1,721,013 research outputs found
Design, construction and modelling of a low cost miniature UAV using machine vision
No full textThe price barrier for the implementation of UAVs commercially is substantial, limiting growth in this area. This paper presents results from a project aimed at developing light-weight and low-cost systems for the on-board control of a small scale commercially available helicopter, targeted at the low-end of the market. This would allow UAVs to be used by relatively untrained operators. The control system consists of two major streams, a vision system for high-level control and a low-level attitude control system. The vision system has been developed using a combination of a blackfun processor and an inexpensive cmos camera to implement colour segmentation algorithms. The attitude control system is developed using Fleck wireless sensor nodes developed at CSIRO. These inexpensive nodes perform sensing and control of the helicopter for data acquisition purposes. Flight data has been used to identify and verify a dynamic model of the helicopter
A vision system for optic-flow-based guidance of UAVs
No full textThere is considerable interest in designing guidance systems for UAVs that use passive sensing (such as vision), rather than active sensing which can be bulky, expensive and stealth-compromising. Here we describe and evaluate a sensor that uses optic flow for measurement and control of height above the ground. A video camera is used in conjunction with a specially shaped reflective surface to simplify the computation of optic flow, and extend the range of aircraft speeds over which accurate data can be obtained. The imaging system also provides a useful geometrical remapping of the environment, which facilitates obstacle avoidance and computation of 3-D terrain maps. Laboratory tests of the performance of the device, whilst undergoing complex motions, are described
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
A geometrical method for calculating the unreachable workspace of the 3-DOF Gantry-Tau parallel manipulator
No full textOne of the main advantages of the Gantry-Tau machine is a large accessible workspace/footprint ratio compared to many other parallel machines. The Gantry-Tau improves this ratio by allowing a change of assembly mode without internal link collisions or collisions between the links and the moving TCP platform. This paper introduces the geometric approach for the unreachable workspace area for the Gantry-Tau. The unreachable area can occur in the middle of the workspace of reconfigurable PKMs with fixed length actuators. It is important to eliminate unreachable areas when designing the Gantry-Tau PKM because they appear in the middle of the workspace which is often the most useful part of the workspace. This approach is significantly faster than analytical workspace calculation methods based on the inverse kinematics. Because of the fast computational speed of the geometric approach, the method is ideal for inclusion in a design optimisation framework. The design presented in this paper achieves a workspace/footprint ratio of more than 2.7 with a zero unreachable workspace. Typical PKMs, for example the Delta robot, has a ratio less than one. In addition, a workspace optimisation method is presented where the parameters are the support frame lengths and the robot's arm lengths
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
Detecting moving pedestrians and vehicles in fluctuating lighting conditions
No full textDetecting moving pedestrians and vehicles with foreground segmentation algorithms is problematic during fluctuating lighting conditions. Edge-based approaches are more robust to lighting than the conventional intensity-based ones. The issue with edge-based approaches though is segmenting the internal foreground areas. In this work a strategy is developed to detect complete foreground areas. Firstly, edge-extraction is performed at multiple scales which increases the initial area detected. To complete the detection of object areas, edge motion-history-images are introduced. The final segmentation is achieved with a region growing algorithm in the edge-motion-history-image. Examples are shown of the successful extraction of foreground objects through changing lighting conditions
A panoramic stereo imaging system for aircraft guidance
Full text linkThis paper describes an imaging system for aircraft guidance that provides panoramic stereo vision to facilitate surveillance, obstacle detection and avoidance, terrain following and landing. The system uses a single video camera in conjunction with a set of specially shaped reflective surfaces to enable the detection of objects in the environment and estimation of their range through stereo. The advantage of this device over systems that use optic flow information for visual guidance is that it does not rely on the movement the aircraft. Therefore, it can be used even at low flight speeds or hover
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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