• Journal of Advanced Marine Engineering and Technology
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• 제15권4호
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• pp.54-69
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• 1991

This study deals with the position control of a hydraulic cylinder system operated by two port 3-way high speed solenoid valve in Pulse-Width-Modulation mode, instead of using conventional electro-hydraulic servovalve. Due to the complexity and the relatively poor reliability of the servovalve, an actuator using simpler and more study high speed solenoid valve will be presented. The high speed solenoid valve acts as converters of electronic pulse signal to hydraulic ones. It has been pointed out that there are practical problems to be solved in the PWM system, that is (1) accuracy of positioning control becomes considerably insufficient because the system is affected by on/off action of the solenoid valves, and (2) serious nonlinerality appears in the valve characteristics as a result of the switching behavior of the valves. As a method to overcome these defects, the differential PWM driving method of a hydraulic cylinder that improved the steady-state-error, flow rate nonlinearity in simple PWM, and the hydraulic hunting of dead time compensated-PWM driving is proposed in this study.

• 유공압시스템학회논문집
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• 제2권4호
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• pp.7-13
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• 2005

This paper presents modeling and ostimator/controller design for the hydraulic system in Vehicle Stability Control(VSC) system. A nonlinear mathematical model of the VSC hydraulic system is proposed and its accuracy is experimentally verified. A brake pressure estimator is then designed based on the derived mathematical model of VSC hydraulic system. And a disturbance observer, which compensates the estimation error between the brake pressure and the computed brake pressure is also designed to enhance the accuracy of the estimator. The proposed controller has the form of a feedback controller and determines explicitly the on/off ratio of valves' driving PWM signals by means of making use of the simplified mathematical model in the VSC hydraulic system. The performance of the designed controller whose feedback signal is generated by the brake pressure estimator is validated through experimental results.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.1225-1230
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• 2007

The turnover-type sluice gate is typically actuated by the hydrauic system. The hydraulic system may be a open circuit type or a closed circuit type. The open circuit type hydraulic system is composed of a uni-directional pump, a directional control valve, pilot operated check valves, flow control valves, single-rod cylinders. The closed circuit type hydraulic system is composed of a bi-directional pump, pilot operated check valves, check valves, a counter balance valve, single-rod cylinders. The energy efficiencies of two hydraulic systems for the turnover-type sluice gate are compared here.

• 한국항행학회논문지
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• 제14권5호
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• pp.760-766
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• 2010

본 논문에서는 유압 비례 제어 밸브로 구동되는 유압모터 부하계에 존재하는 정지마찰토크와 점성마찰토크를 해석하였다. 이에 기초 실험으로 유압시스템의 에너지인 압력과 유량에 대한 특성실험을 수행하였고, 공압브레이크 시스템을 이용하여 브레이크 압력의 변화를 인가하여 마찰토크의 변화를 실험하였다. 비선형마찰과 선형마찰에 대한 해석은 유압 시스템의 마찰특성에 대하여 수행하였다.

• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 2000년도 THE THIRD INTERNATIONAL CONFERENCE ON AGRICULTURAL MACHINERY ENGINEERING. V.III
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• pp.684-689
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• 2000

In harvesting rice and barley using combine, the inclination of the body caused by the irregular surface condition of the field and the soil sinking from the unbalanced weight during the grain collection used to make harvesting operation difficult and even impossible. To overcome such a problem, automatic leveling control system for a combine has been developed and tested. The system was composed of the sensor for measuring left and right inclination of the combine chassis and the hydraulic control system. The adaptability of the control system was investigated by analyzing system response in time domain. And the limit angle of the leveling control was set up to be +/- 7$^{\circ}$. The proposed control and hydraulic power system was implemented to the prototype combine. The prototype combine was designed and built as a separable structure with chassis and track. This paper shows results of the leveling performance tested in the laboratory and the grain field.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2003년도 춘계학술대회 논문집
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• pp.282-287
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• 2003

DTTS(Dynamic Track Tensioning System) system requires robust control performance for the various maneuvering tasks. However, it is very difficult to tune the controller gains in experiments. In this paper, the hydraulic unit is modeled and constructed into the DTTS control module in Matlab/Simulink The control module is interfaced to the vehicle dynamics module so that the control performance of the DTTS system can be evaluated in simulations. The dynamics data and control input data are exchanged between two modules at each control time-step. The gains in the fuzzy-logic controller are varied and the control performance is evaluated in simulations. The proposed simulation tool can be very useful for the gain tuning of track tension controller in bucked vehicles

• 대한기계학회논문집A
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• 제27권5호
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• pp.789-797
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• 2003

In the procedure of the hydraulic control system design, a linearized approximate equation described by the first order terms of Taylor series has been widely used. Such a linearized equation is effective just near the operating point, However, pressure and flowrate in actual hydraulic systems are usually not confined near an operating point. This study suggests a new linearized flow equation for a servovalve as a modified form of the conventional linearized flow equation. Subsequently, a procedure to determine effective operating point for the new linearized equation is proposed. From the evaluations of time responses and frequency responses obtained from simulations for a hydraulic control system, the effectiveness of the new linearized equation and the procedure to determine effective operating point is confirmed.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2004년도 춘계학술대회 논문집
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• pp.897-902
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• 2004

The hydraulic brake system is recently apply to the AGT system such merit as installation is convenient and brake force is stronger than pneumatic brake system. The hydraulic brake system consist of brake operating unit, electronic control unit, air compressor and pneumatic/hydraulic tranducer. The components of it are controlled and designed to perform the function of brake system. Therefore, This paper design and the hydraulic brake system and propose the derection of development for Urban Transit System.

• 한국정밀공학회지
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• 제11권2호
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• pp.65-74
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• 1994

Backcap is an electric remote control system for the operation of directional flow control valves. This paper presents a new type of basckcap system which is characterized by its simple construction. The backcap is essentially a hydraulic cylinder of which the piston is connected to a spool of hydraulic valve and controlled by input current. An inherent feedback is imposed on its mechanism so that no artificial noe is needed. Characteristics of the backcap is verified by stability analysis, transient motion and steady state positioning for step inputs. Design parameter analyses have been executer by some analytical approaches and computer simulations, which lead to their optimal valves. These results contributed to an effective new backcap system and its design strategy.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.290-295
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• 2005

Hydraulic actuators are important in modern industry due to high power, fast response, and high stiffness. In recent years, hybrid actuation system, which combines electric and hydraulic technology in a compact unit, can be adapted to a wide variety of force, speed and torque requirements. Moreover, the hybrid actuation system has dealt with the energy consumption and noise problem existed in the conventional hydraulic system. Therefore, hybrid actuator has a wide range of application fields such as plastic injection-molding and metal forming technology, where force or pressure control is the most important technology. In this paper, the solution for force control of hybrid system is presented. However, some limitations still exist such as deterioration of the performance of transient response due to the variable environment stiffness. Therefore, intelligent switching control using Learning Vector Quantization Neural Network (LVQNN) is newly proposed in this paper in order to overcome these limitations. Experiments are carried out to evaluate the effectiveness of the proposed algorithm with large variation of stiffness of external environment. In addition, it is understood that the new system has energy saving effect even though it has almost the same response as that of valve controlled system.