Yazar "Tan, N" seçeneğine göre listele
Listeleniyor 1 - 14 / 14
Sayfa Başına Sonuç
Sıralama seçenekleri
Öğe Analysis of uncertain transfer functions in factored form(Ieee, 2002) Tan, N; Atherton, DPIt is well known that the mathematical representations of real physical systems suffer from parametric uncertainty due to modelling errors, nonlinearities, manufacturing tolerances and operating conditions. Therefore, it is very important to take parametric variations into account while analysing and designing control systems. This paper presents some results for computation of the robust stability of control systems with an uncertain transfer function in factored form which is the form of most real physical systems. The technique presented uses the narrowest possible Bode envelopes, which are constructed from new results obtained by the authors, and therefore it can be used for the stability analysis and design of robust controllers to meet certain closed loop stability and performance requirements for such systems less conservatively than other methods. The importance of the method for the computation of stability is discussed and illustrative examples are given.Öğe Computation of stabilizing Lag/Lead controller parameters(Pergamon-Elsevier Science Ltd, 2003) Tan, NOne of the central problems in control theory relates to the design of controllers for stabilization of systems. The paper deals with the problem of computing all stabilizing values of the parameters of Lag/ Lead controllers for linear time-invariant plant stabilization. It is well known that linear controllers of Lag/ Lead type are still widely used in many industrial applications. In this paper, an extension of a new approach to feedback stabilization based on the Hermite-Biehler theorem to the Lag/Lead controller structure is given. In addition, the problem of stabilization of uncertain systems defined by an interval plant is studied using the Kharitonov and the Hermite-Biehler theorems. The proposed method is analytical and it can be applied successfully using today's advanced computer technology. Examples are included to illustrate the method presented. (C) 2003 Elsevier Ltd. All rights reserved.Öğe Computation of stabilizing PI and PID controllers(Ieee, 2003) Tan, N; Kaya, I; Atherton, DPIn this paper, a simple method for the calculation of stabilizing PI controllers is given. The proposed method is based on plotting the stability boundary locus in the (k(p),k(i))-plane and then computing stabilizing values of the parameters of a PI controller. The technique presented does not require sweeping over the parameters and also does not need linear programming to solve a set of inequalities. Thus it offers several important advantages over existing results obtained in this direction. Beyond stabilization, the method is used to shift all poles to a shifted half plane that guarantees a specified settling time of response. Furthermore, computation of stabilizing PI controllers which achieve user specified gain and phase margins is studied. It is also shown via an example that the stabilizing region in the (k(p), k(i)) -plane is not always a convex set. The proposed method is also used to design PID controllers. The limiting values of a PID controller which stabilize a given system are obtained in the (k(p), k(i)) -plane, (k(p), k(d)) -plane and (k(i), k(d))-plane. Examples are given to show the benefit of the method presented.Öğe Computation of stabilizing PI and PID controllers for processes with time delay(Elsevier Science Inc, 2005) Tan, NIn this paper, a new method for the computation of all stabilizing PI controllers for processes with time delay is given. The proposed method is based on plotting the stability boundary locus in the (k(p),k(i)) plane and then computing the stabilizing values of the parameters of a PI controller for a given time delay system. The technique presented does not need to use Pade approximation and does not require sweeping over the parameters and also does not use linear programming to solve a set of inequalities. Thus it offers several important advantages over existing results obtained in this direction. Beyond stabilization, the method is used to compute stabilizing PI controllers which achieve user specified gain and phase margins. The proposed method is also used to design PID controllers for control systems with time delay. The limiting values of a PID controller which stabilize a given system with time delay are obtained in the (k(p),k(i)) plane, (k(p),k(d)) plane, and (k(i),k(d)) plane. Examples are given to show the benefits of the method presented. (c) 2004 ISA-The Instrumentation, Systems, and Automation Society.