• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.282-287
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• 2004

Noise and vibrations in the pipe systems may be arisen from pumps. compressors, etc. The source mechanism is classified with the mechanical and hydraulic. Mechanical vibrations may be excited by the unbalance in rotating machinery. Hydraulic source may be generated in the turbulent flow. The vibro-acoustic behaviour of flexible, fluid-filled pipe system is a very complex and determined by two parameters: the frequency and the mass ratio of fluid and pipe wall. As the frequency increases, the mode number in the pipe increases. The mass ratio is close to one, the structure and the fluid are strongly coupled. In ease the diameter is very small to the length of pipe, the behaviour of pipe is same as a beam. The finite element formulation when the fluid and the structure are coupled is derived by using beam element. The Numerical results are compared with the package (Sysnoise) which is using the shell element.

• Aerospace Engineering and Technology
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• v.6 no.2
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• pp.188-196
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• 2007

A composite case was designed to satisfy the required condition of KSLV-I kick motor system. we performed the structure and combustion tests to insure the reliability of the case before the production of the flight model. The hydraulic, vacuum and non destruction testes as the structure test were carried out to confirm the strength of the components of the case and the characteristics of the thermal and structure were investigated through the ground combustion test.

• Water Engineering Research
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• v.1 no.4
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• pp.259-266
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• 2000

Scour hole is formed due to the high shear stress of the jet flow at the outlet of a hydraulic structure and vortex erosion occurs in the scour hole. It is important to determine the amount of vortex erosion occurs in the scour hole. It is important to determine the amount of vortex erosion for the design of bed protection. If the vortex erosion continues and reaches to the hydraulic structure, it causes the deformation of the structure itself. To obtain the amount of the vortex erosion, it is necessary to determine the shear velocity of the line vortex in the scour hole was derived by the theory of energy conservation and found to be related to the upstream overflow velocity. The amount of vortex erosion from the scour hole was obtained using entrainment equation for given value of shear velocity. For a design purpose, if the flow velocity at the end of an apron and the properties of bed material are given, the amount of vortex erosion was obtained.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.577-580
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• 1995

This paper suggests direct-acting hydraulic circuit to control clutches and brakes in automatic transmission. As only one pressure control valve controls the pressure of several friction elements with accumulators in conventional hydraulic circuit, the controllable range is limited. In addition, it is difficult to control the fine timing between apply clutch and release clutch. So, we designed new method to control the pressure of clutch which uses ressure control valve and pressure control solenoid valve independently in each friction element. through this structure improvement of hydraulic circuit, we can control the pressure of clutches and brakes finely and fine timing of between apply clutch and release clutch.

• The Journal of Korea Robotics Society
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• v.15 no.1
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• pp.77-89
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• 2020

This paper proposes a simple and intuitive model-free torque-tracking control for rotary electro-hydraulic actuators. The undesirable natural-velocity-feedback effect is discussed by introducing mechanical impedance into the electro-hydraulic actuation system. The proposed model-free torque control comprises inner- and outer-loop control to achieve two control objectives. Inner-loop control reduces the mechanical impedance passively and optimally. To improve the tracking accuracy, a certain form of proportional-integral-derivative control is applied to the outer loop. The robustness of the proposed closed-loop system against external disturbances is demonstrated by transforming the two-loop control structure into a disturbance observer form. The proposed method is validated on a single joint electro-hydraulic actuator.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.134.4-134
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• 2001

Hydraulically driven manipulators are superior to electrically driven ones in the power density and electrical insulation. But an electro-hydraulic manipulator using hydraulic actuators has many nonlinear elements, and its parameter fluctuations are greater than those of electrically driven manipulator. So it is relatively difficult to realize not only stable contact work but also accurate force control for the autonomous field tasks such as the maintenance task of high voltage active electric line or the automatic excavation task by hydraulic excavator. In this report, we propose robust force control algorithm, which can be applied to the real field task such as the construction field, nuclear plant and so on. Proposed force controller has the same structure as that of disturbance observer for position control. The difference between force and position disturbance ...

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.2 no.4
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• pp.46-52
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• 2003

For position control of electro-hydraulic servo system, single rod cylinders and double rod cylinders are used. Single rod cylinders have simple structure for manufacturing but different volume ratio of two sides induce to non-linearity in process of then mathematical modeling. So only with conventional PID control method it is difficult to control single rod cylinders precisely. For mole precise position control of single rod cylinders, a controller which is inserted a velocity feedback PID controller and MRAC controller are proposed. With experiment control performances of three control methods are compared. In case of experiment, for external varying load to the system, a hydraulic cylinder and a pressure control valve are used. In conclusion a MRAC is considered a suitable control method for external varying load.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 1999.10c
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• pp.465-472
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• 1999

Hydraulic model tests are performed to find economical and hdrqulically stable design of cooling water intake channel of steam power plant. The result of tests show that the standard distributiion of y-components in the chamber of CWP(circulating Water Pump) are recommended below 3.5 to maintain hydraulic stability, so that this value is considered as the design criteria. Common basin is necessary to improve the hydraulic stability of inflow, however the longer basin does not always improve the hydraulic stability , and the optimal length of basin can be found in some range. From the results the flow stability maintained the best condition when the length of basin is 7.2m. Beside the standard tests the auxiliary tests like edge , baffle, trapezoidal section and increase of pump capacity are carried out based on the optimal condition foudn in the standard tests. From the series of tests the economical and hydraulically stable design of intake channel was proposed.

• Proceedings of the KIPE Conference
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• 2005.07a
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• pp.555-557
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• 2005

This paper proposed a hydraulic pump system that is driven by a variable SR drive. The operating pressure of hydric pump is limited by the pump speed and the mechanical structure. The operating of hydraulic pump is separated as constant pressure and constant flow region. Under fixed speed, the pressure can be controlled as constant value, and then decreased by increasing of pump speed. A 2.2[kW], 12/8-pole SR motor and DSP based digital controller are designed and tested for hydraulic pump system. The test results show that the system has some good features such as high efficiency and high response characteristics.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.733-738
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• 2004

This paper deals with feedback control of a hydraulic unit for direct yaw moment control, a method used to actively maintain the dynamic stability of an automobile. The uncertain parameters and complex structure naturally call for empirical modeling of the hydraulic unit, which readily results in a control-oriented model with high fidelity. The identified model is cross-validated against experimental data under various conditions, which helps to establish model uncertainty. Then, the $H_{\infty}$ optimization technique is employed to synthesize a controller with guaranteed robust stability and performance against the model uncertainty. The performance of the synthesized controller is verified using experimental results, which shows the viability of the proposed approach in a real-world application.