• 항공우주시스템공학회지
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• 제12권2호
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• pp.7-14
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• 2018

본 연구에서는 소형 압전유압펌프가 적용된 브레이크 시스템의 부하압 개선을 위해 체크밸브에 대한 연구를 수행하였다. 가압 과정에서 부하의 정상상태 압력은 챔버압과 부하압이 체크밸브에 작용하는 단면적 비에 영향을 받는다. 체크밸브 유로 덮개는 역류 방지를 위해 유로의 단면적보다 넓게 제작되었기 때문에 단면적 비 조절을 위해 박판 스프링 형 체크밸브에 부가질량을 부착하는 방식을 제안하였다. 부가질량 부착에 의한 부하압 개선 효과를 확인하기 위해 상용코드를 이용하여 소형 압전유압펌프가 적용된 단순 브레이크 시스템의 모델링을 수행하였다. 모델링의 검증을 위해 부가질량이 부착되지 않은 박판 스프링 형 체크밸브를 적용한 펌프의 가압 실험결과와 시뮬레이션 결과를 비교하였다. 검증된 아메심 모델링에 부가질량을 추가하였고 시뮬레이션을 통해 단면적 비 조절에 의한 고 부하압 형성 효과를 확인하였다. 부가질량 추가에 따른 소형 압전유압펌프 구성품을 새롭게 설계/제작한 후 브레이크 시스템의 가압 성능 실험을 수행하여 부하압 35% 의 성능 개선을 확인하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 추계학술대회 논문집 전력기술부문
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• pp.63-65
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• 2007

Recently with increase consumption of electric power, the scale of the electric system becomes bigger and complex. Then, it is increasing the hardship in the operation of electric system and the continuance of stability. Especially, as the differences between demand and supply in electric power keeping low frequency oscillating attenuation from electric power have been very important in the continuance part of stability. The more control time of electricity system is getting faster with digitalization the more stability of electricity system is getting worse. As solutions of these problems, by establishing Power System Stabilizing Controller putting PSS output signal and putting damping to vibration of the rotor at generators's AVR in area where is oscillated, We are willing to contribute the electricity system by holding in generator output vibration.

• 한국지능시스템학회논문지
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• 제10권5호
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• pp.401-408
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• 2000

본 논문에서 제안한 제어기 구조는 일반적인 궤환제어기를 기초로 구성한다. 일반적인 궤환제어기는 플랜트 입력과 기준신호 사이의 오차에 제어기의 적당한 이득을 곱한 제어입력을 공급한다. 설계한 궤환 퍼지제어는 3개의 루프로 구성되며, 내부 루프는 보통의 궤환제어기와 플랜트로 구성된다. 제어기는 퍼지 모델링과 퍼지추론기로 이루어진 외부 루프에 의해서 조절되며 제안한 궤환 퍼지 시스템의 출력이 기준신호를 향해서 잘 수렴하는가를 확인하기 위해 직접구동 밸브를 사용한 비선형 유압 서보시스템을 제어대상으로 부동 소수점 DSP 프로세서를 사용하여 구현한 후 실험결과를 관찰하였다. 실험결과 궤환 퍼지제어기는 정상상태 도달시간은 느리지만 오버슈트나 언더슈트는 일어나지 않는다. 그러므로 새로운 궤환제어 방식을 사용한 궤환 퍼지제어 알고리즘이 비선형 플랜트에 효과적으로 잘 적응됨을 확인하였다.

• 한국군사과학기술학회지
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• 제12권4호
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• pp.540-547
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• 2009

In the near future, military robots are likely to be substituted for military personnel in the field of battle. The power system of a legged robot is considerably more complex than the one used for a land vehicle because of the coordination and stability issues due to the large number of degree of freedom. In this paper, a servovalve-piston combination system for a straight-line motion of robot leg is modeled as three degree of freedom based on double inputs and single output transfer function. The output is the displacement of piston from neutral. The inputs are valve displacement from neutral and arbitrary load force in this system. LQR(Linear Quadratic Regulator) technique is applied in order to achieve robust stability and fast responses of the system. The Kalman filter loop, rejection of disturbance and noise, riccati equation, filter gain matrix, and frequency domain equality are analyzed and designed.

• Structural Engineering and Mechanics
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• 제46권5호
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• pp.673-693
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• 2013

This paper presents a systematic design and training procedure for the feed-forward back-propagation neural network (NN) modeling of both forward and inverse behavior of a rotary magnetorheological (MR) damper based on experimental data. For the forward damper model, with damper force as output, an optimization procedure demonstrates accurate training of the NN architecture with only current and velocity as input states. For the inverse damper model, with current as output, the absolute value of velocity and force are used as input states to avoid negative current spikes when tracking a desired damper force. The forward and inverse damper models are trained and validated experimentally, combining a limited number of harmonic displacement records, and constant and half-sinusoidal current records. In general the validation shows accurate results for both forward and inverse damper models, where the observed modeling errors for the inverse model can be related to knocking effects in the measured force due to the bearing plays between hydraulic piston and MR damper rod. Finally, the validated models are used to emulate pure viscous damping. Comparison of numerical and experimental results demonstrates good agreement in the post-yield region of the MR damper, while the main error of the inverse NN occurs in the pre-yield region where the inverse NN overestimates the current to track the desired viscous force.

