• Title, Summary, Keyword: nonlinear scaling

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Time-Discretization of Nonlinear Systems with Time Delayed Output via Taylor Series

  • Yuanliang Zhang;Chong Kil-To
    • Journal of Mechanical Science and Technology
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    • v.20 no.7
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    • pp.950-960
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    • 2006
  • An output time delay always exists in practical systems. Analysis of the delay phenomenon in a continuous-time domain is sophisticated. It is appropriate to obtain its corresponding discrete-time model for implementation via a digital computer. A new method for the discretization of nonlinear systems using Taylor series expansion and the zero-order hold assumption is proposed in this paper. This method is applied to the sampled-data representation of a nonlinear system with a constant output time-delay. In particular, the effect of the time-discretization method on key properties of nonlinear control systems, such as equilibrium properties and asymptotic stability, is examined. In addition, 'hybrid' discretization schemes resulting from a combination of the 'scaling and squaring' technique with the Taylor method are also proposed, especially under conditions of very low sampling rates. A performance of the proposed method is evaluated using two nonlinear systems with time-delay output.

Design of observer for a class of Lipschitz nonlinear systems

  • Choi, H.L.;Lim, J.T.
    • 제어로봇시스템학회:학술대회논문집
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    • pp.2099-2101
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    • 2005
  • The problem of observer design for a class of Lipschitz nonlinear systems is considered. We propose a new observer design method which takes into account the structure of perturbed nonlinear terms with a scaling factor ${\epsilon}$. An example is provided to demonstrate the usefulness of our result over the existing method.

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Toxicokinetic Models and Data Interpretation (독성동태 모델과 데이터의 해석)

  • 유선동
    • Toxicological Research
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    • v.18 no.4
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    • pp.311-324
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    • 2002
  • Toxicokinetic studies are intended to provide critical evaluation of drug disposition at toxico-logical doses and help understand the relationship between blood or tissue levels and the time course of toxic events. Relatively high dose levels wed in toxicokinetics, compared to pharmacokinetics, complicates absorption, protein binding, metabolism and elimination processes. In this mini review, frequently wed toxicokinetic models such as linear compartment models, physiological models, and nonlinear kinetic mod-ec are introduced. In addition, optimization of toxicokinetic studies, their role in the drug development process, and prediction oj human toxicokinetics based on animal data by interspecies scaling are briefly discussed.

Dynamic stabilization for a nonlinear system with uncontrollable unstable linearization (제어불가능 불안정 선형화를 가지는 비선형 시스템에 대한 다이나믹 안정화)

  • Seo, Sang-Bo;Seo, Jin-Heon;Shim, Hyung-Bo
    • Proceedings of the IEEK Conference
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    • pp.79-81
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    • 2009
  • In this paper, we design a dynamic state feedback smooth stabilizer for a nonlinear system whose Jacobian linearization may have uncontrollable because its eigenvalues are on the right half-plane. After designing an augmented system, a dynamic exponent scaling and backstepping enable one to explicitly design a smooth stabilizer and a continuously differentiable Lyapunov function which is positive definite and proper.

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The Design Methodology of Fuzzy Controller by Means of Evolutionary Computing and Fuzzy-Set based Neural Networks

  • Roh, Seok-Beom;Oh, Sung-Kwun
    • Proceedings of the Korean Institute of Intelligent Systems Conference
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    • pp.438-441
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    • 2004
  • In this study, we introduce a noble neurogenetic approach to the design of fuzzy controller. The design procedure dwells on the use of Computational Intelligence (CI), namely genetic algorithms and Fuzzy-Set based Neural Networks (FSNN). The crux of the design methodology is based on the selection and determination of optimal values of the scaling factors of the fuzzy controllers, which are essential to the entire optimization process. First, the tuning of the scaling factors of the fuzzy controller is carried out by using GAs, and then the development of a nonlinear mapping for the scaling factors is realized by using GA based FSNN. The developed approach is applied to a nonlinear system such as an inverted pendulum where we show the results of comprehensive numerical studies and carry out a detailed comparative analysis.

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STOCHASTIC SCALING EFFECT AND STATISTICS OF COSMOLOGICAL DENSITY FLUCTUATIONS

  • Yi, In-Su;Vsihniac, Ethan T.
    • Publications of The Korean Astronomical Society
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    • v.7 no.1
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    • pp.51-61
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    • 1992
  • The nonlinear stochastic behavior of chaotic inflation is characterized by the 'scaling' effect. Using a simple criterion for the appearance of scaling behavior in the ${\lambda}{\phi}^4$ inflation model, we show explicitly that in this limit the onset of the scaling regime does not require any special initial conditions and that it is independent of the self-coupling constant ${\lambda}$. Non-Gaussian statistics in adiabatic fluctuations are important only for super-horizon scales and the scaling regime does not lead to any significant statistical properties on currently observable scales. However, the scaling effect gives some cosmological consequences very different from what we expect in the naive diffusion approximation for quantum fluctuations. The classical (deterministic) treatment of the inflation field (essentially a quantum mechanical object.) becomes valid towards the end of inflation.

