1,720,958 research outputs found
Adaptive Robust Three-dimensional Trajectory Tracking for Actively Articulated Tracked Vehicles
No full textA new approach is proposed for an adaptive robust three-dimensional (3D) trajectory-tracking controller design.
The controller is modeled for actively articulated tracked vehicles (AATVs). These vehicles have active subtracks,
called flippers, linked to the ends of the main tracks, to extend the locomotion capabilities in hazardous
environments, such as rescue scenarios. The proposed controller adapts the flippers configuration and simultaneously
generates the track velocities, to allow the vehicle to autonomously follow a given feasible 3D path.
The approach develops both a direct and differential kinematic model of the AATV for traversal task execution
correlating the robot body motion to the flippers motion. The benefit of this approach is to allow the controller
to flexibly manage all the degrees of freedom of the AATV as well as the steering. The differential kinematic
model integrates a differential drive robot model, compensating the slippage between the vehicle tracks and the
traversed terrain. The underlying feedback control law dynamically accounts for the kinematic singularities of
the mechanical vehicle structure. The designed controller integrates a strategy selector too, which has the role of
locally modifying the rail path of the flipper end points. This serves to reduce both the effort of the flipper servo
motors and the traction force on the robot body, recognizing when the robot is moving on a horizontal plane
surface. Several experiments have been performed, in both virtual and real scenarios, to validate the designed
trajectory-tracking controller, while the AATV negotiates rubble, stairs, and complex terrain surfaces. Results
are compared with both the performance of an alternative control strategy and the ability of skilled human
operators, manually controlling the actively articulated components of the robot
Learning the dynamic process of inhibition and task switching in robotics cognitive control
No full textModeling cognitive control is a major issue in robot control, and it is about deciding when a task cannot succeed and a new task need to be initiated. These decisions are induced by incoming stimuli alerting of events taking place while the robot is executing its duties. To learn cognitive control we address the human inspired mechanisms that govern cognitive control and that have been widely studied in neuroscience, namely, shifting and inhibition. Shifting and inhibition are, in fact, executive cognitive functions responding selectively to stimuli, so as to switch from one activity to a more compelling one or to inhibit inappropriate urges and preserve focus on the current task. In an autonomous system these cognitive skills are crucial to assess a well-regulated reactive behavior, which is of particular relevance in critical circumstances. In this paper we illustrate a new method developed for learning shifting and inhibition, based on Gaussian Processes, and using examples provided by skilled operators. We finally show that the learning method is promising and can be seen as a new view for modeling robot reactive and proactive behaviors. © 2013 IEEE
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
Real-time autonomous 3D navigation for tracked vehicles in rescue environments
No full textThe paper presents a novel framework for 3D
autonomous navigation for tracked vehicles. The framework
takes care of clustering and segmentation of point clouds,
traversability analysis, autonomous 3D path planning, motion
planning and flippers control. Results illustrated in an experiment
section show that the framework is promising to face
harsh terrains. Robot performance is proved in three main
experiments taken in a training rescue area, on fire escape
stairs and in a non-planar testing environment, built ad-hoc to
prove 3D path planning functionalities. Performance tests are
also presented
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
An Augmented Reality approach for trajectory planning and control of tracked vehicles in rescue environments
No full textIn this paper we propose a framework for trajectory planning and control of tracked vehicles for rescue environments, based on Augmented Reality (AR). The framework provides the human operator with an AR-based interface that facilitates both 3D path planning and obstacle negotiation. The interface converts the 3D movements of a marker pen, handheld by the operator, into trajectories feasible for the tracked vehicle. The framework implements a trajectory tracking controller to allow the tracked vehicle to autonomously follow the trajectories, decided by the operator. This controller relies on a localization system which provides, at real-time, position feedback. The localization system exploits the performance of a Dead Reckoning System together with the accuracy of an ICP-based SLAM in pose estimation, to determine the pose of the tracked vehicle within the 3D map. We demonstrate the application of the planning framework in autonomous robot navigation for evaluating the robot capabilities in rescue environments. Our experiments show the effectiveness of the trajectory tracking control method. © 2013 IEEE
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
- …
