Browsing by Author "Gündeş, A. N."

Now showing 1 - 17 of 17

Open Access
Approximations in compensator design: a duality
(The Institution of Engineering and Technology (IET), 2002) Özgüler, A. B.; Gündeş, A. N.
In classical controller design, poles fat to the left of dominant poles are sometimes ignored. Similarly, in some proportional-integral compensation techniques, the controller zero is placed close to the origin and design proceeds after cancelling this zero with a pole at the origin. A rigorous basis for these methods is provided, it being shown that there is a duality between the two.
Open Access
Controller design for delay margin improvement
(IEEE, 2019) Gündeş, A. N.; Özbay, Hitay
Two important design objectives in feedback control are steady-state error minimization and delay margin maximization. In general these two objectives work against each other. This paper starts with an initial controller designed to satisfy the steady-state error requirement, and shows how one can modify it to improve the delay margin without changing the steady-state error
Open Access
Controller design for plants with internal delayed feedback
(Institute of Electrical and Electronics Engineers, 2022-05-01) Gündeş, A. N.; Özbay, Hitay
A special class of retarded and neutral time delay systems is considered. These are plants with internal delayed feedback, and they may have finitely many or infinitely many unstable poles. Stabilizing controllers are obtained from a particular interpolation. A parametrization of all stabilizing integral-action controllers is obtained. Examples are given to illustrate this simple design procedure and its robustness properties for various uncertainties.
Open Access
Controller redesign for delay margin improvement
(Elsevier, 2020-01) Gündeş, A. N.; Özbay, Hitay
Two important design objectives in feedback control are steady-state error minimization and delaymargin maximization. For many practical systems it is not possible to have infinite delay margin andzero steady state error for unit step reference input. This paper proposes a re-design method forcontrollers initially designed to satisfy the steady-state error requirement. The objective is to makestructural changes in the controller so that a lower bound of the delay margin is improved withoutaffecting the steady-state error. The order of the new controller is (ν+1) higher than the order of theoriginal controller, whereνis the number of unstable poles of the plant.
Open Access
Integral action controllers for systems with time delays
(Springer, 2009) Özbay, Hitay; Gündeş, A. N.
Consider a stabilizing controller C 1 for a given plant P. If C 1 and P do not have any zeros at the origin, then one can use a cascade connected PI (proportional plus integral) controller C pi with C 1 and keep the feedback system stable. In this work we examine the allowable range of the integral action gain in C pi , and discuss how C 1 should be chosen to maximize this range for systems with time delays.
Open Access
Low order controller design for systems with time delays
(2011-12) Gündeş, A. N.; Özbay, Hitay
Finite-dimensional controller synthesis methods are developed for some classes of linear, time-invariant, single-input single-output, or multi-input multi-output systems, which are subject to time delays. The proposed synthesis procedures give low-order stabilizing controllers that also achieve integral-action so that constant reference inputs are tracked asymptotically with zero steady-state error. © 2011 IEEE.
Open Access
PID and low-order controller design for guaranteed delay margin and pole placement
(John Wiley & Sons Ltd., 2021-04-03) Özbay, Hitay; Gündeş, A. N.
This article provides a simple low-order controller design method (including PID controllers as special cases) for a class of unstable systems. First, PID controller design is considered for systems with two unstable poles and pole placement and delay margin issues are discussed. Then, a chain of integrators is considered with arbitrary stable dynamics in cascade. For a given desired minimum delay margin for this class of plants, a PID and low-order controller design method is obtained in terms of an inequality constraint on the sum of k of the desired closed-loop poles, where k is number of the integrators in the open-loop transfer function.
Open Access
PID controller synthesis for a class of unstable MIMO plants with I/O delays
(Elsevier BV, 2007-01) Gündeş, A. N.; Özbay, Hitay; Özgüler, A. B.
Conditions are presented for closed-loop stabilizability of linear time-invariant (LTI) multi-input, multi-output (MIMO) plants with I/O delays (time delays in the input and/or output channels) using PID (Proportional + Integral + Derivative) controllers. We show that systems with at most two unstable poles can be stabilized by PID controllers provided a small gain condition is satisfied. For systems with only one unstable pole, this condition is equivalent to having sufficiently small delay-unstable pole product. Our method of synthesis of such controllers identify some free parameters that can be used to satisfy further design criteria than stability.
Open Access
PID controller synthesis for a class of unstable MIMO plants with I/O delays
(Elsevier, 2006-07) Gündeş, A. N.; Özbay, Hitay; Özgüler, A. Bülent
Conditions are presented for closed-loop stabilizability of linear time-invariant (LTI) multi-input, multi-output (MIMO) plants with I/O delays (time delays in the input and/or output channels) using PID (Proportional + Integral + Derivative) controllers. We show that systems with at most two unstable poles can be stabilized by PID controllers provided a small gain condition is satisfied. For systems with only one unstable pole, this condition is equivalent to having sufficiently small delay-unstable pole product. Our method of synthesis of such controllers identify some free parameters that can be used to satisfy further design criteria than stability. Copyright © 2006 IFAC.
