Majda Ltaief

• École Nationale d'Ingénieurs de Gabès

In this work, the authors propose an analytical and systematic technique to represent the discrete nonlinear singularly perturbed system (SPS) by a coupled state multimodel (MM). This approach is realized without loss of information. This strategy can be applicable to any order SPSs. Another significant characteristic of this technique is to choose...

This paper presents a novel approach to deal with ummeausrable premise variables (UMPVs) in observer design for discrete non linear singularly perturbed systems (DNSPSs). The considered system is represented by a coupled state multi model (MM) with UMPVs. The proposed approach consists to immerse the DNSPSs with UMPVs in new representation depend o...

This paper treats the observability bound problem of discrete-time linear multivariable singularly perturbed system (SPS). Using appropriate Lyapunov functionals, satisfactory conditions formulated in term of Linear Matrix Inequalities (LMIs) are elaborated to analyse the asymptotic stability of the system in one hand and in the other hand to prove...

This article deals with the observability bound problem of a discrete-time nonlinear singularly perturbed systems (SPSs) subject to disturbances and noises. This nonlinear SPS is represented by a coupled state multimodel (MM) with unmeasurable premise variables. A [Formula: see text] proportional-integral multiobserver ([Formula: see text] PI multi...

Many control and observability theories for singularly perturbed systems require the full knowledge of system model parameters exceptionally if the system is considered as black box. To overcome this problem and to obtain an accurate and faithful model, this paper describes a new identification method for discrete-time nonlinear singularly perturbe...

In this paper we deal with a control scheme based on Multi-Smith Predictor for the compensation of systems with time-varying parameters and/or time delay. In fact, the study of Adaptive Smith Predictor in presence of varying parameters and time delay was evoked. A high variation of time delay leads to a degradation in closed-loop system performance...

In this paper, the problems of asymptotic stability and stabilization for linear discrete singularly perturbed systems (SPS) with time delay are investigated. First, using an appropriate Lyapunov functional, new Linear Matrix Inequalities (LMIs) are proposed to analyse the asymptotic stability of discrete SPS with time delay. Delaydependent stabili...

This article investigates the problem of state feedback stabilisation for discrete nonlinear singularly perturbed system with time-delay which is represented by a coupled multimodel. Based on an appropriate Lyapunov function, new sufficient conditions are given as a set of Linear Matrix Inequalities (LMIs) that are used to get the gains of controll...

Harmonic disturbance rejection is an important field of control theory and applications. In this paper a discrete first and second order sliding mode control for multivariable systems are investigated. The necessary conditions of harmonic disturbances rejection using first and second order sliding mode control laws are elaborated. In order to impro...

The multimodel approach is a powerful and practical tool to deal with analysis, modeling, observation, emulation and control of complex systems. In the modeling framework, we propose in this paper a new method for optimal systematic determination of models’ base for multimodel representation. This method is based on the classification of data set p...

In this work, a nonstationary sinusoidal unknown inputs multiobserver is proposed for discrete-time nonlinear systems represented by a decoupled multimodel. The existence conditions of this type of multiobserver will be addressed and a new strategy allowing the minimization of the impact of nonstationary sinusoidal unknown inputs on the state estim...

Owing to its potential for real applications, many researchers have studied the problem of modelling and control of time-varying delay systems. In this paper, we propose a new strategy called multi-delay approach for modelling and control of these systems. In this new strategy, the time-varying delay systems are modelled by a multi-delay model repr...

In this paper, we apply a hierarchical identification principle to identify simultaneously the unknown time delay and dynamic parameters of discrete-time delay systems. In our approach, we separate the nonlinear cost function into two simple cost functions and present a gradient iterative algorithm for estimating directly the time delay and the par...

In this paper, we apply a hierarchical identification principle to identify simultaneously the unknown time delay and dynamic parameters of discrete-time delay systems. In our approach, we separate the nonlinear cost function into two simple cost functions and present a gradient iterative algorithm for estimating directly the time delay and the par...

This paper suggests a new approach for simultaneous recursive identification of an unknown time delay and dynamic parameters of discrete-time delay systems. The proposed algorithm is based on a new formulations allowing to admit the unknown time delay in the parameter vector. The recursive least-squares method is then used to solve the obtained sys...

