• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.4
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• pp.139-145
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• 2007

The motion of single-rod cylinder is typically controlled by the directional control valve. In some case, the hydraulic system should be energized by the man power and at the same time the motion of a cylinder is controlled manually. It may be confusing for a man to do two things at the same time. The solution is to make up the closed hydraulic circuit with the bi-directional pump and single-rod cylinder without using a directional control valve. In the case of single-rod cylinder, the flows at the rod side and head side are so different that several valves should be installed to make the motion of single-rod cylinder possible. The hydraulic system is composed of a bi-directional pump, a single-rod cylinder, pilot operated check valves, a check valve and a counter balance valve for the purpose of actuating the lifter. The characteristics of a suggested system are analysized mathematically and numerically.

• Journal of Drive and Control
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• v.15 no.4
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• pp.61-66
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• 2018

Almost every hydraulic system is equipped with a pressure relief valve, to maintain working pressure of the system at a pre-determined level. Thus, dynamic characteristics of such a relief valve, in conjunction with other hydraulic components, are important in designing the hydraulic control system. The single stage pressure relief valve is dynamically undesirable, due to relatively low viscous damping, that causes high frequency oscillations. This problem is overcome by introducing orifices in the inner pilot line, and drain line. In this study, for the single stage spool type pressure relief valve, the system equations were derived through an adequate linearisation and several simplifications were made, to use the transfer function formulation technique. All coefficients were evaluated and used, to make some results by using Matlab software. Results of analysis are compared with experimental results. In this study, parameters affecting stability of valve design are determined and suggested relative to the design.

• Transactions of the Korean Society of Automotive Engineers
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• v.4 no.6
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• pp.52-64
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• 1996

This paper presents an active position control of a single-rod cylinder system featuring an electrorheological(ER) fluid-based valve. The ER fluid consisting of silicone oil and chemically treated particles is firstly composed and its Bingham property is tested as a function of imposed electric field. A multi-channel plate type of ER valve is then designed and manufactured on the basis of the field-dependent Bingham model. Performance test of the ER valve is undertaken by evaluating pressure drop with respect to the number of electrode as well as the intensity of the electric field. Subsequently, the ER valve-cylinder system is constructed and its governing equation of motion is derived. A neural control scheme for position control of the cylinder is formulated by incorporating proportional-plus-derivative(PD) controller and implemented. Experimental results of both regulating and tracking control responses are presented in order to demonstrate the efficacy of the proposed ER valve-cylinder control system.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.27 no.2
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• pp.168-174
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• 2017

In this work, a piezostack single-stage valve (PSSV) system is proposed and its control performance is experimentally evaluated at high temperature up to $150^{\circ}C$. In order to achieve this goal, a PSSV system is designed and operating principle and mechanical dimensions are discussed. A displacement amplifier and an adjust bolt are used to generate target displacement and to compensate thermal expansion. Then, an experimental apparatus is constructed to evaluate control performance of the PSSV system. The experimental apparatus consists of a heat chamber, a hydraulic circuit, a pneumatic circuit, pneumatic-hydraulic cylinders, thermal insulator, electronic devices, sensors, data acquisition (DAQ) board and a voltage amplifier. The flow rate and displacement control performance of the valve system are evaluated via experiment. The experimental results are evaluated and discussed at different temperatures and frequencies showing the controlled flow rate and spool displacement.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.4
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• pp.404-408
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• 2013

In this Study, another way to accomplish the goal of meeting large steam-flow requirements is the use of multiple valves. Multiple valves can provide better control in meeting the precision pressure controller requirements. Simulation demonstrates the effectiveness of the pressure controller. The key point of this study is to precisely control the position of the control valve on the outside of the electro-hydraulic system using a special PID controller. Simulation and experiments verify the performance of the controller.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.3311-3316
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• 2007

