1,720,967 research outputs found
Design of a beam-based variable stiffness actuator via shape optimization in a CAD/CAE environment
No full textIndustrial robots are commonly designed to be very fast and stiff in order to achieve extremely precise position control capabilities. Nonetheless, high speeds and power do not allow for a safe physical interaction between robots and humans. With the exception of the latest generation lightweight arms, purposely design for human-robot collaborative tasks, safety devices shall be employed when workers enter the robots workspace, in order to reduce the chances of injuries. In this context, Variable Stiffness Actuators (VSA) potentially represent an effective solution for increasing robot safety. In light of this consideration, the present paper describes the design optimization of a VSA architecture previously proposed by the authors. In this novel embodiment, the VSA can achieve stiffness modulation via the use of a pair of compliant mechanisms with distributed compliance, which act as nonlinear springs with proper torque-deflection characteristic. Such elastic elements are composed of slender beams whose neutral axis is described by a spline curve with non-trivial shape. The beam geometry is determined by leveraging on a CAD/CAE framework allowing for the shape optimization of complex flexures. The design method makes use of the modeling and simulation capabilities of a parametric CAD software seamlessly connected to a FEM tool (i.e. Ansys Workbench). For validation purposes, proof-concept 3D printed prototypes of both non-linear elastic element and overall VSA are finally produced and tested. Experimental results fully confirm that the compliant mechanism behaves as expected
Design of a Twisted-String Actuator for Haptic Force Rendering
No full textIn this paper, the design of a Twisted-String Actuation (TSA) module suitable for a wide set of robotic applications is presented. The TSA module is characterized by an integrated force sensor based on optoelectronic components and embedded controller with power electronics. The proposed actuation system is particularly suited for very compact, light-weight, wearable and low cost robotic devices, such as haptic devices, wearable systems and rehabilitation exoskeletons. The whole module design and the basic force sensor working principle are illustrated and discussed. Particular attention is given to the integration of the force sensor into the TSA module to solve the drawbacks of previous solutions. Moreover, the structure of the TSA module electronics and embedded controller is presented. Finally, the actuation module has been experimentally tested, and the ability of the system of controlling the actuation force has been demonstrated
Synergy-based control of anthropomorphic robotic hands with contact force sensors
No full textA study on the synergy-based control of an anthropomorphic hand is proposed in this paper. The robotic hand is equipped with three-axis optical force sensors placed on thumb, index, and middle fingertips in order to obtain a better grasping quality in terms of adaptability and contact forces with respect to the physical object properties. A fully-actuated hand is used in the experiments since this allows to select different postural synergies and explore how the hand behaves in case of decoupled finger motion. Therefore, the proposed method can be extended to two different application cases: purely synergy-based contact force control and synergy-based contact force control with decoupled fingers. While the first control strategy allows to simplify the grasping by selecting only the synergy weights in order to obtain the desired value of the mean contact forces among the fingers, the second allows both to control the contact force individually on each finger in order to better adapt the hand to the object and to preserve the simplicity in the grasp design provided by the synergy-based approach. Experimental tests have been performed in both the cases to show the performance of the proposed methods and to highlight the capability of the proposed control strategies to regulate the contact forces properly
Towards a Twisted String Actuated Haptic Device: Experimental Testing of a 2-D Virtual Environment and Teleoperation Interface
Full text linkIn the article, a first stage implementation of a haptic device towards a complete 3-D workspace twisted-string actuated haptic interface is discussed. In the present work, a 2-D setup is presented, with the aim of preliminarly testing the behaviour of this novel haptic system, especially with respect to the adopted cable-based actuation solution. In particular, the component descriptions, kinematics of the planar device and the controller for teleoperation purposes are illustrated. Results regarding the behaviour of the system in rendering a virtual environment and in a robot teleoperation scenario with haptic force feedback are reported. The experimental outcomes show that the designed and implemented system is suitable for teleoperation with haptic interfaces, providing positive perspectives for the realization of the fully functional 3-D haptic interface in the future work
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
An sEMG-Based Human-Robot Interface for Robotic Hands Using Machine Learning and Synergies
Full text linkDeveloping natural control strategies represents an intriguing challenge in the design of human–robot interface (HRI) systems. The teleoperation of robotic grasping devices, especially in industrial, rescue, and aerospace applications, is mostly based on nonintuitive approaches, such as remote controllers. On the other hand, recent research efforts target solutions that mimic the human ability to manage multifinger grasps and finely modulate grasp impedance. Since electromyography (EMG) contains information about human motion control, it is possible to leverage such neuromuscular knowledge to teleoperate robotic hands for grasping tasks. In this paper, we present an HRI system based on eight fully differential EMG sensors connected to a wearable sensor node for acquisition and processing. By virtue of a novel bio-inspired approach, the embedded myocontroller merges pattern recognition and factorization techniques to combine a natural selection of the robotic hand configuration with the proportional control of the related grasps. The HRI system has been fully designed, implemented, and tested on two robotic hands: a dexterous anthropomorphic hand and a three-fingered industrial gripper mounted on a robotic manipulator. The results of the test performed on four able-bodied subjects show success rates greater than 90% reached in grasping objects that require different hand shapes and impedance regulations for the task completion. The outcomes also show that the users modulate the bio-inspired degrees of control in a natural manner, proving the pertinence of the proposed system for an effective human-like control of robotic grasping devices in a wearable form factor
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
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