Öğe Computation of stabilizing PI parameters for vehicle suspension system using the stability boundary locus(Ieee, 2004) Yeroglu, C; Tan, NThis paper presents a new approach for the design of vehicle suspension system with the goal to maximise passenger comfort by minimising vertical acceleration. For this reason PI controlled suspension system, at which controller parameters are computed by using the stability boundary locus, is proposed. In order to select the best parameters in the stability region obtained using the stability boundary locus, the phase margin and the gain margin of system is studied and step response of the system is evaluated. The proposed method offers several important advantages over existing results since it is simple to apply and does not need to sweep over the parameters.Öğe Computation of the frequency response of multilinear affine systems(Ieee-Inst Electrical Electronics Engineers Inc, 2002) Tan, NThis note deals with the problem of computing the frequency response of an uncertain transfer function whose numerator and denominator polynomials are multiples of independent uncertain polynomials of the form P(s, q) = l(0) (q) + l(1) (q) s + ... + l(n) (q) s(n) whose coefficients depend linearly on q = [q(1), q(2),...,q(q)](T) and the uncertainty box is Q = {q: q(i) is an element of [q(i), q(i)], i = 1, 2,..,q}. Using the geometric structure of the value set-of P(s, cl), a powerful edge elimination procedure is proposed for computing the Bode, Nyquist, and Nichols envelopes of these uncertain systems. A numerical example is included to illustrate the benefit of the method presented.Öğe Extensions of classical methods to uncertain systems: An educational perspective(Pergamon-Elsevier Science Ltd, 2001) Tan, N; Atherton, DPMuch of the material being taught in a first course on control appears to have changed little over the last two decades. Whilst the basic theories on classical control in textbooks remain unchanged, there have been many new developments in the field of control theory in recent years. One such topic is the relatively recent development in methods to analyse systems with parametric uncertainty. The purpose of this paper is to show how some of these methods can be easily introduced into a typical first course on classical control. Copyright (C) 2000 IFAC.Öğe New approach to assessing the effects of parametric variations in feedback loops(Iee-Inst Elec Eng, 2003) Tan, N; Atherton, DPA method for the computation of the magnitude and phase envelopes of uncertain transfer functions is presented. The idea is to factor the transfer function into its real and complex pair roots and find the maximum and minimum magnitudes of the gain and phase of each factor. The Bode envelopes of the given uncertain system are then found from those of the individual factors. This approach, which is different from those based on the interval polynomial method of Kharitonov, has the major advantage that the representation is more applicable to practical situations where typically the coefficients of the various factored terms relate to physical parameters of a mathematical model. Further, the method results in the narrowest Bode envelopes and therefore can yield improved controller designs. The describing function analysis and the absolute stability problem of nonlinear systems with variable plant parameters are also studied. An approach which enables one to predict the existence of limit cycles in a control system which simultaneously contains nonlinearities and parametric uncertainties is given. The proposed method makes use of the popular describing function technique and these narrowest possible Bode envelopes of linear uncertain transfer functions in factored form. The technique can be used to cover the cases of linear elements, which have a multilinear or nonlinear uncertainty structure, and a nonlinear element with or without memory. New formulations of the circle and off-axis circle criteria are given for use with Bode diagrams so that the absolute stability of nonlinear systems with variable plant parameters can be studied. Examples are given to show how the proposed method can be used to assess the effects of parametric variations in feedback loops.Öğe A new approach to the stability of nonlinear systems with uncertain plant parameters(Ieee, 2003) Tan, N; Atherton, DPThe purpose of this paper is to study the problem of the stability of nonlinear systems with variable plant parameters. A new approach which enables one to predict the existence of limit cycles in a control system which simultaneously contains nonlinearities and parametric uncertainties is given. The proposed method makes use of the popular describing function technique and the Bode envelope of linear uncertain transfer functions. The narrowest possible Bode envelopes are obtained from new results obtained by the authors where the plant transfer function is taken in factored form. The technique can be used to cover the cases of linear elements, which have multilinear or nonlinear uncertainty structure, and a nonlinear element with or without memory. Examples are given to show how the proposed method can be used to assess the stability of nonlinear systems with uncertain plant parameters.