• Journal of Power System Engineering
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• v.4 no.1
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• pp.51-59
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• 2000

Active suspension systems have been using for improving ride quality and stability for vehicles. An active suspension system is composed of a hydraulic pump, pressure control valves, hydraulic dampers, vehicle body, tires and other components. In this study, the mathematical model for the active suspension system based on the quarter car concept is derived, and a program for analysing the dynamic behaviour of the suspension system is developed. The computed results by the developed program are compared with the experimental results for confirming the reliability and usefulness of the developed program.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.8
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• pp.40-48
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• 1997

In this study, an analysis and design for hydraulic control system was developed. By using this system, the operator is able to simulate dynamic performance of the system without possessing special knowledge of software or control engineering. A graphical user interface was adopted in the system and all speration for simulation can be done by using window facilities on the display. The electro-hydraulic servo system is simulated to present the performances of the program and compared with the result of Matlab and experiment.

• Journal of Drive and Control
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• v.18 no.2
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• pp.1-8
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• 2021

In this work, a circuit with a hydraulic power unit is formulated as a means of predicting the behavior of the prefill valve in the future. The behavior of the prefill valve can be examined by the measurements of the configured power unit, and the performance is determined by using hydraulic pumps, relief valves, and hydraulic hoses that make up the power unit. In particular, pressure/flow pulsation generated by hydraulic pumps can cause instability in the prefill valve and cause noise-induced degradation of the overall performance and reliability of the hydraulic system containing the prefill valve. Therefore, to study the behavior and performance of the prefill valve in a relatively accurate manner, the prediction of the characteristics of the hydraulic power unit driving the prefill valve is very important. In this study, the pulsation characteristics of the hydraulic pump were analyzed to theoretically demonstrate its relationship with different settings of the power unit, such as relief valve pressure settings and the presence/absence of the hose.

• Journal of Engineering Education Research
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• v.4 no.2
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• pp.11-19
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• 2001

Current educational hydraulic oil systems consist of the composites for the hydraulic circuits. These systems not only could attract students' interests, but also increase the teaching efficiency during the lectures. Thus, the visual hydraulic oil system has been developed to enhance educational efficiency and to improve learning methods. With this new system, the students can easily examine the oil flow for hydraulic oil parts in mechanical engineering experiments. In order to develop the new system, the hydraulic constitute was made of acryl resin, and previous pipes were replaced by transparent and flexible tubes. Red colored oil was also used to visualize the oil flow. Furthermore, if OHP (Over Head Projector) was used for a theoretical lectures, the visual units can be used to classify the differences of the valve structure or the circuits. If lecturers use the developed visual hydraulic system, students can make an effective experiment on the basic theories and principles. Therefore, we can promote the students' interests and materialize the objectives of the subject. The results of this paper can be widely used to improve the efficiency of the mechanical engineering education.

• Journal of Drive and Control
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• v.18 no.3
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• pp.1-7
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• 2021

In a hydraulic control system, since a hydraulic cylinder drives a relatively large mass of an object, an external load force acts as a disturbance on the control performance of the system. Additionally, as the hydraulic system is used for a long period, there are disturbances that occur gradually, such as a drop in supply pressure because of abrasion of the pump, oil leakage from a valve, and oil leakage from a cylinder. In this study, a state feedback controller based on a linearization technique is applied. To prevent the performance degradation of the controller from the load disturbance, an Extended Luenberger observer (ELO) is used for the Extended system. The case of using the proportional controller, which is a representative linear controller, and the result of using the controller designed in this study are compared and reviewed through simulation. Also, we propose an experimental gain-setting method for a state feedback controller that can be used at industrial sites, and examine how the stability and control performance of the system changes because of the disturbance inputs through the experimental results.

• Journal of Soil and Groundwater Environment
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• v.19 no.3
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• pp.39-46
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• 2014

Hydraulic conductivity is an important parameter, representing permeable property of the groundwater in aquifers, in the issues of groundwater development, groundwater contamination, and groundwater flow, etc. We estimated a relationship between hydraulic conductivity and electrical properties (formation factor, chargeability, and time constant) of silty sand in the laboratory. For this study, we conducted grain size analysis, constant head permeameter test, and measured electrical resistivity and spectral induced polarization of silty sand samples collected from the riverside alluvium of the Nakdong River in Nogok-ri area, Dasan-myeon, Goryeong-gun in Gyeongbook Province, Korea. In the laboratory test, we used soil samples of approximately uniform porosity with 0.5% error range, and kept the electrical resistivity of pore water with 100 ohm-m. As a result, the relationship between effective particle size and hydraulic conductivity agrees fairly well with the existing empirical formulas. Hydraulic conductivity was correlated with formation factor, chargeability, and time constant: hydraulic conductivity increased with increasing formation factor and time constant as well as with decreasing chargeability.

• Journal of Ocean Engineering and Technology
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• v.30 no.5
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• pp.361-366
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• 2016

The aim of this study was to experimentally investigate the hydrodynamic performance of a hemispheric wave energy converter (WEC) and its wave power takeoff. The WEC is a heaving body-type point absorber with a hydraulic-pump power take-off (PTO) system. The hydraulic PTO system consists of a hydraulic cylinder, hydraulic motor, and generator, with consideration given to the hydraulic pressure and flow rate. Two body model shapes, including the original hemisphere and a bottom-chopped hemisphere, were considered. The heave RAOs of the two models were evaluated for various body drafts. The effects of the hydraulic PTO system on the RAOs were also investigated.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2005.10a
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• pp.257-258
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• 2005

• Tribology and Lubricants
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• v.20 no.3
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• pp.163-167
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• 2004

Reducing friction torque of the oil hydraulic vane pump used as the power source of power steering system should consider friction torque including viscous and mechanical friction torque according to the changes of rpm and pressure. This paper analyzes the forces acting on the vane to reduce the friction torque of the vane of the hydraulic vane pump used for Hydraulic Power Steering(HPS) system, and futhermore, the forces according to the shapes of cam profiles are analyzed.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.5
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• pp.119-126
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• 2003

The simulator of a vehicle equipped with hydrostatic transmission and hydraulic accumulator type-braking energy regeneration system is developed using a PC. The simulator receives the accelerator pedal angle and the brake pedal angle generated by the operator using the keyboard, updates the state variables of the energy regeneration system responding to the input signals, and draws the moving pictures of the accumulator piston, pump plate angle and pump/motor plate angle every drawing time on the PC monitor. Also, the operator can observe the accel pedal angle, brake pedal angle, pressures of accumulators, vehicle speed, hydraulic torque, engine torque and air brake torque representing the operation of braking energy regeneration system through the PC monitor every drawing time. The simulator can be a very useful tool to design and improve the braking energy regeneration system.