• Nuclear Engineering and Technology
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• 제50권8호
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• pp.1306-1313
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• 2018

The randomness and incipient nature of certain faults in reactor systems warrant a robust and dynamic detection mechanism. Existing models and methods for fault diagnosis using different mathematical/statistical inferences lack incipient and novel faults detection capability. To this end, we propose a fault diagnosis method that utilizes the flexibility of data-driven Support Vector Machine (SVM) for component-level fault diagnosis. The technique integrates separately-built, separately-trained, specialized SVM modules capable of component-level fault diagnosis into a coherent intelligent system, with each SVM module monitoring sub-units of the reactor coolant system. To evaluate the model, marginal faults selected from the failure mode and effect analysis (FMEA) are simulated in the steam generator and pressure boundary of the Chinese CNP300 PWR (Qinshan I NPP) reactor coolant system, using a best-estimate thermal-hydraulic code, RELAP5/SCDAP Mod4.0. Multiclass SVM model is trained with component level parameters that represent the steady state and selected faults in the components. For optimization purposes, we considered and compared the performances of different multiclass models in MATLAB, using different coding matrices, as well as different kernel functions on the representative data derived from the simulation of Qinshan I NPP. An optimum predictive model - the Error Correcting Output Code (ECOC) with TenaryComplete coding matrix - was obtained from experiments, and utilized to diagnose the incipient faults. Some of the important diagnostic results and heuristic model evaluation methods are presented in this paper.

• Nuclear Engineering and Technology
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• 제52권8호
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• pp.1677-1688
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• 2020

In the sodium-cooled fast reactor, the steam generator is a heat exchange device between sodium and water, which may cause leakage, resulting in a sodium-water reaction accident, which in turn affects the safe operation of the entire nuclear reactor. To this end, the electromagnetic vortex flowmeter is used to detect leakage of the steam generator and its signal processing method is studied in this paper. The hydraulic experiment was carried out by using water instead of liquid sodium, and the sensor output signal of the electromagnetic vortex flowmeter under different gas injection volumes was collected. The bubble noise signal is reflected by the base line of the sensor output signal. According to the relationship between the proportion of the bubble noise signal in the sensor output signal and the gas injection volume, a signal processing method based on the energy ratio calculation is proposed to detect whether the water contains bubbles. The gas injection experiment of liquid sodium was conducted to verify the effectiveness of the signal processing method in the detection of bubbles in sodium, and the minimum detectable leak rate of water in the steam generator was detected to be 0.2 g/s.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2000년도 봄 학술발표회논문집
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• pp.271-276
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• 2000

Optimal neuro-control algorithm is extended to the control of a multi-degree-of-freedom structure. An active mass driver(AMD) system on the top roof used as a controller. The control signals are made by a multi-layer perceptron(MLP) which is trained by minimizing a sub-optimal performance index. The performance index is a function of both the output responses and the control signals. Structure having nonlinear hysteretic behavior is also trained and controlled by using proposed control algorithm. Bothe the time delay effect and the dynamics of hydraulic actuator are included in the simulation. Example shows that optimal neuro-control algorithm can be applicable to the multi-degree of freedom structures.

• 한국정밀공학회지
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• 제5권3호
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• pp.81-90
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• 1988

In recent, the requirement of remote control of hychaulic system is in- creasing. The actuator unit whose output position is proportional to input electrical signal needs a pressure reducer and a dump valve. The pressure reducer provides a constant regulated pressure and filters contaminants. The dump valve supplies proper pressure to the pressure reducer and unloads when the system is not operated. In this thesis, dump valve and pressure reducer with auxiliary function are studied. The choke in the pressure reducer prevents actuator from supplying higher pressure than necessary pressure at beginning, and the spring constant affects on the dynamic characterisics. In dump valve, it is proved that diameter of servo-slide hold and choke diameter of dump plunger affects on damping response.

• 대한기계학회논문집A
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• 제23권6호
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• pp.922-930
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• 1999

This paper describes a new 14-CPU real-time distributed automatic gauge control (AGC) system for POSCO's No. 2 Hot Strip Mill at Pohang Works. The new AGC system has adopted gaugemeter AGC, Monitor AGC, and roll gap disturbance compensators. The computer system for the new AGC system has been developed based on VMEbus computer systems and a commercial real-time operating system. A VMEbus computer system is also used for the position servo control of hydraulic cylinders. All the application programs and input/output signals have been reasonably distributed over the control computer systems for the maximum reliability and effectiveness of the system. The new AGC system has been successfully used for the No. 2 Hot Strip Mill.