1,721,317 research outputs found
Computer vision methods for improved mobile robot state estimation in challenging terrains
No full textExternal perception based on vision plays a critical role in developing improved and robust localization algorithms, as well as gaining important information about the vehicle and the terrain it is traversing. This paper presents two novel methods for rough terrain-mobile robots, using visual input. The first method consists of a stereovision algorithm for real-time 6DoF ego-motion estimation. It integrates image intensity information and 3D stereo data in the well-known Iterative Closest Point (ICP) scheme. Neither a-priori knowledge of the motion nor inputs from other sensors are required, while the only assumption is that the scene always contains visually distinctive features which can be tracked over subsequent stereo pairs. This generates what is usually referred to as visual odometry. The second method aims at estimating the wheel sinkage of a mobile robot on sandy soil, based on edge detection strategy. A semi-empirical model of wheel sinkage is also presented referring to the classical terramechanics theory. Experimental results obtained with an all-terrain mobile robot and with a wheel sinkage test bed are presented to validate our approach. It is shown that the proposed techniques can be integrated in control and planning algorithms to improve the performance of ground vehicles operating in uncharted environments. © 2006 ACADEMY PUBLISHER
Adaptive Tank-based Control for Aerial Physical Interaction with Uncertain Dynamic Environments Using Energy-Task Estimation
No full textWhile aerial manipulation has witnessed noticeable growth as a field in the last decade, most works investigated forms of interaction with static and rigid environments only. Whenever dynamic environments were considered, the employed methods often relied on the knowledge of the model of the environment, which in most real applications cannot be obtained. In this work, we propose an adaptive controller for a fully actuated UAV performing stable and efficient physical interaction tasks with unmodeled and dynamic objects moving in unknown environments. We develop a passive time-varying impedance controller and wrench tracking controller, whose adaptable parameters allow us to minimize tracking error and instabilities during the execution of the interaction task. Robust stability is guaranteed by energy tanks, with the addition of a task-based formulation for adapting online the tank parameters in order to always provide the system with an adequate amount of energy. The control framework is validated both in simulations and experimentally by interacting with an unmodeled cart moving in passive time-varying environments, while subjected to unknown disturbances
Climbing robot for corrosion monitoring of reinforced concrete structures
No full textThis paper introduces a climbing robot for corrosion monitoring of reinforced concrete structures such as cooling towers, dams or bridges. The robot combines a vortex adhesion mechanism with a wheel electrode sensor for potential mapping of the concrete surface. A detailed description of the system is presented first. A special effort was made during the design in order to develop a lightweight device. The climbing robot is well suited for rough surfaces and can climb on vertical surfaces or move upside-down. The experiments that have been done to validate the concept are presented afterwards. They show that the climbing robot has several advantages over the traditional corrosion monitoring technique. This robot will therefore provide engineers in charge of infrastructure maintenance with the means to do their job much better than they can today. It offers them a way to circumvent all present barriers and brings a radical innovation in this area
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
A Survey on Policy Search for Robotics
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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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