• Title, Summary, Keyword: nonlinear

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A study on the nonlinear normal modes of rotors (회전체의 비선형 정규 모우드에 관한 연구)

  • 김용철
    • Journal of Ocean Engineering and Technology
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    • v.10 no.1
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    • pp.17-24
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    • 1996
  • In the present paper nonlinear normal modes of a rotor system is studied. The methodology to obtain the nonlinear normal modes is based on center manifold reduction technique. It also provides a way of nonlinear coordinate transform from the physical cordinates to the modal coordinates and an idea of individual nonlinear modal dynamics. In order to apply the present method to a rotor dynamics a single mass rotor system on nonlinear elastic supports is employed and the nonlinear normal modes of the system are obtained.

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Stochastic vibration response of a sandwich beam with nonlinear adjustable visco-elastomer core and supported mass

  • Ying, Z.G.;Ni, Y.Q.;Duan, Y.F.
    • Structural Engineering and Mechanics
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    • v.64 no.2
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    • pp.259-270
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    • 2017
  • The stochastic vibration response of the sandwich beam with the nonlinear adjustable visco-elastomer core and supported mass under stochastic support motion excitations is studied. The nonlinear dynamic properties of the visco-elastomer core are considered. The nonlinear partial differential equations for the horizontal and vertical coupling motions of the sandwich beam are derived. An analytical solution method for the stochastic vibration response of the nonlinear sandwich beam is developed. The nonlinear partial differential equations are converted into the nonlinear ordinary differential equations representing the nonlinear stochastic multi-degree-of-freedom system by using the Galerkin method. The nonlinear stochastic system is converted further into the equivalent quasi-linear system by using the statistic linearization method. The frequency-response function, response spectral density and mean square response expressions of the nonlinear sandwich beam are obtained. Numerical results are given to illustrate new stochastic vibration response characteristics and response reduction capability of the sandwich beam with the nonlinear visco-elastomer core and supported mass under stochastic support motion excitations. The influences of geometric and physical parameters on the stochastic response of the nonlinear sandwich beam are discussed, and the numerical results of the nonlinear sandwich beam are compared with those of the sandwich beam with linear visco-elastomer core.

ON STRICT STATIONARITY OF NONLINEAR ARMA PROCESSES WITH NONLINEAR GARCH INNOVATIONS

  • Lee, O.
    • Journal of the Korean Statistical Society
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    • v.36 no.2
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    • pp.183-200
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    • 2007
  • We consider a nonlinear autoregressive moving average model with nonlinear GARCH errors, and find sufficient conditions for the existence of a strictly stationary solution of three related time series equations. We also consider a geometric ergodicity and functional central limit theorem for a nonlinear autoregressive model with nonlinear ARCH errors. The given model includes broad classes of nonlinear models. New results are obtained, and known results are shown to emerge as special cases.

Analysis of Nonlinear Resistive Networks (비선형저항(resistive)회로망의 해석)

  • Kyun Hyon Tchah
    • 전기의세계
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    • v.23 no.3
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    • pp.70-76
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    • 1974
  • Computer is used to analyze nonlinear networks. Integrated circuits and new nonlinear elements have generated much interest in nonlinear circuit theory. A key to the understanding and analysis of nonlinear circuits is the study of characteristics for nonlinear elements and nonlinear resistive networks both in theory and in computation. In this apper, an iteration method using cut set analysis for nonlinear dc analysis based on Branin's method is described. Application of this algorithm to solve two nonlinear problems, is presented and a possible method of improving the basic algorithm by means of a sparse matrix technique is described.

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Nonlinear Parameter Estimation of Suspension System (현가장치의 비선형 설계변수 추정)

  • 박주표;최연선
    • Transactions of the Korean Society of Automotive Engineers
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    • v.11 no.4
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    • pp.158-164
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    • 2003
  • The suspension system of cars is composed of dampers and springs, which usually have nonlinear characteristics. The nonlinear characteristics make the differences in the results of analytical models and experiments. In this study, the nonlinear system identification method which does not assume a special form for nonlinear dynamic systems and minimize the error by calculating the error reduction ratio is devised to estimate the nonlinear parameters of the suspension system of an EF-SONATA car from the field running test data. The results show that the spring has a cubic nonlinear term and the damper has a coupled nonlinear term. Also, the numerical results with the estimated nonlinear parameters agree well with the field test data for the different running speeds.

