• 유공압시스템학회논문집
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• 제4권1호
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• pp.1-6
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• 2007

The typical hydraulic system of hoist is composed of a hydraulic supply unit, a directional control valve, two pilot operated check valves, two flow control valves. The capacity coefficients of flow control valves should be adjusted for the hoist to operate at moderate speed and minimize the hydraulic energy loss. However, it is difficult to adjust the four capacity coefficients of flow control valves by trial and error for optimal operation. The steady state model of the hoist hydraulic system is derived and the optimal capacity coefficients of flow control valves are obtained using the complex method that is one kind of constrained direct search method.

• 한국자동차공학회논문집
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• 제4권6호
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• pp.97-108
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• 1996

A modeling technique is proposed for dynamic simulations of OHC valve trains with HLA(hydraulic lash adiuster). HLA is expressed by an air-oil mixture model considering HLA leak-down and aeraton effects. A compact nonlinear equation is derived which describe the short term dynamic behavior of the HLA. Valve spring is analyzed by a distributed parameter model including nonlinear characteristics in the spring surge phenomena. Global behavior of the remaining valve train is expressed by a lumped mass model. The experiental results prove that the simulation model developed here is accurate and useful for the dynamic simulations of OHC valve trains with HLA.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 추계학술대회 논문집
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• pp.505-508
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• 1995

This paper suggests new hydraulic circuit to control the pressure of clutches and brakes which has several advantages than conventional hydraulic circuit in automatic transmissions. In conventional hydraulic circuit, the pressures of all friction elements are controlled by only one pressure control valve and accumlators. So, controllable range is limited and it is unable to control the friction elements independently. Therefore, we can not do the fine control of timing between apply clutch and release clutch which is needed in clutch-to clutch shifting automatic transmissions. To overcome these faults, we designed the direct-acting hydraulic circuit where one pressure control valve and pressure control solenoid valve are allocated to each friction element and control that independently. Through this structural improvement of hydraulic circuit, we can achieve elaborate aontrol to clutch pressure. Specially, We can control the timing between apply clutch and release clutch delicately which is needed in clutch-to-clutch shifting.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 추계학술대회 논문집
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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.

• 유공압시스템학회논문집
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• 제5권1호
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• pp.13-19
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• 2008

The typical hydraulic system of hoist is composed of a hydraulic supply unit, a directional control valve, counter balance valve, and flow control valves. The flow capacity coefficients of flow control valves should be adjusted so that the hoist is operated at moderate speed and the hydraulic energy loss is minimized. However, it is difficult to adjust the flow coefficients of flow control valves by trial and error for optimal operation. Here, the steady state model of the hoist hydraulic system including the differential cylinder circuit is derived and the optimal flow capacity coefficients of flow control valves are obtained using the complex method that is one kind of constrained direct search method.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2002년도 추계학술대회 논문집
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• pp.225-230
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• 2002

Machine of textiles let off is equipment supplying constantly fabrics. Nowdays, as it is replaced band - brake type with hydraulic motor driven type, we looked into characteristic of hydraulic solenoid pilot direction valve(SPDV) for controlling acceleration performance of hydraulic motor. This study deals with controlling the initial speed of textiles let off machine. Finally, to control the initial speed of hydraulic motor, we controlled the adjustment screw of SPDV by a hand. Test which was carried out in the laboratory shows that initial speed of textiles let off could be improved by controlling adjustment screw of SPDV. Also, the results of experiment work were compared with dynamic characteristic of other on/off solenoid direction valve(SDV).

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 추계학술대회 논문집
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• pp.710-714
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• 2005

A dynamical analysis and PID control of a compressed gas expulsion system is performed. The purpose of this study is to develop a compressed gas discharging system and to verify the validity of the system. The electro-hydraulic servo valve is modeled as a 3th order transfer function to calculate flow force affecting expulsion valve is significantly considered. The friction force in the expulsion valve is considered as a nonliner model of stribeck effect. The dynamic characteristics of this system is examined by the computer simulation. The position control of the expulsion valve is performed by PID controller.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2007년도 제29회 추계학술대회논문집
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• pp.174-177
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• 2007

본 연구에서는 액체로켓엔진의 제어기구로서 많이 사용되는 유압식 레귤레이터에서의 제어 프로세스와 제어 변수의 조절에 관한 정적 및 동적 특성을 연구하였다. 본 연구의 대상으로는 8K14 "SCUD"의 9D21 엔진에 사용되는 유압식 레귤레이터를 선택하였으며, 본 유압식 레귤레이터의 수학적 모델링을 거쳐, 액체로켓엔진 내부에서의 유압식 레귤레이터의 응답속도와 자동제어시스템의 정밀도 분석을 수행함으로써, 유압식 레귤레이터의 유압조절기구인 니들밸브 유로면적의 설계값을 도출하였다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.1755-1759
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• 2003

The hydraulic excavator has been a popular research object for automation because of its multi-workings and economic efficiency. The objective of this paper is to design each components and to construct boom, arm, bucket circuit. These models modeled with AMESim show us change of variables and behavior of excavator. Simulation model will be used for simulator of excavator.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2007년도 춘계학술발표회 초록집
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• pp.59-60
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• 2007

전기 정유압장치는 밸브플레이트, 실린더 배럴, 피스톤, 샤프트등으로 이루어진 유압펌프의 부품에 요구되는 기계적 성질을 향상하기위하여 이온 질화를 포함한 다양한 연구가 진행 되어지고 있다. 그러나 본실험에서는 이온질화시 발생하는 열변형등의 단점을 해결하기 위하여 PVD 박막을 실시하여 유압펌프 부품의 마모특성 향상에 관한 연구를 실시하였다.