Bita Labibi - Academia.edu (original) (raw)

Papers by Bita Labibi

Time-delay in dynamical systems is often a source of instability and poor performance which prese... more Time-delay in dynamical systems is often a source of instability and poor performance which presents in many applications. This paper deals with the robust control problem for class of uncertain linear neutral systems with multiple state and state derivatives delays. The parametric uncertainties are time varying and unknown but norm bounded. In this paper by introducing a new Lyapunov functional, the stability condition is extended to structured uncertain neutral systems. so new ( Descriptor ) model transformation and a corresponding Lyapunov functional are introduced for stability analysis of systems with discrete and distributed multiple delay.Sufficient conditions are given in terms of linear matrix inequalities ( LMI ) and refer to neutral systems with discrete and distributed delays. Based on the stability condition, designing delay dependent / independent state feedback control is formulated. Solving the LMI problems, a robust memoryless state feedback control law is designed ...

International Journal of Systems Science, 2014

ABSTRACT In this paper a new method for robust decentralised control of large-scale systems using... more ABSTRACT In this paper a new method for robust decentralised control of large-scale systems using quantitative feedback theory (QFT) is suggested. For a given large-scale system an equivalent descriptor system is defined. Using this representation, closed-loop diagonal dominance sufficient conditions over the uncertainty space are derived. It is shown by appropriately choosing output disturbance rejection model in designing QFT controller for each isolated subsystem, these conditions are achieved. Then a single-loop quantitative feedback design scheme is applied to solve the resulting series of individual loops to guarantee the satisfaction of predefined MIMO quantitative specifications.

2006 14th Mediterranean Conference on Control and Automation, 2006

This paper discusses the design of a cascade controller for active suspension systems, to improve... more This paper discusses the design of a cascade controller for active suspension systems, to improve ride quality. In order to do this, in the main loop, a model reference adaptive controller is designed to attenuate disturbances due to rough roads. An internal loop provides the required control force for the main controller. The closed loop system has desired robust stability and performance in the presence of uncertainty due to time varying parameters and nonlinear dynamics of the actuator. The simulation results show the effectiveness of the suggested method in increasing ride comfort and safety while constrains of suspension system maneuverability is also satisfied

IEEE Transactions on Circuits and Systems II: Express Briefs, 2006

In this paper a simple approach is proposed for decentralized control of linear large-scale syste... more In this paper a simple approach is proposed for decentralized control of linear large-scale systems. Sufficient conditions for diagonal dominance of closed-loop largescale systems are derived. Based on these conditions, the interactions between the subsystems can be considered as external disturbances for each isolated subsystem. Then a previously proposed approach is used to attenuate disturbances via dynamic output compensators based on complete parametric eigenstructure assignment. Through attenuation of the disturbances, the closed-loop poles of the overall system are assigned to the desirable region, by assigning the eigenstructure of each isolated subsystem appropriately. An example is given to show the effectiveness of the proposed method.

2003 European Control Conference (ECC), 2003

The existing methods of decentralized control suffer from two major restrictions. First, almost a... more The existing methods of decentralized control suffer from two major restrictions. First, almost all of them hinge on Lyapunov's method, and second, they do not address the problem of performance robustness. A novel methodology to overcome the above defects is presented in this paper. Central to this approach is the notion of a finite-spectrum-equivalent descriptor system in the input-output decentralized form. By way of this notion, a new formulation of the interaction which introduces some degrees of freedom into the design procedure is offered. The main result, i.e. a sufficient condition for decentralized performance stabilization in a desirable performance region and maximal robustness to unstructured uncertainties in the controller and plant parameters, nevertheless, is in terms of regular systems. Based on minimal sensitivity design of isolated subsystems via eigenstructure assignment, an analytic method for the satisfaction of the aforementioned sufficient condition is also presented.

