• Title, Summary, Keyword: Nonlinear systems

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A Study on the Modeling of Nonlinear System Using Genetic Programming (유전자 프로그래밍을 이용한 비선형시스템 모델링에 관한 연구)

  • Kim, B.Y.;Park, K.S.
    • Proceedings of the KOSOMBE Conference
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    • v.1996 no.05
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    • pp.18-21
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    • 1996
  • Even though there are several deterministic methods for the modeling of linear systems, there is no standard method for the modeling of nonlinear systems. For the modeling of nonlinear systems we have applied the genetic programming method to estimate nonlinear time sereis. We get the time series from the simple known nonlinear dynamics, and fed those to genetic programming. For the tested nonlinear systems, suggested method estimated the nonlinear dynamics correctly.

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Forced Vibration Analysis for Duffing's Vibration Systems with the Multi-Degree-of-Freedom Systems (다자유도계를 갖는 듀핑 진동계의 강제진동해석)

  • 전진영;박용남;김정렬;김의간
    • Journal of Advanced Marine Engineering and Technology
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    • v.24 no.1
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    • pp.18-24
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    • 2000
  • As ship's propulsion shafting system has been complicated, many linear methods that have been used until now are not sufficient enough to produce proper solutions and these solutions are ofter unreasonable. So we need to solve nonlinear systems, and many methods for solving nonlinear vibration system have been developed. In this study, the propulsion shafting system was modeled with Duffing's nonlinear vibration system and multi-degree-of-freedom, and analyzed by using Quasi-Newton method. And for the purpose of confirming the reliability of the calculating results for nonlinear forced torsional vibration of the propulsion shafting system, the nonlinear calculated results were compared with the linear calculated ones for ship's propulsion shafting system. In the result, for analysis of the forced torsional vibration of the propulsion systems with nonlinear elements, the modified Newton's method is confirmed reasonable.

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A Study of Nonlinear Behaviors in Power Systems with SMES (SMES를 포함하는 전력계통의 비선형현상 해석에 관한 연구)

  • Ahn, Byong-Hak;Lee, Byong-Jun
    • The Transactions of the Korean Institute of Electrical Engineers A
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    • v.48 no.4
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    • pp.379-387
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    • 1999
  • In general, solving or analyzing nonilinear dynamical equations is very difficult and requires special techniques. To avoid these difficulties, systems are generally linearized in an attempt to predict their begavior. These linearized equations, however, may not predict true system behavior. Therefore, the nonlinear dynamical analysis using bifurcation theory may become a fundamental framework in understanding nonlinear situation in power systems. In this paper, we propose a systematic procedure based on a bifurcation theory to analyze nonlinear behaviors in power systems. We show usefulness of our procedure by applying 3-bus model system. In addition, we consider nonlinear model of SMES and verify the effect of SMES in power system's nonlinear behaviors.

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Nonlinear Attitude Control for Uncertain Quad-rotors Using a Global Approximation-Free Control Scheme (GAFC 비선형 제어기법을 적용한 쿼드로터의 자세 및 고도제어)

  • Kim, Young-Ouk;Park, Seong-Yong;Leeghim, Henzeh
    • Journal of Institute of Control, Robotics and Systems
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    • v.22 no.10
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    • pp.779-787
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    • 2016
  • A nonlinear control law for the quad-rotor of a low-complexity, global approximation-free from system uncertainties and external disturbances are described in this paper. The control law guarantees convergence to a small bounded error using a prescribed performance function. The stability of the proposed nonlinear control system is also proven by the Lyapunov stability theorem. The advantage of this technique is that it has a simpler form than any other nonlinear compensators and is applicable to any nonlinear systems without precise knowledge of the systems. In this paper, the proposed approach is applied to attitude/altitude control of a quad-rotor. Numerical simulations are performed to investigate the proposed nonlinear attitude control law by applying it to an uncertain quadcopter system with external disturbances.

