• 제어로봇시스템학회:학술대회논문집
• /
• 1996.10b
• /
• pp.1450-1454
• /
• 1996

Even though digital control type high speed solenoid valve is a little inferior to analog control type servo valve and proportional control valve in performance, it is cheap and has secure performance against pollutant and simple control circuit. But high speed solenoid valve is hardly used for heavy machinery instead of servo valve or proportional control valve that is used in severe condition because the valve itself is small capacity and it shows wide dead zone during on-off control and chattering of hydraulic cylinder by chattering of pressure. It is desirable to use low-priced and strong pollutant resistant high speed solenoid valve for obtaining reliability of operation from severe working condition because it isn't necessary to acquire response characteristic of high frequency when we consider the characteristic of heavy machinery operation. In this study, PWM control algorithm for pilot pressure control of large capacity pilot operating valve will be used for precision position control of heavy machinery hydraulic cylinder. Not only cost reduction of main control valve but also high reliability of heavy machinery in severe condition can be obtained by using this pilot operating spool valve with high speed solenoid valve.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.14 no.3
• /
• pp.142-149
• /
• 2006

A PIV(Particle Image Velocimetry) was applied to measure in-cylinder velocity field according to inlet valve angle during intake stroke. Two engines, one is conventional DOHC 4 valve and the other is narrow valve angle, were used to compare real intake flow. The results show that the intake flow pattern of conventional engine is more complicated than that of narrow angle one in horizontal plane and the vertical component of in-cylinder flow is rapidly decayed at the end stage of intake. On the other hand, the flow pattern of narrow angle one is relatively well arranged in horizontal plane and the vertical velocity component remains so strongly that forms large-scale strong tumble. Two engines also form commonly three tumble; two are small and bellow the intake valve and one is large-scale. The center of large scale tumble moves to bottom of cylinder as the vertical velocity increases.

• Journal of the Korean Society of Safety
• /
• v.25 no.6
• /
• pp.22-27
• /
• 2010

Flow Coefficients of intake port in an engine cylinder head were measured by a newly designed flow rig. In measuring the flow coefficient with traditional method, the valve lift was manually varied by technician with adjusting a micrometer which is directly connected to the intake valve of the cylinder head. The cam shaft of the cylinder head is directly rotated by a step motor and the valve lift was automatically varied with cam shaft profile in the newly designed flow rig. The measurement of the flow coefficient was automated by rotating the cam shaft with the step motor. Automatic measurement of the flow coefficient could be safely measured by separating a technician from the noise and vibration of the traditional flow rig. Also, the automatic measurement of the flow coefficient reduce the measurement time and provide meaningful statistical data.

• International Journal of Precision Engineering and Manufacturing
• /
• v.2 no.2
• /
• pp.48-56
• /
• 2001

This paper presents the position tracking control of a closed-loop cylinder system using electro-rheological (ER) valve actuators. After manufacturing three sets of cylindrical ER valves on the basis of Bingham model of ER fluid, a 3 dof(degree-freedom) closed-loop cylinder system having the heave, roll and pitch motions is constructed. The governing equations of motion are derived using Lagrange's equation and a control model is formulated by considering nonlinear characteristics of the system, Sliding mode controllers are the designed for these ER valve actuators in order to achieve position tracking control. The effectiveness of trajectory tracking control performance of the proposed cylinder system is demonstrated through computer simulation and experimental implementation of the sliding mode controller.

• Journal of the Korean Society for Precision Engineering
• /
• v.17 no.3
• /
• pp.165-173
• /
• 2000

This Paper presents the position tracking control of a closed-loop cylinder system using electro-rheological(ER) valve actuators. After manufacturing three sets of cylindrical ER valves on the basis of Bingham model of ER fluid, a 3 dof(degree-of-freedom) closed-loop cylinder system having the heave, roll and pitch motions is constructed. The governing equations of motion are derived using Lagrange's equation and a control model is formulated by considering nonlinear characteristics of the system. Sliding mode controllers are then designed fer these ER valve actuators in order to achieve position tracking control. The effectiveness of trajectory tracking control performance of the proposed cylinder system is demonstrated through computer simulation and experimental implementation of the sliding mode controller.