IDENTIFICATION OF HAMMERSTEIN-TYPE NONLINEAR SYSTEM

  • Hishiyama, Eiji;Harada, Hiroshi;Kashiwagi, Hiroshi
    • 제어로봇시스템학회:학술대회논문집
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    • pp.280-284
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    • 1998
  • Many classes of nonlinear systems can be represented by Volterra kernel expansion. Therefore, identification of Volterra kernels of nonlinear system is an important task for obtaining the nonlinear characteristics of the nonlinear system. Although one of the authors has recently proposed a new method for obtaining the Volterra kernels of a nonlinear system by use of M-sequence and correlation technique, our mettled of nonlinear system identification is limited to Wiener-type nonlinear system and we can not apply this method to the identification of Hammerstein-type nonlinear system. This paper describes a new mettled for obtaining Volterra kernels of Hammerstein nonlinear system by adding a linear element in front of tile Hammerstein system. First we calculate the linear element of Hammerstein system by use of conventional correlation method. Secondly, we put a linear element in front of Hammerstein system. Then the total system becomes Wiener-type nonlinear system. Therefore we can use our method on Volterra kernel identification by use of M-sequence. Thus we get the coefficients of the approximation polynomial of nonlinear element of Hammerstein system. From the results of simulation, a good agreement with theoretical considerations is obtained, showing a wide applicability of our method.

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Automatic System Development by Using Friction Force and Stiffness with Nonlinear Characteristic (비선형 마찰과 강성을 이용한 자동화 시스템 개발)

  • Lee, Jeong-Wook;Cho, Yong-Hee;Chang, Yong-Hoon;Kim, Jung-Ha
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.28 no.7
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    • pp.1055-1063
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    • 2004
  • In this study, we developed an automatic veneer sorting system controlled by nonlinear friction and nonlinear stiffness. With these nonlinear characteristics, it was difficult to analysis and to control the system in the fast. However it is necessary to consider nonlinear characteristics to satisfy accurate and rapid control demand in these days. We used not only nonlinear friction but also nonlinear stiffness and combined both to control the system. An experimental device was designed with 4 AC servo-motors and 2 Sensors. Through a series of experiment, we found nonlinear friction characteristics among roller versus veneer and veneer versus veneer and nonlinear stiffness characteristics with stacked veneers. Finally, we showed that the proposed control algorithm was very effective for veneer sorting system with nonlinear friction and stiffness.

A New Robust Variable Structure Controller With Nonlinear Integral-Type Sliding Surface for Uncertain More Affine Nonlinear Systems with Mismatched Uncertainties and Disturbance (부정합조건 불확실성과 외란을 갖는 비선형 시스템을 위한 비선형 적분형 슬라이딩 면을 갖는 새로운 강인한 가변구조제어기)

  • Lee, Jung-Hoon
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.59 no.7
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    • pp.1295-1301
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    • 2010
  • In this note, a systematic general design of a new robust nonlinear variable structure controller based on state dependent nonlinear form is presented for the control of uncertain affine nonlinear systems with mismatched uncertainties and mismatched disturbance. After an affine uncertain nonlinear system is represented in the form of state dependent nonlinear system, a systematic design of a new robust nonlinear variable structure controller is presented. To be linear in the closed loop resultant dynamics, the nonlinear integral-type sliding surface is applied. A corresponding control input is proposed to satisfy the closed loop exponential stability and the existence condition of the sliding mode on the nonlinear integral-type sliding surface, which will be investigated in Theorem 1. Through a design example and simulation studies, the usefulness of the proposed controller is verified.

Observer Design for Multi-Output Unobservable Nonlinear Systems (관측가능하지 않은 다중출력 비선형 시스템의 관측기 설계기법)

  • 조남훈
    • Journal of Institute of Control, Robotics and Systems
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    • v.10 no.7
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    • pp.575-582
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    • 2004
  • The observer design problem is studied for a class of multi-output nonlinear systems that are not necessarily observable. Generalized nonlinear observer canonical form is introduced for multi-output nonlinear systems to design nonlinear observers. Sufficient conditions are given for a nonlinear system to be transformed by state-space change of coordinates into generalized nonlinear observer canonical form. Based on this canonical from, a sufficient condition is also given for the existence of nonlinear observers. An illustrative example is presented to show the design procedure of the proposed method.

Detection and parametric identification of structural nonlinear restoring forces from partial measurements of structural responses

  • Lei, Ying;Hua, Wei;Luo, Sujuan;He, Mingyu
    • Structural Engineering and Mechanics
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    • v.54 no.2
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    • pp.291-304
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    • 2015
  • Compared with the identification of linear structures, it is more challenging to conduct identification of nonlinear structure systems, especially when the locations of structural nonlinearities are not clear in structural systems. Moreover, it is highly desirable to develop methods of parametric identification using partial measurements of structural responses for practical application. To cope with these issues, an identification method is proposed in this paper for the detection and parametric identification of structural nonlinear restoring forces using only partial measurements of structural responses. First, an equivalent linear structural system is proposed for a nonlinear structure and the locations of structural nonlinearities are detected. Then, the parameters of structural nonlinear restoring forces at the locations of identified structural nonlinearities together with the linear part structural parameters are identified by the extended Kalman filter. The proposed method simplifies the identification of nonlinear structures. Numerical examples of the identification of two nonlinear multi-story shear frames and a planar nonlinear truss with different nonlinear models and locations are used to validate the proposed method.