Browsing by Author "Mahmoud M.S."

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Control of uncertain state-delay systems: Guaranteed cost approach
(Oxford Univ Press, Oxford, United Kingdom, 2001) Mahmoud M.S.; Department of Engineering; MSA University; Amer Street; Mesaha Square; Dokki; Egypt
In this paper, we address the problems of robust performance analysis and control synthesis for a class of linear continuous-time systems with parameter uncertainty and unknown state-delay. The parameter uncertainty is real time-varying norm-bounded and the state-delay is a constant within a prescribed interval. For the robust performance analysis problem, we adopt appropriate notions of robust stability independent of delay and delay dependent. In both cases, we show that the adopted notion guarantees an upper bound on a linear quadratic cost function. For the synthesis problem, we show that a robust state-feedback controller can be constructed to render the closed-loop system robustly stable while guaranteeing a prescribed level of performance. The developed results are expressed in terms of algebraic Riccati or linear matrix inequalities.
Guaranteed cost observer-based control of uncertain time-lag systems
(Elsevier Ltd, 2003) Mahmoud M.S.; Zribi M.; October University for Modern Science and Arts; Amer Street; Mesaha Square; Dokki-Giza; Egypt; Department of Electrical Engineering; College of Engineering and Petroleum; Kuwait University; P.O. Box 5969; 13060 Safat; Kuwait
This paper investigates the design of robust observer-based controllers for a class of uncertain linear time-lag systems. The uncertainties are assumed to be norm-bounded. We extend the previous results on quadratic-cost control to the case of observer-based control for uncertain systems with unknown state and input time-lags. By introducing an appropriate definition of quadratic stability for uncertain time-lag systems, it is shown that observer-based controllers can be constructed via solutions of linear-matrix inequalities. A simulation example is given to illustrate the theoretical developments. 2002 Elsevier Science Ltd. All rights reserved.
H?-filtering for a class of nonlinear time-delay systems
(2002) Mahmoud M.S.; Xie L.; Faculty of Engineering; MSA University; Amer Street; Mesaha Square; Dokki; Egypt; School of Electrical and Electronic Engineering; Nanyang Technological University; Nanyang Avenue; Singapore 639798; Singapore
In this paper, we consider the problem of robust H ?-filtering for a class of uncertain time-delay systems. This calss is nominally linear and has a known cone-bounded, state-dependent nonlinear term. The parametric uncertainty is real time-varying and the state-delay factor is unknown. We design a nonlinear estimator which renders the estimation error dynamics quadratically stable and provides a guaranteed H?-performance of the filtering error for all admissible uncertainties and unknown state-delay. � 2002 Taylor & Francis Ltd.
A nonlinear controller for offshore structures under wave excitations
(2001) Terro M.J.; Mahmoud M.S.; Abdel-Rohman M.; Department of Civil Engineering; Kuwait University; PO Box 5969; Safat-13060; Kuwait; Modern Sciences and Arts University; Amer Street; Dokki; Egypt
In this paper, a new feedback-control design is developed and applied to an offshore structure under wave excitation. The nonlinear Morison equation is employed to estimate the wave forces. The feedback-control design proceeds in two consecutive stages: a nominal stage based on linear quadratic theory for regulating a linear part of the system dynamics, and an adjustment stage in the form of a nonlinear controller with a tuning gain factor for accommodating the nonlinearities while maintaining the overall stability. A SIMULINK model is designed to simulate the response of a three-floor steel jacket platform example. Results of the simulation of this structure with and without feedback-control are discussed to demonstrate the effectiveness of this control method.
Passive control synthesis for uncertain systems with multiple-state delays
(2002) Mahmoud M.S.; Zribi M.; Faculty of Engineering; MSA University; Amer Street; Mesaha Square; Dokki; Egypt; Department of Electrical and Computer Engineering; Kuwait University; P.O. Box 5969; Safat 13060; Kuwait
In this paper, we investigate the robust passivity synthesis problem for a class of uncertain systems with multiple state delays. Both the delay-independent and the delay-dependent cases are treated. In each case, a sufficient condition for which the uncertain multi-state delay system is robustly stable and strictly passive (SP) for all admissible uncertainties is provided in terms of a linear matrix inequality. Then, we propose a dynamic feedback design methodology based on either state measurements or output measurements. For both types of controllers, it is proven that the closed-loop uncertain time-delay system is asymptotically stable and SP for all admissible uncertainties. A detailed simulation example is given to illustrate the theoretical developments. � 2002 Published by Elsevier Science Ltd.
