Electrical and Electronic Engineering - Research Publications

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Author: Skafidas, Efstratios × Author: Evans, Robin × Start date: 1997 × End date: 1999 ×

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    On the use of switched linear controllers for stabilizability of implicit recursive equations
    Nesic, D (IEEE, 1998-01-01)
    Stabilizability of implicit recursive equations is investigated. These equations arise naturally in the context of output dead-beat control for systems described by NARMAX models. Due to non-uniqueness of the solutions of these equations a special kind of a constrained stabilizability problem is considered. We take a hybrid switching control approach in testing the existence of a locally stabilizing controller. A method for the design of a stabilizing switching controller is also presented.
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    Analysis of minimum phase properties for non-affine nonlinear systems
    Nesic, D ; Skafidas, E ; Mareels, IMY ; Evans, RJ (IEEE, 1997-01-01)
    A system can be termed non-minimum phase according to some definitions available in the literature and yet the same system may exhibit stable zero output constrained dynamics. We show that for non-affine nonlinear systems there may not exist a continuous control law which would keep the output identically equal to zero and for which the zero output constrained dynamics are stable, whereas a discontinuous controller which achieves this exists. We give conditions for existence and present a method for design of discontinuous switching controllers which yield stable zero dynamics. In this sense, the results of this paper enlarge the class of non-affine nonlinear systems that can be termed minimum-phase.
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    Minimum phase properties for input nonaffine nonlinear systems
    Nesic, D ; Skafidas, E ; Mareels, IMY ; Evans, RJ (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 1999-04-01)
    For input nonaffine nonlinear control systems, the minimum phase property of the system in general depends on the control law. Switching or discontinuous controllers may offer advantages in this context. In particular, there may not exist a continuous control law which would keep the output identically equal to zero and for which the zero output constrained dynamics are locally stable, whereas a discontinuous controller which achieves this exists. For single-input/single-output input nonaffine nonlinear systems we give sufficient conditions for existence and present a method for the design of discontinuous switching controllers which yield locally stable zero dynamics.