• Title, Summary, Keyword: Parametric uncertainty

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Robustness of discrete-time variable structure control to parametric uncertainties (매개변수의 불확실성에 대한 이산시간 가변구조 제어기법의 견실성)

  • 은용순;조동일
    • 제어로봇시스템학회:학술대회논문집
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    • pp.293-296
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    • 1997
  • Robust stability conditions for discrete-time variable structure control is proposed. Conventionally the discrete-time variable structure control method with a variable structure uncertainty compensator approach requires a bounded changing rate of the uncertainties to ensure robust stability. However, when uncertainties vary as a function of state variables, which occur with parametric uncertainties, it is not reasonable to assume a bounded variation on the uncertainties. In this paper, uncertainties are assumed to consist of exogenous disturbances and parametric uncertainties. An uncertainty compensator is used to deal with the former, and a robust stability condition is derived using Small Gain Theorem for the latter.

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Hydrologic Utilization of Radar-Derived Rainfall (II) Uncertainty Analysis (레이더 추정강우의 수문학적 활용 (II): 불확실성 해석)

  • Kim Jin-Hoon;Lee Kyoung-Do;Bae Deg-Hyo
    • Journal of Korea Water Resources Association
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    • v.38 no.12
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    • pp.1051-1060
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    • 2005
  • The present study analyzes hydrologic utilization of optimal radar-derived rainfall by using semi-distributed TOPMODEL and evaluates the impacts of radar rainfall and model parametric uncertainty on a hydrologic model. Monte Carlo technique is used to produce the flow ensembles. The simulated flows from the corrected radar rainfalls with real-time bias adjustment scheme are well agreed to observed flows during 22-26 July 2003. It is shown that radar-derived rainfall is useful for simulating streamflow on a basin scale. These results are diagnose with which radar-rainfall Input and parametric uncertainty influence the character of the flow simulation uncertainty. The main conclusions for this uncertainty analysis are that the radar input uncertainty is less influent than the parametric one, and combined uncertainty with radar and Parametric input can be included the highest uncertainty on a streamflow simulation.

Study on Numerical Sensitivity and Uncertainty in the Analysis of Parametric Roll (파라메트릭 횡동요 수치해석의 민감도 및 불확실성에 대한 연구)

  • Park, Dong-Min;Kim, Tae-Young;Kim, Yong-Hwan
    • Journal of the Society of Naval Architects of Korea
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    • v.49 no.1
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    • pp.60-67
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    • 2012
  • This study considers the numerical analysis on parametric roll for container ships. As a method of numerical simulation, an impulse-response-function approach is applied in time domain. A systematic study is carried out for the parametric roll of two container ships, particularly observing the sensitivity of computational results to some parameters which can affect the analysis of parametric roll. The parameters to be considered are metacentric height (GM), simulation time window, and the discretization of wave spectrum. Based on the result of parametric roll simulation, numerical sensitivity and uncertainty in computational analysis are discussed.

Modeling radon diffusion equation in soil pore matrix by using uncertainty based orthogonal polynomials in Galerkin's method

  • Rao, T.D.;Chakraverty, S.
    • Coupled systems mechanics
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    • v.6 no.4
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    • pp.487-499
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    • 2017
  • This paper investigates the approximate solution bounds of radon diffusion equation in soil pore matrix coupled with uncertainty. These problems have been modeled by few researchers by considering the parameters as crisp, which may not give the correct essence of the uncertainty. Here, the interval uncertainties are handled by parametric form and solution of the relevant uncertain diffusion equation is found by using Galerkin's Method. The shape functions are taken as the linear combination of orthogonal polynomials which are generated based on the parametric form of the interval uncertainty. Uncertain bounds are computed and results are compared in special cases viz. with the crisp solution.

Attitude Control using Quantitative Feedback Theory of a Quad-Rotor Vehicle with Plant Parametric Uncertainty (플랜트 파라미터의 불확실성을 포함한 4-회전익(Quad-Rotor) 비행체의 정량적 궤환 이론을 이용한 자세 제어)

  • Lee, ByungSeok;Heo, Moon-Beom;Lee, Joon Hwa
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.42 no.3
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    • pp.243-253
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    • 2014
  • This paper deals with the Quantitative Feedback Thoery(QFT) guaranteeing robustness in spite of the plant parametric uncertainty. In the frequency domain, the QFT guarantees the robustness of the design specification on the uncertainty of plant parameters and disturbance. In order to use the QFT, a selected plant is a Quad Rotor Vehicle(QRV) which has excellent maneuverability and possibility of vertical take-off and landing like the helicopter. And attitude control is examined the possibility satisfied the requirement specification under the setting parametric uncertainty of motors driving 4-blades. Additionally, in an attitude control, the pre-filter considering parameter range and operating range of a QRV was used. For these purpose, in this paper, by using QFTCT, that is the QFT Control Toolbox designing the controller in MATLAB by the QFT, each design phases are introduced.

