1,721,003 research outputs found
Evaluation of Two Tension Sensors for Cable-Driven Parallel Manipulators
Get PDFCable-driven parallel manipulators (CDPMs) constitute a class of parallel robots in which the frame is connected to the end-effector through a set of cables. The weight reduction achieved by replacing rigid links with cables, along with their exceptionally large workspace, makes CDPMs suitable for applications such as positioning devices, large surface inspection, motion support systems, and automated storage systems. For effective use in these applications, accurate positioning capabilities are essential, which in turn require accurate measurements of the tension on each cable, and at a sampling rate that is less than or equal to the time constant of the actuator response. This paper first analyses the dynamics of the actuator for an over-constrained robot and provides concrete values of this constant considering the cable elasticity. Then, it proposes two tension sensors, presents the calibration procedures, and the methodologies to evaluate them in CDPMs so that they can be replicated and subsequently included in another CDPM configuration. They also serve as critical safety devices, continuously monitoring cable tension to detect any operations or situations that are out of range. Ensuring the safe and reliable condition of cables is crucial not only for CDPMs but also for lifting systems, transmission systems, and other mechanical or mechatronic systems that rely on cables
On the effects of the design of cable-Driven robots on kinematics and dynamics models accuracy
No full textThis paper tackles the problem of improving the connection between the fixed frame and the end-effector of planar and spatial cable-driven robots. A new design concept is detailed, which consists in adding pulleys to the attachment between the cables and the end-effector. These reflective pulleys must have the same radius as the ones at the frame in order to compensate their geometry. Without this modification in the end-effector, the usual simplification of the point-to-point method used to model the connection between frame and end-effector leads to significant errors in the Kinematics and Dynamics of the system due to the fact that the geometry of the frame pulleys is disregarded. By adding the reflective pulleys in the end-effector, the equations of the Kinematics and Dynamics of the real system are equivalent to those of the point-to-point model, and therefore, this simplified method can be used without inherent errors. This solution may be of great importance for computational issues because it leads to codes that may run at real time. An analytical proof of the equivalence of both models is presented. Finally, experimental results have been conducted for both, planar and spatial cable-robots, in order to illustrate the advantages of using this novel design concept for the connection between the end-effector and the fixed frame
Imputation of complex dependent data by conditional copulas: analytic versus semiparametric approach
No full textImputation of complex dependent data by conditional copulas: analytic versus semiparametric approach
No full textGoing 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
PTP1B deficiency increases glucose uptake in neonatal hepatocytes: involvement of IRA/GLUT2 complexes
No full textInspection Robotic System: Design and Simulation for Indoor and Outdoor Surveys
No full textIn this paper, the design and simulation are presented for a wheeled robot designed for indoor and outdoor inspections. In particular, for a large number of cases, an automatic or tele-operated survey can be performed by wheeled mobile robots, which represent the most efficient solution in terms of power consumption, control, robustness and overall costs. Referring to the analysis of structures and infrastructure, such as bridges and pipelines, wheeled robots must be able to move on horizontal or sloped surfaces and overpass obstacles that in most of cases are steps, i.e. longitudinal internal stiffeners. In this paper, we present a mechatronic design and simulations of a wheeled robot being used in indoor and outdoor inspections, taking as illustrative example an infrastructure inspection. In particular, the wheeled robot is equipped with suitable sensors in order to take information on the main structural elements, avoiding the need of experienced personnel to get directly inside the site to be inspected
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