• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1268-1273
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• 2003

This paper presents a case history of piping failures on power plant. The root cause of the failure was defined to set the optimal countermeasures. The failure comes from transient vibration and the 1st stress increased at the hydraulic oil supply system of control valves for high pressure steam turbine.

• Tribology and Lubricants
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• v.19 no.6
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• pp.370-375
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• 2003

The radial acting load of vane on the camring in oil hydraulic vane pumps with and without intra­vanes have been investigated. The influences of the discharge pressure and rotating speed of the vane to the load were discussed. The variations of the radial acting load of a vane were calculated on the basis of the results measured for the dynamic internal pressure in the four chambers surrounding a vane. It provides essential information for the study of pump dynamics and control, the pump design and the analysis of tribological problems in the sliding components.

• Proceedings of the KIEE Conference
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• 2009.04b
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• pp.106-108
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• 2009

This paper presents the practical pressure control of hydraulic oil-pump system using SR drive for industrial application. In order to get a high performance of pressure dynamics in actual application, a data based PID control scheme is proposed in this paper. The proposed control scheme is verified by the experimental test.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.2071-2075
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• 2005

Hydraulic excavators have been popular devices in construction field because of its multi-workings and economic efficiency. The mathematical models of excavators have many nonlinearities because of nonlinear opening characteristics and dead zone of main control valve, oil temperature variation, etc. The objective of this paper is to develop a simulator for hydraulic excavator using AMESim. Components and whole circuit are expressed graphically. Parameters and nonlinear characteristics are inputted in text style. The simulator can be used to forecast excavator behavior when new components, new mechanical attachments, hydraulic circuit changes, and new control algorithm are applied. The simulator could be a kind of development platform for various new excavators.

• 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.

• Geomechanics and Engineering
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• v.9 no.5
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• pp.645-667
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• 2015

Single treatment and staged treatments in vertical wells are widely applied in sandstone and mudstone thin interbedded (SMTI) reservoir to stimulate the reservoir. The keys and difficulties of stimulating this category of formations are to avoid hydraulic fracture propagating through the interface between shale and sand as well as control the fracture height. In this paper, the cohesive zone method was utilized to build the 3-dimensional fracture dynamic propagation model in shale and sand interbedded formation based on the cohesive damage element. Staged treatments and single treatment were simulated by single fracture propagation model and double fractures propagation model respectively. Study on the changes of fracture vicinity stress field during propagation is to compare and analyze the parameters which influence the interfacial induced stresses between two different fracturing methods. As a result, we can prejudge how difficult it is that the fracture propagates along its height direction. The induced stress increases as the pumping rate increasing and it changes as a parabolic function of the fluid viscosity. The optimized pump rate is $4.8m^3/min$ and fluid viscosity is $0.1Pa{\cdot}s$ to avoid the over extending of hydraulic fracture in height direction. The simulation outcomes were applied in the field to optimize the treatment parameters and the staged treatments was suggested to get a better production than single treatment.

• Journal of the Korean Society of Industry Convergence
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• v.4 no.1
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• pp.21-26
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• 2001

A method for the control of pulsating pressure transients in the hydraulic brake system has been presented and experimentally verified. This control is accomplished by installing flow restricting devices at appropriate locations in the brake oil pipe line. The experimental results presented are expected to provide a basis for transient control design of hydraulic brake systems.

• Proceedings of the KIPE Conference
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• 2007.11a
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• pp.163-165
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• 2007

Direct Instantaneous Pressure Control(DIPC) method of SRM using pressure predict method is presented in this paper. A hydraulic pump system has an inherent defect that its dynamic behavior causes by interaction between the sensor and hydraulic load. It will make sometimes the whole system become oscillatory and unstable. Proposed system integrates direct instantaneous torque control (DITC) and Smith predictor to improve dynamic performance and stabilization. The proposed hydraulic oil pump system is verified by computer simulation and experimental results.

• Transactions of The Korea Fluid Power Systems Society
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• v.1 no.3
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• pp.14-19
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• 2004

The Direct Drive Valve used in this study contains a pressure-feedback-loop in itself, then it can eliminate nonlinearity such as the square-root-term in flow rate calculation and the change of bulk modulus of hydraulic oil. In this study, assuming that the dynamic characteristic of the DDV is modelled as a first order lag system, an parameter identification method using the input data and the output data is applied to obtain DDV's mathematical model. Then, a state feedback controller was designed to implement the force control of hydraulic system, and the control performance was evaluated.

• Journal of Drive and Control
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• v.20 no.4
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• pp.35-44
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• 2023

This study aimed to analyze the performance of hydraulic systems for dental chair when long working hours makes the temperature of hydraulic fluid rise. The study was carried out in the following manner. First, 'cylinder's clearance' was reflected in the three kinds of hydraulic circuits, which were developed through the preceding study, in order to analyze oil leak. Second, 12 cases of simulations comprised of the up and down of cylinders were carried out. Third, it was determined whether the cylinder velocity of dental chair surpasses 1cm/s required in the development even in the hydraulic fluid temperature of 60℃. In conclusion, this study used SimulationX to verify the performance stability at high temperatures using three types of hydraulic circuits designed to develop a Korean unit chair.