6,435 research outputs found
Long-term experiments with an adaptive spherical view representation for navigation in changing environments
Real-world environments such as houses and offices change over time, meaning that a mobile robot’s map will become out of date. In this work, we introduce a method to update the reference views in a hybrid metric-topological map so that a mobile robot can continue to localize itself in a changing environment. The updating mechanism, based on the multi-store model of human memory, incorporates a spherical metric representation of the observed visual features for each node in the map, which enables the robot to estimate its heading and navigate using multi-view geometry, as well as representing the local 3D geometry of the environment. A series of experiments demonstrate the persistence performance of the proposed system in real changing environments, including analysis of the long-term stability
Model-Based Environmental Visual Perception for Humanoid Robots
The visual perception of a robot should answer two fundamental questions: What? and Where? In order to properly and efficiently reply to these questions, it is essential to establish a bidirectional coupling between the external stimuli and the internal representations. This coupling links the physical world with the inner abstraction models by sensor transformation, recognition, matching and optimization algorithms. The objective of this PhD is to establish this sensor-model coupling
Impact of random obstacles on the dynamics of a dense colloidal fluid
Using molecular dynamics simulations we study the slow dynamics of a
colloidal fluid annealed within a matrix of obstacles quenched from an
equilibrated colloidal fluid. We choose all particles to be of the same size
and to interact as hard spheres, thus retaining all features of the porous
confinement while limiting the control parameters to the packing fraction of
the matrix, {\Phi}m, and that of the fluid, {\Phi}f. We conduct detailed
investigations on several dynamic properties, including the tagged-particle and
collective intermediate scattering functions, the mean-squared displacement,
and the van Hove function. We show the confining obstacles to profoundly impact
the relaxation pattern of various quantifiers pertinent to the fluid. Varying
the type of quantifier (tagged-particle or collective) as well as {\Phi}m and
{\Phi}f, we unveil both discontinuous and continuous arrest scenarios.
Furthermore, we discover subdiffusive behavior and demonstrate its close
connection to the matrix structure. Our findings partly confirm the various
predictions of a recent extension of mode-coupling theory to the
quenched-annealed protocol.Comment: 16 pages, 20 figures, minor revision
Learning to Find Eye Region Landmarks for Remote Gaze Estimation in Unconstrained Settings
Conventional feature-based and model-based gaze estimation methods have
proven to perform well in settings with controlled illumination and specialized
cameras. In unconstrained real-world settings, however, such methods are
surpassed by recent appearance-based methods due to difficulties in modeling
factors such as illumination changes and other visual artifacts. We present a
novel learning-based method for eye region landmark localization that enables
conventional methods to be competitive to latest appearance-based methods.
Despite having been trained exclusively on synthetic data, our method exceeds
the state of the art for iris localization and eye shape registration on
real-world imagery. We then use the detected landmarks as input to iterative
model-fitting and lightweight learning-based gaze estimation methods. Our
approach outperforms existing model-fitting and appearance-based methods in the
context of person-independent and personalized gaze estimation
Learning to See the Wood for the Trees: Deep Laser Localization in Urban and Natural Environments on a CPU
Localization in challenging, natural environments such as forests or
woodlands is an important capability for many applications from guiding a robot
navigating along a forest trail to monitoring vegetation growth with handheld
sensors. In this work we explore laser-based localization in both urban and
natural environments, which is suitable for online applications. We propose a
deep learning approach capable of learning meaningful descriptors directly from
3D point clouds by comparing triplets (anchor, positive and negative examples).
The approach learns a feature space representation for a set of segmented point
clouds that are matched between a current and previous observations. Our
learning method is tailored towards loop closure detection resulting in a small
model which can be deployed using only a CPU. The proposed learning method
would allow the full pipeline to run on robots with limited computational
payload such as drones, quadrupeds or UGVs.Comment: Accepted for publication at RA-L/ICRA 2019. More info:
https://ori.ox.ac.uk/esm-localizatio
Assessing the role of static lengthscales behind glassy dynamics in polydisperse hard disks
The possible role of growing static order in the dynamical slowing down
towards the glass transition has recently attracted considerable attention. On
the basis of random first-order transition (RFOT) theory, a new method to
measure the static correlation length of amorphous order, called "point-to-set
(PTS)" length, has been proposed, and used to show that the dynamic length
grows much faster than the static length. Here we study the nature of the PTS
length, using a polydisperse hard disk system, which is a model that is known
to exhibit a growing hexatic order upon densification. We show that the PTS
correlation length is decoupled from the steeper increase of the correlation
length of hexatic order, while closely mirroring the decay length of two-body
density correlations. Our results thus provide a clear example that other forms
of order can play an important role in the slowing down of the dynamics,
casting a serious doubt on the order agnostic nature of the PTS length and its
relevance to slow dynamics, provided that a polydisperse hard disk system is a
typical glass former
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