• Journal of Biosystems Engineering
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• v.16 no.4
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• pp.355-362
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• 1991

The objective of this study was to develop an electronic-hydraulic depth control system. Simulation was carried out to investigate the responses of the control system, and indoor experiments were carried out to confirm the simulation results of the control system. Field experiments were carried out to compare the newly-developed electronic-hydraulic depth-control system with the existing mechanical-hydraulic position control system in terms of the performance of depth control. The electronic-hydraulic depth control system showed better performance than the existing mechanical-hydraulic hitch control system for the forward speeds of tractor less than 7 km/h. It is concluded that the new control system could be adapted to the existing tractors with slight modifications to the conventional mechanical-hydraulic hitch control systems.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.4
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• pp.32-38
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• 2006

A clutch hydraulic system for automotive manual transmissions transfers hydraulic pressure generated by driver's pedal manipulation to the clutch mechanism. The foot effort when the clutch pedal is pushed is different than that when the clutch is returned. The effort or load difference, called hysteresis, is caused by the friction produced between rubber seal and inner wall inside the hydraulic cylinder. This clutch pedal travel foot effort hysteresis is essential for a clutch hydraulic system design and analysis. The dynamic model for a clutch hydraulic system is developed and a simulation analysis is performed to estimate the fiction coefficient as a function of the cylinder pressure. The simulation result is then compared to the measurements obtained from a clutch hydraulic system tester to ensure the reliability of the dynamic model and the coefficients estimated. Also the estimated friction coefficients at various pressure values are compared to those reported by an independent study.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.1
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• pp.168-173
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• 2004

This article describes the design of a hydraulic system for a power split type continuously variable transmission (CVT). The CVT considered here, is composed of planetary gears, clutches, and a torque converter which is mainly used for the realization of CVT function. Similar to automatic transmissions, the hydraulic system of CVT is designed for supplying hydraulic flows and pressures to each component of CVT, in order to activate the clutch engagements and torque converter operation, and to cool the drivetrain. By using the mathematical models of drivetrain, a simulation program was developed to investigate the power performance of CVT equipped vehicle and the operating conditions of each component of CVT. And the design parameters of the hydraulic system and clutches were calculated using the operating conditions and power requirements which obtained from the simulation results. Finally the hydraulic circuit design of prototyped valve body is presented based on the numerical results of this analysis.

• Journal of Drive and Control
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• v.20 no.2
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• pp.1-6
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• 2023

This study aims to develop a Korean dental chair hydraulic circuit by improving the existing equipment in order to localize foreign leading companies' products. The suggested Hydraulic circuit can be applicable to varied sectors where height and backrest angle control of chair-type equipment are required. The study followed the steps below. First, three kinds of foreign hydraulic circuits were analyzed and three kinds of Korean dental chair hydraulic circuits were suggested. Second, it was determined whether the three kinds of Korean hydraulic circuits operate normally through SimulationX, a software specialized in multi domain analysis, and the effectiveness of each circuit was examined.

• Journal of computational fluids engineering
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• v.21 no.4
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• pp.19-27
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• 2016

The flow analyses through a porous hydraulic fractures is among the most important tasks in recently developed shale reservoirs but is rendered difficult by non-Darcy effects and geometric changes in the hydraulic fractures during production. In this study, several Computational Fluid Dynamics(CFD) models of hydraulic fractures, with a simple shape such as that of parallel plates, filled with proppants were built. Direct Numerical Simulation(DNS) analyses were then carried out to examine the flow loss characteristics of the fractures. The hydraulic diameters for the simulation models were calculated using the DNS results, and then they were compared with the results from Kozeny's definition of hydraulic diameter which is most widely used in the flow analysis field. Also, the characteristic parameters based on both hydraulic diameters were estimated for the investigation of the flow loss variation features. Consequently, it was checked in this study that the hydraulic diameter based on Kozeny's definition is not accordant to the results from the DNS analyses, and the case using the CFD results exhibits f Re robustness like general pipe flows, whereas the other case using Kozeny's definition doesn't. Ultimately, it is expected that discoveries reported in this study would help further porous flow analyses such as hydraulic fracture flows.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.1 s.94
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• pp.246-252
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• 1999

