinder flow field were investigated by 2-frame cross-correlation particle image velocimetry (PIV) method. In the investigation of intake turbulent characteristics using PIV method, the different flow characteristics were showed according to OCV or SCV figures. The OCV or SCV installed engine had higher vorticity and turbulent kinetic energy than a baseline engine, especially around the wall and lower part of the cylinder. Above all, SCV B type was superior to the others. About energy dissipation and reynolds shear stress distribution, a baseline engine had larger loss than OCV or SCV installed one because flow impinged on the cylinder wall. It should be concluded, from what has been said above, as swirl component was added to existing tumble flow adequately, it was confirmed that turbulent intensity was enlarged, flow energy was conserved effectively through the experiment. In other words, there is a suggestion that flow characteristics as these affected to in-cylinder combustion positively.