On the trade-off between electrical power consumption and flight performance in fixed-wing UAV autopilots

This paper sets out a study of the autopilot design for fixed wing Unmanned Aerial Vehicles (UAVs) taking into account the aircraft stability, as well as the power consumption as a function of the selected control strategy. To provide some generality to the outcomes of this study, construction of a reference small-UAV model, based on averaging the main aircraft defining parameters, is proposed. Using such a reference model of small, fixed-wing UAVs, different control strategies are assessed, especially with a view towards enlarging the controllers' sampling time. A beneficial consequence of this sample time enlargement is that the clock rate of the UAV autopilots may be proportionally reduced. This reduction in turn leads directly to decreased electrical power consumption. Such energy saving becomes proportionally relevant as the size and power of the UAV decrease, with benefits of lengthening battery life and, therefore, the flight endurance. Additionally, through the averaged model, which is derived from both published data and computations made from actual data captured from real UAVs, it is shown that behavior predictions beyond that of any particular UAV model may be extrapolated.Peer ReviewedPostprint (author's final draft

Active control of vibrant actuators with adaptive adjustment of the reference

An improved adaptive filter for eliminating periodic vibrations of unknown frequency in rotary machinery is presented. The proposed canceller is based on a usual bank of digital adaptive notch filters, each filter tuned in the cancellation of one harmonic. The amplitude and phase of each harmonic is adaptively adjusted by an LMS-based algorithm. Moreover, the central frequency of each notch filter is also adaptively adjusted (fine tuning). The resulting algorithm, tested in an industrial application, shows effectiveness in cancelling unknown periodic disturbances, reducing environmental noise and maintenance problems.Peer ReviewedPostprint (published version

Adaptive us-mrac for disturbance cancellation

A variable structure, model reference adaptive control (VS-MRAC) devoted to cancel interferences without the requirement of an auxiliary input is proposed. This method is an improved alternative to the strategies recently proposed in the control theory literature.Peer ReviewedPostprint (published version

An experimental course on digital communications

In this paper a laboratory course on digital communications is presented. This course has been designed for medium degree professionals in the telecommunications field, and it is based on training equipment developed to change the usual theoretical classrooms for laboratory seminars.Peer ReviewedPostprint (published version

The activity-based costing model trajectory: A path of lights and shadows

Purpose: To present a literature review showing the trajectory of the ABC model. Design/methodology: Literature review. Findings: This paper analyzes the history of the ABC model and its dissemination process, in the form of articles published in the specialized press. Research limitations/implications: The bibliometric study has been carried out based on specialized journals. Practical implications: Before a new strategic management tool is adopted, its strategic or operational contribution to the organization should be analyzed. The adoption of new tools based on current trends or as part of mimetic processes, could imply financial investments that do not produce the desired effects. Originality/value: This work is an analysis of the trajectory of the ABC model from its appearance to the present time.Peer Reviewe

Enumeration of labelled chain graphs and labelled essential directed acyclic graphs

AbstractA chain graph is a digraph whose strong components are undirected graphs and a directed acyclic graph (ADG or DAG) G is essential if the Markov equivalence class of G consists of only one element. We provide recurrence relations for counting labelled chain graphs by the number of chain components and vertices; labelled essential DAGs by the number of vertices. The second one is a lower bound for the number of labelled essential graphs. The formula for labelled chain graphs can be extended in such a way, that allows us to count digraphs with two additional properties, which essential graphs have

Si3N4 single-crystal nanowires grown from silicon micro and nanoparticles near the threshold of passive oxidation

A simple and most promising oxide-assisted catalyst-free method is used to prepare silicon nitride nanowires that give rise to high yield in a short time. After a brief analysis of the state of the art, we reveal the crucial role played by the oxygen partial pressure: when oxygen partial pressure is slightly below the threshold of passive oxidation, a high yield inhibiting the formation of any silica layer covering the nanowires occurs and thanks to the synthesis temperature one can control nanowire dimensions

El Vallès Oriental : problemes induïts per l'artificialització del sòl i la preservació del medi ambient

El paisatge i els recursos naturals al Vallès Oriental estan sotmesos a una forta pressió deguda a la progressiva artificialització del medi. L'article proposa una metodologia per tal d'avaluar l'impacte d'aquesta pressió i les mesures correctores que s'hi apliquen. Així, comença per establir una tipologia d'àrees que permet distingir entre municipis desenvolupats, dinàmics, primaris i desafavorits. A continuació proposa un índex sintètic de prestació i cobertura de serveis ambientals bàsics (IPSA), que permet resumir per a cada municipi el nivell de cobertura en proveïment d'aigua potable, recollida de residus urbans i sanejament. Del creuament dels resultats d'aquest exercici amb la tipologia municipal establerta se'n deriven dues conclusions: per un costat, l'alt nivell d'artificialització del medi (que coincideix amb els municipis desenvolupats i dinàmics) té una relació directa (i no inversa, com podria pensar-se) amb l'existència de prestacions ambientals acceptables; per l'altre, les grans tasques a resoldre a la comarca en l'àmbit del medi ambient són la preservació de les dues serralades (litoral i prelitoral), la connexió de les mateixes a través d'un corredor ecològic i la recuperació de la conca fluvial del Besòs.El paisaje y los recursos naturales del Vallès Oriental están sometidos a una fuerte presión debida a la progresiva artificialización del medio. El articulo propone una metodología para evaluar el impacto de esta presión y la cobertura de las medidas correctoras que se aplican en este campo. Así, se establece una topología de áreas que permite distinguir entre municipios desarrollados, dinámicos, primarios y desfavorecidos. A continuación se propone un índice sintético de prestación y cobertura de servicios ambientales básicos (IPSAI, que permite resumir el nivel de cobertura municipal de abastecimiento de agua potable, recogida de residuos urbanos y saneamiento. Del cruce de los resultados de este ejercicio con la tipología municipal establecida se derivan las conclusiones: el alto nivel de artificialización del medio (que coincide con los municipios desarrollados y dinámicos) tiene una relación directa (y no inversa, como podría suponerse) con la existencia de prestaciones ambientales aceptables; por otra parte, las principales tareas que en la comarca hay que acometer en el campo del medio ambiente son la preservación de las dos sierras (litoral y prelitoral), la conexión de éstas mediante un corredor ecológico y la recuperación de la cuenca fluvial del Besòs