Wyniki wyszukiwania - Biblioteka Nauki

1

Robust Control of Nonlinear Time-Delay Systems

100%

Antoniades C. , Christofides P. D.

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tom Vol. 9, no 4

811-837

EN

This paper focuses on single-input single-output nonlinear differential difference equation (DDE) systems with uncertain variables. For such systems, a general methodology is developed for the synthesis of robust nonlinear state feedback controllers that guarantee boundedness of the states and ensure that the ultimate discrepancy between the output and the external reference input in the closed-loop system can be made arbitrarily small by an appropriate choice of controller parameters. The controllers are synthesized by using a novel combination of geometric and Lyapunov-based techniques and enforce the above properties in the closed-loop system independently of the size of the state delay. The proposed control method is successfully applied to a fluidized catalytic cracking unit with a time-varying uncertain variable and is shown to outperform a proportional integral (PI) controller, a nonlinear controller that does not account for the uncertainty, and anonlinear controller that does not account for the state delays.

2

Analysis of maintenance models’ parameters estimation for technical systems with delay time

100%

Jodejko-Pietruczuk A. , Werbińska-Wojciechowska S.

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tom Vol. 16, no. 2

288--294

PL

W pracy analizie poddano system trzyelementowy (struktura niezawodnościowa progowa), którego procesy obsługiwania realizowane są zgodnie z założeniami Polityki Przeglądów Blokowych (BIP). Strategia ta może być zastosowana w procesie utrzymania systemów technicznych, gdy znane są pewne jego charakterystyki niezawodnościowe, bazujące m.in. na informacjach o czasach pomiędzy uszkodzeniami elementów systemu. W badaniach skupiono się na trzech rozkładach prawdopodobieństwa tej zmiennej losowej (normalny, Weibull, prostokątny). Model symulacyjny opracowano przy wykorzystaniu oprogramowania GNU Octave. Analiza okresu opóźnienia czasowego, przy założeniu różnych postaci rozkładów prawdopodobieństwa tej zmiennej losowej, pozwoliła na ocenę: czy znajomość typu rozkładu prawdopodobieństwa zmiennej losowej h ma istotne znaczenie dla wyników ekonomicznych funkcjonowania systemu, oraz jakie konsekwencje mogą wystąpić w wyniku niewłaściwej estymacji wartości średniej E(h).

EN

In the article authors are interested in BIP performance for three-element system (“k-out-of-n” reliability structure), the maintenance policy which is one of most commonly used in practice. The BIP may be implemented in technical systems when some information about reliability characteristics is known. The basic reliability parameters that have to be specified in such systems are: an estimation of system components’ time to failure and some delay time characteristics. In order to determine the effects of possible errors and to specify sufficient accuracy of the estimation, the analysis of system costs was done for various values of the expected delay time, assuming three different probability distributions of the delay time (Weibull, Uniform, and Normal). The modelling process was based on the use of GNU Octave software. Test analysis of delay time parameter, assuming different types of probability distributions is the base to conclude: if the form of the distribution has any meaning for economic results of the system, and what kind of consequences may result from improper mean delay time estimation E(h).

3

Fault tolerant control of switched nonlinear systems with time delay under asynchronous switching

84%

Xiang Z. , Wang R. , Chen Q.

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2010

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tom Vol. 20, no 3

497-506

EN

This paper investigates the problem of fault tolerant control of a class of uncertain switched nonlinear systems with time delay under asynchronous switching. The systems under consideration suffer from delayed switchings of the controller. First, a fault tolerant controller is proposed to guarantee exponentially stability of the switched systems with time delay. The dwell time approach is utilized for stability analysis and controller design. Then the proposed approach is extended to take into account switched time delay systems with Lipschitz nonlinearities and structured uncertainties. Finally, a numerical example is given to illustrate the effectiveness of the proposed method.

4

Time-varying time-delay estimation for nonlinear systems using neural networks

84%

Tan Y.

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2004

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tom Vol. 14, no 1

63-68

EN

Nonlinear dynamic processes with time-varying time delays can often be encountered in industry. Time-delay estimation for nonlinear dynamic systems with time-varying time delays is an important issue for system identification. In order to estimate the dynamics of a process, a dynamic neural network with an external recurrent structure is applied in the modeling procedure. In the case where a delay is time varying, a useful way is to develop on-line time-delay estimation mechanisms to track the time-delay variation. In this paper, two schemes called direct and indirect time-delay estimators are proposed. The indirect time-delay estimator considers the procedure of time-delay estimation as a nonlinear programming problem. On the other hand, the direct time-delay estimation scheme applies a neural network to construct a time-delay estimator to track the time-varying time-delay. Finally, a numerical example is considered for testing the proposed methods.

5

Realization problem for positive multivariable discrete-time linear systems with delays in the state vector and inputs

84%

Kaczorek T.

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tom Vol. 16, no 2

169-174

EN

The realization problem for positive multivariable discrete-time systems with delays in the state and inputs is formulated and solved. Conditions for its solvability and the existence of a minimal positive realization are established. A procedure for the computation of a positive realization of a proper rational matrix is presented and illustrated with examples.

6

Stability conditions for linear continuous-time fractional-order state-delayed systems

84%

Busłowicz M.

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tom Vol. 64, nr 1

3--7

EN

The stability problem of continuous-time linear fractional order systems with state delay is considered. New simple necessary and sufficient conditions for the asymptotic stability are established. The conditions are given in terms of eigenvalues of the state matrix and time delay. It is shown that in the complex plane there exists such a region that location in this region of all eigenvalues of the state matrix multiplied by delay in power equal to the fractional order is necessary and sufficient for the asymptotic stability. Parametric description of boundary of this region is derived and simple new analytic necessary and sufficient conditions for the stability are given. Moreover, it is shown that the stability of the fractional order system without delay is necessary for the stability of this system with delay. The considerations are illustrated by a numerical example.