1,720,959 research outputs found
Unmanning UAVs – Addressing Challenges in On-Board Planning and Decision Making
No full textPlanning and decision making, especially the planning of dynamically negotiable collision free paths, is an integral part in the operation of Unmanned Aerial Vehicles (UAVs). Effective path planning ensures that the UAV operates safely, and conforms to the rules and regulations governing flight within the National Airspace System (NAS). To demonstrate an Equivalent Level Of Safety (ELOS) to that of piloted aircraft for certification purposes, UAVs must demonstrate a high level of autonomy without a human\ud
in the loop. This research surveys the literature as to how human experts perform planning tasks and forms a framework which promotes shared authority of UAV mission (re)planning and path planning, and can adopt sole authority should the UAV communications link fail or the human operator relinquishes decisions. It has been demonstrated through simulation that the optimization of flight manoeuvre sets using multiple objectives allows for convergence to a solution which better represents civilian mission requirements whilst emulating common flight patterns of trained pilots. These initial findings highlight the challenges involved in replicating the skills of human pilots onboard a UAV. It is revealed that UAV planning and decision making is a multi-disciplinary problem that combines the fields of path planning (search optimization), trajectory generation, and human cognitio
A High Performance Fuzzy Logic Architecture for UAV Decision Making
No full textThe majority of Unmanned Aerial Vehicles (UAVs) in\ud
operation today are not truly autonomous, but are instead\ud
reliant on a remote human pilot. A high degree of\ud
autonomy can provide many advantages in terms of cost,\ud
operational resources and safety. However, one of the\ud
challenges involved in achieving autonomy is that of\ud
replicating the reasoning and decision making capabilities\ud
of a human pilot. One candidate method for providing this\ud
decision making capability is fuzzy logic. In this role, the\ud
fuzzy system must satisfy real-time constraints, process\ud
large quantities of data and relate to large knowledge\ud
bases. Consequently, there is a need for a generic, high\ud
performance fuzzy computation platform for UAV\ud
applications. Based on Lees’ [1] original work, a high\ud
performance fuzzy processing architecture, implemented\ud
in Field Programmable Gate Arrays (FPGAs), has been\ud
developed and is shown to outclass the performance of\ud
existing fuzzy processors
An Intelligent Control Architecture for Unmanned Aerial Systems (UAS) in the National Airspace System (NAS)
No full textIn recent times, Unmanned Aerial Systems (UAS) have been employed in an increasingly diverse range of applications. Numerous UAS market forecasts portray a burgeoning future, with many applications in both the military and civilian domains. Within the civilian realm, UAS are expected to be useful in performing a wide range of missions such as disaster monitoring (e.g. wildfires, earth-quakes, tsunamis and cyclones), search and support, and atmospheric observation. \ud
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However, to realise these civilian applications, seamless operation of UAS within the National Air Space (NAS) will be required. Increasing the levels of onboard autonomy will help to address this requirement. Additionally, increased autonomy also reduces the impact of onboard failures, potentially lower operational costs, and decrease operator workload. \ud
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Numerous intelligent control architectures do exist in the literature for mobile robots, space based robots and for UAS. These include: the WITAS project, Open Control Platform, Remote Agent and TRAC/ReACT. However, none of these are specifically targeted at providing the required support for a wide range of civilian UAS missions. Operation of UAS in the NAS for civil applications require robust methods for dealing with emergency scenarios such as performing forced landings and collision avoidance to preserve the safety of people and property. \ud
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This paper presents a new multi layered intelligent control architecture. The highest layer provides deliberative reasoning and includes situational awareness and mission planning subsystems. The middle layers deals with navigational aspects (such as path planning and manoeuvre generation). Finally, there is a functional control layer which comprises sensor and actuator subsystems and provides reactive functionality to enable forced landings and collision avoidance. Collision avoidance and forced landing technologies are currently under development at the Australian Research Centre for Aerospace Automation (ARCAA)
Computationally adaptive multi-objective trajectory optimization for UAS with variable planning deadlines
Full text linkThis paper presents a new approach which allows for the computation and optimization of feasible 3D flight trajectories within real time planning deadlines, for Unmanned Aerial Systems (UAS) operating in environments with obstacles present. Sets of candidate flight trajectories have been generated through the application of maneuver automaton theory, where smooth trajectories are formed via the concatenation of predefined trim and maneuver primitives; generated using aircraft dynamic models. During typical UAS operations, multiple objectives may exist, therefore the use of multi-objective optimization can potentially allow for convergence to a solution which better reflects overall mission requirements. Multiple objective optimization of trajectories has been implemented through weighted sum aggregation. However, real-time planning constraints may be imposed on the multi-objective optimization process due to the existence of obstacles in the immediate path. Thus, a novel Computationally Adaptive Trajectory Decision (CATD) optimization system has been developed and implemented in simulation to dynamically manage, calculate and schedule system execution parameters to ensure that the trajectory solution search can generate a feasible solution, if one exists, within a given length of time. The inclusion of the CATD potentially increases overall mission efficiency and may allow for the implementation of the system on different UAS platforms with varying onboard computational capabilities. This approach has been demonstrated in this paper through simulation using a fixed wing UAS operating in low altitude environments with obstacles present
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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