Open Access
PID stabilization of MIMO plants
(Institute of Electrical and Electronics Engineers, 2007) Gündeş, A. N.; Özgüler, A. B.
Closed-loop stabilization using proportional-integral-derivative (PID) controllers is investigated for linear multiple-input-multiple-output (MIMO) plants. General necessary conditions for existence of PID-controllers are derived. Several plant classes that admit PID-controllers are explicitly described. Plants with only one or two unstable zeros at or "close"to the origin (alternatively, at or close to infinity) as well as plants with only one or two unstable poles which are at or close to origin are among these classes. Systematic PID-controller synthesis procedures are developed for these classes of plants.
Open Access
Plant Order Reduction for Controller Design
(IEEE, 2003-06) Özgüler, A. Bülent; Gündeş, A. N.
Two dual methods of plant order reduction for controller design are proposed for linear, time-invariant, multi-input multi-output systems. The model reduction methods are tailored towards closed-loop stability and performance and they yield estimates for the stability robustness and performance of the final design. They can be considered as formalizations of two classical heuristic model reduction techniques: One method neglects a plant-pole sufficiently far to the left of dominant poles and the other cancels a sufficiently small stable plant-zero with a pole at the origin.
Open Access
Reliable decentralised control of delayed MIMO plants
(Taylor & Francis, 2010-03) Gündeş, A. N.; Özbay, Hitay
Reliable decentralised proportional-integral-derivative controller synthesis methods are presented for closed-loop stabilisation of linear time-invariant plants with two multi-input, multi-output (MIMO) channels subject to time delays. The finite-dimensional part of plants in the classes considered here are either stable or they have at most two poles in the unstable region. Closed-loop stability is maintained with only one of the two controllers when the other controller is turned off and taken out of service.
Open Access
Resilient PI and PD controller designs for a class of unstable plants with I/O delay
(Applied Mathematics Scientific Research Institute, 2007) Özbay, Hitay; Gündeş, A. N.
In [8] we obtained stabilizing PID controllers for a class of MIMO unstable plants with time delays in the input and output channels (I/O delays). Using this approach, for plants with one unstable pole, we investigate resilient PI and PD controllers. Specifically, for PD controllers, optimal derivative action gain is determined to maximize the allowable controller gain interval. For PI controllers, optimal proportional gain is determined to maximize a lower bound of the largest allowable integral action gain
Open Access
Resilient PI and PD controllers for a class of unstable MIMO plants with I/O delays
(Elsevier, 2006-07) Özbay, Hitay; Gündeş, A. N.
Recently (Gündeş et al., 2006) obtained stabilizing PID controllers for a class of MIMO unstable plants with time delays in the input and output channels (I/O delays). Using this approach, for plants with one unstable pole, we investigate resilient PI and PD controllers. Specifically, for PD controllers, optimal derivative action gain is determined to maximize a lower bound of the largest allowable controller gain. For PI controllers, optimal proportional gain is determined to maximize a lower bound of the largest allowable integral action gain. Copyright © 2006 IFAC.
Open Access
Robust controller design based on reduced order plants
(Taylor & Francis, 2006) Özgüler, A. B.; Gündeş, A. N.
Two dual controller design methods are proposed for linear, time-invariant, multi-input multi-output systems, where designs based on a reduced order plant robustly stabilizer higher order plants with additional poles or zeros in the stable region. The additional poles (or zeros) are considered as multiplicative perturbations of the reduced plant. The methods are tailored towards closed-loop stability and performance and they yield estimates for the stability robustness and performance of the final design. They can be considered as formalizations of two classical heuristic model reduction techniques. One method neglects a plant-pole sufficiently far to the left of dominant poles and the other cancels a sufficiently small stable plant-zero with a pole at the origin.
Open Access
Strong stabilization of high order plants
(Elsevier, 2022-06) Özbay, Hitay; Gündeş, A. N.
Designing stable feedback controllers that stabilize a given plant, known as strong stabilization, has been explored in the literature by using several algorithmic construction procedures. Many of these methods rely on step-by-step interpolation or solving an auxiliary H∞ control problem, or a set of LMIs. This paper gives an explicit construction of simple strongly stabilizing controllers for plants that have restrictive number of zeros in the extended right half plane, without any restrictions on the number or location of poles. A similar construction is also developed for the case of plants with restrictions on the poles. The order of the proposed stable controllers is at most one less than that of the plant, and they are computed by selecting just a few positive parameters determined from the H∞ norms of certain transfer functions.
Open Access
Two-channel decentralized integral-action controller design
(IEEE, 2002) Gündeş, A. N.; Özgüler, A. B.
We propose a systematic controller design method that provides integral-action in linear time-invariant two-channel decentralized control systems. Each channel of the plant is single-input-single-output, with any number of poles at the origin but no other poles in the instability region. An explicit parametrization of all decentralized stabilizing controllers incorporating the integral-action requirement is provided for this special case of plants. The main result is a design methodology that constructs simple low-order controllers in the cascaded form of proportional-integral and first-order blocks.