• 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.

• Transactions of The Korea Fluid Power Systems Society
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• v.6 no.3
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• pp.10-15
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• 2009

The major system of an agricultural power-shift tractor is the transmission, using power-shift. Because the transmission performance depends on the hydraulic control system, the most important aspect of the optimization is the design of the hydraulic control system. This study was conducted to improve a pressure modulation characteristics of the power-shift transmission hydraulic system. It has been tried to replace an existing pressure modulation method with a digital control by using HSSV(High Speed Solenoid Valve). The performance of the PWM control system in power-shift hydraulic transmission has been evaluated by means of experiment.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.11
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• pp.25-33
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• 1997

This study deals with controlling the velocity of Electr-Hydraulic servo system through the non-stan-dard PIC control. This was done as follows. First, we modeled nonlinearised model and linearised model, second designed analytic program for electro-hydraulic servo system velocity control Lastly, to im- prove dynamic characteristics of system we designed non-standard PID contoller and verifed throughth experi- ment and MATLAB program, commercial used software.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.2
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• pp.219-225
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• 2015

Because a hydraulic actuator has high power and force densities, this allows the weight of the robot's limbs to be reduced. This allows for good dynamic characteristics and high energy efficiency. Thus, hydraulic actuators are used in some exoskeleton robots and quadrupedal robots that require high torque. Force control is useful for robot compliance with a user or environment. However, force control of a hydraulic robot is difficult because a hydraulic servo system is highly nonlinear from a control perspective. In this study, a nonlinear model was used to develop a simulation program for a hydraulic servo system consisting of a servo valve, transmission lines, and a cylinder. The problems and considerations with regard to the force control performance for a hydraulic servo system were investigated. A force control method using the nonlinear model was proposed, and its effect was evaluated with the simulation program.

• Journal of Biosystems Engineering
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• v.31 no.2 s.115
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• pp.88-94
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• 2006

The market of rice transplanter has already been changed for riding and to be turned large size of chassis. Because an automation is rapidly expanded, It is strongly need to analyze a mechanism and develop a hydraulic circuit. In this study, we analyzed the mechanism of working equipment of rice transplanter for riding and developed hydraulic circuits. We proposed the operating mechanism of rice transplanter for riding through the mechanistic analysis of working equipment. And the simulation and experiment were performed. In order to up and down the working equipment of rice transplanter for riding, we designed the mechanism which was installed hydraulic circuit and hydraulic cylinder, and it was manufactured. The pressure of developed hydraulic circuit was set by 800 $N/cm^2$. In the field testing, the hydraulic response presented at 50 msec in the maximum driving velocity, 0.8 m/sec of rice transplanter for riding, and it was well performed. The results of experiments showed the system characteristics sufficient to use as the hydraulic mechanism for a rice transplanter for riding.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.2024-2030
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• 2003

Design for a quite operation of fluid power system requires the understanding of noise and vibration characteristics of the system. This paper presents a dynamic response for design of hydraulic circuit. Experimental investigations on the attenuation characteristics of pressure ripple in automotive power steering hydraulic pipe with dynamic response of hydraulic pipe line is examined. Also, a mathematical model of hydraulic pipe is proposed to support design of the hydraulic circuit and analyze the attenuation characteristics of pressure ripples in a hydraulic pipe line. And analyze the impedance characteristics to determine the postion to construct accumulator for attenuation the pressure pulsation. The experimental results show that the pulsation attenuation characteristics of hydraulic hoses is remarkably affected by the flexible metal tube inserted coaxially inside a hydraulic hose with a finite length as well as viscoelastic properties of hose wall. It is also shown that the predicted results by the model proposed here agree well with the measured results over a wied range of frequency;

• Journal of Mechanical Science and Technology
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• v.17 no.7
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• pp.999-1010
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• 2003

Uninterrupted power supply has become indispensable during the maintenance task of active electric power lines as a result of today's highly information-oriented society and increasing demand of electric utilities. This maintenance task has the risk of electric shock and the danger of falling from high place. Therefore it is necessary to realize an autonomous robot system using electro-hydraulic manipulators because hydraulic manipulators have the advantage of electric insulation and power/mass density. Meanwhile an electro-hydraulic manipulator using hydraulic actuators has many nonlinear elements, and its parameter fluctuations are greater than those of an electrically driven manipulator. So it is relatively difficult to realize not only stable contact work but also accurate force control for the autonomous assembly tasks using hydraulic manipulators. In this paper, the robust force control of a 6-link electro-hydraulic manipulator system used in the real maintenance task of active electric lines is examined in detail. A nominal model for the system is obtained from experimental frequency responses of the system, and the deviation of the manipulator system from the nominal model is derived by a multiplicative uncertainty. Robust disturbance observers for force control are designed using this information in an H$\_$$\infty$/ framework, and implemented on the two different setups. Experimental results show that highly robust force tracking by a 6-link electro-hydraulic manipulator could be achieved even if the stiffness of environment and the shape of wall change.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.1
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• pp.112-119
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• 2009

An automatic transmission of construction equipment is controlled by hydraulic and electronic system for doing in various functions like as shifting and operation. The shifting is operated by the engaged and disengaged clutch motion from hydraulic power. On the shifting process, suitable pressure control to the clutch is required for smooth shifting. Hydraulic control system in the automatic transmission is divided by the pilot control type and the direct control type greatly. The direct control type has an advantage than the pilot control type. Because the structure is simple, the design and the manufacture are having less troubles and the system can be maximized precision pressure control. However, the excellent performance proportional control valve should be used to achieve proper control-ability. In this study, the dynamic analysis model composing the automatic transmission and hydraulic system for forklift truck is presented to simulate the characteristics of hydraulic system about the direct control type. That model is verified the validity compared the results of the testing examination. Parameters of input signal are analyzed to reduce the output torque according to input control signal is affected in shifting characteristic.

• Journal of Drive and Control
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• v.13 no.3
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• pp.1-7
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• 2016

A cold gas blow-down hydraulic actuation system is widely used in missiles that require an actuation system with a fast response time under a limited space with a short operating time and large loads on the actuators. The system consists of a pneumatic part that supplies the regulated high-pressure gas to a reservoir, and a hydraulic part that supplies pressurized hydraulic oil to the actuators by the pressurized gas in the reservoir. This paper proposes a mathematical model to analyze and simulate the pneumatic part of an actuation system that supplies the operating power to the actuators. The mathematical model is based on the ideal gas equation and also considers the models for heat transfer. The model is applied to the pressure vessel and the gas part of the reservoir, and the model for the pneumatic part is established by connecting the two models for the parts. The model is validated through a comparison of the simulation results with the experimental results. The comparison shows that the suggested model could be useful in the design of the pneumatic part of a cold gas blow-down type hydraulic actuation system.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.06a
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• pp.283-284
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• 2009