• 제목/요약/키워드: Stability Regions

검색결과 397건 처리시간 0.03초

Lyapunov 함수를 이용한 동기전동기의 안전도 해석과 동특성 시뮬레이션 (Stability Analysis of Synchronous Motor by Lyapunov Functions and Dynamic Simulation)

  • 이준탁;윤병도;우중인;정형환
    • 대한전기학회논문지
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    • 제39권11호
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    • pp.1163-1173
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    • 1990
  • In the stability analysis of a synchronous motor, the considerations of the initial conditions, that is, field application points and the determination techniques of stability regions to assure stable operations over four quadrants are very important. In this paper, Lyapunov stability regions obtained from a newly proposed algorithm with Lyapunov function of simple type on the basis of numerical analysis method are shown to be true stability regions which can accurately pull in within 2 (rad) after field application.

천천히 변하는 선형 시변 시스템의 안정도 영역 (Stability Regions of Linear Slowly Time-Varying Systemsa)

  • 최종호;장태정
    • 제어로봇시스템학회:학술대회논문집
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    • 제어로봇시스템학회 1988년도 한국자동제어학술회의논문집(국내학술편); 한국전력공사연수원, 서울; 21-22 Oct. 1988
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    • pp.210-213
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    • 1988
  • By using Lyapunov method, sufficient conditions for linear time-varying continuous-time and discrete-time systems to be stable are presented under the assumption that the systems are slowly time-varying. Though it is not simple to find the stability regions immediately, one could find practical and large stability regions by constructing an appropriate algorithm.

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변형된 선합성수 디지털 필터의 안정도 해석 (Stability Analysis of Modified Coupled-Form Digital Filter Using a Constructive Algorithm)

  • 남부희;김남호
    • 대한전기학회논문지
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    • 제34권11호
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    • pp.430-435
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    • 1985
  • Using the constructive algorithm proposed by Brayton and Tong, we analyze the stability of a modified coupled-form digital filter with quantization and overflow nonlinearities, and find the regions in the parameter plane where the filter is globally asymptotically stable. In these regions, the absence of zero-input limit cycles is ensured. This constructive algorithm gives less conservative stability results than the application of Jury-Lee stability criterion does.

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파랑중 부선의 침로안정성에 관한 연구 (Study on the Course Stability of a Barge in Waves)

  • 이상민
    • 해양환경안전학회지
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    • 제24권4호
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    • pp.430-437
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    • 2018
  • 파랑중을 항행하는 선박에는 저항증가와 함께 파랑에 의한 횡력 및 회두모멘트가 정수중과 다르게 작용하여 선박의 조종성능에 영향을 미치게 된다. 따라서 파랑에 의해 발생하는 횡력 및 회두모멘트를 추정하는 것이 중요하므로 본 연구에서는 이와 같은 문제를 해결할 수 있는 수치계산을 이행하였다. 본 연구에서는 CFD를 이용하여 정수중 및 파랑중에서 부선에 작용하는 유체력 계산을 위한 수치시뮬레이션을 수행하였으며, 이 결과를 토대로 최종적으로 파랑중 부선의 침로안정성 특성에 대하여 조사 및 분석하였다. 정수중보다는 파랑중에서 부선에 작용하는 유체력이 강해지고 있으며, 파랑중에서도 파장이 길어질수록 유체력이 커지고 있는 모습을 확인할 수 있다. 장파장 영역에서는 yaw damping lever의 (-) 값이 정수중보다 커지고 있으나, 단파장 영역과 파장이 선박길이와 일치하는 영역에서는 각각 작아지고 있어서 이 영역에서는 침로안정성이 향상되고 있다고 추정할 수 있다. 즉 장파장 영역에서는 침로안정성이 정수중 및 단파장 영역보다 상대적으로 나빠지고 있으므로 항행시 주의가 필요하다고 할 수 있다.

Combustion Stability Characteristics of the Model Chamber with Various Configurations of Triplet Impinging-Jet Injectors

  • Sohn Chae-Hoon;Seol Woo-Seok;Shibanov Alexander A.
    • Journal of Mechanical Science and Technology
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    • 제20권6호
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    • pp.874-881
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    • 2006
  • Combustion stability characteristics in actual full-scale combustion chamber of a rocket engine are investigated by experimental tests with the model (sub-scale) chamber. The present hot-fire tests adopt the combustion chamber with three configurations of triplet impinging-jet injectors such as F-O-O-F, F-O-F, and O-F-O configurations. Combustion stability bound-aries are obtained and presented by the parameters of combustion-chamber pressure and mixture (oxidizer/fuel) ratio. From the experimental tests, two instability regions are observed and the pressure oscillations have the similar patterns irrespective of injector configuration. But, the O-F-O injector configuration shows broader upper-instability region than the other configurations. To verify the instability mechanism for the lower and upper instability regions, air-purge acoustic test is conducted and the photograph or the flames is taken. As a result, it is found that the pressure oscillations in the two regions can be characterized by the first impinging point of hydraulic jets and pre-blowout combustion, respectively.

