• 드라이브 ㆍ 컨트롤
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• 제18권2호
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• pp.9-19
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• 2021

The spool displacement signal of a directional control valve, including the servo valve, can be considered as the standard signal to measure dynamic characteristics. When the spool displacement signal is not available, the velocity signal of a metering cylinder piston can be used. In this study, the frequency response characteristics of the metering cylinder are investigated for the spool displacement input. The transfer functions of the servo valve-metering system are derived taking into consideration the oil inertia effect in the transmission lines. The theoretical results of the transfer functions are verified through computer simulations and experiments. The oil inertia effect in the transmission lines was found to have a very significant effect on the bandwidth frequency of the servo valve-metering cylinder system. In order to more precisely measure the dynamic characteristics of a servo valve, the metering cylinder should be set up to minimize the oil inertia effect by increasing the inner diameters of the transmission lines or shortening their lengths.

• 유공압시스템학회논문집
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• 제3권1호
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• pp.1-6
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• 2006

A servo actuator with a valve using MR (Magneto-Rheological) fluid is proposed for fluid control systems. The MR fluid is well known as a functional fluid whose apparent viscosity is controlled by the applied magnetic field strength. The pressure in the MR cylinder can be controlled by the applied magnetic field strength. Good points of the MR cylinder are more simple, compact and reliable structure than a conventional oil hydraulic cylinder. The experimental results show that the MR cylinder could be used as a servo actuator.

• 유공압시스템학회논문집
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• 제3권1호
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• pp.7-14
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• 2006

In this paper, an in-process diagnosis method for performance of position control servo system was studied, which was based upon null bias, slew-rate ratio and delay time measurement. Slew-rate ratio and delay time were analyzed by theoretical analysis, computer simulation and experiment. As a result of these analysis, when spool of servovalve was weared, slew-rate ratio was decreased and delay time was increased.

• 유공압시스템학회논문집
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• 제6권2호
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• pp.22-30
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• 2009

An in-process method of diagnosing the spool wear of hydraulic servovalves was explored. The diagnostic method discussed in this paper is for force-control hydraulic servo systems. The key principle used is that pressure sensitivity of a servovalve drops as the valve spool wears out so that it is possible to determine the spool condition by monitoring pressure sensitivity. A diagnostic algorithm was developed and evaluated through numerical simulation and experiments. Two major steps of diagnosis are the evaluation of null bias of the servovalve and the approximation of pressure sensitivity, both of which could be successfully done during normal operation of a servo system. The difference between a new servovalve and a worn valve could be clearly detected in-process, and the diagnostic test was found to be repeatable.

• 드라이브 ㆍ 컨트롤
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• 제12권3호
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• pp.44-51
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• 2015

In this study, a metering cylinder was constructed, and the velocity obtained from the linear velocity transducer (LVT) of the cylinder piston was used to evaluate the dynamic performance of an electro-hydraulic servovalve. Frequency response experiments involving the spool displacement and piston velocity (LVT signal) were conducted with different input signal amplitudes, hydraulic pipe diameters, and supply pressures. The spool displacement signal accurately reflected the performance of the servovalve. Meanwhile, the -3 dB bandwidth frequency of the LVT signal was similar to the spool displacement signal, except for a small-amplitude input signal, and the $-90^{\circ}$ phase lag bandwidth frequency showed some differences.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1989년도 한국자동제어학술회의논문집; Seoul, Korea; 27-28 Oct. 1989
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• pp.266-271
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• 1989

In eliminating the nonliner charateristics such as piston displacement drift and difference in speeds of the reciprocating motion due to their nonsymetrical structure of single rod cylinder, modelling was carried out by additional outside disturbance, suggest the position control of single rod cylinder servosystem using VSS and compared with PD control of fixed structure system.

