Browsing by Subject "Time-delay"

Now showing 1 - 6 of 6

Open Access
Dwell time-based stabilisation of switched delay systems using free-weighting matrices
(Taylor and Francis, 2018) Koru, A. T.; Delibaşı, A.; Özbay, Hitay
In this paper, we present a quasi-convex optimisation method to minimise an upper bound of the dwell time for stability of switched delay systems. Piecewise Lyapunov-Krasovskii functionals are introduced and the upper bound for the derivative of Lyapunov functionals is estimated by free-weighting matrices method to investigate non-switching stability of each candidate subsystems. Then, a sufficient condition for the dwell time is derived to guarantee the asymptotic stability of the switched delay system. Once these conditions are represented by a set of linear matrix inequalities, dwell time optimisation problem can be formulated as a standard quasi-convex optimisation problem. Numerical examples are given to illustrate the improvements over previously obtained dwell time bounds. Using the results obtained in the stability case, we present a nonlinear minimisation algorithm to synthesise the dwell time minimiser controllers. The algorithm solves the problem with successive linearisation of nonlinear conditions.
Embargo
On Smith predictor based controllers for plants with time delay and multiple unstable modes
(Elsevier BV, 2022-12-31) Yeğin, Mustafa Oğuz; Özbay, Hitay
This work proposes an extension of the Smith predictor to design stabilizing controllers for linear time-invariant (LTI) time-delay single-input single-output (SISO) systems with multiple unstable modes. The main contribution of this method is that it simplifies earlier predictor-based control designs for unstable plants. The predictor filters are designed by solving a Nevanlinna–Pick interpolation problem for optimal robust stability.
Open Access
Optimizing low-order controllers for haptic systems under delayed feedback
(Elsevier, 2013-05) Liacu, B.; Koru, A. T.; Özbay, Hitay; Niculescu, S. -I.; Andriot, C.
In this paper, a PD controller design for haptic systems under delayed feedback is considered. More precisely, a complete stability analysis of a haptic system where local dynamics are described by some second-order mechanical dynamics is presented. Next, using two optimization techniques (H∞ and stability, margin optimization) an optimal choice for the controller gains is proposed. The derived results are tested on a three degree-of-freedom real-time experimental platform to illustrate the theoretical results.
Open Access
Remarks on H ∞ controller design for SISO plants with time delays
(2006-07) Gümüşsoy, Suat; Özbay, Hitay
The skew Toeplitz approach is one of the well developed methods to design H ∞ controllers for infinite dimensional systems. In order to be able to use this method the plant needs to be factorized in some special manner. This paper investigates the largest class of SISO time delay systems for which the special factorizations required by the skew Toeplitz approach can be done. Reliable implementation of the optimal controller is also discussed. It is shown that the finite impulse response (FIR) block structure appears in these controllers not only for plants with I/O delays, but also for general time-delay plants.
Open Access
Sensitivity minimization by stable controllers for a class of unstable time-delay systems
(IEEE, 2006) Gümüşsoy, S.; Özbay, Hitay
In this paper sensitivity minimization problem is considered for a class of unstable time delay systems. Our goal is to find a stable controller stabilizing the feedback system and giving rise to smallest H∞ norm for the sensitivity function. This problem has been solved by Ganesh and Pearson (1986) for finite dimensional plants using Nevanlinna-Pick interpolation. We extend their technique to include possibly unstable time delay systems. Moreover, we illustrate suboptimal solutions, and their robust implementation.
Open Access
Sensitivity minimization by strongly stabilizing controllers for a class of unstable time-delay systems
(Institute of Electrical and Electronics Engineers, 2009) Gumussoy, S.; Özbay, Hitay
Weighted sensitivity minimization is studied within the framework of strongly stabilizing (stable) Hinfin controller design for a class of infinite dimensional systems. This problem has been solved by Ganesh and Pearson, for finite dimensional plants using Nevanlinna-Pick interpolation. We extend their technique to a class of unstable time delay systems. Moreover, we illustrate suboptimal solutions, and their robust implementation.