1,721,141 research outputs found
G. Avanzini et M.-J. Thiel, Éduquer à la beauté, éduquer aux valeurs, 1999
No full textWagner Jean-Pierre. G. Avanzini et M.-J. Thiel, Éduquer à la beauté, éduquer aux valeurs, 1999. In: Revue des Sciences Religieuses, tome 74, fascicule 4, 2000. pp. 534-535
Adaptive control of launch vehicles in atmospheric flight
Full text linkThe research focuses on the development of innovative control techniques for attitude control of a launch vehicle (LV) during the atmospheric flight, and to investigate their possible benefits in terms - for instance - of improved disturbance rejection capability, as well as, a means for reducing the burden of recurrent activities of mission integration and flight program software finalization.
In this respect, a complete nonlinear mathematical model of the launch vehicle dynamics, comprehensive of all relevant aspects for the attitude control problem is first developed. Next, linearized equations of motion are derived under the assumption of small deviations of the vehicle motion from a reference trajectory. The time-invariant linear model is used to synthesize a baseline controller (BC) that features two proportional-derivative (PD) components for attitude and translational motion control, plus filters to phase-stabilize and notch the bending modes by using classical, frequency-based, analysis, and control design techniques.
Among several advanced algorithms referenced in the literature, the Adaptive Augmenting Control (AAC) has been selected and implemented in the LV flight control system in order to retain the functionality and proven record of success of classically designed linear control systems, while consistently and predictably improving their performance and robustness in expanded flight and/or uncertainty parameter envelopes. AAC adjusts the action of a baseline PID-type controller by means of a forward loop gain multiplicative adaptive law that, basically, on-line modulates BC output either to minimize the error with respect to a reference model or to limit undesirable high-frequency response in the control path.
In order to fully exploit the AAC potentiality, an effective and reliable tuning procedure for AAC gains is developed, where a robust design optimization (RDO) problem is formulated, and the goal is to maximize a statistical metric that describes FCS performance measured over a set of LV simulations.
Finally, an analysis of the effects of uncertainties on bending mode characteristics is carried out. Variations of bending mode parameters have a significant and negative impact on AAC performance and, consequently, on LV stability. In this respect, the use of adaptive filters is investigated in order to further improve flight control system robustness. An adaptive notch filter is designed, the parameters of which are updated continuously by an adaptation algorithm that uses the pitch rate sensor output so as to estimate the unknown parameters of the filter and precisely match the actual bending mode frequency
L'ordinamento forestale: prospettive di tutela e gestione sostenibile
Full text linkL'ordinamento forestale, tema della ricerca, è stato studiato nelle sue dimensioni storica, giuridica e scientifica al fine di vagliare la percorribilità normativa del connubio tra i principi dello sviluppo sostenibile e della sussidiarietà orizzontale. Attraverso l'analisi, in particolare, dei servizi ecosistemici forestali e dei relativi sistemi di remunerazione (PES) come vettori dello sviluppo sostenibile in materia, unita allo studio della vasta gamma di soggetti e istituti formanti l'organizzazione multilivello dell'ordinamento forestale, si è individuata nel modello dell'agenzia amministrativa la sintesi organizzativa che può sovrintendere alla funzione relativa al monitoraggio e alla gestione dei sistemi PES e costituire, al contempo, il foro partecipativo dei soggetti dell'ordinamento forestale. Il modello agenziale è coerente con i principi di integrazione e sussidiarietà nonché con il canone costituzionale dell'imparzialità e del buon andamento dell'azione amministrativa, rispondendo quindi positivamente alla sempre più necessaria integrazione tra amministrazione nazionale ed europea
Performance and Stability of a Ducted-Fan Uninhabited Aerial Vehicle
No full textThe nonlinear model of a ducted-fan uninhabited aerial vehicle is presented, where the aerodynamic coefficients are determined by numerical analysis of the flow field about the airframe. The model is used to investigate performance and stability characteristics of the vehicle, and to gain a sound physical understanding of its dynamic behavior and response characteristics. In addition, the influence of uncertainty in the aerodynamic derivatives on the open-loop dynamics is determined. ©2001 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved
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