In this paper, the frequency response characteristics of the velocity controlled EHS system obtained by linear simulation method, nonlinear simulation method, and experimentation are compared one another, in order to verify propriety of the linearization method in case of analysis of hydraulic systems. The Bode diagrams are obtained by transforming time domain data of experimental results and nonlinear simulated ones with Fourier transform. The results of nonlinear simulation are more similar to the frequency response of the real systems than those of linear simulation. It is found that nonlinearity of hydraulic systems is mainly occurred from servo valve, and nonlinearity is increased as displacement of servo valve spool increases.

• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.4
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• pp.107-114
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• 2010

Coupling systems for trains need more complicated buffer equipments than existing systems because the recent tendency of the regulations enforces trains to be safe for collisions even when the driving speed is higher than before. Using hydraulic buffer is an effective way to satisfy the requirement while it causes the increase of the cost for the coupling system. In this study, we introduce the methodology to build a simulation model for the hydraulic buffer, which could be installed into the coupling systems. In the simulation model of the hydraulic buffer, the reacting force is determined by both buffer stroke and speed whereas the elastic buffer model is designed by using only the buffer stroke in other studies. The simulation results with the advanced hydraulic buffer model shows that the simulating results can be close the real experimental results around 10%, and, if we considers friction forces, the simulation calculates the maximum force within 10% comparing to the experimental.

• Journal of the Korean Society of Safety
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• v.31 no.1
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• pp.41-47
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• 2016

The rolling stock is composed of several cars. In order to operate in combination, it is necessary to connect the device, called coupler, between the rolling stocks. When the collision occurs between cars, couplers should be able to absorb the shock. Urban railway has used only rubber absorbers. But recently, the hydraulic buffer has been considered in general railway. In order to know the performance of the buffer it should be conducted to experiments. But whenever this combination change, we should experiments to know a lot of the dynamic behavior of each coupler. These experiments are generally replaced by the simulation, since a lot of time and cost consuming. The quasi-static map of hydraulic buffer obtained by the experiments is required for the simulation. However, the experiments for obtaining such a quasi-static map is costly and time consuming. In this paper, it proposes a method for deriving the quasi-static map of hydraulic buffer from the theoretical model.

• Journal of Advanced Marine Engineering and Technology
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• v.20 no.5
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• pp.82-92
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• 1996

A computer simulation with predict the fuel injection rates and the fuel injection pressure behaviors in diesel engine fuel injection systems would by very useful in designing or improving fuel injection systems. In this paper we developed computer program in order to predict the behaviors of the fuel injection rate and the injection pressure for Electronic Hydraulic Ultra-High Pressure Fuel Injection System. We've applied the continuity and momentum equations for the hydraulic phenomena and the dynamics of individual components of the Electronic Hydraulic Fuel Injection System. To solve all the equations numerically we've applied the Runge-kutta IV method. Water hammer equations were applied for the hydraulic pipe solution, and the method of characteristics was employed in our calculations. The simulation results were compared with the experimental results for: Accumulator pressure, Injection pressure and unjection rate. As a result, The simulation results agree very well with our experimental results. We found that a large accumulator and the high speed solenoid valve were required, and the compression volume of the fuel had to be as small as possible in order to acheive ultra-high pressure fuel injection.

• Journal of Power System Engineering
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• v.15 no.6
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• pp.86-94
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• 2011

In this paper, an electro hydraulic power steering system based on electro hydrostatic actuator (EHA) is proposed. A detailed steering model for the proposed electro hydraulic power steering system including mechanical and hydraulic subsystems is established. A conventional electro hydraulic power steering system is also modeled to evaluate the performance of the proposed power steering system such as responsiveness, assist force, command tracking and steering feel by computer simulation. From the computer simulation results, it is found that the proposed power steering system based on EHA has desirable performance.