Passivity Analysis and Synthesis for Uncertain Time-Delay Systems
(Taylor and Francis Inc., 2001) Mahmoud M.S.; Xie L.; Faculty of Engineering; MSA University; Amer Street; Mesaha Square; Dokki; Egypt; Sch. of Elec. and Electron. Eng.; Nanyang Technological University; Nanyang Avenue; Singapore 639798; Singapore
In this paper, we investigate the robust passivity analysis and synthesis problems for a class of uncertain time-delay systems. This class of systems arises in the modelling effort of studying water quality constituents in fresh stream. For the analysis problem, we derive a sufficient condition for which the uncertain time-delay system is robustly stable and strictly passive for all admissible uncertainties. The condition is given in terms of a linear matrix inequality. Both the delay-independent and delay-dependent cases are considered. For the synthesis problem, we propose an observer-based design method which guarantees that the closed-loop uncertain time-delay system is stable and strictly passive for all admissible uncertainties. Several examples are worked out to illustrate the developed theory.
Robust control of a class of nonlinear uncertain time-delay systems
(2002) Mahmoud M.S.; Zribi M.; MSA University; Amer Street; Mesaha Square; Dokki; Egypt; Department of Electrical and Computer Engineering; Kuwait University; PO Box 5969; Safat-13060; Kuwait
The robust ?? control problem of a class of uncertain nonlinear time-delay systems is considered in this paper. The parametric uncertainties are real time-varying and norm-bounded and the nonlinearities are state-dependent and cone-bounded. The delays are time-varying and bounded both in the state and at the input. We provide sufficient conditions for robust stability and robust state-feedback stabilization with disturbance attenuation. Then, we establish sufficient conditions for designing a linear dynamic observer-based controller which stabilizes the uncertain time-delay system and guarantees an ??-norm bound constraint on the disturbance attenuation for all admissible uncertainties and unknown delays. Several examples are simulated to illustrate the developed theory. � 2002 Taylor & Francis Ltd.
Robust H filtering for a class of linear parameter-varying systems
(2001) Mahmoud M.S.; Boujarwah A.S.; MSA University; Dokki; Egypt; Department of Computer Engineering; Kuwait University; Safat-13060; Kuwait
In this paper, we investigate the problem of H? filtering for a class of linear parameter-varying (LPV) systems in which the state-space matrices depend affinely on time-varying parameters. We employ the notion of affine quadratic stability using parameter-dependent Lyapunov functionals. We develop a linear parameter-dependent filter such that the estimation erorr is affinely quadratically stable with a prescribed performance measure. It is established that the solvability conditions can be expressed by linear matrix inequalities which are then evaluated at the extreme points of the admissible parameter set. Simulation results of a typical example are presented.
Robust Kalman filtering for discrete state-delay systems
(IEE, Stevenage, United Kingdom, 2000) Mahmoud M.S.; Xie L.; Soh Y.C.; Department of Electrical and Computer Engineering; Kuwait University; Kuwait; Department of Engineering; MSA University; Amer St.; Mesaha Square; Dokki; Egypt; School of Electrical and Electronic Engineering; Nanyang Technological University; Nanyang Avenue; Singapore 639798; Singapore
A robust estimator design methodology has been developed for a class of linear uncertain discrete-time systems. It extends the Kalman filter to the case in which the underlying system is subject to norm-bounded uncertainties and constant state delay. A linear state estimator is constructed via a systematic procedure such that the estimation error covariance is guaranteed to lie within a certain bound for all admissible uncertainties. The solution is given in terms of two Riccati equations involving scaling parameters. A numerical example is provided to illustrate the theory.
Robustness of high-gain observer-based nonlinear controllers to unmodeled actuators and sensors
(2002) Mahmoud M.S.; Khalil H.K.; Dean of Engineering; MSA University; Amer Street; Mesaha Square; Dokki; Egypt; Department of Electrical and Computer Engineering; Michigan State University; East Lansing; MI 48824-1226; United States; Faculty of Engineering; Arab Academy for Science and Technology; PO Box 2033; Cairo; Egypt
We investigate the robust stabilization of a class of nonlinear systems in the presence of unmodeled actuator and sensor dynamics. We show that, given any globally bounded stabilizing state-feedback control, the closed-loop system performance can be recovered by a sufficiently fast high-gain observer in the presence of sufficiently fast actuator and sensor dynamics. The performance recovery includes recovery of exponential stability of the origin, the region of attraction and state trajectories. Moreover, it is shown that the sensor dynamics should be sufficiently faster than the observer dynamics; a restriction that does not apply to the actuator dynamics. � 2001 Elsevier Science Ltd. All rights reserved.