Nonlinear H$\infty$ Control for Linear Systems using Nonlinear Weight

  • Kubota, K.;Samei, M.;Shimizu, E;Koga, M.
    • 제어로봇시스템학회:학술대회논문집
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    • pp.60-63
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    • 1996
  • This study deals with the nonlinear H$_{\infty}$ control problem of linear system using nonlinear weight. Generally the solvable condition of nonlinear H$_{\infty}$ control problem is given by the Hamilton Jacobi equality or inequality, but it is very difficult to solve. In this study, some constraints of nonlinear weight reduce the solvable condition to linear Riccati equation. Some examples of the control system design using nonlinear weight are shown.n.

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Adaptive Observer Design for Nonlinear Systems Using Generalized Nonlinear Observer Canonical Form

  • Jo, Nam-Hoon;Son, Young-Ik
    • Journal of Mechanical Science and Technology
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    • v.18 no.7
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    • pp.1150-1158
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    • 2004
  • In this paper, we present an adaptive observer for nonlinear systems that include unknown constant parameters and are not necessarily observable. Sufficient conditions are given for a nonlinear system to be transformed by state-space change of coordinates into an adaptive observer canonical form. Once a nonlinear system is transformed into the proposed adaptive observer canonical form, an adaptive observer can be designed under the assumption that a certain system is strictly positive real. An illustrative example is included to show the effectiveness of the proposed method.

Output Feedback Stabilization of Non-Minimum Phase Nonlinear Systems

  • Jo, Nam-H.;Son, Young-I.;Shim, Hyung-Bo
    • 제어로봇시스템학회:학술대회논문집
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    • pp.60.1-60
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    • 2002
  • . an output feedback stabilizing controller for non-minimum phase nonlinear systems . Assumption 1 : the Jacobi linearization of the given nonlinear linear system is controllable . Assumption 2: an appropriate transformation which transforms the zero dynamics into a special form . Assumption 3: the system satisfies the observability rank condition . Augmentation of systems by augmented by a chain of integrators

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DUALITY IN THE OPTIMAL CONTROL PROBLEMS OF NONLINEAR PARABOLIC SYSTEMS

  • Lee, Mi-Jin
    • East Asian mathematical journal
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    • v.16 no.2
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    • pp.267-275
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    • 2000
  • In this paper, we study the duality theory of nonlinear parabolic systems. The main objective is to prove the duality theorem under general conditions within an infinite-dimensional framework. As an application, an example is given.

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Linearization of the Nonlinear Control Systems (비선형 제어 시스템의 선형화)

  • 이홍기
    • Journal of Institute of Control, Robotics and Systems
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    • v.9 no.9
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    • pp.651-657
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    • 2003
  • Linearization is one of the most successful approaches nonlinear system control. The objective of this paper is to survey the recent results in linearization theory. It is hoped to be useful in understanding various linearization problems and challenging unsolved problems.

Anti-shock Controller Design for Optical Disk Drive Systems with a Nonlinear Controller (광디스크 드라이브 시스템을 위한 비선형 Anti-shock 제어기 설계)

  • Baek Jong-Shik;Chung Chung Choo
    • Journal of Institute of Control, Robotics and Systems
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    • v.11 no.9
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    • pp.741-749
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    • 2005
  • This paper presents a nonlinear controller design for optical disk drive systems to improve anti-shock performance. The nonlinear anti-shock controller is added parallel to the original linear servo control loop. In the previous work, a dead-zone nonlinear element is used for the nonlinear controller and a PID control method is used for the linear controller. Although this parallel structure of the controller improves anti-shock performance, it has a narrow stability bound. In this paper, the dead-zone with saturation nonlinear element is proposed for the nonlinear controller. Since this nonlinear element improves stability margin, we can use higher slope gain of dead-zone than that of nonlinear controller using dead-zone only. In the linear controller design, it is shown that the lead-lag control has an improved stability margin over PID control. Numerical simulation results and experimental results show that the proposed method can get better performance to the external shock than previously proposed methods.