54 research outputs found
Navigation Among Movable Obstacles: Real-Time Reasoning in Complex Environments
Electronic version of an article published as International Journal of Humanoid Robotics, Vol. 2, No. 4, December, 2005 pp. 479-504; DOI: 10.1142/S0219843605000545 ; © World Scientific Publishing Company ; http://www.worldscinet.com/ijhr/ijhr.shtmlIn this paper, we address the problem of Navigation Among Movable Obstacles (NAMO):
a practical extension to navigation for humanoids and other dexterous mobile robots.
The robot is permitted to reconfigure the environment by moving obstacles and clearing
free space for a path. This paper presents a resolution complete planner for a subclass
of NAMO problems. Our planner takes advantage of the navigational structure through
state-space decomposition and heuristic search. The planning complexity is reduced to
the difficulty of the specific navigation task, rather than the dimensionality of the multi-object
domain. We demonstrate real-time results for spaces that contain large numbers
of movable obstacles. We also present a practical framework for single-agent search that can be used in algorithmic reasoning about this domain
Towards S-NAMO: Socially-aware Navigation Among Movable Obstacles
International audienc
Sampling-based Algorithms for Optimal Motion Planning
During the last decade, sampling-based path planning algorithms, such as
Probabilistic RoadMaps (PRM) and Rapidly-exploring Random Trees (RRT), have
been shown to work well in practice and possess theoretical guarantees such as
probabilistic completeness. However, little effort has been devoted to the
formal analysis of the quality of the solution returned by such algorithms,
e.g., as a function of the number of samples. The purpose of this paper is to
fill this gap, by rigorously analyzing the asymptotic behavior of the cost of
the solution returned by stochastic sampling-based algorithms as the number of
samples increases. A number of negative results are provided, characterizing
existing algorithms, e.g., showing that, under mild technical conditions, the
cost of the solution returned by broadly used sampling-based algorithms
converges almost surely to a non-optimal value. The main contribution of the
paper is the introduction of new algorithms, namely, PRM* and RRT*, which are
provably asymptotically optimal, i.e., such that the cost of the returned
solution converges almost surely to the optimum. Moreover, it is shown that the
computational complexity of the new algorithms is within a constant factor of
that of their probabilistically complete (but not asymptotically optimal)
counterparts. The analysis in this paper hinges on novel connections between
stochastic sampling-based path planning algorithms and the theory of random
geometric graphs.Comment: 76 pages, 26 figures, to appear in International Journal of Robotics
Researc
Evaluation of young smokers and non-smokers with Electrogustometry and Contact Endoscopy
<p>Abstract</p> <p>Background</p> <p>Smoking is the cause of inducing changes in taste functionality under conditions of chronic exposure. The objective of this study was to evaluate taste sensitivity in young smokers and non-smokers and identify any differences in the shape, density and vascularisation of the fungiform papillae (fPap) of their tongue.</p> <p>Methods</p> <p>Sixty-two male subjects who served in the Greek military forces were randomly chosen for this study. Thirty-four were non-smokers and 28 smokers. Smokers were chosen on the basis of their habit to hold the cigarette at the centre of their lips. Taste thresholds were measured with Electrogustometry (EGM). The morphology and density of the fungiform papillae (fPap) at the tip of the tongue were examined with Contact Endoscopy (CE).</p> <p>Results</p> <p>There was found statistically important difference (<it>p </it>< 0.05) between the taste thresholds of the two groups although not all smokers presented with elevated taste thresholds: Six of them (21%) had taste thresholds similar to those of non-smokers. Differences concerning the shape and the vessels of the fungiform papillae between the groups were also detected. Fewer and flatter fPap were found in 22 smokers (79%).</p> <p>Conclusion</p> <p>The majority of smokers shown elevated taste thresholds in comparison to non-smokers. Smoking is an important factor which can lead to decreased taste sensitivity. The combination of methods, such as EGM and CE, can provide useful information about the vascularisation of taste buds and their functional ability.</p
Navigation among movable obstacles: Real-time reasoning in complex environments
In this paper, we address the problem of Navigation Among Movable Obstacles (NAMO): a practical extension to navigation for humanoids and other dexterous mobile robots. The robot is permitted to reconfigure the environment by moving obstacles and clearing free space for a path. This paper presents a resolution complete planner for a subclass of NAMO problems. Our planner takes advantage of the navigational structure through state-space decomposition and heuristic search. The planning complexity is reduced to the difficulty of the specific navigation task, rather than the dimensionality of the multiobject domain. We demonstrate real-time results for spaces that contain large numbers of movable obstacles. We also present a practical framework for single-agent search that can be used in algorithmic reasoning about this domain
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