1,720,975 research outputs found
Safe and Efficient Human-Robot Collaboration Part I: Estimation of Human Arm Motions
Get PDFA significant barrier regarding a successful im-
plementation of fenceless robot cells into manufacturing ar-
eas with humans is given by the inefficiency due to safety
requirements. Robot motions have to be slowed down so that
an unexpected collision with a human does not result in human
injuries. This velocity reduction leads to longer cycle times
and, hence, fenceless robot cells turn out as uneconomic. In
this paper, a new approach for human-robot collaboration
in assembly tasks is presented. For a better performance of
the robot, methods are investigated on how the robot can
exploit a maximum performance while maintaining the safety
of collaborating humans. For this purpose, the kinematics and
dynamics of a human arm are described by a control-oriented
dynamic model to determine its capability and reachability.
Successful experiments validate the dynamic model as well as
a corresponding projection approach for calculating possible
movements of the human arm that may lead to a collision
with the robot. Finally, this information is used to calculate an
admissible path velocity that minimizes the danger of human
injuries
Towards a Real-Time Optimal Motion Framework
No full textVariable stiffness robots have a distinct feature that makes them especially interesting to application of energetic optimality: their ability to mechanically store and release energy. However, solving any kind of optimization problem for such highly nonlinear dynamics is only possible numerically, i.e. offline. In turn, numerical optimal solutions would only contribute a clear benefit for dynamic environments / tasks (apart from rather general insights), if they would be accessible/ generalizable in real-time. In this thesis, a general framework for executing near-optimal motions for Rigid Robots and Variable Stiffness Arms in real-time is proposed. The approach for the problem is formulated as follows. First, a set of prototypical optimization problems, which represent a reasonable set of motions are sought to execute is defined. For some of these distinct tasks, the optimization problem for an ensemble roughly covering the respective task space is solved. Then, the associated cost function is used as a clustering metric for learning manifolds of the optimal solution space and encode them in a dynamical system via Dynamic Movement Primitives (DMPs). Then, a distance and cost function based metric is proposed to generalize from the learned parameterizations to a new optimization problem in real-time. In short, this thesis intense to overcome some of the well known problems of optimal control and nonlinear optimization, which are offline schemes, and the one of learning with associated generalization, which is suboptimality. The developed verified on two robotic systems, namely the DLR Light Weight Robot and the DLR Hand-Arm System. Several dynamic tasks as ball throwing or energy optimal point-to-point motions are considered and experimental
validated
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
Industrial Human-Robot Collaboration: Maximizing Performance While Maintaining Safety
Get PDFFor many years, separated autonomous robotic systems have been an essential component in industrial manufacturing. In particular, these heavy-payload robots perform a wide range of tasks, where high precision and repeatability is crucial. A flexible adaptation of fast changing tasks or environments as well as the interaction with humans can rather not be realized by these types of robots. Recently, a paradigm shift regarding customer demand could be observed. Short product life-cycles as well as increasing individualization of products require flexible manufacturing processes. Therefore, novel light-weight robot technology was developed, which enables the collaboration of humans and robots. In particular, highly productive robots are combined with the high flexibility of humans. However, only a few collaborative applications have been established in industry, which is mainly due to the low efficiency, i.e., large cycle times caused by safety regulations.
The goal of this thesis is to maximize performance in collaborative applications, while maintaining safety. For this, assembly workplaces are analyzed, typical tasks identified, and the potential of collaborative robots is elaborated. Current safety regulations are analyzed in order to identify the challenges in safe human-robot collaboration. Then, a novel control method is presented, which enables intuitive, safe, and efficient control of robots. The Mirroring Human Arm Motions approach presents a velocity-limited trajectory generation, in particular, for orientations in quaternion space. This method is extended to an online via-point trajectory generation in order to enable an adjustment of velocity limits for guaranteeing safety in realtime. Furthermore, in collaborative applications particularly collisions with the human arm are likely to occur. Therefore, human-arm performance is analyzed and experiments similar to typical collaborative scenarios are executed, to determine the dynamic properties. By exploiting the obtained information on human arm dynamics, a novel approach to improve the performance of robot motions is presented. From the experiments, a simplified human arm model is derived, which enables the calculation of movements of the human into the path of the robot. With this approach, a maximum robot velocity depending on kinematic limitations of robots and human-in-the-loop constraints can be determined. This idea is further developed into a nonlinear optimization problem, where minimal-time motions are found and applications with low-cycle times can be realized. In order to enable flexible robot motions within the entire workspace of the robot, a generalization method using Dynamic Movement Primitives is presented. It contains a novel real-time consideration of spacial and kinematic constraints, to fulfill the requirements on safe human-robot collaboration. Experiments on a collaborative workbench prove the effectiveness of the presented methods. Finally, a novel airbag technology is proposed, which enables a protective coverage of dangerous tools and objects and protects humans against injuries, caused by a collision with the robot. The so called Robotic Airbag is inflated with pressured air to create a cushion around sharp edges of tool and object. Intrinsic safety is guaranteed, as the airbag is always inflated before initiating a robot motion. In order to exclude an affect of the tool functionality, the Robotic Airbag can be deflated whenever required. Experiments with a crash-test dummy, and finally with a volunteer, prove the functionality and compliance with current safety standards. In Summary, the presented methods in this thesis enable a significant improvement of efficiency and safety in collaborative applications
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
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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