Stabilisation robuste et ultrarapide au moyen d'une double boucle de rétroaction et application à un système de lévitation magnétique

Traditionnellement les méthodes de commande étaient intéressées par le maintien de la stabilité et de marges de robustesse sécuritaires. L’amélioration des performances temporelles n’a pas été prioritaire. Il est proposé dans cette thèse d’améliorer une nouvelle méthode de commande robuste et ultra rapide récemment développée à l’École de Technologie Supérieure. Cette méthode est basée sur le principe de la commande quasi linéaire, c’est-à-dire une commande dans laquelle les gains sont reliés à la bande passante, ce qui assure la souplesse désirée de la commande en rapport au maintien des marges de stabilité. L’amélioration consiste à réaliser une commande à double boucle. La boucle interne sera une commande à retour d’état, ou une commande LQG, qui assure la stabilité du système. La boucle extérieure vise à améliorer la performance du système stabilisé. L’amélioration principale est la réduction de l’amplitude du signal d’entrée au processus ce qui permet d’éviter des saturations tout en garantissant la rapidité et la robustesse du système. Ainsi la stabilisation et la réduction de sensibilité en dessous de valeurs seuils minimales peuvent être réalisées de façon indépendante. Par ailleurs la sensibilité minimale sur la bande passante désirée est obtenue au moyen d’une compensation à haut gain sans que cela influence la sensibilité globale sur l’ensemble des fréquences. Cette technique assure des temps de réponse très courts et compétitifs. Elle peut également être améliorée au moyen de circuits de phase opérant dans les frequencies intermédiaires. La comparaison des résultats obtenus avec ceux obtenus par d’autres méthodes montre non seulement la supériorité de la commande à double boucle mais également l’avantage important consistant à limiter le signal d’entrée au processus évitant ainsi des risques de saturation tout en assurant une économie d’énergie. Par ailleurs, une méthode de simulation graphique extrêmement facile à utiliser rend la méthode accessible et facile d’utilisation pour le concepteur de systèmes de commande performants

Genetic algorithms in speech recognition systems

Abstract In speech recognition, the training process plays an important role. When a good training model for a speech pattern is obtained, this not only enhances the speed of recognition tremendously .but also improves the quality of the overall performance in recognizing the speech utterance. In general, there are two classic approaches for this development, namely Dynamic Time Warping (DTW) and Hidden Markov Model (HMM). In this article, Genetic Algorithm (GA) is applied to solve involved nonlinear, discrete and constrained problems for DTW .Because of the intrinsic properties of GA, the associated non trival K-best paths of DTW can be identified without extra computational cost. The obtained results show the important contribution of the genetic algorithms in temporal alignment through the increasingly small factor of distortion

A study of maintenance contribution to joint production and preventive maintenance scheduling problems in the robustness framework.

International audienceIn this paper, we deal with a joint production and Preventive Maintenance (PM) scheduling problem in the robustness framework. The contributions of this paper are twofold. First, we will establish that the insertion of maintenance activities during production scheduling can hedge against some changes in the shop environment. Furthermore, we will check if respecting the optimal intervals of maintenance activities guarantees a minimal robustness threshold. Then, we will try to identify from the used optimisation criteria those that allow making predictive schedules more robust. The computational experiments in a flowshop show that joint production and PM schedules are more robust than production schedules and maintenance provides an acceptable tradeoff between equipment reliability and performance loss under disruption

A Case Study of Conformance and Interoperability Testing: AAL 3/4 layer implementations

This paper deals with a case study of conformance testing and interoperability testing of ATM Adaptation Layer type 3/4 (AAL 3/4) implementations. A set of conformance test purposes for AAL 3/4 sublayers is developped. The implementation of these test purposes is analysed using the transverse conformance test method and the interoperability test method. This analysis leads to the identification of some general reasons that prevent the implementation of a given test purpose. As a complement for the conformance testing study, some criteria are given for interoperability between AAL 3/4 implementations. Keywords: SMDS, ATM, AAL 3/4, testing, interoperability. 1 Introduction Conformance testing plays a important role in ensuring correct behaviour and interoperability of communication equipment. For this purpose, ISO has developped a standard describing the methodology and framework of OSI conformance testing [8, 9]. Some general concepts of this standard, such as, Implementation Under Tes..

Host discrimination and egg laying in Anisopteromalus calandrae (Hymenoptera: Pteromalidae) ectoparasitoid of Callosobruchus maculacus (Coleoptera : chrysomelidae)

International audienceThe recognition and avoidance of already parasitized hosts is a major issue in parasitoid behavioral ecology, particularly for solitary species. Superparasitism avoidance is often described as an adaptive strategy, and the discrimination abilities of parasitized hosts have been selected in many species. The recognition of parasitized hosts often relies on olfactory cues or a marking pheromone that could decay with the time between successive host encounters. The intraspecific discrimination abilities of the solitary parasitoid Anisopteromalus calandrae (Hymenoptera: Pteromalidae) have been studied in the laboratory under several conditions. While the discrimination abilities of recently parasitized hosts and those parasitized for a longer time (i.e. when the first egg is about to hatch) are known in this species, their capacity to discriminate hosts containing eggs at intermediate stages and their capacity to adapt superparasitism avoidance depending on the identity of the first female has not been explored. The present study investigated (i) females' behavior in the presence of hosts parasitized by themselves or conspecifics with varying time intervals, and (ii) whether these females were able to adapt their reproductive strategy when placed in a choice and a no-choice situation. Our experiments confirmed that A. calandrae females are able to discriminate between parasitized and unparasitized hosts, as they laid more eggs on the latter. However, they did not recognize hosts containing eggs of a conspecific at intermediate developmental stages, when placed in either a choice or a no-choice situation. The same phenomenon was observed in a self-superparasitism situation in a choice experiment. By contrast, in a no-choice situation, they recognized hosts containing eggs that had been freshly laid by themselves, but not those at an intermediate stage of development

Click synthesis of symmetric bis-triazol ligands and full characterisation of their copper(II)-complexes

International audienceEight novel ligands were prepared from a known symmetric diaza-18-crown-6 (cyclic ligand) and two commercial N,N'-dimethyl-alkyl diamines (acyclic ligands) via the Cu(I)-catalyzed Huisgen dipolar cycloaddition, All C-2-symmetric isolated ligands readily formed stable crystalline 1:1-copper(II) complexes with cupric perchlorate. Their structural, electrochemical and physico-chemical properties were fully investigated with the help of X-ray diffraction, cyclic voltammetry, FT-IR, UV-visible, and electron paramagnetic resonance (EPR) spectroscopies. Planar - or nearly planar - arrangement of the two N3-triazole nitrogens and the two tertiary amine pivot nitrogens was found in one single four-coordinated species, in four five-coordinated species, and three six-coordinated species, with one or two solvent molecule(s), or two oxygen atoms of the crown ether, occupying the axial position(s) in the solid sate. The electron-donating or electron-withdrawing effect of the N1-substituent on the triazol was found to influence the Cu(II)/Cu(I) redox potential of all studied complexes in DMF. The EPR-spectrum of cyclic complexes in frozen DMF at 100 K exhibited two mononuclear species, one of them likely promoting the formation of dinuclear species as a minor component, whereas most acyclic complex spectra were quite similar