1,720,990 research outputs found
On the programming effort required to generate Behavior Trees and Finite State Machines for robotic applications
No full textIn this paper we provide a practical demonstration of how the modularity in a Behavior Tree (BT) decreases the effort in programming a robot task when compared to a Finite State Machine (FSM). In recent years the way to represent a task plan to control an autonomous agent has been shifting from the standard FSM towards BTs. Many works in the literature have highlighted and proven the benefits of such design compared to standard approaches, especially in terms of modularity, reactivity and human readability. However, these works have often failed in providing a tangible comparison in the implementation of those policies and the programming effort required to modify them. This is a relevant aspect in many robotic applications, where the design choice is dictated both by the robustness of the policy and by the time required to program it. In this work, we compare backward chained BTs with a fault-tolerant design of FSMs by evaluating the cost to modify them. We validate the analysis with a set of experiments in a simulation environment where a mobile manipulator solves an item fetching task.</p
Safe whole-body control of a mobile collaborative robotic manipulator
No full textLAUREA MAGISTRALEL’interazione fisica uomo-robot rappresenta una frontiera cruciale nella ricerca robotica, in cui macchine ed esseri umani collaborano fisicamente per svolgere compiti che nessuno dei due potrebbe eseguire in modo ottimale da solo. Lo studio esplora come permettere ai manipolatori mobili di interagire in modo sicuro e fluido con l’uomo, evitando eventuali ostacoli in un ambiente a priori sconosciuto.
Questa tesi propone un nuovo controllo unificato per un manipolatore a 7 gradi di libertà montato su una base mobile omnidirezionale, con l’obiettivo di un’interazione fisica sicura e reattiva. Il cuore del sistema è un’architettura di controllo a cascata che separa la pianificazione dell'anello esterno dall’applicazione di vincoli di sicurezza dell'anello interno. L’anello esterno utilizza un controllore Model Predictive Path Integral (MPPI) per generare comandi di velocità per l’intero corpo del robot. La funzione di costo dell’MPPI integra tre obiettivi principali: seguire l’intenzione dell’utente, inferita dalla forze sull’end-effector; evitare configurazioni indesiderate tramite barrier functions; evitare gli ostacoli elaborando dati da LiDARs 2D. All’interno del framework MPPI viene introdotto un nuovo algoritmo predittivo per evitare gli ostacoli, che valuta il rischio di collisione in funzione della velocità del robot. Questo è completato da un anello interno ad alta frequenza, in cui un filtro di sicurezza basato sulla programmazione quadratica perfeziona i comandi generati dall’MPPI. Il filtro garantisce che vincoli cinematici ed energetici siano rispettati dal comando di velocità.
La validazione del controllore è stata effettuata sia tramite simulazioni che, in parte, con prove sperimentali su hardware fisico. I risultati dimostrano che il filtro di sicurezza impedisce al robot di opporsi all’utente, mentre l’algoritmo per aggirare gli ostacoli consente una navigazione con forze d’interazione ridotte. I test su hardware confermano la robustezza dell'algoritmo all’incertezza e al rumore dei sensori. Integrando una pianificazione predittiva a vincoli di sicurezza, questo lavoro contribuisce ad una collaborazione uomo-robot più sicura ed efficace.Physical human-robot interaction represents a pivotal frontier in robotics research,
where machines and humans physically interact to accomplish tasks that neither
could perform optimally alone. The focus of this work is to unify fluid, safe physical interaction with real-time obstacle avoidance for mobile manipulators. Current approaches typically decouple interaction and navigation functions, thereby hindering physical guidance during mobile operations in unknown environments.
This thesis presents a novel, unified control framework for a 7-Degrees-of-Freedom manipulator mounted on an omnidirectional mobile base to enable safe and responsive physical interaction. The core of the system is a cascade control architecture that separates high-level planning from low-level safety enforcement. The outer loop employs a Model Predictive Path Integral (MPPI) controller to generate optimal whole-body velocity commands. The MPPI cost function integrates three key objectives: tracking human intention inferred from end-effector forces, preventing undesired configurations through barrier functions, and avoiding obstacles by processing 2D LiDARs data. A novel predictive obstacle avoidance algorithm is introduced within the MPPI framework, which evaluates collision risk based not only on proximity but also on the robot's velocity. This is complemented by a high-frequency inner loop, where a Quadratic Programming safety filter refines the MPPI-generated commands to rigorously enforce joint limits, self-collision avoidance, and a crucial passivity-based energy constraint that guarantees stable interaction.
The proposed controller was validated using high-fidelity simulations and, in part, through hardware experiments. Results show that the safety filter prevents the robot from opposing the user, while the obstacle avoidance algorithm ensures smooth navigation with low interaction forces, even in unknown environments. Hardware tests confirm its robustness to uncertainty and sensor noise. By integrating predictive planning with strong safety guarantees, this work aims to lay the foundations for more natural, safe, and effective human–robot collaboration in unstructured settings
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Full text linkWe 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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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