• 드라이브 ㆍ 컨트롤
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• 제2권2호
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• pp.8-12
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• 2005

• 유공압시스템학회논문집
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• 제7권2호
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• pp.19-26
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• 2010

The typical trunk lid system for vehicle is composed of a hinge having 4-bar link and gas lifter. Here, the energy regenerative brake of hydraulic driven systems is applied to the tail gate system for vehicle and removed the gas lifter. The new tail gate system is composed of a hydraulic pump by electric motor, a hydraulic motor, four check valves, an accumulator, a relief valve and a directional control valve. The dynamic characteristics of the hydraulic motor system, such as the surge pressure and response time, are investigated in both brake action and acceleration action. The capacity selection method of accumulator by mathematical model is based upon trial and error approach and computer simulation by AMEsim software is carried out.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2004년도 유체기계 연구개발 발표회 논문집
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• pp.546-551
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• 2004

An applying Thermodynamic method for the purpose of measuring hydraulic efficiency of pump-motor system, based on IEC60041 code, is not easy to adopt at field test. Even though there were splendid development in measuring technic in discharge measuring through the hydraulic machina lots of unsolved problems concerned in flow-rate are still remain in measuring hydraulic efficiency in hydraulic machine. The key point in measuring hydraulic efficiency is to measure exact flow-rate. So, Thermodynamic methode provides a good solution. This methode measures hydraulic efficiency by detecting the difference of temperature and pressure between the hydraulic process of machine, without measuring flow-rate of pump or turbine. By measuring temperature in mk level and absolute pressure in pascal, we can get a difference of thermodynamic specific energy in Moliere chart before and after of hydraulic process, md that difference is equal to hydraulic loses. Following the standard in proceeding Thermodynamic methode, I hope these trial and records make others be familiar to the thermal methode and make it easer to beginner for trial.

• 드라이브 ㆍ 컨트롤
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• 제12권4호
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• pp.28-34
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• 2015

Because heavy-duty construction vehicles such as excavators are required for good engine-room cooling capacity, a hydraulic gear motor is adopted in the cooling fan drive mechanism to actively control the output speed, instead of adopting the conventional ON/OFF type belt drive. While gear motors are normally limited to 140bars of operating pressure, those for the cooling fan are capable of operating at continuous pressures of up to 220bars. After assembly, all gear motors for high pressure must pass an aging test which is a kind of the wearing process between the gear teeth and motor housing. During the aging process with gradual pressure increments, gear sticking sometimes occurs due to abnormal wear, resulting in defects. This paper focuses on a gear-sticking free aging test controller that is designed together with the knowledge of an experienced operator and the analysis results of experimental data of the gear jamming phenomenon. From the aging experiment, it is demonstrated that the developed controller that can alter the setting pressure of the load pump is effective for stabilizing the abrupt increase in the motor input pressure, thus preventing the hydraulic motor from stopping. This is expected to be helpful for the reduction of defects and increase in productivity.

• 한국정밀공학회지
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• 제26권2호
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• pp.45-53
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• 2009

Today, reduction of $CO_2$ exhaustion gas for global-warming prevention becomes important issues in all industrial fields. Hydraulic systems have been widely used in industrial applications due to high power density and so on. However hydraulic pump is always being operated by engine or electric motor in the conventional hydraulic system. Therefore most of the conventional hydraulic system is not efficient system. Recently, an electro-hydraulic hybrid system, which combines electric and hydraulic technology in a compact unit, can be adapted to a wide variety of force, speed and torque requirements. In the electro-hydraulic hybrid system, hydraulic pump is operated by electric motor only when hydraulic power is needed. Therefore the electro-hydraulic system can reduce the energy consumption drastically when compared to the conventional hydraulic systems. This paper presents a new kind of hydraulic load simulator which is composed of electro-hydraulic hybrid system. Disturbances in the real working condition make the control performance decrease or go bad. QFT controller is designed to eliminate or reduce the disturbance and improve the control performance of the electro-hydraulic load simulator. Experimental results show that the proposed controller is verified to apply for electro-hydraulic hybrid system with varied external disturbances.

