Ridha Ben Abdennour
University of Gabès
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Featured researches published by Ridha Ben Abdennour.
Automatica | 2014
M. Farza; I. Bouraoui; Tomas Menard; Ridha Ben Abdennour; Mohammed M'Saad
In this paper, we propose an adaptive observer for a class of uniformly observable nonlinear systems with nonlinear parametrization and sampled outputs. A high gain adaptive observer is first designed under the assumption that the output is continuously measured and its exponential convergence is investigated, thanks to a well defined persistent excitation condition. Then, we address the case where the output is available only at (non uniformly spaced) sampling instants. To this end, the continuous-time output observer is redesigned leading to an impulsive observer with a corrective term involving instantaneous state impulses corresponding to the measured samples and their estimates. Moreover, it is shown that the proposed impulsive observer can be put under the form of a hybrid system composed of a continuous-time observer coupled with an inter-sample output predictor. Two design features are worth to be emphasized. Firstly, the observer calibration is achieved through the tuning of a scalar design parameter. Secondly, the exponential convergence to zero of the observation and parameter estimation errors is established under a well defined condition on the maximum value of the sampling partition diameter. More specifically, the observer design is firstly carried out in the case of linear parametrization before being extended to the nonlinear one. The theoretical results are corroborated through simulation results involving a typical bioreactor.
International Journal of Modelling, Identification and Control | 2009
Anis Messaoud; Majda Ltaief; Ridha Ben Abdennour
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 commutation is controlled by a set of partial predictors which constitute a supervisor. The experimental results show that the multimodel generalised predictive control based on supervisor leads to good performances in terms of precision and tracking, relatively to the case where the direct adaptive generalised predictive control (DAGPC), is applied.
Automatica | 2015
I. Bouraoui; M. Farza; Tomas Menard; Ridha Ben Abdennour; Mohammed M'Saad; Henda Mosrati
A continuous-discrete time observer is proposed for a class of uncertain nonlinear systems where the output is available only at non uniformly spaced sampling instants. The underlying correction term depends on the output observation error and is updated in a mixed continuous-discrete fashion. The proposed observer is first introduced under a set of differential equations with instantaneous state impulses corresponding to the measured samples and their estimates. Two features of the proposed observer are worth to be pointed out. The first one consists in the simplicity of its calibration while the second one lies in its comprehensive convergence analysis. More specifically, it is shown that in the case of noise-free sampled outputs, the observation error lies in a ball centered at the origin and its radius is proportional to the bounds of the uncertainties and the sampling partition diameter. Moreover, in the free uncertainties case, the exponential convergence to zero of the observation error is established under a well-defined condition on the maximum value of the sampling partition diameter. The ability of the proposed observer to perform a suitable estimation of the reactions rates in biochemical reactors is highlighted through a simulation study dealing with an ethanolic fermentation.
Archive | 2011
Mohamed Mihoub; Ahmed Said Nouri; Ridha Ben Abdennour
The variable structure control is principally characterized by its robustness with respect to the system’s modeling uncertainties and external disturbances (Decarlo et al. (1988); Filippov (1960); Lopez & Nouri (2006); Utkin (1992)). Sliding Mode Systems are a particular case of the Variable Structure Systems (VSS). They are feedback systems with discontinuous gains switching the system’ s structure according to the state evolution, in order to maintain the trajectory within some specified subspace called the sliding surface (Utkin (1992)). However, the application of this control law is confronted to a serious problem. In fact, sliding mode necessitates an infinite switching frequency which is impossible to realize in numerical applications because of the calculation time and of the sensors dynamics that can not be neglected. The discontinuous control generates in that case oscillations on the state and on the switching function (Utkin (1992)). Owing to the many advantages of the digital control strategy (Ben Abdennour et al. (2001)), the discretization of the sliding mode control (SMC) has become an interesting research field. Unfortunately, the chattering phenomenon is more obvious in this case, because the sampling rate is more reduced. Many approaches have been suggested in order to resolve this last problem. Most of them propose a reduction in the oscillation amplitude at cost of the robustness of the control law (Utkin et al. (1999)). In the eighties, a new control technique, called high order sliding mode control, have been investigated. Its main idea is to reduce to zero, not only the sliding function, but also its high