380 research outputs found
Designing Behavior Trees from Goal-Oriented LTLf Formulas
Temporal logic can be used to formally specify autonomous agent goals, but
synthesizing planners that guarantee goal satisfaction can be computationally
prohibitive. This paper shows how to turn goals specified using a subset of
finite trace Linear Temporal Logic (LTL) into a behavior tree (BT) that
guarantees that successful traces satisfy the LTL goal. Useful LTL formulas for
achievement goals can be derived using achievement-oriented task mission
grammars, leading to missions made up of tasks combined using LTL operators.
Constructing BTs from LTL formulas leads to a relaxed behavior synthesis
problem in which a wide range of planners can implement the action nodes in the
BT. Importantly, any successful trace induced by the planners satisfies the
corresponding LTL formula. The usefulness of the approach is demonstrated in
two ways: a) exploring the alignment between two planners and LTL goals, and b)
solving a sequential key-door problem for a Fetch robot.Comment: Accepted as "Most Visionary Paper" in Autonomous Robots and
Multirobot Systems (ARMS) 2023 workshop affiliated with the 22nd
International Conference on Autonomous Agents and Multiagent Systems (AAMAS
2023
Mice Infected with Low-virulence Strains of Toxoplasma gondii Lose their Innate Aversion to Cat Urine, Even after Extensive Parasite Clearance
Toxoplasma gondii chronic infection in rodent secondary hosts has been
reported to lead to a loss of innate, hard-wired fear toward cats, its primary
host. However the generality of this response across T. gondii strains and the
underlying mechanism for this pathogen mediated behavioral change remain
unknown. To begin exploring these questions, we evaluated the effects of
infection with two previously uninvestigated isolates from the three major
North American clonal lineages of T. gondii, Type III and an attenuated strain
of Type I. Using an hour-long open field activity assay optimized for this
purpose, we measured mouse aversion toward predator and non-predator urines. We
show that loss of innate aversion of cat urine is a general trait caused by
infection with any of the three major clonal lineages of parasite.
Surprisingly, we found that infection with the attenuated Type I parasite
results in sustained loss of aversion at times post infection when neither
parasite nor ongoing brain inflammation were detectable. This suggests that T.
gondii-mediated interruption of mouse innate aversion toward cat urine may
occur during early acute infection in a permanent manner, not requiring
persistence of parasitecysts or continuing brain inflammation.Comment: 14 pages, 3 figure
Fully Retroactive Approximate Range and Nearest Neighbor Searching
We describe fully retroactive dynamic data structures for approximate range
reporting and approximate nearest neighbor reporting. We show how to maintain,
for any positive constant , a set of points in indexed by time
such that we can perform insertions or deletions at any point in the timeline
in amortized time. We support, for any small constant ,
-approximate range reporting queries at any point in the timeline
in time, where is the output size. We also show how to
answer -approximate nearest neighbor queries for any point in the
past or present in time.Comment: 24 pages, 4 figures. To appear at the 22nd International Symposium on
Algorithms and Computation (ISAAC 2011
Tracking Paths in Planar Graphs
We consider the NP-complete problem of tracking paths in a graph, first introduced by Banik et al. [Banik et al., 2017]. Given an undirected graph with a source s and a destination t, find the smallest subset of vertices whose intersection with any s-t path results in a unique sequence. In this paper, we show that this problem remains NP-complete when the graph is planar and we give a 4-approximation algorithm in this setting. We also show, via Courcelle\u27s theorem, that it can be solved in linear time for graphs of bounded-clique width, when its clique decomposition is given in advance
Comparing the Usefulness of Video and Map Information In Navigation Tasks
One of the fundamental aspects of robot teleoperation is the ability to successfully navigate a robot through an environment. We define successful navigation to mean that the robot minimizes collisions and arrives at the destination in a timely manner. Often video and map information is presented to a robot operator to aid in navigation tasks. This paper addresses the usefulness of map and video information in a navigation task by comparing a side-by-side (2D) representation and an integrated (3D) representation in both a simulated and a real world study. The results suggest that sometimes video is more helpful than a map and other times a map is more helpful than video. From a design perspective, an integrated representation seems to help navigation more than placing map and video side-by-side
Semi-autonomous human-UAV interfaces for fixed-wing mini-UAVs
Abstract-We present several human-robot interfaces that support real-time control of a small semi-autonomous UAV. These interfaces are designed for searching tasks and other missions that typically do not have a precise predetermined flight plan. We present a detailed analysis of a PDA interface and describe how our other interfaces relate to this analysis. We then offer quantative and qualitative performance comparisons of the interfaces, as well as an analysis of their possible real-world applications
HST Imaging Polarimetry of the Gravitational Lens FSC10214+4724
We present imaging polarimetry of the extremely luminous, redshift 2.3 IRAS
source FSC10214+4724. The observations were obtained with HST's Faint Object
Camera in the F437M filter, which is free of strong emission lines. The 0.7
arcsec long arc is unresolved to 0.04 arcsec FWHM in the transverse direction,
and has an integrated polarization of 28 +/- 3 percent, in good agreement with
ground-based observations. The polarization position angle varies along the arc
by up to 35 deg. The overall position angle is 62 +/- 3 deg east of north. No
counterimage is detected to B = 27.5 mag (), giving an observed arc to
counterimage flux ratio greater than 250, considerably greater than the flux
ratio of 100 measured previously in the I-band. This implies that the
configuration of the object in the source plane at the B-band is different from
that at I-band, and/or that the lensing galaxy is dusty.Comment: 17 pages, 3 figures. Accepted for publication in Astronomical
Journal, February 199
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