• 유공압시스템학회논문집
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• 제2권4호
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• pp.14-22
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• 2005

The safety factor of hydraulic piston pumps & motors due to high pressurization, high speedization and low weight/volume realization to enhance the output density shows a tendency to decrease. Therefore more effective test methods are necessary to predict the exact life. The failure of hydraulic pumps & motors operating in high pressure and high speed mainly occurs in piston-shoe assemblies, and the major failure mode is wearout of the shoe surface. The sensitive parameters in the endurance life test are speed, pressure and temperature, and the failure production increases in proportion to the operating time. In this research, the authors propose the combined accelerated life test model using the analysis method of the combined accelerated life test results of piston-shoe assemblies by applying simultaneously high speed, high pressure and high temperature in accordance with variation of speed, pressure and temperature to reduce the life test time.

• 드라이브 ㆍ 컨트롤
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• 제16권3호
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• pp.23-32
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• 2019

This study proposed a fault tolerant control algorithm for electro-hydraulic brake systems where permanent magnet synchronous motor (PMSM) drive is adopted to boost the braking pressure. To cope with motor position sensor faults in the PMSM drive, a braking pressure controller based on an open-loop speed control method for the PMSM was proposed. The magnitude of the current vector was determined from the target braking pressure, and motor rotational speed was derived from the pressure control error to build up the braking pressure. The position offset of the pump piston resulting from a leak in the hydraulic system is also compensated for using the open-loop speed control by moving the piston backward until it is blocked at the end of stroke position. The performance and stability of the proposed controller were experimentally verified. According to the results, the control algorithm can be utilized as an effective means of degraded control for electro-hydraulic brake systems in the case that a motor position sensor fault occurs.

• 한국항공우주학회지
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• 제35권4호
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• pp.316-322
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• 2007

정유압 방식 EHA는 종래의 밸브 제어 방식 전기유압 구동장치와 전혀 다른 특성을 나타낸다. 본 논문에서는 EHA의 비선형 요소를 포함한 수학적 모델을 유도하고 실험적으로 검증하였다. 이 수학적 모델을 근거로 전기 모터로 구동되는 유압 펌프, 파이프 배관 그리고 유압 실린더로 구성되는 EHA의 시물레이션 모델을 개발하여 주요 설계 인자인 모터 토크의 피크치, 펌프의 관성 모멘트 등이 제어 성능에 미치는 영향을 분석하였다. 여기에서 실험 조건은 의도적으로 과도기에서 모터 토크가 포화되도록 선정하였다. 그 결과로서 최대 속도로 동작하는 EHA의 제어 정밀도를 개선하기 위한 설계 조건을 조사하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.863_864
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• 2009

Design and drive characteristics of SR drive for hydraulic pump system using passive converter is presented in this paper. In oder to get the high performance, a simple passive circuit is added in the front-end of a conventional asymmetric converter, which consists of three diodes and one capacitor. This passive converter has the high demagnetization voltage, to reduce the demagnetization time. Futhermore optimal turn-off angle for the proposed passive converter is proposed. According to motor speed and current, an optimal turn-off angle can be achieved by look-up table to reduce torque ripple. The characteristic of proposed hydraulic pump system using passive converter is verified by simulation and experimental results.

• 드라이브 ㆍ 컨트롤
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• 제14권1호
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• pp.23-28
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• 2017

A wind power heat generation system that converts wind power directly to heat instead of electric power is considered in this study. The system consists of a wind turbine part and a heat generation part. The heat generation part is materialized by a hydraulic system including a hydraulic pump, a flow control valve, a hydraulic oil tank, etc. The flow control valve primarily converts hydraulic energy generated in the pump to heat energy. It should have a function of overspeed protection under excessive wind speeds. In this study, a novel flow control valve design is proposed for excellent flow control characteristics under excessive pump driving torque (excessive wind speed). The performance of the suggested valve is analyzed using numerical simulation.