• Title/Summary/Keyword: Hydraulic Valve

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A Study on PWM Control of an Electro-Hydraulic Servo Indexing System (전기유압식 서보인덱싱 시스템의 PWM 제어에 관한 연구)

  • 허준영
    • Journal of Advanced Marine Engineering and Technology
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    • v.23 no.2
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    • pp.236-243
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    • 1999
  • This study deals with the application of high speed on-off valves to an electro-hydraulic servo indexing system incorporated electro-hydraulic servo valces. Comparing with the electro-hydraulic servo valve the high speed on-off valve has some merits. Which included low price robustness to the oil contamination and dircect control without D/A converter. The considered sys-tem of this study is controlled by pulse width modulation(PWM) of the control law which is pro-duced by a PID controller which is used broadly in industrial equipments. The dynamic character-istics corresponding to variations of system parameters such as inertia moment system gain and supply pressure are investigated by computer simulation and experiment. Consequently the availability of the application of high speed on-off valve to servo indexing system instead of electro-hydraulic servo valve is confirmed.

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Analysis of Characteristics of Load Movement in Mobile Hydraulic Equipment (모바일 유압장치에서 부하의 유지와 내림 특성 비교)

  • Jo, Mi Hyeon;Huh, Jun Young
    • Journal of Drive and Control
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    • v.15 no.4
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    • pp.17-22
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    • 2018
  • Mobile hydraulics require higher energy efficiency, and a simpler as well as robust design, than general industrial hydraulics. The 6/3-way directional control valve is widely used as a mobile hydraulic control valve. However, since the 6/3-way directional control valve is a spool type valve, it is difficult to maintain the load. A counterbalance valve is typically used, to maintain the load, and lift down. However, in an industrial field using a mobile hydraulics device, a pilot controlled check valve may be used to implement holding and lifting operation of the self-weight load, and a relief valve may be used simply to exert back pressure. But no comparative analysis of advantages and disadvantages of each method was revealed. In this study, various methods of holding and unloading load with self-weight in mobile hydraulics are investigated, and compared through simulation using AMESim software. This is experimentally verified by using Festo's mobile hydraulic test rig TP800.

A Study on a Novel Flow Control Valve for Wind Power Heat Generation Hydraulic Systems (풍력 열발생 유압 시스템을 위한 새로운 유량제어밸브에 관한 연구)

  • Choi, Sae Ryung;Lee, Ill Yeong;Han, Bong Jun
    • Journal of Drive and Control
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    • v.14 no.1
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    • pp.23-28
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    • 2017
  • A wind power heat generation system that converts wind power directly to heat instead of electric power is considered in this study. The system consists of a wind turbine part and a heat generation part. The heat generation part is materialized by a hydraulic system including a hydraulic pump, a flow control valve, a hydraulic oil tank, etc. The flow control valve primarily converts hydraulic energy generated in the pump to heat energy. It should have a function of overspeed protection under excessive wind speeds. In this study, a novel flow control valve design is proposed for excellent flow control characteristics under excessive pump driving torque (excessive wind speed). The performance of the suggested valve is analyzed using numerical simulation.

A Study on Dynamic Characteristics of Hydraulic Motor Brake System with Counter Balance Valve (카운터 밸런스 밸브를 내장한 유압 모터 브레이크 시스템의 동특성)

  • Yun, So-Nam;Lee, Ill-Yeong
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.29 no.3
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    • pp.214-219
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    • 1993
  • Counter balance valve is used as one part of hydraulic motor brake system. The function of this valve is to protect over-run or free falling of inertia load. But occasionally the brake system with counter balance valve makes some undesirable problems such as pressure surges or vibrations. These problems may hurt system safety and driver's conformability. Nevertheless, studies on dynamic characteristics of hydraulic system including counter balance valve are very rare, so further accumulation of research results are required. In this study, for the purpose of easy estimation about dynamic characteristics of hydraulic system including counter balance valve, precise formulation describing fluid dynamics and valve dynamics under various boundary conditions were made. The equations obtained in the preceding process include some parameters that must be got experimentally. Flow coefficients of valve and choke are the most significant ones among the parameters. So these parameters are obtained experimentally in this study, and experimental equations obtained from the experimental data were used for numerical calculation. The equations were analysed by numerical integration using Runge-Kutta method, because the equations contain various nonlinear terms. From the numerical analysis, it was verified that the dynamic response of counter balance valve and pressure variation at each elements can be estimated very easily. So the analysing method developed in this study enabled very easy estimating the relation between the performances of counter balance valve and various physical parameters related to the valve. Conclusively, it is said that the results obtained in this study can be used very usefully to develop a new type counter balance valve or to apply the valve to actual hydraulic system for various industrial equipments.