ASSESSMENT OF THE SAFETY OF ULCHIN NUCLEAR POWER PLANT IN THE EVENT OF TSUNAMI USING PARAMETRIC STUDY

  • Kim, Ji-Young;Kang, Keum-Seok
    • Nuclear Engineering and Technology
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    • v.43 no.2
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    • pp.175-186
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    • 2011
  • Previous evaluations of the safety of the Ulchin Nuclear Power Plant in the event of a tsunami have the shortcoming of uncertainty of the tsunami sources. To address this uncertainty, maximum and minimum wave heights at the intake of Ulchin NPP have been estimated through a parametric study, and then assessment of the safety margin for the intake has been carried out. From the simulation results for the Ulchin NPP site, it can be seen that the coefficient of eddy viscosity considerably affects wave height at the inside of the breakwater. In addition, assessment of the safety margin shows that almost all of the intake water pumps have a safety margin over 2 m, and Ulchin NPP site seems to be safe in the event of a tsunami according to this parametric study, although parts of the CWPs rarely have a margin for the minimum wave height.

Bootstrap simulation for quantification of uncertainty in risk assessment

  • Chang, Ki-Yoon;Hong, Ki-Ok;Pak, Son-Il
    • Korean Journal of Veterinary Research
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    • v.47 no.2
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    • pp.259-263
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    • 2007
  • The choice of input distribution in quantitative risk assessments modeling is of great importance to get unbiased overall estimates, although it is difficult to characterize them in situations where data available are too sparse or small. The present study is particularly concerned with accommodation of uncertainties commonly encountered in the practice of modeling. The authors applied parametric and non-parametric bootstrap simulation methods which consist of re-sampling with replacement, in together with the classical Student-t statistics based on the normal distribution. The implications of these methods were demonstrated through an empirical analysis of trade volume from the amount of chicken and pork meat imported to Korea during the period of 1998-2005. The results of bootstrap method were comparable to the classical techniques, indicating that bootstrap can be an alternative approach in a specific context of trade volume. We also illustrated on what extent the bias corrected and accelerated non-parametric bootstrap method produces different estimate of interest, as compared by non-parametric bootstrap method.

Nonlinear Adaptive Control of EMS Systems with Mass Uncertainty (무게 변화를 고려한 자기부사열차의 비선형 적응제어기법)

  • Jo, Nam-Hoon;Joo, Sung-Jun;Seo, Jin-Heon
    • The Transactions of the Korean Institute of Electrical Engineers D
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    • v.49 no.10
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    • pp.563-571
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    • 2000
  • In this paper, a nonlinear adaptive control method for an EMS(Electro-Magnetic Suspension) system with mass uncertainty is proposed. Using the coordinate transformation and feedback linearizing control, EMS system has been transformed into the form of parametric strict-feedback system with unknown virtual control coefficients. With this transformed system, tuning functions approach, which is an advanced from of adaptive backstepping, has been applied in order to stabilize the system against mass uncertainty. Computer simulation is also carried out in order to compare the performance of the proposed controller with that of feedback linerizing controller.

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Controller Design and Stability Analysis of Affine System with Dead-Time (불감시간을 갖는 Affine 시스템의 안정도 해석과 제어기 설계)

  • Yang Hai-Won;Byun Hwang-Woo
    • Journal of Institute of Control, Robotics and Systems
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    • v.11 no.2
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    • pp.93-102
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    • 2005
  • The Nyquist robust stability margin is proposed as a measure of robust stability for systems with Affine TFM(Transfer Function Matrix) parametric uncertainty. The parametric uncertainty is modeled through a Affine TFM MIMO (Multi-Input Multi-Output) description with dead-time, and the unstructured uncertainty through a bounded perturbation of Affine polynomials. Gershgorin's theorem and concepts of diagonal dominance and GB(Gershgorin Bands) are extended to include model uncertainty. Multiloop PI/PID controllers can be tuned by using a modified version of the Ziegler-Nichols (ZN) relations. Consequently, this paper provides sufficient conditions for the robustness of Affine TFM MIMO uncertain systems with dead-time based on Rosenbrock's DNA. Simulation examples show the performance and efficiency of the proposed multiloop design method for Affine uncertain systems with dead-time.

Analysis of Uncertainties in Estimation of Critical Speeds from Tire Yaw Marks (타이어 요마크로부터 임계속도 추정의 불확실성 해석)

  • Han, Inhwan
    • Transactions of the Korean Society of Automotive Engineers
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    • v.23 no.4
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    • pp.361-370
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    • 2015
  • There will inevitably be errors and uncertainties in tire yaw mark related critical speed formula, which is derived merely from the relationship between the centrifugal force and the friction force acting on the point-mass vehicle. Constructing and measuring yaw marks through appropriate simulation works have made it possible to perform uncertainty analysis in calculation of critical speeds under variation of variety of conditions and parameters while existing yaw mark experimental tests have not performed properly. This paper does not present only the critical speed analysis results for parametric sensitivity and uncertainty of chord and middle ordinate, coefficient of friction and road grade, but also modeling uncertainty such as variation of braking level during turning and vehicle size. The yaw mark analysis methods and results may be now applied in practice of traffic accident investigation.