축 방향 가속을 받는 보 구조물의 동적 안정성 해석 (Dynamic Stability Analysis of an Axially Accelerating Beam Structure)

  • 은성진;유홍희
    • 한국소음진동공학회:학술대회논문집
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    • 한국소음진동공학회 2005년도 춘계학술대회논문집
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    • pp.877-882
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    • 2005
  • Dynamic stability of an axially accelerating beam stucture is investigated in this paper. The equations of motion of a fixed-free beam are derived using the hybrid deformation variable method and the assumed mode method. Unstable regions due to periodical acceleration are obtained by using the Floquet's theory. Stability diagrams are presented to illustrate the influence of the dimensionless acceleration, amplitude, and frequency. Also, buckling occurs when the acceleration exceeds a certain value. It is found that relatively targe unstable regions exist around the first bending natural frequency, twice the first bending natural frequency, and twice the second bending natural frequency. The validity of the stability diagram is confirmed by direct numerical integration of the equations of motion.

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축 방향 가속을 받는 보 구조물의 동적 안정성 해석 (Dynamic Stability Analysis of an Axially Accelerating Beam Structure)

  • 은성진;유홍희
    • 한국소음진동공학회논문집
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    • 제15권9호
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    • pp.1053-1059
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    • 2005
  • Dynamic stability of an axially accelerating beam structure is investigated in this paper. The equations of motion of a fixed-free beam are derived using the hybrid deformation variable method and the assumed mode method. Unstable regions due to periodical acceleration are obtained by using the Floquet's theory. Stability diagrams are presented to illustrate the influence of the dimensionless acceleration, amplitude, and frequency. Also, buckling occurs when the acceleration exceeds a certain value. It is found that relatively large unstable regions exist around the first bending natural frequency, twice the first bending natural frequency, and twice the second bending natural frequency. The validity of the stability diagram is confirmed by direct numerical integration of the equations of motion.

Optimum Radius Size between Cylindrical Ion Trap and Quadrupole Ion Trap

  • Chaharborj, Sarkhosh Seddighi;Kiai, Seyyed Mahmod Sadat;Arifin, Norihan Md;Gheisari, Yousof
    • Mass Spectrometry Letters
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    • 제6권3호
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    • pp.59-64
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    • 2015
  • Quadrupole ion trap mass analyzer with a simplified geometry, namely, the cylindrical ion trap (CIT), has been shown to be well-suited using in miniature mass spectrometry and even in mass spectrometer arrays. Computation of stability regions is of particular importance in designing and assembling an ion trap. However, solving CIT equations are rather more difficult and complex than QIT equations, so, analytical and matrix methods have been widely used to calculate the stability regions. In this article we present the results of numerical simulations of the physical properties and the fractional mass resolutions m/Δm of the confined ions in the first stability region was analyzed by the fifth order Runge-Kutta method (RKM5) at the optimum radius size for both ion traps. Because of similarity the both results, having determining the optimum radius, we can make much easier to design CIT. Also, the simulated results has been performed a high precision in the resolution of trapped ions at the optimum radius size.

상압기상연소시험을 통한 동축형 스월 분사기와 충돌형 분사기의 연소 안정성 평가 (An Experimental Assessment of Combustion Stability of Coaxial Swirl Injectors and an Impinging Injector through Simulating Combustion Test)

  • 박준형;김홍집
    • 한국연소학회지
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    • 제22권1호
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    • pp.46-52
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    • 2017
  • High-frequency combustion instabilities may occur during the development of feasible engine combustors. These instabilities can result in irreparable damages to the wall of combustors or the degradation of engine performance. So, it is essential to identify injectors that have high stability characteristics during the early stages of development. The objective of present study was to assess the stability of coaxial injectors and an impinging injector with different recess lengths in order to develop stable injectors optimally. Stability margin was evaluated based on the distance from operating condition to the unstable regions. A simulating combustion test method was used to analyze the stability of injectors. A small-scale combustion chamber was designed to simulate the first tangential acoustic mode of the actual combustor. Gaseous oxygen and a mixture of methane and propane were used as simulant propellants to satisfy their flow similarity to the actual propellants of a combustor in a liquid rocket combustor. The results indicated that injectors having small recess lengths showed relatively large combustion stability margins. For the injectors of large recess lengths, instability regions with large and super-large amplitude oscillations were observed. Thus, injector with shorter recess lengths had a higher stability than that of longer one due to the different mixing processes.

Observer-based Fault Tolerant Control for Constrained Switched Systems

  • Yang, Hao;Jiang, Bin;Cocquempot, Vincent
    • International Journal of Control, Automation, and Systems
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    • 제5권6호
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    • pp.707-711
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    • 2007
  • An observer-based fault tolerant control (FTC) method is proposed for constrained switched systems (CSS) with input constraints. A family of Lyapunov-based bounded controllers are designed to ensure that, whenever actuator faults occur at the dwell time period of each continuous mode, the mode is always within its corresponding stability region. A set of switching laws are designed to guarantee the asymptotic stability of the overall CSS. The fixed stability regions on which the FTC method is based are also relaxed by the proposed variable stability regions. An example of CPU processing illustrates the effectiveness of proposed method.