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Effect of design spectral shape on inelastic response of RC frames subjected to spectrum matched ground motions

  • Ucar, Taner;Merter, Onur
    • Structural Engineering and Mechanics
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    • v.69 no.3
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    • pp.293-306
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    • 2019
  • In current seismic design codes, various elastic design acceleration spectra are defined considering different seismological and soil characteristics and are widely used tool for calculation of seismic loads acting on structures. Response spectrum analyses directly use the elastic design acceleration spectra whereas time history analyses use acceleration records of earthquakes whose acceleration spectra fit the design spectra of seismic codes. Due to the fact that obtaining coherent structural response quantities with the seismic design code considerations is a desired circumstance in dynamic analyses, the response spectra of earthquake records used in time history analyses had better fit to the design acceleration spectra of seismic codes. This paper evaluates structural response distributions of multi-story reinforced concrete frames obtained from nonlinear time history analyses which are performed by using the scaled earthquake records compatible with various elastic design spectra. Time domain scaling procedure is used while processing the response spectrum of real accelerograms to fit the design acceleration spectra. The elastic acceleration design spectra of Turkish Seismic Design Code 2007, Uniform Building Code 1997 and Eurocode 8 are considered as target spectra in the scaling procedure. Soil classes in different seismic codes are appropriately matched up with each other according to $V_{S30}$ values. The maximum roof displacements and the total base shears of considered frame structures are determined from nonlinear time history analyses using the scaled earthquake records and the results are presented by graphs and tables. Coherent structural response quantities reflecting the influence of elastic design spectra of various seismic codes are obtained.

Neural Network based Fuzzy Type PID Controller Design (신경 회로망 기반 퍼지형 PID 제어기 설계)

  • 임정흠;권정진;이창구
    • 제어로봇시스템학회:학술대회논문집
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    • pp.86-86
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    • 2000
  • This paper describes a neural network based fuzzy type PID control scheme. The PID controller is being widely used in industrial applications. however, it is difficult to determine the appropriate PID gains for (he nonlinear system control. In this paper, we re-analyzed the fuzzy controller as conventional PID controller structure, and proposed a neural network based fuzzy type PID controller whose scaling factors were adjusted automatically. The value of initial scaling factors of the proposed controller were determined on the basis of the conventional PID controller parameters tuning methods and then they were adjusted by using neural network control techniques. Proposed controller was simple in structure and computational burden was small so that on-line adaptation was easy to apply to. The result of practical experiment on the magnetic levitation system, which is known to be hard nonlinear, showed the proposed controller's excellent performance.

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Control of Electromagnetic Levitation System using ε-scaling Partial State Feedback Controller (ε조절 요소를 가진 부분 상태 궤환 제어기를 이용한 자기부상 시스템의 제어)

  • Park, Gyu-Man;Choi, Ho-Lim
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.60 no.8
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    • pp.1572-1576
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    • 2011
  • The electromagnetic levitation(EMS) system is one of the well-known nonlinear system because of its nonlinearity and several control techniques have been proposed. We propose an ${\epsilon}$-scaling partial feedback controller for the ball position control of the EMS system. The key feature of our proposed controller is the use of the scaling factor ${\epsilon}$ which provides a function of controller gain tuning along with robustness. In this paper, we show the stability analysis of our proposed controller and the convergence analysis of the state observer in terms of ${\epsilon}$-scaling factor. In addition, the experimental results show the validity of the proposed controller and improved control performance over the conventional PID controller.

An Adaptive Maximum Power Point Tracking Scheme Based on a Variable Scaling Factor for Photovoltaic Systems (태양광 시스템을 위한 가변 조정계수 기반의 적응형 MPPT 제어 기법)

  • Lee, Kui-Jun;Kim, Rae-Young;Hyun, Dong-Seok;Lim, Chun-Ho;Kim, Woo-Chull
    • The Transactions of the Korean Institute of Power Electronics
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    • v.17 no.5
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    • pp.423-430
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    • 2012
  • An adaptive maximum power point tracking (MPPT) scheme employing a variable scaling factor is presented. A MPPT control loop was constructed analytically and the magnitude variation in the MPPT loop gain according to the operating point of the PV array was identified due to the nonlinear characteristics of the PV array output. To make the crossover frequency of the MPPT loop gain consistent, the variable scaling factor was determined using an approximate curve-fitted polynomial equation about linear expression of the error. Therefore, a desirable dynamic response and the stability of the MPPT scheme were maintained across the entire MPPT voltage range. The simulation and experimental results obtained from a 3 KW rated prototype demonstrated the effectiveness of the proposed MPPT scheme.