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A Study on the PWM Control of Hydraulic Equipment Using High Speed On-Off Valve (고속전자밸브를 사용한 유압장치의 PWM 제어에 관한 연구)

  • ;Wennmacher,G.
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.19 no.3
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    • pp.868-876
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    • 1995
  • This study deals with a position control of an electro-hydraulic servo system which consist of cylinder and high speed on-off valves operated by microcomputer. The merits of PWM control of hydraulic equipment are the robustness of the high spee on-off valve, its low price and the direct control without D/A converter. In the PWM control of high speed on-off valve, the time lag and switching time existing between the input and output signals of valve are considered as demerit points. To get analytical results, the effects of these demerits have to be clarified in detail. The object of this study is to propose a mathematical model for the behavior of high speed on-off valve and to get analytical results of this system. The dynamic characteristics of this system is examined by digital computer simulation analytically and compared with experimental results to varify the proposed mathematical model.

Lubrication Analysis of Hydraulic Spool Valve with Groove Cross Sectional Shapes (Groove 단면형상에 따른 유압 Spool Valve의 윤활해석)

  • Park, Tae-Jo;Hwang, Yun-Geon
    • Tribology and Lubricants
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    • v.25 no.1
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    • pp.13-19
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    • 2009
  • The spools in most hydraulic spool type control valve have several circumferential grooves to pre-vent well known hydraulic locking problems which result in high friction force and excessive wear. In this paper, a commercial computational fluid dynamics (CFD) code, FLUENT is used to investigate the flow and lubrication characteristics of grooved hydraulic spool valve. The stream lines and pressure distributions are obtained for various groove cross sectional shapes and film thicknesses. The stream lines are highly affected by groove cross sectional shape but pressure distributions mainly depend on the film shape and its magnitude. Therefore the numerical method adopted in this paper and results can be use in designing of various grooved spool valve.

A Study on the Improvement of Dynamic Characteristics of ABS Outlet Valve (ABS 출구 밸브의 동특성 향상에 관한 연구)

  • 김병우;송창섭;이용주
    • Transactions of the Korean Society of Automotive Engineers
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    • v.10 no.1
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    • pp.133-142
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    • 2002
  • To improve the hydraulic control performance of ABS, it is necessary to establish an efficient control algorithm. And also it is necessary to ova]Hate a hydraulic modulator with solenoid valve quantitatively. In this paper, FEM and permeance method are used to analyze dynamic characteristics of outlet valve. In return, mathmatical modeling of a hydraulic modulator and operating pressure is presented, and the model parameters of an outlet valve are moving plunger, spring constant and orifice diameter. This study shows the way to improve the dynamic characteristic of an ABS outlet valve heavily depending on operating pressure. It is recommended that operating pressure should be justified at the first step toward the design to get the optimal design of an outlet valve.

A study on Dynamic Characteristics of Hydraulic Motor Brake System Integrated Counter Balance Valve (유압 모터 브레이크 시스템의 동특성에 관한연구)

  • Yun, So-Nam;Kim, Hyeong-Ui
    • 한국기계연구소 소보
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    • s.20
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    • pp.27-32
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    • 1990
  • A counter balance valve is used as one part of hydraulic motor brake system. The function of this valve is to protect over-run or free falling of inertia load. But occasionally the brake system with counter balance valve makes some undesirable problems such as pressure surges or vibrations. In this study, for the purpose of easy estimation about dynamic chrcteristics of hydraulic system including counter balance valve, precise formulation describing fluid dynamics and valve dynamics under various boundary conditions were made. dynamic caracteristics were analysed by numerical intergration using Runge-Kutta method, because the equations in this circuit with counter balance valve contain various nonlinear terms. So the analyzing method developed in this study enabled very easy estimating the relation between the performance of counter balance valve and various physical parameters related to the valve.

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Modeling and Simulation of an EPPR Valve Coupled with a Spool Valve

  • Khan, Haroon Ahmad;Yun, So-Nam
    • Journal of Drive and Control
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    • v.16 no.2
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    • pp.30-35
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    • 2019
  • EPPR (Electro-hydraulic Proportional Pressure Reducing) valves are pressure control valves. In this study, an independent metering valve (IMV), which is a combination of a spool valve opened and closed with the help of an EPPR valve, was discussed. The overall performance of the valve (IMV) was obtained by the respective modeling and simulation of the system. The valve investigated in this study is to be used for independent metering of hydraulic excavator actuator e.g. boom, arm, bucket etc. To design the model, continuity equations and force balance equations were used. The set of differential equations were then simulated in Simulink using ODE45 option in the configuration toolbox. The valve has to be able to control the flow rate going in and out of the cylinder separately, which is why the particular configuration was needed and selected.

Position Control of a Hydraulic Cylinder by a Differential PWM Method (차동PWM방식에 의한 유압실린더의 위치제어)

  • 권기수;이창돈;이진걸
    • 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.

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