1,721,018 research outputs found
High-stiffness Control of Series Elastic Actuators using a Noise Reduction Disturbance Observer
No full textRendering a high impedance on a series-elastic actuator (SEA) can improve motion control performance while retaining collision safety by a lower physical stiffness. The safe impedance range can be increased with high gain velocity feedback control, but in practice this is limited by noise. This paper applies the noise reduction disturbance observer (NRDOB) to inner-loop velocity control of an SEA, attenuating noise and allowing higher safe rendered stiffness compared with standard torque and torque/velocity hierarchical control. Closed-form expressions for maximum passive stiffness and Z-region are found, shown to depend strongly on the high-frequency noise gain, and used to optimize the control gains. Performance is experimentally verified on a reaction-force SEA; validating the passivity of the high stiffness control in impact (free space and stiff environment) while rendering a safe stiffness 3.0 times the intrinsic stiffness. IEEE1
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
Sampling and gradient based planning for contact-rich manipulation tasks
No full textLAUREA MAGISTRALELe applicazioni robotiche ricche di contatto formano un insieme molto importante in contesti industriali e medicali, richiedendo una frequente interazione con degli agenti esterni complessi e aleatori. Al fine di permettere ad un manipolatore robotico di approcciarsi a tali contesti con un livello di destrezza ed agilità paragonabile a quello umano, è molto importante studiare un metodo che permetta di affrontare efficaciemente questo tipo di applicazioni con una forte interazione fisica esterna. Nel presente elaborato, tale di tipo di interazione viene modellata mediante un modello dinamico ibrido, al fine di sfruttare la natura discontinua di tali applicazioni, consentendo allo stesso tempo lo sviluppo di un algoritmo di controllo più sicuro. Verrà proposto un metodo innovativo per la stima dello stato del sistema ibrido, garantendo un'informazione accurata riguardo la più probabile modalità di contatto. Tale informazione, verrà utilizzata in real-time da un controllore di alto livello Model Predictive Control (MPC) al fine di stabilire il livello di coppia di riferimento del blocco di impedance control interno al manipolatore. L'algoritmo di controllo sviluppato si basa su una combinazione di tecniche di ottimizzazione sampling-based e gradient-based; il Cross-entropy Method (CEM) viene utilizzato per fornire un punto di inizializzazione più accurato al solver gradient-based, garantendo una migliore convergenza ed un miglior comportamento rispetto al problema dei minimi locali. Attraverso prove di simulazione e sperimentali viene mostrato come il metodo svilupato sia in grado di ottenere un controllo sicuro ed affidabile per applicazioni robotiche con interazioni di contatto caratterizzate da un'elevata rigidezza.Contact-rich manipulation tasks forms a crucial application in industrial, medical and household settings, requiring strong interaction with a complex environment. In order to efficiently engage in such tasks with human-like agility, it is crucial to search for a method which can effectively handle such contact-rich scenarios. In this work, contact-rich tasks are approached and modeled from the perspective of a hybrid dynamical system, trying to exploit their discontinuous nature in order to built an efficient and safe planning framework. A novel method for estimating the full hybrid state space is proposed, that can efficiently provide information about the most probable active contact state. This information is used by an high-level Model Predictive Control (MPC) planner to set the torque reference of an impedance controller. We propose a planning method with both sampling- and gradient-based elements, using the Cross-entropy Method to initialize a gradient-based solver, providing better search over local minima and the ability to handle explicit constraints. We show the approach allows smooth, stable contact-rich planning for an impedance-controlled robot making contact with a stiff environment, benchmarking against gradient-only MPC and CEM
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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