• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.06a
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• pp.641-642
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• 2008

• Journal of Drive and Control
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• v.8 no.3
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• pp.48-52
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• 2011

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1999.10a
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• pp.405-410
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• 1999

Hydraulic pipeline between servo valve and actuator affect the dynamic characteristics of electrohydraulic servo systems in serveral ways. This paper deal with the speed control of oil hydraulic gear motor using electrohydraulic servo valve. The frequency and transient response of electrohydraulic servo valve coupled to a gear motor is anlayzed. In particular, the effect of short and long hydraulic pipelines between servo valve and gear motor is investigated. The dynamic characteristics of the speed control systems of gear motor with short pipeline is first described via frequency response experiments with small signal linearized analysis. Loner pipeline is applied distributed parameter pipeline model with consideration of frequency dependent viscous friction.

• Plant Journal
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• v.15 no.4
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• pp.36-42
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• 2019

In recent, according to the tightening of environment regulation policy, the height of the site of the power plant is increased and the length of the cooling water pipe is increased. This has a serious impact on the stability of the plant. This study analyzes the transient phenomenon using LIQT 7.2, an unsteady state one-dimensional analysis software, to secure the stability of 1,000 MW high-capacity coal-fired power plant cooling water system with high head. To prevent water hammer, The effects on performance characteristics were predicted by individual and combination application. The surge pressure of the cooling water which occurs when the pump was stopped without installing the anti-surge devices was the largest at the pump outlet side. The most effective and simple way to reduce surge pressure in these cooling water systems is to combine a vacuum breaker with a hydraulic non-return valve, which is an essential device for pump protection.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.5
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• pp.601-607
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• 2013

This paper presents the development and validation of a wheel loader simulation model. The objective of doing so is to evaluate the performance of the wheel loader and improve its overall performance using Matlab/Simulink. The wheel loader simulation model consists of 4 parts: mechanical/hydraulic powertrain model and vehicle/working dynamic model. An integrated simulation model is required to evaluate and improve the performance of the wheel loader. It is expected that this model will be applied to fuel economizing, improving the pace of operation by using the hybrid system, and the intelligent wheel loader. The performance of the proposed simulation model has been validated by using Matlab/Simulink to compare the driving and the working experimental data.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.4
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• pp.2424-2429
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• 2015

In an oil hydraulic piston pump, the cylinder block and valve plate in high speed relative sliding motion have the characteristics which should be extremely controlled for the optimization of leakage and friction losses, and pressure-resistance design of them is very important for high pressure performance. But the studies on the stress analysis of those parts have not been performed briskly. Therefore, in this paper, the stress and displacement distributions of the cylinder block and valve plate in the oil hydraulic piston pump with a swash plate type are discussed through the static stress analysis using CATIA V5. The stress and displacement of the cylinder block are more influenced by the axial pressure than by the radial pressure, and are larger by approximately 66% and 30%, respectively. The results show that a review of the material and shape of the valve plate is required.

• Journal of Aerospace System Engineering
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• v.12 no.5
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• pp.32-39
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• 2018

In this paper, the calculation of the theoretical pressure transfer ratio due to the deformation of the thin-plate spring type check valve applied to the small piezoelectric-hydraulic pump was carried out. A thin-plate check valve is a flexible body that is deformed by an external force. The deformation of the check valve affects the rate at which the chamber pressure is transferred to the load pressure. The theoretical pressure transfer ratio for each model was calculated to compare the difference between the assumption that the thin-plate check valve is a rigid body and that of the flexible body model. The P-delta effect was considered for the calculation of the pressure transfer ratio of the flexible check valve model. In addition, a verification test for the calculated pressure transfer ratio obtained by considering the deformation of the flexible check valve model was carried out. The load pressure was measured by applying a thin-plate and ball-thin plate spring type check valves, respectively. The experimental pressure transfer ratio was calculated using the respective load pressure obtained from the experiments. The validity of the pressure transfer analysis of the check valve, taking into consideration the P-delta effect, was verified by comparing it with the theoretically calculated pressure transfer ratio.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.5
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• pp.2106-2112
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• 2013

In a traditional hydraulic elevator, elevator car is descended by down control valve, and the oil hydraulic energy must be lost during the descending stroke. In this paper, hybrid type energy saving unit for a hydraulic elevator is researched to save the hydraulic energy which is lost during the descending stroke. The energy is stored as converted electrical energy, and the saved energy is reused as the auxiliary power for the ascending stroke of elevator car or the main power of other parts. The results show that the output characteristics are stable and good and the research is successful and useful to reuse the saved energy during the descending stroke of elevator car.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.1
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• pp.387-392
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• 2020

This paper proposes a flow-rate control system for industrial valves. Industrial valves are used in piping systems to control the flow rate and pressure. In general, valves used in pipelines are classified into globe valves, butterfly valves, and ball valves according to the shape. Motor, hydraulic, and pneumatic systems are used for operating valves. The flow meter should measure the flow rate when configuring the flow-rate control system. On the other hand, because the flow rate of the valve can be expressed by flow coefficient, a control scheme is proposed using the pressure deviation, which measures at the front and rear of the valve. The transfer function for the valve, according to the control input, was estimated using the signal compression method. Based on the induced transfer function, the disturbance observer was designed to improve the command following the performance of the valve stem. The performance of the proposed control method is compared with the flow-rate control result using the flow meter used.

• Journal of Power System Engineering
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• v.14 no.6
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• pp.102-108
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• 2010

In this study, the authors investigate the basic characteristics of a two stage directional control valve with pilot spool assembled in main spool coaxially. The step response characteristics and effects of major design parameters' values on valve performances arc clarified through numerical simulations. In addition, the authors examined the possibility of applying the object valve for this study as a proportional control valve. Based on the numerical simulation results, new design values for the reformed design as a proportional control valve were suggested.