1,721,000 research outputs found
Control implementation of compliant composite material actuators for wearable robotic exoskeleton
No full textIn previous work [1], [2], a novel actuator is presented that merges traditional electromechanical motors and multistable composite structures. It has been shown that these structures are able to arrange themselves in multi-stable configurations corresponding to local minima of their strain enery. When this composite structure is connected with the electromechanical motor as proposed, the resulting actuator shows significant benefits in terms of safety, energy saving and control implementation using the compliant property of the overall structure, the particular shape of the strain energy landscape, and the accurately predictable non-linear behavior. Hence the proposed actuator is well-suited for many robotic applications requiring continuous assistance and robust stability. In this paper, the structure's multistability property is exploited for energy saving purpose. In order to do that, a supervised learning method named Extreme Learning Machine is introduced to approximate the elastic force applied by the structure and Gradient Descent algorithm is used to compute the local minimum points equivalent to local minima of structure's strain energy
Localized Extreme Learning Machine for online inverse dynamic model estimation in soft wearable exoskeleton
No full textIn recent years, actuation technology have been increasingly developed new fields and utilized widely in applications differing from automation and industry , but also robotic rehabilitation, haptics and wearable exoskeleton devices where safety, limitation of peak forces and gentle interaction are extremely important. To date, several examples of robotic applications have been designed to address the demanding needs of these disciplines that require the compliance in actuation and manipulation. However, the control performance is still limited due to lack of accuracy in robotic dynamics model and unmodeled nonlinearities such as friction. In such cases, estimating inverse dynamic model from collected data will provide an interesting alternative solution in order to achieve the compliance interaction and the good performance in position tracking. In this paper, an algorithm for online robotic inverse dynamics learning is proposed and explained using localization approach combined with Extreme Learning Machine
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
Design and preliminary characterization of a soft wearable exoskeleton for upper limb
No full textExoskeletons targeting the upper limb have been broadly developed both for rehabilitation and to augment user's physical performance. Generally, they are rigid robotic interfaces characterized by a non negligible mechanical impedance at the end effector and consequently perceived by the upper limbs as an external body. The rigid frame, moreover, adds kinematic constrains to the natural joint kinematics which may result in discomfort and ultimately in pain. The concept of soft wearable exoskeleton (or exosuit) has been developed and tested for the lower limb and the hand to address such issues thanks to their minimal inertial contribution and influence on the natural kinematics. In the current paper the design of an soft robotic interface for the elbow joint is presented, whose aim is to provide assistance torque to the targeted joint to facilitate the execution of the activities of daily living. Differently from the state-of-The-Art design solutions, our system is able to drive both flexion and extension of the same joint with a single motor in an agonist-Antagonist fashion, making the actuation stage compact and energy efficient. A clutching mechanism is also included in the design in order to save power during static configuration, preventing the motor to hold the joint position for a large amount of time. An exosuit has been designed to transfer the torque of the actuator to the biomechanical joint by means of Bowden cables. Two series elastic elements are employed to overcome the drawbacks of the agonist-Antagonist mechanism and to provide additional compliance at the end effector. A preliminary test has been finally performed in order to characterize the actuation
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