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1

Expert schemes for the obtaining of discrete models for LTI systems using real sampling and parameter identification

De La Sen M., Garrido A.J., Barambones O., Maseda F.J.

Systems Science

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2003

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Vol. 29, nr 2

95-112

EN

In this paper, we present an expert network scheme designed to obtain discrete transfer functions for LTI systems under real sampling of finite duration rather than an instantaneous ideal one. For this purpose, the expert network handles two different identification methods to derive parametric discrete models techniques of reduced mathematical complexity from measured input-output data series. One of the methods is based on a typically used least-squares minimization, while the other one is based on the Leverrier's algorithm; that is, using a data series of the impulse response of the system to identify a parametric discrete model. These techniques are of particular practical interest when the continuous-time system is unknown or when dealing with discrete-time systems whose analytical expression becomes very complex due, for instance, to the use of finite duration real sampling. The expert network improves the discretization process implementing a biestimation mechanism that switches to the model that provides a better performance at each estimation instant considered for different values of the hold order.

2

Application of uncertain variables to stability analysis for a class of discrete uncertain systems

Bubnicki Z.

Systems Science

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2001

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Vol. 27, nr 1

103-110

EN

The nonlinear and time-varying uncertain system with a constant unknown vector of parameters is considered. The unknown parameter is assumed to be a value of an uncertain variable described by a certainty distribution given by an expert. The estimation of the certainty index that the system is globally asymptotically stable based on the necessary and sufficient stability conditions is proposed and considered. A simple example illustrates the approach presented.

3

A fractional-flow model of serial manufacturing systems with rework and its reachability and controllability properties

James G., Rumchev V.

Systems Science

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2001

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Vol. 27, nr 2

49-59

EN

A dynamic fractional-flow model of a serial manufacturing system incorporating rework is considered. Using some recent results on reachability and controllability of positive linear systems the ability of serial manufacturing systems with rework to "move in space", that is their reachability and controllability properties, are studied. These properties are important not only for optimising the performance of the manufacturing system, possibly off-line, but also to improve its functioning by using feedback control on-line.

4

Generic two-degree of freedom control systems for linear and nonlinear processes

Keviczky L., Banyasz C.

Systems Science

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2000

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Vol. 26, nr 4

5-24

EN

The paper discusses a generic two-degree of freedom controller scheme for linear plants and then extends the results to block-oriented factorable nonlinear processes. This generalization is quite straightforward for both IS and IU Hammerstein models, however, it can be performed only for IS Wiener models. An iterative controller refinement scheme is also presented.

5

Feedback holdability of singular discrete-time linear systems

Kaczorek T.

Systems Science

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2000

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Vol. 26, nr 4

25-37

EN

The feedback holdability problem for singular discrete-time linear systems is considered. Conditions are established for the existence of solutions to the following three problems for singular system (1) with regular pencil (E, A). Problem 1: find a gain matrix K such that the closed-loop trajectory is inside the nonnegative orthant R+n. Problem 2: find a gain matrix K such that the state vector xi of the closed-loop system xi = 0 for i greater than or equal k - 1, k = 1,...,n. Problem 3: find a gain matrix K such that ui = Kxi ∈ R+m and the trajectory of closed-loop system is inside R+n