L'OBJET DE CETTE THESE EST L'ETUDE ET LA VALIDATION EXPERIMENTALE DE DEUX STRATEGIES DE COMMANDE NUMERIQUE DE LA MACHINE ASYNCHRONE : LA COMMANDE LINEAIRE ET LA COMMANDE PAR RETOUR D'ETAT NON LINEAIRE. LA METHODE LINEAIRE, SE BASANT SUR L'HYPOTHESE DE LA SEPARATION DES MODES ELECTRIQUE (RAPIDE) ET MECANIQUE (LENT), OFFRE DES RESULTATS SATISFAISANTS TANT QUE CETTE HYPOTHESE EST JUSTIFIEE. D'AUTRE PART, LA VARIATION DES PARAMETRES, TELS QUE LES RESISTANCES STATORIQUE ET ROTORIQUE DE LA MACHINE, NECESSITE, EN PLUS DE LEUR IDENTIFICATION EN TEMPS REEL, LA MISE AU POINT D'UNE COMMANDE ADAPTATIVE AFIN DE MAINTENIR LES PERFORMANCES PREDEFINIES POUR LE SYSTEME. DANS LE CAS DE LA COMMANDE NON LINEAIRE OU LES DYNAMIQUES MECANIQUE ET ELECTRIQUE SONT EGALEMENT CONSIDEREES, DEUX BOUCLES DE REGULATION SONT UTILISEES : UNE BOUCLE DE VITESSE ET UNE BOUCLE DE FLUX. AVEC CETTE NOUVELLE APPROCHE, LE PROBLEME DE LA LIMITATION DU COURANT ALIMENTANT L'ENSEMBLE CONVERTISSEUR-MACHINE EST RECONSIDERE. PAR AILLEURS, LA COMMANDE NON LINEAIRE DANS LE REPERE FIXE DU STATOR MONTRE UNE MEILLEURE ROBUSTESSE VIS-A-VIS DE LA VARIATION DE LA CONSTANTE DE TEMPS ROTORIQUE T R EN COMPARAISON AVEC LES COMMANDES LINEAIRE ET NON LINEAIRE DANS LE REPERE DU CHAMP TOURNANT. DE PLUS, MEME SI LA COMMANDE NON LINEAIRE NECESSITE AUSSI UNE IDENTIFICATION DE T R, CELLE-CI PERMET DE SE PASSER DE LA COMMANDE ADAPTATIVE PUISQUE LA CONNAISSANCE DE CE PARAMETRE SUFFIT POUR ASSURER UN DECOUPLAGE PARFAIT DES BOUCLES DE VITESSE ET DE FLUX. EN EFFET, UNE FOIS DECOUPLEES, LES BOUCLES DEVIENNENT INDEPENDANTES DE T R GRACE A UN CHOIX ADEQUAT DES CORRECTEURS. CE CHOIX AMELIORE EGALEMENT LA ROBUSTESSE VIS-A-VIS DE LA MECONNAISSANCE DE LA RESISTANCE STATORIQUE.

Cette étude présente des stratégies linéaires et non-linéaires de contrôle appliquées à l'asservissement en vitesse d'une Machine Asynchrone à Double Alimentation (MADA) dont les enroulements statoriques et rotoriques sont reliés à des onduleurs de tensions à Modulation de Largeur d'Impulsion indépendants. Nous avons choisi de répartir les puissances actives entre le stator et le rotor suivant un certain rapport de proportionnalité. Cela nous conduit à garantir, en régime permanent, une répartition des pulsations statoriques et rotoriques. Cette répartition est assurée dans un premier temps par deux régulateurs de pulsations réparties, et dans un deuxième temps par le biais des angles de transformation directement. Nous développons ensuite deux modèles analytiques de la MADA : le premier exprime les courants, et le second les flux. Les simulations des stratégies de contrôle linéaire (contrôle vectoriel), et non-linéaire (contrôle par mode de glissement), démontrent un bon découplage entre l'axe magnétisant et l'axe du couple. Une validation expérimentale est présentée. Les premiers résultats expérimentaux montrent le bon contrôle de l'état magnétique de la machine, ainsi que la répartition des puissances désirées à travers les pulsations.

Policy concepts; Identification of policy issues; Production systems, supply and demand; Market, price and trade policies; Marketing and distribution systems; Budget and manpower planning; Land tenure police for the livestock sector; Policy analysis report writing and communication; Livestock production and marketing in alphabeta - a case study.

Covering everything from the basics to recent applications, this monograph represents an advanced overview of the field. Edited by internationally acclaimed experts respected throughout the community, the book is clearly divided into sections on fundamental and applied surface organometallic chemistry. Backed by numerous examples from the recent literature, this is a key reference for all chemists.

An Introduction to Tourism is the essential guide to the tourism industry. It provides a comprehensive and authoritative introduction to all facets of tourism including: the history of tourism; factors influencing the tourism industry; tourism in developing countries; sustainable tourism; forecasting future trends. Tourism has changed radically in recent years with the onset of many technological and economic changes and an ever increasing concern for the environment. This book provides a down-to-earth introduction to this complex and multi-faceted industry. This invaluable introduction is written for all students of tourism and all those involved in the industry who want to know more about the structure, component activities and environment within which they work.

Masters Theses in the Pure and Applied Sciences was first conceived, published, and dis· seminated by the Center for Information and Numerical Data Analysis and Synthesis (CINDAS) *at Purdue University in 1957, starting its coverage of theses with the academic year 1955. Beginning with Volume 13, the printing and dissemination phases of the ac· tivity were transferred to University Microfilms/Xerox of Ann Arbor, Michigan, with the thought that such an arrangement would be more beneficial to the academic and general scientific and technical community. After five years of this joint undertaking we had concluded that it was in the interest of all concerned if the printing and distribution of the volume were handled by an international publishing house to assure improved service and broader dissemination. Hence, starting with Volume 18, Masters Theses in the Pure and Applied Sciences has been disseminated on a worldwide basis by Plenum Publishing Corporation of New York, and in the same year the coverage was broadened to include Canadian universities. All back issues can also be ordered from Plenum. We have reported in Volume 20 (thesis year 1975) a total of 10,374 theses titles from 28 Canadian and 239 United States universities. We are sure that this broader base for theses titles reported will greatly enhance the value of this important annual reference work. The organization of Volume 20 is identical to that of past years. It consists of theses titles arranged by discipline and by university within each discipline.

Agricultural English is a collection of essays on the English of Agriculture. The approach is a linguistic one: the different aspects of the English used in the field of agriculture (agricultural practices, agricultural systems) and in some fields related to agriculture (agricultural zoology, agri-tourism, biology, botany, ecology, entomology, gastronomy, land measurement, plant pathology, zoology) are analysed from a morphological (combination, derivation), syntactical (nominal phrases, verbal phrases), lexical and lexicographical, semantic (homonymy, semantic fields, synonymy, terminology), pragmatic (academic discourse, idiom, metaphor), etymological (etymon, Latin heritage), and contrastive (English–Croatian, English–French, English–German, English–Romanian, Romanian–English) points of view. The book will appeal to agriculturists, animal breeders, professors, researchers, students, and translators from Croatian-, English-, French-, German-, and Romanian-speaking countries, active in their own countries or abroad. The types of academic readership it would appeal to include academic teaching staff, researchers and students in the fields of agriculture and related fields – agricultural zoology, agri-tourism, biology, botany, ecology, entomology, gastronomy, land measurement, plant pathology, and zoology.