A new algorithm for simultaneous online identification of unknown time delay and parameters of discrete-time delay systems is proposed in this paper. This algorithm consists in constructing a linear-parameters formulation and using the recursive least squares approach to solve the obtained system. Simulation example and experimental test results ar...

In this paper, the problem of identification of time delay systems is addressed. This problem involves both the estimation of the dynamic parameters and the identification of the time delay. In fact, we propose a gradient based iterative algorithm for time delay discrete systems using the hierarchical identification principle. This method consists...

In this paper, we propose a new adaptive control law with Q-parametrization for discrete multi-input multi-output systems subjected to sinusoidal disturbances with time-varying frequency. The rejection of sinusoidal disturbances with known frequency is obtained using partial state reference model control with Youla-Kucera parametrization. However,...

This work addresses the problem of the identification of time delay systems. Firstly, we have considered the problem of simultaneous identification of the time delay and dynamic parameters of monovariable time delay discrete systems described by transfer function representation. Indeed, we have proposed a new formulation of the problem allowing to...

Modeling the discrete-time systems with time varying delay had several difficulties, such as, the determination of an adequate model describing the real output evolution. Also, controlling such systems is another problem to be resolved. In this paper, we propose a Multi-Structure approach for modeling and controlling discrete-time systems with time...

In this paper we deal with a control scheme based on Multi-Smith Predictor for the compensation of systems with time-varying parameters and/or time delay. In fact, the study of Adaptive Smith Predictor in presence of varying parameters and time delay was evoked. A high variation of time delay leads to a degradation in closed-loop system performance...

This paper addresses the problem of simultaneous identification of linear discrete time delay multivariable systems. This problem involves both the estimation of the time delays and the dynamic parameters matrices. In fact, we suggest a new formulation of this problem allowing defining the time delay and the dynamic parameters in the same estimated...

A new approach for simultaneous online identification of unknown time delay and dynamic parameters of discrete-time delay systems is proposed in this paper. The proposed algorithm involves constructing a new generalized regression vector and defining the time delay and the rational dynamic parameters in the same vector. The gradient algorithm is us...

An algorithm for simultaneous identification of unknown time delays and parameters of interconnected discrete-time delay multivariable systems is proposed in this paper. This algorithm consists in constructing a linear-parameter formulation by building a generalized vector observation of each subsystem and using the recursive least squares approach...

A new algorithm for simultaneous online identification of unknown time delay and parameters of discrete-time delay systems is proposed in this paper. This algorithm consists in constructing a linear-parameters formulation and using the recursive least squares approach to solve the obtained system. Simulation example and experimental test results ar...

A new algorithm for simultaneous online identification of unknown time delay and parameters of discrete-time delay systems is proposed in this paper. This algorithm consists in constructing a linear-parameters formulation and using the recursive least squares approach to solve the obtained system. Simulation example and experimental test results ar...

A new approach for simultaneous recursive identification of an unknown time delay of discrete-time delay systems is proposed in this paper. The proposed Levenberg-Marquardt's algorithm is used to deal with the identification problem. The effectiveness of this method has been illustrated through simulation.

Disturbances rejection is an important field of control theory. In this context, our paper is proposed to deal with asymptotic rejection of periodic disturbances affecting discrete multivariable systems with an interactor matrix. A multivariable repetitive sliding mode control is proposed to cancel the disturbances when the system is nondecouplable...

In this paper, we propose a new method for the systematic determination of the model's base of time varying delay system. This method based on the construction of the classification data related to the considered system. The number, the orders, the time delay and the parameters of the local models are generated automatically without any knowledge a...

The design of accurate control becomes more difficult due to the complexity of industrial processes. In this paper, we are interested on the tracking of reference trajectories and the rejection of harmonic disturbances for discrete multi-input multi-output systems. A new control strategy based on the combination of partial state reference model con...

The design of accurate control becomes more difficult due to the complexities of real systems. In this paper, a new discrete second order sliding mode control for nonlinear multivariable systems with external disturbances is proposed. The new control strategy is designed in order to reduce the chattering phenomenon that appears in classical sliding...

The Sliding Mode Control (SMC) is well known by its robustness to parameter uncertainties or external disturbances. The repetitive control (RC) is able to track or reject periodic and multi-periodic signals. This paper presents a new control strategy as a combination of a Sliding Mode approach and Repetitive Control to reject periodic and multi-per...

