• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1033-1034
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• 2011

공작기계에 유압동력을 공급하는 유압동력발생장치의 신뢰성은 공작기계 전체의 신뢰성과 밀접한 관계를 가진다. 전기모터에 의해 유량을 직접제어하는 유압펌프의 시제품에 대한 신뢰성을 평가하기 위해서 성능시험, 내환경시험, 그리고 수명내구시험을 실시할 필요가 있다. 본 연구에서는 2단계 품질기능 전개를 통해 전기모터에 의한 직접유량 제어방식 유압펌프의 신뢰성평가 시험항목을 결정하였다. 시험항목에는 전기모터에 대한 항목, 유압펌프에 대한 항목, 하우징 및 냉각시스템에 대한 항목이 포함되어 있다. 신뢰성평가 시험 항목 중, 가장 큰 비중을 차지하는 수명내구시험에 대해 무고장수명시험을 산출하고, 시험소요시간 단축을 위한 가속모델을 제안하고, 실제 구동 조건을 적용하여 가속수명시험시간을 산출하였다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.12
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• pp.2352-2360
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• 2007

Due to the friction characteristics of cylinders and the rail of a passenger car, in the elevator actuated with hydraulic systems, there exist dead zones, which can not be controlled by a PID controller. In this paper, the friction characteristics of a cylinder is examined, which may cause the abrupt increase of the acceleration in the zero-costing speed region. To overcome the drawbacks of a PID controlled hydraulic elevator system, a zooming fuzzy logic controller is designed and finally an improved hybrid fuzzy controller is proposed. The effectiveness of the proposed control scheme are shown by simulation and experimental results, which the proposed fuzzy hybrid control method yields good control performance not only in the zero-crossing speed region but also in the overall control region including steady-state region.

• Journal of Advanced Marine Engineering and Technology
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• v.28 no.1
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• pp.136-144
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• 2004

In general a hydraulic system which uses a single rod hydraulic as an actuator is modeled as a nonlinear system and reveals uncertain Parameter characteristics such as the density variation of hydraulic oil and is subject to load variations and severe disturbances during operation. A variable design-parameter fuzzy PID controller is adopted to solve these undesirable internal and external problems and its effectiveness is verified through computer simulations for control performance and real time control possibility.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.2
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• pp.195-201
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• 2015

An electric excavator consumes battery energy to drive an electric motor attached to a hydraulic pump to generate hydraulic power. In a conventional hydraulic excavator, the hydraulic pump is controlled by regulators, which are used to optimize the diesel engine efficiency. Because of a lack of battery energy capacity, an electric excavator controller should consider not only the electric motor efficiency but also the hydraulic pump efficiency. Thus, electric motor and hydraulic pump efficiency maps were constructed. An optimal operating map (OOM) was created based on the most efficient operating points under each input condition. An integrated control algorithm controlled the speed of the electric motor and displacement of the hydraulic pump according to the OOM. To confirm the utility of this algorithm, a model-in-the-loop simulator for the algorithm with an electric excavator was established. The simulation results showed that the integrated control algorithm improved the energy efficiency of an electric excavator.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.7
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• pp.947-952
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• 2010

Components such as pressure vessel, hydraulic hose assembly, accumulator, hydraulic cylinder, hydraulic valve, pipe, etc., are tested under the impulse-pressure conditions prescribed in ISO and SAE standards. The impulse pressure test machine needs to have a high pressure, a precise control system and a long life. It should satisfy the requirements for fabrication of the impulse tester to generate ultra high pressure in the hydraulic system. In the impulse tester, a servo-valve control system is adopted; although the control application is convenient, it is expensive owing to the cost of developing the system. The type of the control system determines the pressure wave, which affects the components that are tested. In this study, the manufacturing process and the intensifier system design related to the flow, pressure, and the increasing rate of pressure are investigated. The results indicate the ultra high pressure waves in the system.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.9
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• pp.1249-1255
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• 2010

An ultra high- pressure system generally consists of a hydraulic power unit, an oil supply unit, an electrical power supply device, and an electrical control device. The hydraulic power unit supplies the hydraulic power to the intensifier to create generate ultra high pressure. The intensifier amplifies increases the pressure using the oil supplied from by the hydraulic power unit. The electrical supply devices and control devices maintain are provided for the electric motors, valves, and sensors. In this study, instead of a flow-control device, a pressure-control type device was mounted on a manifold block in the hydraulic power unit instead of the flow-control type. A servo valve was fitted in the intensifier, and the performance characteristics of the intensifier varied according to the variations of in the pressure cycle and with the temperature of the operating oil in the hydraulic power unit.

