Browsing by Subject "Robust stabilization"

Now showing 1 - 4 of 4

Open Access
On stable controller design for robust stabilization of time delay systems
(IFAC, 2015) Yücesoy, Veysel; Özbay, Hitay
This paper studies the problem of robust stabilization of an infinite dimensional plant by a stable and possibly low order controller. The plant of interest is assumed to have only finitely many simple unstable zeros, however, may have infinitely many unstable poles. In the literature, it has been shown that the problem can be reduced to an interpolation problem and it is possible to obtain lower and upper bounds of the multiplicative uncertainty under which an infinite dimensional stable controller can be generated by a modified Nevanlinna-Pick formulation. We propose that the same interpolation problem can be solved approximately by a finite dimensional approach and present a finite dimensional interpolation function which can be used to find a stable controller. We illustrate this idea by a numerical example and additionally show the effects of the free design parameters of the rational interpolating outer function approach on the numerical example.
Open Access
Stable and robust controller synthesis for unstable time delay systems via ınterpolation and approximation
(Elsevier B.V., 2018) Yücesoy, V.; Özbay, Hitay
In this paper, we study the robust stabilization of a class of single input single output (SISO) unstable time delay systems by stable and finite dimensional controllers through finite dimensional approximation of infinite dimensional parts of the plant. The plant of interest is assumed to have finitely many non-minimum phase zeros but is allowed to have infinitely many unstable poles in the open right half plane. Conservatism of the proposed methods is illustrated by numerical examples for which infinite dimensional strongly stabilizing controllers are derived in the literature.
Open Access
Stable controllers for robust stabilization of systems with infinitely many unstable poles
(Elsevier, 2013) Wakaiki, M.; Yamamoto, Y.; Özbay, Hitay
This paper studies the problem of robust stabilization by a stable controller for a linear time-invariant single-input single-output infinite dimensional system. We consider a class of plants having finitely many simple unstable zeros but possibly infinitely many unstable poles. First we show that the problem can be reduced to an interpolation-minimization by a unit element. Next, by the modified Nevanlinna-Pick interpolation, we obtain both lower and upper bounds on the multiplicative perturbation under which the plant can be stabilized by a stable controller. In addition, we find stable controllers to provide robust stability. We also present a numerical example to illustrate the results and apply the proposed method to a repetitive control system.
Open Access
A switching control approach to stabilization of parameter varying time delay systems
(IEEE, 2009) Yan, P.; Özbay, Hitay; Şansal, M.
Robust stabilization problem is considered for time varying time delay systems, where the system parameters are scheduled along a measurable signal trajectory. A switching control approach is proposed for a class of parameter varying systems, where candidate controllers are designed for robust stabilization at certain operating regions. A dwell time based hysteresis switching logic is proposed to guarantee the stability of the switched parameter varying time delay system in the whole operating range. It is shown that if the parameter variation is slow enough (upper bound of the time derivative is determined in terms the dwell time for the switched delay system), then the system is stable with the proposed switched controllers.