• Journal of Advanced Marine Engineering and Technology
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• v.30 no.2
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• pp.291-295
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• 2006

Recently, greenhouse effect by $CO_2$ gas emitted by use of fossil fuel causes earth environmental problem. As a countermeasure of the global warming. micro hydropower under 100kW becomes the focus of attention for its clean and renewable energy sources. Newly developed micro positive displacement hydraulic turbine shows high efficiency and good applicability for the micro hydropoewer. The purpose of this study is to clarify the influence of leakage loss and effective head on the performance of the positive displacement hydraulic turbine for the further improvement of the turbine performance. The results show that the turbine. with a smaller side clearance. has much higher efficiency than that with bigger side clearance and it can sustain the high efficiency under the wider range of operation conditions. The turbine torque is proportional to the effective head and independent of the flow rate. The leakage is also dependent on the effective head but nearly independent of the flow rate.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1992.10a
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• pp.177-181
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• 1992

For this study, a new hydraulic control unit which designed in compact compared to the currently manufactured hydraulic control unit for ABS has been introduced and its experimental model has been made. Based on the basic principle as ABS using braking force characteristics against slip ratio of tire, half car model bench tester were designed and made to make an analysis of braking effect of the new hydraulic control unit. Experiment for slip ratio characteristics of tire has been carried out using half car model bench tester and with the results of this experiment and control experiment of the new hyraulic control unit, the experiment result of the characteristics of tire and control experiment were compared to find out their correspondence. And furthermore, slip ratio characteristics of the new hydraulic control unit has been studied based on the experiment result of slip ratio characteristics of tire through simulation and compared with experiment result.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1999.10a
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• pp.405-410
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• 1999

Hydraulic pipeline between servo valve and actuator affect the dynamic characteristics of electrohydraulic servo systems in serveral ways. This paper deal with the speed control of oil hydraulic gear motor using electrohydraulic servo valve. The frequency and transient response of electrohydraulic servo valve coupled to a gear motor is anlayzed. In particular, the effect of short and long hydraulic pipelines between servo valve and gear motor is investigated. The dynamic characteristics of the speed control systems of gear motor with short pipeline is first described via frequency response experiments with small signal linearized analysis. Loner pipeline is applied distributed parameter pipeline model with consideration of frequency dependent viscous friction.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1572-1577
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• 2003

The powershift transmission have the advantage of easier operation and higher efficiency by using the hydraulic clutch and mechanical power transfer system. It is important to control the engaging pressure and time. The hydraulic control system is used for these controls of the modulator valve, the accumulator, the sump valve and etc. This study have made a simulator for verifying the pressure characteristic of the shuttle powershift transmission and developed the computer simulation model of the hydraulic components and system by using 'AMESim'. As a result, the design parameters which have an effect on the pressure modulation are verified to the spring stiffness of the modulator valve and the volume of the accumulator.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.10
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• pp.127-133
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• 2001

In this study, the effect of the factors of a hydraulic modulator of ASMS was analysed. The modeling of ASMS was presented and the equation of ASMS was derived from the modeling. With this background, GUI analysis tool was developed. After the verification of the reasonability of simulation, the response of a hydraulic modulator is investigated through simulation of modeling. With this simulation, each behavior was predicted with changing the various parameters and determined the influenced factors to apply the designing process.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.04b
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• pp.267-272
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• 1995

The paper describes an approach for measuring flow ripple generated by oil hydraulic axial piston pumps. Flow ripple has periodic waveforms due to the cyclic nature of a pump's operation, and interacts with the connected hydraulic systems such as pipes and components to produce a pressure ripple, also known as fluid-borne noise. It is indispensable to measure a flow ripple because increasing of vibration and noise caused by a flow ripple has become a point to be considered and has need of solving these problems. The measurement of flow ripple with high frequencies from oil hydraulic axial piston pumps is msde by using the remote instantaneous flow rate measurement method. As a result, the reverse flow through the relief groove in valve plate has an important effect upon a flow ripple generated by a pumps.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.11
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• pp.984-989
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• 2008

Hydraulic excavators have been one of the most popular devices in the various industries for construction, forestry and agriculture etc. Because the excavators generally work in poor environment, the various organizations study to automate those. In this paper, a hydraulic simulation for evaluation of automatical excavation system is presented. It is using the AMESim based on the 1.5 ton excavator with fixed displacement pumps, and operated by signals those control pilot pressure to spools of the main control valve. The main control valve is regarded that only consists of boom, arm and bucket. This simulation program is expected to apply to evaluation of the controller for automatic excavation system and to estimate of effect in accordance with change of some components or parameter.

• International Journal of Automotive Technology
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• v.3 no.2
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• pp.57-62
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• 2002

It is well known that the entrained air in oil causes appreciable reduction in the stiffness of hydraulic systems. It makes the response delay of the systems and sometimes destroys the stability. Because the hydraulic systems of automatic transmissions are operated in relatively low pressure and high temperature, it is very important to analyze the effects of the air included in automatic transmission fluid. However, it is difficult to derive the generalized model to describe the effective bulk modulus theoretically or measure it in actual operating conditions of automatic transmissions. This paper reviews previous studies of the air effects in hydraulic systems and the measurement techniques of the effective bulk modulus in operating conditions. Based on this work, the theoretical model with moderate complexity and the measurement technique of the effective bulk modulus considering entrained air effect at real operating conditions are suggested. Our paper also shows that the quantity of the entrained air in the automatic transmission fluid can be estimated from the experimental results.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.10
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• pp.130-140
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• 2003

This paper presents an $H_\infty$controller synthesis based on disturbance observer for the trajectory control of a hydraulic excavator. Compared to conventional robot manipulators driven by electrical motors, hydraulic excavator have more nonlinear and coupled dynamics. In particular, the interactions between an excavation tool and the materials being excavated are unstructured and complex. In addition, its operating modes depend on working conditions, which make it difficult to not only derive the exact mathematical model but also design a controller systematically. In this study, the approximated linear model obtained through off-line system identification is used as nominal plant model for a disturbance observer. A disturbance observer based tracking controller which considers the effect of disturbance and model uncertainty is synthesized in $H_\infty$frameworks. Simulation results are used to demonstrate the applicability of the proposed control scheme.

• 한국방재학회:학술대회논문집
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• 2008.02a
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• pp.637-640
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• 2008

Flood control and river improvement works are carried out every year for the defense of the flood disaster, it is impossible to avoid the damage when there is a flood exceeding the capacity of hydraulic structures. Therefore, nonstructural counter plans such as the establishment of flood hazard maps, the flood warning systems are essential with structural counter plans. In this study, analysis of the internal inundation effect using rainfall runoff model such as PC-SWMM was applied to Woo Ee experimental stream basin. Also, the design frequency analysis for effects of the external inundation was accomplished by main parameter estimation for conclusive hydraulic routing using HEC-RAS model. Finally, inundated areas for flood hazard map were estimated at Woo Ee downstream basin according to flood frequency using HEC-GeoRAS model linked by Arc View GIS.