1,720,957 research outputs found
On the Convergence of a Closed-Loop Inverse Kinematics Solver with Time-Varying Task Functions
No full textMany control algorithms devised to allow redundant robots to execute complex multiple tasks with priorities require a numerical inverse kinematics (IK) solver. The present letter investigates the conditions that, if satisfied, guarantee that a specific module of closed-loop numerical IK solvers, which is at the kernel of some of the aforementioned algorithms, converges to a feasible solution. The investigation has the objective to prove the convergence in those cases when the task function is time-varying. The conditions found to ensure convergence include not only the initial task error and the loop gain-as it happens for stationary task functions-but also the maximum sampling time to be used in the computation of the solution
Discrete-time closed-loop inverse kinematics: A comparison between Euler and RK4 methods
No full textThis paper investigates the effects of the numerical method employed to solve the system of differential equations that characterise a closed-loop inverse kinematics (CLIK) algorithm in the discrete-time domain. The paper presents a detailed comparison between a 4th order method, namely the Runge-Kutta 4 (RK4) and the explicit Euler 1-st order method, that is the one most often used in applications. In spite of a lower complexity of the mathematical model, simulations on a 7-Degree-Of-Freedom (DOF) show that using explicit Euler produces better performance in some conditions, such as when considering a constant Cartesian reference. On the other hand, significantly lower tracking error is observed for time-varying Cartesian reference when using RK4. This method also generates smoother joint trajectories when moving through a kinematic singularity. Finally, the results suggest that the stability of the closed-loop algorithm is retained for larger gain values when using RK4
A general constraint-based programming framework for multi-robot applications
No full textClassic task programming methods based on the specification of desired Cartesian frames can easily generate overconstrained task specifications, reducing the motion capabilities of the involved robot(s) and increasing the total programming effort. This paper presents a general constraint-based programming framework for the specification of a task as minimum set of constraints and the automatic generation of motion optimization problems. The framework can handle constraints involving both robot joint and Cartesian coordinates, as well as including explicit time dependency. The proposed formalism naturally scales to robotic applications with multiple robots, on which multiple frames might be of interest. Additionally, the paper proposes a theoretical comparison with already existing constraint-based programming methods. Finally, the validity and the effectiveness of the proposed approach is numerically supported by illustrative examples, as well as by case studies mocking real industrial setups
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
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