• Aerospace Engineering and Technology
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• v.1 no.1
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• pp.141-146
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• 2002

During dynamic flight by propulsion of rocket engine, in the atmosphere, the attitude control of flight vehicle can be accomplished by the aerodynamic fin actuator. But, in the outer space, the method of TVC(Thrust Vector Control) is only depend on for it. There are many systems which were developed for TVC. In our research, among them we adopted gimbal engine actuation system which could control the vector of thrust by swivelling rocket engine connected by gimbal. There are electro-hydraulic, electro-mechanical and pneumatic system which can be used as gimbal engine actuation system, but the electro-hydraulic system that has high ratio of output power to mass is preferred for the high power system. In this note, we made a mathematical model of the electro-hydraulic gimbal engine actuation system for the TVC of KSR-III in detail and on the base of this model we performed a simulation study. And then, we verified the model by making a comparison between the simulation and the experiments on the real system.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.19 no.3
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• pp.85-92
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• 2005

Due to the friction characteristic of pump, cylinder, and between passenger car and the rail, there exist dead zone in the hydraulic system actuated with inverter, which can not be controlled by a PID controller. In this paper, the friction characteristic of a cylinder is considered first, which may cause the uncontrolled speed in the zero-crossing speed region. And then, the zooming fuzzy logic controller is designed to overcome the drawback by the existing PID speed controller. Finally, The proposed hybrid fuzzy controller is applied to the PID controller in the normal speed region and to the fuzzy controller in the zero-crossing speed region. The reason is that the problem of the uncontrolled speed in the zero-crossing speed region caused by the friction characteristic of the cylinder in hydraulic elevator can be solved, and the effectiveness of the controlling system not only in the zero-crossing speed region but also the overall controlling region including steady-state can be simulated and performed.

• Transactions of The Korea Fluid Power Systems Society
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• v.7 no.3
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• pp.13-19
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• 2010

Hydraulic systems are widely used as a power transfer and/or power control system due to its flexibility, controllability, accuracy and high power density. Valve controlled and/or pump capacity controlled systems are normally adopted as a control device, but nowadays pump speed controlled systems are emerging as a new energy-efficient hydraulic control system. In this paper the pump speed controlled system for the cylinder position control of a counter balance circuit is investigated by simulation study and position control experiments were carried out. As a result, the possibility and efficiency of the pump speed controlled system were verified.

• Proceedings of the KOSOMBE Conference
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• v.1995 no.05
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• pp.78-81
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• 1995

본 연구에서는 슬라이딩 모드를 전기유압식 심실보조기의 직류모터제어기의 속도와 위치제어에 적용하였다. 슬라이딩 모드 컨트롤은 가변구조시스템(varaiable sturucture system)의 일종으로 적절한 내부스위칭 논리를 갖는 연속적인 부시스템(subsystem)의 모임으로 구성된다는 접에서 고정된 제어구조를 갖는 일반적인 제어시스템과 다르다. 이 시스템은 불연속적인 동적시스템이나 시변적인 요소를 갖는 시스템등에서 사용되고 있다. 이 논문에서는 슬라이딩 모드 제어를 적용하여 좌심실보조기를 제어하는 경우에 넓은 작동범위에서도 시스템이 안정적이며 혈류역학적인 외란에 대해서도 기준입력에 대한 속도의 추종이 잘 이루어지는지의 여부를 실제의 구현에 앞서 컴퓨터모델을 통해 검증하고 문제점들을 조사하였다.