26,157 research outputs found
Efficiently learning metric and topological maps with autonomous service robots
Models of the environment are needed for a wide range of robotic applications, from search and rescue to automated vacuum cleaning. Learning maps has therefore been a major research focus in the robotics community over the last decades. In general, one distinguishes between metric and topological maps. Metric maps model the environment based on grids or geometric representations whereas topological maps model the structure of the environment using a graph. The contribution of this paper is an approach that learns a metric as well as a topological map based on laser range data obtained with a mobile robot. Our approach consists of two steps. First, the robot solves the simultaneous localization and mapping problem using an efficient probabilistic filtering technique. In a second step, it acquires semantic information about the environment using machine learning techniques. This semantic information allows the robot to distinguish between different types of places like, e. g., corridors or rooms. This enables the robot to construct annotated metric as well as topological maps of the environment. All techniques have been implemented and thoroughly tested using real mobile robot in a variety of environments
Topology of the universe from COBE-DMR; a wavelet approach
In this paper we pursue a new technique to search for evidence of a finite
Universe, making use of a spherical mexican-hat wavelet decomposition of the
microwave background fluctuations. Using the information provided by the
wavelet coefficients at several scales we test whether compact orientable flat
topologies are consistent with the COBE-DMR data. We consider topological sizes
ranging from half to twice the horizon size. A scale-scale correlation test
indicates that non-trivial topologies with appropriate topological sizes are as
consistent with the COBE-DMR data as an infinite universe. Among the finite
models the data seems to prefer a Universe which is about the size of the
horizon for all but the hypertorus and the triple-twist torus. For the latter
the wavelet technique does not seem a good discriminator of scales for the
range of topological sizes considered here, while a hypertorus has a preferred
size which is 80% of the horizon. This analysis allows us to find a best fit
topological size for each model, although cosmic variance might limit our
ability to distinguish some of the topologies.Comment: 10 pages, 13 figures (12 coloured), submitted to MNRAS. Figures 1,2
and 3 are not included but a complete version of the paper with high
resolution figures can be downloaded from
(http://www.mrao.cam.ac.uk/~graca/topol/
Incremental spectral clustering and its application to topological mapping
This paper presents a novel use of spectral clustering algorithms to support cases where the entries in the affinity matrix are costly to compute. The method is incremental – the
spectral clustering algorithm is applied to the affinity matrix after each row/column is added – which makes it possible to inspect the clusters as new data points are added. The method is well suited to the problem of appearance-based, on-line topological mapping for mobile robots. In this problem domain, we show that we can reduce environment-dependent parameters of the clustering algorithm to just a single, intuitive parameter. Experimental results in large outdoor and indoor environments
show that we can close loops correctly by computing only a fraction of the entries in the affinity matrix. The accompanying video clip shows how an example map is produced by the
algorithm
Keyframe-based monocular SLAM: design, survey, and future directions
Extensive research in the field of monocular SLAM for the past fifteen years
has yielded workable systems that found their way into various applications in
robotics and augmented reality. Although filter-based monocular SLAM systems
were common at some time, the more efficient keyframe-based solutions are
becoming the de facto methodology for building a monocular SLAM system. The
objective of this paper is threefold: first, the paper serves as a guideline
for people seeking to design their own monocular SLAM according to specific
environmental constraints. Second, it presents a survey that covers the various
keyframe-based monocular SLAM systems in the literature, detailing the
components of their implementation, and critically assessing the specific
strategies made in each proposed solution. Third, the paper provides insight
into the direction of future research in this field, to address the major
limitations still facing monocular SLAM; namely, in the issues of illumination
changes, initialization, highly dynamic motion, poorly textured scenes,
repetitive textures, map maintenance, and failure recovery
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