• Journal of Advanced Marine Engineering and Technology
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• 제27권3호
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• pp.412-420
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• 2003

This study describes the merits of PWM control of hydraulic system using high speed on-off valves. Generally, Electro-hydraulic valves can be classified into two classification: valves which are controlled by analog signal and which are controlled by digital. The former includes hydraulic servo valves and proportional valves which require A/D converters as interface to digital computer and too costly and sensitive to oil contamination because of complexity in structures. The latter includes high speed on-off valves which do not require A/D converters because they are normally operated in a pulse width modulation(PWM) method, and are low in price and robust to oil contamination because of their simple structures. The objectives of this study is to analyze the limit cycle which regularly appear in the position control system using 2/2way high speed on-off valves and to give a criterion for the stability of this system. The nonlinear characteristics of PWM and cylinder friction of this system are described by harmonic linearization and the effects of parameter variations to the system stability are simulated.

• 로봇학회논문지
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• 제16권2호
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• pp.86-93
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• 2021

This paper proposes a controller to regulate the supply pressure of the hydraulic power unit (HPU) for driving a bipedal robot. We establish flow rate models for charging accumulator, actuating joints and leaking from actuators and spool valves. This determines the pump driving motor speed to satisfy the demanded flow rate for operating the bipedal robot without the energy loss caused by the bypass through a pressure regulating valve. We apply proposed controller to an onboard HPU mounted on top of bipedal robot platform with twelve degrees of freedom. We implement air-walking motion and squat motion which require variable flow rate to the bipedal robot. Through this experiment, the energy efficiency of proposed controller was verified by comparing the electric energy consumed when the controller was applied and when the pump operated at constant speed. We also shows the capability of the HPU's control performance to regulate supply pressure.

• 대한기계학회논문집A
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• 제34권9호
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• pp.1249-1255
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• 2010

초고압 시스템은 유압동력 발생장치, 충격압력 발생장치, 초고압부 오일 보충장치, 기동 및 제어반 등으로 일반적으로 구성된다. 유압동력 발생장치는 초고압 발생기에 유압원을 공급하고, 초고압 발생기에서는 공급되어진 유압원을 이용하여 초고압으로 압력을 증폭한다. 기동 및 제어반에서는 시스템을 운전하기 위한 전기모터, 밸브, 센서 등에 대한 제어 및 관찰을 하기 위해 사용된다. 본 연구에서는 초고압 압력을 발생시키기 위한 제어 방법을 서보밸브를 사용한 유량제어 방식에서 비례 릴리프 밸브를 사용한 압력제어 방법을 사용하여 연구하며, 초고압 압력 발생기의 압력을 가하는 주기와 유압동력 발생장치의 작동유의 온도 변화에 따라 충격압력을 발생시키는 성능이 변화하는 특성을 연구하는 것을 목적으로 한다.

• 한국시뮬레이션학회논문지
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• 제23권2호
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• pp.17-24
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• 2014

본 논문은 항공기용 EHA의 열유동 해석모델을 개발하고 활용하는 사례를 보여준다. 연구진행 절차는 다음과 같다. 첫째, 설계 컨셉에 맞는 물리량을 반영하는 유압단품 해석모델을 개발한다. 둘째, 유압단품 모델을 조합하여 EHA 유압모델로 확장한다. 셋째, 열유동이 포함된 해석모델을 개발하여 초기온도와 부하의 변화에 따른 유온의 상승시간을 검토한다. 마지막으로, 여러 케이스의 열유동 해석결과가 조합된, 설계에 활용이 가능한 지배그래프를 작성하여 제안한다. 이 모든 과정은 상용 소프트웨어인 AMEsim을 사용하여 진행한다.

• 대한기계학회논문집A
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• 제35권5호
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• pp.555-559
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• 2011

본 연구는 유압 피스톤 펌프 재료로 사용되고 있는 SACM645소재를 사용하여 모재, QT(quenching & tempering) 시험편 및 QT 질화시험편의 피로특성을 조사하였다. 피로특성 조사결과는 다음과 같다. QT 질화시험편은 피로한도가 인장강도의 80%로 나타나 아주 높은 값을 나타내었다. 이것은 시험편 표면에 단단한 질화처리를 실시하여 피로균열의 발생을 지연시켰고, 피로균열이 발생하더라고 소재가 단단하여 균열진전속도가 늦었다고 판단된다. 파면 관찰결과 피로균열진전 영역에서는 모두 스트라이에이션이 관찰되었고, 피로균열진전 이외의 영역에서 QT 시험편은 벽개파괴의 양상을, 모재와 Qt 질화시험편은 딤플 파괴의 양상을 나타내었다.

• 한국정밀공학회지
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• 제16권12호
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• pp.214-221
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• 1999

In this research, a power-assisted steering system is modeled as a part of a full vehicle dynamic model. The dynamic model of the steering system incorporates hydraulic and dynamic relations between major parts of a steering system, such as steering column, control valve, rack and pinion gear. Through an experimental setup of the steering system, the steering system model is validated. The steering model is included in a full vehicle dynamic model of a car, where kinematic relations between steering and suspension system are defined, and various simulations are performed to evaluate the performance of steering system in conjunction with overall dynamic performance of the vehicle.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1991년도 추계학술대회 논문집
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• pp.171-179
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• 1991

This paper refers to the results of a study on the usefulness of simulation techniques based on both modeling and experiments of KICK DOWN pressure control circuit using an duty solenoid valve controlled by pulse width modulation for an automatic transmission. In this study, dynamic characteristics of solenoid valve plunger and first pressure are verified. Besides, this paper shows the design data for improvement of feeling in changing of gear by means of simulation according to varying the size of jet orifice and temperature of automatic transmission fluid, which are the important variables of the first pressure.

• 해양환경안전학회:학술대회논문집
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• 해양환경안전학회 2009년도 춘계학술발표회
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• pp.177-178
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• 2009

관로내의 유속이 급격히 변하면 압력도 크게 상승하거나 강하하게 되어 유체 과도현상을 일으키게 된다. 이러한 수격현상에 대한 연구는 펌프스테이션이 커지고 유체를 이송하는 시스템이 대형화되어 그 중요성이 더욱 증가하였다. 이것은 파이프라인이 길어지고 복잡해지기 때문이다. 이 연구에서는 특성법을 이용하여 대형펌프 시스템의 밸브 개폐로 발생하는 수격현상을 평가하였다.

• 한국유체기계학회 논문집
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• 제8권5호
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• pp.22-28
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• 2005

As the water supply facilities are recently getting larger, the domestic waterworks become multi-regional water supply system. Large water supply facilities generally consist of the intake pumping station, water treatment plant and water supply/distribution facilities. Although the pumping stations and the pipeline systems are used to pump up water, it often happens pipeline damage and flooding accident by the water hammer. In this paper, the intake pumping station is guaranteed by both the computer simulation and the field test analysis. This study is contributed to the safe operation program for the pumping station in which results of the adjustment on the safety plan of the pumping station, the air valve and the valve closing time.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.170.3-170
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• 2001

Antilock brake system(ABS) prevent the wheels of road vehicle from locking up and skidding so that the braking force is from static friction instead of kinetic friction. Therefore ABS helps drivers maintain steering control during breaking situation particularly at an emergency stopping situation. So when trying to stop the road vehicle it is best to have the most friction possible for faster deceleration ABS keep the wheels turning which means there is more friction between the tires of vehicles and the road surface. Because of this advantage, ABS are now a commonly installed feature for passenger's safety in road vehicles. In this study, hydraulic system of ABS of vehicle is composed of 3port-2position solenoid valve. In order to minimize ...