To analyze the influence of valve overlap period on a backfire occurrence, the single cylinder research engine with MCVVT(Mechanical Continuous Variable Valve Timing) system is developed and backfire limit equivalence ratio defined as fuel-air ratio equivalence ratio at which backfire occurs is examined according to various valve overlap period. The MCVVT is the system to control valve overlap period by mechanical device. It is estimated that the lower valve overlap period has the higher backfire limit equivalence ratio though the same energy is supplied. When the valve overlap period is changed from 30$^{circ}$ CA to 0$^{circ}$ CA, backfire limit equivalence ratio is increased 74%, approximately. It means that valve overlap period is concern in backfire occurrence, and may be one of the methods for controlling back fire occurred in a $H_2$ engine.

• Journal of the Korea Institute of Military Science and Technology
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• v.24 no.2
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• pp.219-227
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• 2021

In the present study, the effect of command signals of the flow control valve on performance of underwater discharge systems using a linear pump was investigated numerically. For that, the improved mathematical model was developed. The improvement is to calculate the flow leakage between the water cylinder and the piston. Also the model of the hydraulic cylinder is simplified. To validate the improved model, calculation results were compared with experiment results. The results of the study is as follows: Double ramp command signals of the flow control valve had an advantage over single ramp signals. The parametric study on the effect of double ramp command signals on performance of the system was performed. In case of using double ramp signals, the maximum acceleration of the underwater vehicle was reduced by approximately 50 % compared with using single ramp signals.

• Progress in Superconductivity and Cryogenics
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• v.12 no.4
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• pp.36-40
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• 2010

In this paper, a noble method for rapid cooldown of pulse tube refrigerator (PTR) was proposed and experimentally investigated. An orifice pulse tube refrigerator generates refrigeration effect by expansion PV work at the cold-end, and its amount is affected by the orifice valve opening. There exists the optimum valve opening for maximum cooling capacity and it varies as cold-end temperature. It is verified from simulation results using isothermal model that the optimum valve opening increases as the cold-end temperature increases. In the experiments, a single stage orifice pulse tube refrigerator is fabricated and tested. The fabricated PTR shows 97.5 K of no-load temperature and 10 W at 110 K of cooling capacity with the fixed orifice valve opening. From experiments, the initial cooldown curve with four cases of valve opening control scenario are obtained. And it is experimentally verified that the initial cooldown time can be reduced through the control of orifice valve opening.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.5
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• pp.650-658
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• 1997

Analysis and control of intake charge motion such as swirl and tumble are very important factors in improving the gasoline engine performance. In this paper, single-frame PTV (particle tracking velocimetry) is used to investigate intake tumble patterns in a steady flow test rig of gasoline engine with dual-intake-valve and pent-roof combustion chamber. Intake tumble pattern is quantified in accordance with blockage ratio of TIV (tumble intensifying valve) with single- frame PTv.The view of the instantaneous 2-D velocity field gives a realistic understanding of in-cylinder flow field. Thus it is confirmed that PTV is a effective tool in engine design. In conventional port, two tumble structures appear clearly, and the larger one is observed under the exhaust valve side and the smaller is right below the intake valve side. The larger vorticity is observed in TIV port, thus it is concluded that TIV have an effect on intensified tumble motion in cylinder flow.

• Journal of Drive and Control
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• v.12 no.2
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• pp.39-48
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• 2015

In order to control the actuators of hydraulic machinery such as excavators, various control valves are typically assembled in a single block. Such a control block is called a main control valve(MCV). In this paper, we analyzed the working principle and the particular purpose of the design of all valves included in the MCV system. To Examine the reliability of the analysis model, the pressure drop of the MCV at each port was measured. The authors developed an analytical model of the control valve(main spool, load poppet, pressure relief, make up, and regeneration). The authors considered the notch shape of the spool while developing the analytical models of the main spool valve. Most importantly, at the stage before the analysis model was applied in the design tuning, the reliability was ensured by comparing the analysis results with the test results. This paper showed a process of developing an analysis model that can be utilized in the design and tuning stages.