Wyniki wyszukiwania - BazTech

1

Investigation of limit cycles and signal stabilization of two dimensional systems with memory type nonlinear elements

Patra K. C., Dakua B. K.

Archives of Control Sciences

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2018

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Vol. 28, No. 2

285--330

EN

The paper presents a simple, systematic and novel graphical method which uses computer graphics for prediction of limit cycles in two dimensional multivariable nonlinear system having rectangular hysteresis and backlash type nonlinearities. It also explores the avoidance of such self-sustained oscillations by determining the stability boundary of the system. The stability boundary is obtained using simple Routh Hurwitz criterion and the incremental input describing function, developed from harmonic balance concept. This may be useful in interconnected power system which utilizes governor control. If the avoidance of limit cycle or a safer operating zone is not possible, the quenching of such oscillations may be done by using the signal stabilization technique which is also described. The synchronization boundary is laid down in the forcing signal amplitudes plane using digital simulation. Results of digital simulations illustrate accuracy of the method for 2×2 systems.

2

Note on describing function analysis of fractional order nonlinear control systems

Yeroglu C., Tan N.

Control and Cybernetics

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2015

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Vol. 44, no. 2

233--255

EN

This paper presents extensions of some results, obtained for the analysis of classical nonlinear control systems, to the nonlinear fractional order systems. It is shown that the results related to limit cycle prediction using describing function method can be applied to the fractional order plants. The frequency and the amplitude of the limit cycle are used for auto-tuning of the PID controller for nonlinear control systems with fractional order transfer functions. Fractional order control system with parametric uncertainty is also considered for the nonlinear case. On the other hand, a New method is provided for stability margin computation for fractional order nonlinear control system with parametric uncertainty structure using the Nyquist envelopes of the fractional order uncertain plant and the describing function that represents the nonlinearity of the system. Maximum perturbation bounds of the parameters of the fractional order plant are computed. Numerical examples are included to illustrate the methods presented.

3

Przybliżona metoda oceny odporności pewnej klasy układów nieliniowych

Żuchowski A.

Pomiary Automatyka Kontrola

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2007

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R. 53, nr 2

35-38

PL

Oceny odporności układów liniowych rozumianej jako dopuszczalny obszar zmian parametrów gwarantujących stabilność (ewentualnie z określonym zapasem) dokonuje się wykorzystując bądź tzw. wielomiany Charitonowa [1], bądź kryterium stabilności Neumarka, nazywane też metodą D-powierzchni [2]. Precyzyjna ocena odporności układów nieliniowych jest problemem otwartym. Zaproponowano przybliżoną metodę takiej oceny dla pewnej klasy układów nieliniowych z wykorzystaniem kryterium Neumarka.

EN

The so-called Kharitonov's polynomials [1] and Neumark's criterion (known as D - decomposition method) [2] can be treated as classic tools for estimation of linear system robustness, if estimation procedures are aimed at determination of allowed areas of changes of system parameters without losing of system stability or violating of requirements for assumed system stability margin. The problem of precise estimation of robustness for non-linear systems is still open one. The approximate method of estimation of robustness for certain class of non-linear systems is proposed in the paper. The presented method uses Neumark's criterion.

4

A 24 GHz PHEMT-based oscillator

Lewandowski A., Kompa G., Mwema W., Wiatr W.

Journal of Telecommunications and Information Technology

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2003

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nr 1

15-19

EN

We present a systematic nonlinear procedure for designing microwave oscillators utilising a nonlinear PHEMT model, the negative resistance approach and the describing function concept. The procedure is applied in the design of a 24 GHz oscillator, which is then realised in hybrid technology. Measurement results show - 6% shift in the frequency but an acceptable agreement in the output power. A detailed analysis shows that the frequency shift arises mainly from inadequate CAD models in the K band, for the microstrip components employed in our design.

5

Structural Formulation and Self-Oscillation Prediction in Multidimensional Nonlinear Closed-Loop Autonomous Systems

Patra K. C., Pati B. B., Łozowicki A.

International Journal of Applied Mathematics and Computer Science

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1999

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Vol. 9, no 2

327-346

EN

This paper describes the structure of a general two-dimensional nonlinear closed-loop system and application of the universal chart, leading to the use of computer graphics, for a systematic analysis of the complex problem of predicting self-oscillations (limit cycles). The graphical approach provides an explicit and novel insight into the conditions for the occurrence of limit cycles in such systems. This technique forms the basis of computer algorithms for predicting limit cycles in multidimensional nonlinear systems. Application of the technique has been illustrated through examples and comparison of results with digital simulation in MATLAB 4.0/SIMULINK 1.3.