1,720,959 research outputs found
Metodi di localizzazione e sensor fusion per la robotica mobile - Localization methods and sensor fusion for mobile robots
Get PDFDuring this work, it was developed an algorithm of sensor fusion for mobile robot, an algorithm of obstacle avoidance called "Reactive Simulation", a localization algorithm environment referred based on LIght Detection And Ranging (LIDAR) data and an algorithm for object localization from range data.Nel corso del presente lavoro è stato sviluppato e testato un algoritmo di sensor fusion per la navigazione inerziale-odometrica. Sensori come encoder e piattaforme inerziali basate su giroscopi hanno caratteristiche
molto diverse in quanto ad accuratezza di misura in relazione alla manovra attuale compiuta da un veicolo autonomo. È quindi possibile utilizzare tali sensori per ottenere una maggior accuratezza nella stima della posa, e limitare la propagazione dell’incertezza a un primo livello di sensor fusion, a cui poi va aggiunto una ulteriore misura proveniente da un sensore riferito all’ambiente, in modo da ridurre periodicamente la propagazione dell’incertezza che cresce ad ogni ciclo di acquisizione e stima della posa a causa della correlazione temporale dei parametri.
Nell’algoritmo proposto, gli encoder e il giroscopio vengono combinati tenendo in considerazione la rispettiva incertezza, stimata in funzione della manovra attuale che viene classificata a partire dai dati stessi.
Un’altra parte del lavoro ha riguardato lo sviluppo di un algoritmo di localizzazione basato sul matching di scansioni ottenute da un sensore LIDAR, per disporre di una misura di posizione riferita all’ambiente, che
può essere integrata in un algoritmo di sensor fusion o in algoritmi di SLAM (Simultaneous Localization And Mapping).
Sempre basandosi sui dati provenienti dal LIDAR, è stato sviluppato un algoritmo di identificazione e localizzazione della posa di oggetti di forma nota descrivibili mediante un modello geometrico.
Di entrambi è stata condotta un’analisi di incertezza utilizzando un setup realizzato allo scopo.
È inoltre stato sviluppato un algoritmo real time di aggiramento ostacoli, denominato Reactive Simulation, che prende in considerazione la cinematica del veicolo, il modello dinamico e la sua incertezza, le condizioni iniziali, le misure dell’ambiente e l’incertezza dei sensori per calcolare la traiettoria che compierebbe il veicolo per raggiungere un target locale. Tale simulazione ha lo scopo di integrare una pianificazione dinamica della traiettoria, calcolando una predizione più accurata della traiettoria in presenza di ostacoli imprevisti e rendere più robusto l’aggiramento ostacoli. Tale algoritmo è stato implementato e ottimizzato per operare in real time su un robot mobile
Reactive Simulation for Real-Time Obstacle Avoidance
No full textThis paper provides a new approach to the dynamic path planning and obstacle avoidance in unknown and dynamic environments. The system is based on the interaction between four different modules: the Path Planner, the Graph which memorizes all the local target, the “Sentinel”, and the module which computes the Reactive Simulation every time an obstacle is detected along the path. The Reactive Simulation takes in account the kinematics model of the vehicle and the actual state conditions to make a real-time simulation in order to predict the trajectory of the differential drive robot that would allow the safe reaching of the local target
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Hematite nucleation and growth in the firing of carbonate-rich clay for pottery production
No full textHere we describe the evolution of iron-bearing phases in the firing of carbonate-rich illite and chlorite clay. Breakdown of chlorite forms an amorphous phase, which continues to retain iron in a (distorted) paramagnetic octahedral Site, until carbonates start to decompose and react at 750 degrees C, forming Ca-silicates. Only at this temperature can hematite nucleate and grow in specific micro-domains located in former chlorite flakes. At 950 degrees C, decomposition of Mite in the presence of an amorphous phase and CaO produces a melt in which nano-sized hematite may nucleate, although its growth is inhibited due to low diffusion with respect to soaking time
- …