• Journal of Advanced Marine Engineering and Technology
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• 제16권1호
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• pp.27-34
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• 1992

In eliminating the nonlinear characteristics such as piston displacement dift and difference in speeds of the reciprocating motion due to their nonsymetrical structure of single rod cylinder, the linear model can be given by equivalent outside disturbance, etc. The position control method of single rod cylinder servosystem using the sliding mode control of VSS was suggested and the good results without off-set are compared with PD control of fixed structure system.

• 대한의용생체공학회:의공학회지
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• 제24권2호
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• pp.127-132
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• 2003

본 논문에서는 관절 경직 환자의 재활 치료를 위한 공압 실린더를 이용한 하이브리드형 로봇을 연구 개발하였다. 공압 실린더는 우수한 컴플라이언스를 가지고 있고 부피나 중량에 비해 높은 구동력을 가지고 있다 낮은 강성을 지닌 공압 구동기는 안정이 보장되어야 하는 물리 치료용 로봇의 구현에 적용하기 적당하다. 본 연구에서 제안한 로봇 시스템은 직렬형과 병렬형을 결합한 하이브리드 형으로 위치 결정부와 자세 결정부로 구분되며 하이브리드 구조를 통해 넓은 작업영역과 구동력을 얻을 수 있었다. 슬라이딩 모드 제어기를 이용하여 로봇 시스템의 공압 서보시스템의 추종성과 안정성을 얻을 수 있었으며 실험을 통하여서 개발된 시스템에 대한 검증을 하였다.

• 한국지능시스템학회:학술대회논문집
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• 한국퍼지및지능시스템학회 2006년도 춘계학술대회 학술발표 논문집 제16권 제1호
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• pp.79-82
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• 2006

본 논문은 원자력 발전소의 주요 제어계통 중에서 터빈 조속기 제어계통에 관련한 성능평가를 목적으로 한다. 터빈 조속기 계통은 고압의 유압계통으로 구성되어 있어 구동설비가 복잡하다. 복잡한 기계설비는 운전 중 많은 오동작에 의한 고장을 일으키고, 유지보수에 어려움이 있다. 이러한 복잡한 기계설비에 있어 운전원에 의한 기계성능 평가는 불리한 점이 많다. 예를 들어 서로 다른 시간에서 일어나는 같은 상황에 대해 다른 판단을 내릴 수 있다는 점이다. 터빈 조속기 계통의 기계설비에 있어서 터빈 밸브 유압공급 및 구동장치는 각 터빈벨브 자체에 부착되어 있어 터빈벨브를 동작시킨다. 터빈벨브들은 구동기 유압 서보실린더(Actuator Hydraulic Servo Cylinder)에 의해 열리고 압축된 스프링에 의해 닫힌다. 이러한 시스템을 진단하기 위해서 본 논문에서는 밸브의 내부 압력의 특징정보를 입력으로 하는 퍼지이론을 적용하여 터빈 밸브 구동설비의 성능을 판단하고자 한다. 퍼지이론에 적용하기위해 터빈 조속기 제어계통의 고압 터빈 조절 벨브와 고압 터빈 정지 밸브의 압력변화 데이터를 이용한다. 퍼지이론의 적용과정에서 퍼지 Rule은 실제 운전원이 압력변화 데이터에 대한 판단기준을 근거로 하여 정하기로 한다. 그리고 퍼지이론에 적용한 결과를 분석하고 실제 터빈 조속기 계통의 전문가가 판단 결과와 비교하였다.

• 대한조선학회 특별논문집
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• 대한조선학회 2008년도 특별논문집
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• pp.136-143
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• 2008

This paper presents the application of a robot which aims at grinding automatically welding-bead remained in the removal job of working pieces for shipbuilding. In specific, the investigation on this application is composed of two parts; one topic is on the development of a robot platform vertically movable on a steel plate of hull, while the other topic is of the development of a grinding tool mechanism in order to remove welding-beads by using a diamond wheel installed on a servo cylinder (which can result in high working pressure on the grinding wheel). Besides, the development of a vision system for tracking welding-beads as well as recognizing welding surfaces is added for the convenience of this robot application to the removal of welding-beads remained in the working pieces for shipbuilding.