In this work, a second order asymptotic discrete sliding mode control with a fuzzy supervised discontinuous term is proposed. The on line variation of the discontinuous term amplitude enhances the convergence rapidity of the sliding function and reduces the chattering phenomenon. These improvements are shown by a numerical simulation and by a real...

The multimodel approach is recently developed in order to resolve complexity of many industrial processes. Nevertheless, this approach is often confronted to several difficulties, such as, the determination of the useful models' base. A new approach for determination of a models' base for the representation of non stationary time delay systems is p...

This paper presents a control strategy using Sliding Mode Control (SMC) and Repetitive Control (RC) for linear multiinput discrete-time systems to reject periodic and multiperiodic disturbances. A new reaching law is used to steer the system trajectories into the sliding surface and then keep them on it without chattering. The repetitive control is...

Reference trajectory asymptotic tracking and disturbance re-jection are an important field of control theory. In this paper, we are interested on the tracking of reference trajectories and the rejection of periodic disturbances with unknown frequency for multivariable systems. If the frequency is known, a classical solution is to use a multivariabl...

The temperature control in chemical reactors has been shown to be of fundamental importance from product quality and process reproducibility points of view. This paper presents an experimental evaluation of multimodel approach involving a batch chemical reactor pilot. Two design features are worth to be mentioned. Firstly, an appropriate system ide...

The multimodel approach has become a major research topic during the last few decades and unlike many other advanced techniques, it has also been successfully applied in industry. This paper describes the application of a multimodel generalised predictive control (MGPC) based on a commutation algorithm to the problem of a semi-batch reactor control...

The multimodel approach is recently developed in order to resolve the problems of the increasing complexity of many industrial processes. In this paper we propose a multi- model generalized predictive control based on a commutation algorithm. This commutation is controlled by partial predictors associated to the local controllers. These predictors...

In this paper, we develop a direct adaptive generalized pre-dictive control based on performances index and we show the limits of this control law in the presence of a highly non stationary system. We present thereafter a method for validities estimation in the case of multi-model generalized predictive control (MGPC). This method is based on an on...

L'approche multimodèle est une approche récemment développée pour la modélisation, l'analyse et la commande des systèmes non linéaires et non stationnaires. Cette approche suppose la définition d'une bibliothèque de modèles locaux. Chaque modèle local décrit le comportement du système autour d'un point de fonctionnement donné. Dans la littérature,...

The multimodel approach is a research subject which is recently developed for modeling, analysis and control of complex non linear and non stationary systems. This approach supposes the definition of a base of local models. Each local model can describe the system’s behavior in a given region. Different strategies exist in the literature dealing wi...

Recently, we have proposed a new approach for the systematic generation of a models’ base for the multimodel representation which does not require any prior knowledge about the operating range of the system. The number of the local models, their orders and their parameters are generated automatically. In this paper we focus on an experimental valid...

L’identification des systèmes non linéaires a attiré beaucoup d’attention pendant la dernière décade. Ceci est justifié par le fait que les procédés industriels sont, en réalité, non linéaires. En effet, plusieurs méthodes de représentation ont été développées. Cependant, la plupart des méthodes ne permettent pas de déterminer un modèle global décr...

Considérant les problèmes liés à l’exploitation des régulateurs PID et plus précisément au niveau de réglage en ligne de ses paramètres de synthèse et devant la souplesse de la logique floue et sa capacité d’extraire des décisions précises en partant des données ambiguës, on propose, dans le présent travail, l’insertion d’une couche de supervision...

In this paper a multimodel numerical control based on a new approach for the determination of a models' library for uncertain discrete linear systems modelling is addressed using a strategy of generalized minimal variance control (GMV). The determination of models' library is based on two steps. The first one classifies the uncertain system's data....

In this paper a multimodel numerical control based on a new approach for the determination of a models’ library for uncertain discrete linear systems modelling is addressed using a strategy of generalized minimal variance control (GMV). The determination of models’ library is based on two steps. The first one classifies the uncertain system’s data...

In this paper we propose a Fuzzy Learning Rate (FLR) for Neural Networks. This rate is obtained by combining an Adaptive Learning Rate (ALR) with a fuzzy logic based supervisor. The obtained results showed the efficiency of the proposed fuzzy strategy for the on-line adjustement of the learning rate. Indeed, we have improved, indifferently from the...