• 한국정밀공학회지
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• 제18권11호
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• pp.58-66
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• 2001

GPC has been reported as a useful self-tuning control algorithm for systems with unknown time-delay and parameters. GPC is easy to understand and implement, and thus has won popularity among many practicing engineers. Despite its success, GPC does not guarantee is nominal stability. So, in this paper, GPC is rederived in frequency domain instead of in the time domain to guarantee its nominal stability. Derivation of GPC in frequency domain involves spectral factorization and Diophantine equation. Frequency domain GPC control law is stable because the zeros of characteristic polynomial are strictly Schur. Recursive least square algorithm is used to identify unknown parameters. To see the effectiveness of the proposed controller, the controller is simulated for a numerical problem that changes in dead-time, in order and in parameters.

• 한국안전학회지
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• 제3권1호
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• pp.21-29
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• 1988

Conventional pwm switching power supply have the disadvantage some aspects of size, light weight, noise and system stability. High frequency Series Resonant Converter (SRC), described in this paper, almost improve above disadvantages. We use the state plane technique as analysis method. This technique is powerful tool which can clearly analyze the peak stress of the state variables inside the converter, Here, we can define each operation mode from frequency ratio Fsn, switching frequency to resonant frequency, and we analyze the output performance in each operation mode. To verify the theoretical analysis, we compose the actual converter, and the experimental results are compared with analysis.

• 한국산업융합학회 논문집
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• 제23권4_2호
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• pp.653-659
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• 2020

In this study, seismic verification of the bellows used in the plant field was conducted. The pressure used in the analysis was analyzed by applying the design pressure of 15.7bar. For the seismic analysis, the natural frequency of the bellows system was obtained and the stability of the system was evaluated by static seismic analysis comparing the lowest order natural frequency with the dominant frequency of 33 Hz. The material of the bellows system is STS304, and the safety factor is obtained in comparison with the allowable stress. For the seismic analysis, the design response spectrum was prepared and the maximum acceleration was applied to the static seismic analysis and the stability of the entire system was confirmed. Compared to the structural analysis results, the maximum stress of the bellows system increased by about 16.4% and the maximum strain increased by about 3 times when seismic analysis was performed.

• 한국항공우주학회지
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• 제37권6호
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• pp.537-544
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• 2009

본 논문에서는 안정성 영역 판별법(stability area) 기반 발사체의 자세제어기 이득결정과정에 대한 내용을 기술하였다. 안정성 영역 판별법은 D-Decomposition 기법으로부터 정의되는 것으로 본 논문에서는 D-Decomposition 기본 이론과 이로부터 산출된 발사체의 자세 안정성 영역을 도시하고, 적용 예로써 일반적인 발사체의 1단 추력 비행구간에서 자세제어기 설계과정을 제시하였다. 제어이득 결정을 위해서 중첩된 안정성 영역을 바탕으로 시스템 파라미터 불확실성을 고려 안정성 영역 경계(stability area boundary)를 설정하고, 선정된 제어이득을 발사체 선형모델에 적용, 자세 안정성 분석 수행 결과를 나타냈다.

• Journal of Advanced Marine Engineering and Technology
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• 제25권2호
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• pp.351-356
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• 2001

In this paper, a general one-loop control system was assumed as a model system which has a time-delay element connected with a first order-lag element in series. After the corresponding parameter set causing stability limit condition for the model system was obtained by mathematical procedures, their loci on the parameter space was taken according of frequency change,. The parameter set loci of stability limit showed a specific pattern, and particularly the curves on the Kp-Ti parameter space were able to generalized in the form of an exponential formula. These properties were also compared with the results taken from experimental procedures by Nyquist response method and Ziegler & Nichols method on the time domain, and both results were confirmed to be nearly same.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 A
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• pp.99-101
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• 2002

This paper is to introduce the R&D project called "System Protection with emphasis on Power System Stability". The principal objective of this project is protection aids to system stability. The objects of this project arc as follows. First, drawbacks of classical under frequency load shedding and implementation issues of the rate-of-change of frequency will be described. Secondly, the project discusses the possibilities of voltage instability in power system and how this risk will affect protective relays in real system. Lastly, special protection system is designed to preserve system stability for KEPCO.

• 한국기계가공학회지
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• 제11권1호
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• pp.56-61
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• 2012

The dynamic instability and natural frequency of axially moving beam with an attached mass are investigated. Thus, the effects of an attached mass on the stability of the moving beam are studied. The governing equation of motion of the moving beam with an attached mass is derived from the extended Hamilton's principle. The natural frequencies are investigated for the moving beams via the Galerkin method under the simple support boundary. Numerical examples show the effects of the attached mass and moving speed on the stability of moving beam. Moreover, the lowest critical moving speeds for the simple supported conditions have been presented. The results can be used in the analysis of axially moving beams with an attached mass for checking the stability.

• 대한기계학회논문집A
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• 제33권12호
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• pp.1410-1416
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• 2009

In this paper, the purpose is to investigate the stability and variation of natural frequency of a cracked cantilever beams subjected to follower force and tip mass. In addition, an analysis of the flutter instability(flutter critical follower force) of a cracked cantilever beam as slenderness ratio and crack severity is investigated. The governing differential equations of a Timoshenko beam subjected to an end tangential follower force is derived via Hamilton's principle. The two coupled governing differential equations are reduced to one fourth order ordinary differential equation in terms of the flexural displacement. Finally, the influence of the slenderness ratio and crack severity on the critical follower force, stability and the natural frequency of a beam are investigated.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.259-262
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• 2002

Application of combustion stabilization devices such as baffle and acoustic cavity to liquid propellant rocket engine is investigated to suppress high-frequency combustion instability, i.e., acoustic instability. First, these damping devices are designed based on linear damping theory. As a principal design parameter, damping factor is considered and calculated numerically in the chambers with various specifications of these devices. Next, the unbaffled chambers with/without acoustic cavities are tested experimentally for several operating conditions. The unbaffled chamber shows the specific stability characteristics depending on the operating condition and has small dynamic stability margin. The most hazardous frequency is clearly identified through Fast Fourier Transform. As a result, the acoustic cavity with the present design has little stabilization effect in this specific chamber. Finally, stability rating tests are conducted with the baffled chamber, where evident combustion stabilization is observed, which indicates sufficient damping effect. Thrust loss caused by baffle installation is about $2{\%}$.

• 한국생산제조학회지
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• 제19권3호
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• pp.340-345
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• 2010

This paper presents the chatter stability lobes of high speed spindle of five-axis machine tools. Using a FEM, we obtained the frequency response function of a spindle and the stability lobes for evaluation of chatter. In addition, this paper suggest FRF using by FEM for the prediction of chatter stable region and critical cutting depth. Therefore, critical cutting depth of is 1.3586mm and X, Y direction's chatter frequency is 901Hz and 900Hz, respectively.