1,720,974 research outputs found
A new class of reconfigurable parallel kinematic machines
No full textThe article presents a class of reconfigurable modular parallel robots stemming from the 3-CPS under-actuated topology. Proposed here is a conceptual design where the spherical joint which connects each leg to the end-effector is realized as a combination of revolute pairs; a locking system allows one to alternatively fix one of the revolute joints, giving the machine different 3-CPU kinematic configurations which correspond to different types of mobility. The first part of the paper demonstrates that the robot is able to perform different types of motion, specifically of pure translation and pure rotation; in the last part a sample design of the reconfigurable robot is proposed. �� 2014 Elsevier Ltd
Configuration-dependent modal analysis of a Cartesian parallel kinematics manipulator: Numerical modeling and experimental validation
Get PDFIn the design optimization of a robot the configuration-dependent modal analysis can be a powerful tool to be exploited when high stiffness and high dynamic performances are concurrently required. In this paper the elastodynamics of a lower-mobility Parallel Kinematic Machine for pure translational motions is analyzed. The vibrational modes and the natural frequencies of the robot are evaluated as functions of the end effector position inside the workspace. A finite element model including kinematic joints is used to perform a series of modal analyses in a grid of points inside the workspace. A polynomial regression gives continuous volume maps of the natural frequencies distributions. The numerical model is validated by comparison with experiments: a modal analysis is conducted on a set of inertance Frequency Response Functions acquired on several points of the machine components as a result of an excitation given by an instrumented hammer. A Natural Frequency Difference analysis validates the model under certain conditions and highlights some critical issues to be focused on in future works. �� 2013 Springer Science+Business Media Dordrecht
Design and testing of a spherical parallel mini manipulator
No full textThe article describes the design, prototyping and preliminary testing of a miniaturized spherical parallel manipulator (SPM) with 2 DOFs of rotation, conceived to handle the orientation of a mobile platform during the assembly of very small components. The paper summarizes the basic equations of position and differential kinematics, and describes all the project phases for the realization of the first prototype. Furthermore, experimental data of preliminary tests are presented
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
Modelling and control of a spherical robotic device
Get PDFThe researchers at the Polytechnic University of Marche developed a spherical parallel manipulator designed for the orientation of parts or tools: the paper presents the first experimental results on such innovative machine. A model of the prototype robot has been realised by means of commercial multibody software then both open-loop and closed loop dynamics has been studied. The relative simplicity of machine kinematics allowed also to experiment the use of controllers with compensation of gravitational terms
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
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