order derivatives. In the case of the r-order slidingmode control, the discontinuity is applied on the (r-1) derivative of the control. The effective control is obtained by (r-1) integrations and can, then, be considered as a continuous signal. In other words, the oscillations generated by the discontinuous control are transferred to the higher derivatives of the sliding function. This approach permits to reduce the oscillations amplitude, the notorious sliding mode systems robustness remaining intact (Levant (1993)). Another problem of the SMC is its vulnerability to external disturbances, parametric variations and non linearity, essentially, during the reaching phase. A solution to this problem, based on the multimodel approach, was proposed by the authors in (Mihoub et al. (2009a)). The combination of the multimodel approach and the second order discrete sliding mode control (2-DSMC) allows resolving both the chattering problem and the vulnerability during Multimodel Discrete Second Order Sliding Mode Control: Stability Analysis and Real Time Application on a Chemical Reactor 25
International Journal of Modelling, Identification and Control | 2009
Mohamed Mihoub; Ahmed Said Nouri; Ridha Ben Abdennour
The esterification reaction requires a tight temperature control. As the different stages of this reaction (the heating, the reaction and the cooling) are characterised by different dynamics, a discrete second order sliding mode control using one global model of the system was not able to ensure the desired performances. We propose, in this paper, an application of the multimodel approach for the discrete second order sliding mode control. Experimental results on the reactor show better control performances both at tracking and disturbance rejection relative to the case where the conventional discrete second order sliding mode control is applied.
mediterranean conference on control and automation | 2010
Mohamed Mihoub; Ahmed Said Nouri; Ridha Ben Abdennour
In this paper, the chattering phenomenon that characterizes discrete sliding mode systems is analyzed and illustrated by a simulation example. In order to resolve this problem, in case of relatively large parameter variations and/or external disturbances, a second order discrete sliding mode observer (2-DSMO) is proposed. A stability analysis of the proposed observer is developed and a real time application on a semi batch reactor is realized. The experimental results show a good performance in terms of precision of the state estimation and of chattering reduction.
International Journal of Modelling, Identification and Control | 2010
Mansoura Elkhalil; Majda Ltaief; Ridha Ben Abdennour; Mohammed M'Saad
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 identification approach is used to elaborate a family of control models describing the input-output behaviour of the reactor over its full operating range. Secondly, the control design is performed using a suitable fusion of robust model reference controllers. The underlying model reference control is particularly motivated by the required tracking performances.
european control conference | 2014
Mondher Farza; I. Bouraoui; Tomas Menard; Ridha Ben Abdennour; Mohammed M'Saad
This paper presents a continuous-discrete time observer for a class of uncertain nonlinear systems with non uniformly sampled measurements. Two features of the proposed observer are worth to be pointed out. The first one consists in the simplicity of its calibration, while the second one lies in its comprehensive convergence analysis. More specifically, it is shown that the observation error lies in a ball centered at the origin and whose radius is proportional to the bounds of the uncertainties and the sampling partition diameter. In the free uncertainties case, the exponential convergence to zero of the observation error is established under a well-defined condition on the maximum value of the sampling partition diameter. The effectiveness of the proposed observer is emphasized throughout simulation results involving the estimation of the reaction rate in a typical bioreactor.
international conference on sciences and techniques of automatic control and computer engineering | 2014
Mouhib Allaoui; Anis Messaoud; Ridha Ben Abdennour
This paper deals with the design of robust non-stationary sinusoidal unknown inputmultiobserver for discrete-time nonlinear systems described by decoupled state multimodel. The particularity of this work resides in the fact that it provides a simultaneous state and non-stationary sinusoidal unknown inputs estimations. A new robust strategy allowing the minimization of the non-stationary sinusoidal unknown inputs and disturbances impact on the state estimation error will be developed.
international conference on sciences and techniques of automatic control and computer engineering | 2013
Nesrine Bahri; Asma Atig; Ridha Ben Abdennour; Fabrice Druaux; Dimitri Lefebvre
In this paper, multimodel and neural emulators are proposed for nonlinear plants with unknown dynamics. The contribution of this paper is to extend the emulators to multi-variable non square systems. The effectiveness of the proposed emulators are shown through an illustrative simulation example. The obtained results are very satisfactory and show the best performances of the multimodel emulator relatively to the neural one.