• 제어로봇시스템학회:학술대회논문집
• /
• 1996.10b
• /
• pp.1441-1444
• /
• 1996

This paper presents the position control of a double-rod cylinder system activated by an electrotheological(ER) valve unit. Following the composition of a silicone oil-based ER fluid, theological properties of the ER fluid are experimentally tested as a function of imposed electric fields to determine appropriate design parameters of the ER valve. The ER valves are then designed and manufactured. Subsequently, the pressure drop of the ER valve is evaluated with respect to the intensity of the electric field. Four ER valves bridge-cylinder system is formulated, and the governing equations for the system are derived. A neural network control scheme is then synthesized to perform the position control of the cylinder system. Tracking control responses are experimentally evaluated and presented in order to demonstrate the effectiveness of the proposed control system.

• Journal of Mechanical Science and Technology
• /
• v.19 no.2
• /
• pp.655-663
• /
• 2005

Tribological characteristics in the sliding parts of oil hydraulic piston pumps are very important in increasing overall efficiency. In this study, the fluid film between the valve plate and the cylinder block was measured by using a gap sensor and the mercury-cell slip ring unit under real working conditions. To investigate the effect of the valve shape, we designed three valve plates each having a different shape. One of the valve plates was without bearing pad, another valve plate had bearing pad and the last valve plate was a spherical valve plate. It was noted that these three valve plates observed different aspects of the fluid film characteristics between the cylinder block and the valve plate. The leakage flow rates and the shaft torque were also investigated in order to clarify the performance difference between these three types of valve plates. From the results of this study, we found that the spherical valve plate estimated good fluid film patterns and good performance more than the other valve plates in oil hydraulic axial piston pumps.

• Journal of ILASS-Korea
• /
• v.21 no.1
• /
• pp.7-12
• /
• 2016

In this study, to research in-cylinder flow characteristics of spark-ignited engine with intake valve closing timing change for Miller cycle. 3D simulation study were used 6 different intake valve profile with $CAD10^{\circ}$ gap for retard intake valve closing timing. Comparison of In-cylinder flow pattern characteristic were accompanied between Base and LIVC. And the efficiency of volume and the work of compression were analyzed with simulation study. When intake valve closing angle was retarded in $CAD50^{\circ}$, the pressure in cylinder was decreased about 12~13 bar and volume efficiency was reduced about 16%. The efficiency of volume and the work of compression were reduced on LIVC.

• Journal of the Korean Institute of Gas
• /
• v.11 no.1 s.34
• /
• pp.34-39
• /
• 2007

In this paper, the FEM result has been presented for a sealing safety between a valve packing and a valve seat during a open and close operation in a LPG cylinder. The sealing operation of a LPG valve is completed when the valve packing in which is made by a nylon-66 polymer is to stop a LP gas flow, which flows out from the outlet of a brass pipe in a LPG cylinder. The contact sealing mechanism of the valve may be classified by a flat contact of an unused valve packing and a circular groove contact of an used valve packing in a current LPG valve. Based on the FEM and experimental investigations the sealing force, 4.9 MPa for a flat contact mode of the unused valve packing is a little high compared to that of the used valve packing, which shows a circular groove contact geometry against a valve seat. But these sealing pressures for two contact modes are very low compared to the ultimate strenath 83 MPa of the nylon-66 and this may be designed with a excess strength of the valve.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
• /
• 2004.11a
• /
• pp.99-107
• /
• 2004

Lubrication characteristics between a cylinder block and a valve plate for high speed bent-axis type hydraulic pump play an important role in volumetric efficiency and durability of pump. In this paper, a finite element method is presented for the computation of the pressure distribution between a cylinder block and a valve plate for high speed bent-axis type hydraulic pump. Also, a Runge-Kutta method is applied to simulate the cylinder block dynamics of three-degrees of freedom motion. From the results of computation, we can draw two major conclusions. One is related to the fluid film characteristics between a cylinder block and a valve plate and the other is related to the average leakage that is determined by the pressure gradient and the clearance near the discharge port. The numerical results of cylinder block dynamics were compared with the experimental results using eddy-current type gap sensors those are fixed at a pump housing.