1,720,959 research outputs found
Adaptive Design and Control of A Robot-assisted Lower Back Exoskeletal Spine System
No full textIn order to help elder people who suffer from lower back pain caused by lower spine degeneration, a novel kind of robot-assisted exoskeleton spine was designed. It was mainly applied to lift their upper bodies for assisting movements and reducing backache during walking. The aim of this system was to control an elastically actuated motor to provide extra torques on a user’s hip by following the gaits in locomotion. And the whole exoskeletal spine mechanism (exo-spine) has been built of flexible material and fixed on an artificial pelvis. Thanks to the use of a cable-pulley-spring structure the torque applied to the hip is greatly amplified and would eventually affect the deformation of exo-spine, so that an auxiliary force is generated on the lower back to support user’s spine during the movements. Although the overall robot-assisted system was easily imaged and designed, its intrinsic complexity needed careful analysis, because the actuating process becomes highly nonlinear and noisy when compliant movements are demanded to mimic human performances in locomotion. Therefore, some appropriate assumptions were introduced, and to enhance the robustness of system, an adaptive controller was designed by applying Lyapunov Stability Theory. Finally, the correctness and feasibility of our proposed system were tested and estimated through a set of experimental simulations
Modeling and Simulating Compliant Movements in a Musculoskeletal Bipedal Robot
No full textThis paper describes the modeling and the simulation of a novel Elastic Bipedal Robot based on Human Musculoskeletal modeling. The geometrical organization of the robot artificial muscles is based on the organization of human muscles. In this paper we study how the robot active and passive elastic actuation structures develop force during selected motor tasks, and how we can model the contact between feet and ground. We then compare the robot dynamics to that of the human during the same motor tasks. The motivation behind this study is to reduce the development time by using a simulation environment for the purpose of developing a bipedal robot that takes advantage of the mechanisms underlying the human musculoskeletal dynamics for the generation of natural movement
Modeling, Dynamics and Control of an Extended Elastic Actuator in Musculoskeletal Robot SystemIntelligent Autonomous Systems 12
No full textThe conventional actuator of robot needs to be improved since the bandwidth of motor is limited and it cannot provide enough flexibility to perform the compliance in robot locomotion interacted with environment. In this paper, we present a novel elastic actuator so as to enhance the range of robot activities for adaptability. Considering the characteristics of elasticity and the demands in reality, a feasible study model is developed and constructed. According to the theory of Newton-Euler dynamics equations, the dynamics of model is mathematically described. To avoid unpredictable errors and manage joint oscillation in advance, we also employ a feedforward controller to operate the actuator. Moreover, the actuator can be regarded as the robotic "muscle-tendon" for its function is similar to the muscle-tendon model in human body. Therefore, we apply this actuation to a virtual robot arm based on the Musculoskeletal Robot System (MRS) to evaluate the performances of elastic actuators. The results of experiments indicate that this actuation is effective and contributed to realize the compliant locomotion
Simulating an Elastic Bipedal Robot Based on Musculoskeletal Modeling
Full text linkMany of the processes involved into the synthesis of human motion have much in common with problems found in robotics research. This paper describes the modeling and the simulation of a novel bipedal robot based on Series Elastic Actuators (SEAs) [1]. The robot model takes inspiration from the human musculoskeletal organization. The geometrical organization of the robot artificial muscles is based on the organization of human muscles. In this paper we study how the robot active and passive elastic actuation structures develop force during selected motor tasks. We then compare the robot dynamics to that of the human during the same motor tasks. The motivation behind this study is to translate the mechanisms underlying the human musculoskeletal dynamics to the robot design stage for the purpose of developing machines with better motor abilities and energy saving performances
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
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