Öğe A refinement procedure for PID controllers(Springer, 2006) Kaya, I; Tan, N; Atherton, DPProportional-Integral-Derivative (PID) controllers are still extensively used in industrial systems. In the literature, many publications can be found considering PID controller design for processes with resonances, integrators and unstable transfer functions. However, due to structural limitations of PID controllers, generally, a good closed-loop performance cannot be achieved with a PID, for controlling the aforementioned processes, and usually a step response with a high overshoot and oscillation is obtained. PI-PD controllers provide very satisfactory closed-loop performances in the case of controlling processes with resonances, integrators and unstable transfer functions. This paper introduces a simple approach to get parameters of a PI-PD controller from parameters of a PID controller so that a good closed-loop system performance can be realized. Extensive simulation examples are given to illustrate the value of the approach proposed.Öğe Robust phase margin, robust gain margin and Nyquist envelope of an interval plant family(Pergamon-Elsevier Science Ltd, 2004) Tan, NIn this paper, robust gain margin, robust phase margin and Nyquist envelope of interval systems are studied. It is first presented that the robust gain and phase margins of a control system with an interval plant family are achieved at one of the Kharitonov plant by using the interlacing theorem and virtual compensator concept. Then, using the generalized Hermite-Biehler theorem, it is shown that the outer boundary of the Nyquist envelope of a stable interval plant is covered by the Nyquist plots of the 16 Kharitonov plants family. Examples are given to illustrate the method presented. (C) 2003 Elsevier Ltd. All rights reserved.Öğe Robustness analysis of control systems with mixed perturbations(Sage Publications Ltd, 2003) Tan, N; Atherton, DPThe paper considers control systems with parametric as well as unstructured uncertainty. Parametric uncertainty is modelled by a transfer function whose numerator and denominator polynomials are independent uncertain polynomials of the form of P (s, q) = l(0) (q) + l(1) (q) s +... + l(n) (q)s(n) where the coefficients depend linearly on q = [q(1), q(2),., q(q)](T) and the uncertainty box is Q = {q: q(i)is an element of[(q(i)) under bar, (q(i)) over bar], i = 1, 2,., q}. The unstructured uncertainty is modelled as H-infinity norm bounded perturbations and perturbations consisting of a family of nonlinear sector bounded feedback gains. Using the geometric structure of the value set of P(s, q), some results are presented for determination of the robust small gain theorem, robust performance, strict positive realness and absolute stability problem of control systems with parametric as well as unstructured uncertainty. Numerical examples are given to illustrate application of the proposed methods.Öğe A simple procedure for improving performance of PID controllers(Ieee, 2003) Kaya, I; Tan, N; Atherton, DPProportional-Integral-Derivative (PID) controllers are still extensively used in industrial systems. In the literature, many publications can be found considering PID controller design for processes with resonances, integrators and unstable transfer functions However, due to structural limitations of PID controllers, good closed loop performance cannot be achieved with a PID controller for the aforementioned processes and usually a step response with a high overshoot and oscillation is obtained. The PI-PD controller has been shown to provide very satisfactory closed loop performance for controlling processes with resonances, integrators and unstable transfer functions. This paper introduces a simple approach to get parameters of a PI-PD controller from parameters of a PID controller so that a good closed loop system performance is obtained. Extensive simulation examples are given to illustrate the value of the approach proposed.Öğe A user friendly toolbox for the analysis of interval systems(Pergamon-Elsevier Science Ltd, 2000) Tan, N; Atherton, DPMost of the methods which are used for the analysis and design of systems with parametric uncertainty require extensive computations. Therefore, it is value to develop computer programs which enable one to deal with uncertain systems in an easy way. This paper describes a user friendly software package(AISTK-Analysis of Interval Systems Toolkit). Algorithms have been developed in the MATLAB environment by using the Kharitonov theorem and related approaches. The objective in developing AISTK was to gather these algorithms under a toolkit and make them easily usable by students or other users. Copyright (C) 2000 IFAC.