Proceedings of the 2000 American Control Conference. ACC (IEEE Cat. No.00CH36334), 2000

ABSTRACT The problem of achieving stability and certain H∞ performance objective for a large-scal... more ABSTRACT The problem of achieving stability and certain H∞ performance objective for a large-scale system by a decentralized feedback law is considered. It is shown in order to reduce the sensitivity to the interactions, the states of the other subsystems can be considered as external disturbances for each subsystem. An appropriate H∞ controller is designed for each subsystem. Solving H∞ problems for the subsystems, the sensitivity to the interactions is reduced and the performance problem which is formulated as the standard weighted mixed sensitivity H∞ problem, is solved. Sufficient conditions are derived when satisfied to assure the overall stability

SMC 2000 Conference Proceedings. 2000 IEEE International Conference on Systems, Man and Cybernetics. 'Cybernetics Evolving to Systems, Humans, Organizations, and their Complex Interactions' (Cat. No.00CH37166), 2000

ABSTRACT A novel method for decentralized stabilization of a large-scale system in general form i... more ABSTRACT A novel method for decentralized stabilization of a large-scale system in general form is presented. An appropriate descriptor system is defined for a large-scale system, such that the new system is in input decentralized form. Sufficient conditions for stability of the closed-loop system are introduced. By appropriately assigning the eigenstructure of each isolated subsystem, these conditions are satisfied. This is accomplished by using the method suggested by R.J. Patton and G.P. Liu (1994), such that the effects of the interconnections between the subsystems are minimized via the combination of genetic algorithms and gradient based optimization

ABSTRACT The problem of achieving stability and block-diagonal dominance for linear large-scale s... more ABSTRACT The problem of achieving stability and block-diagonal dominance for linear large-scale systems by decentralized feedback is considered. Sufficient conditions for stability and block-diagonal dominance of the closed-loop system are introduced. By appropriately assigning the eigenstructure of each isolated subsystem via output feedback or state feedback, these conditions are satisfied. This can also be accomplished by using the method suggested by R.J. Patton and G.P. Liu (1994), such that the effects of the interconnections between the subsystems are minimized via the combination of genetic algorithms and gradient-based optimization

Proceedings of the 44th IEEE Conference on Decision and Control

This paper presents a novel approach to solve the MIMO-QFT problem for tracking error specificati... more This paper presents a novel approach to solve the MIMO-QFT problem for tracking error specification through a method of obtaining exact bounds for the design of individual elements of pre-filter. The paper specifically deals with the appropriate transformation of the MIMO system to the equivalent SISO problems, which allows easy design to find the feedback compensator and pre-filter. A linearized model of quadruple-tank process is used to show the effectiveness of the proposed method.

Systems & Control Letters, 2002

... a Iranian Research Organization for Science and Technology, 76175-191, Kerman, Iran. bUnivers... more ... a Iranian Research Organization for Science and Technology, 76175-191, Kerman, Iran. bUniversity of Bremen, Bremen, Germany. c KN Toosi University of Technology, Tehran, Iran. dUniversity of Tehran, Tehran, Iran. Received 16 October 2000; revised 1 April 2002. ...

International Journal of Systems Science, 2003

In this paper, a method for design of linear decentralized robust controllers for a class of unce... more In this paper, a method for design of linear decentralized robust controllers for a class of uncertain large-scale systems in general form is presented. For a given large-scale system, an equivalent descriptor system in input–output decentralized form is defined. Using this representation, closed-loop diagonal dominance sufficient conditions are derived. It is shown that by appropriately minimizing the weighted sensitivity function of each isolated subsystem, these conditions are achieved. Solving the appropriately defined H∞ local problem for each isolated uncertain subsystem, the interactions between the subsystems are reduced, and the overall stability and robust performance are achieved in spite of uncertainties. The designs are illustrated by a practical example.

Intelligent Automation & Soft Computing, 2003

A novel approach to the design of decentralized controllers for large-scale systems by dynamic/st... more A novel approach to the design of decentralized controllers for large-scale systems by dynamic/static output/state feedback is presented. A new formulation of the interaction which introduces some degrees of freedom into the design procedure is offered. Sufficient conditions for exponential stability with desirable rate of decay and maximal robustness to unstructured uncertainties in the controller and plant parameters are established. The derived conditions are generic, applicable to nonsquare and nonminimum-phase systems, and independent of the number of system states, inputs and outputs. Based on minimal sensitivity design of isolated subsystems, an analytical method for the satisfaction of the aforementioned sufficient conditions is presented. To this end, through eigenstructure assignment, compact-form sufficient conditions for minimal sensitivity are derived. Illustrative examples are presented to demonstrate the effectiveness of the proposed methodology. Genetic algorithm is employed in the simulations.