337 research outputs found
UrbanFly: Uncertainty-Aware Planning for Navigation Amongst High-Rises with Monocular Visual-Inertial SLAM Maps
We present UrbanFly: an uncertainty-aware real-time planning framework for
quadrotor navigation in urban high-rise environments. A core aspect of UrbanFly
is its ability to robustly plan directly on the sparse point clouds generated
by a Monocular Visual Inertial SLAM (VINS) backend. It achieves this by using
the sparse point clouds to build an uncertainty-integrated cuboid
representation of the environment through a data-driven monocular plane
segmentation network. Our chosen world model provides faster distance queries
than the more common voxel-grid representation, and UrbanFly leverages this
capability in two different ways leading to as many trajectory optimizers. The
first optimizer uses a gradient-free cross-entropy method to compute
trajectories that minimize collision probability and smoothness cost. Our
second optimizer is a simplified version of the first and uses a sequential
convex programming optimizer initialized based on probabilistic safety
estimates on a set of randomly drawn trajectories. Both our trajectory
optimizers are made computationally tractable and independent of the nature of
underlying uncertainty by embedding the distribution of collision violations in
Reproducing Kernel Hilbert Space. Empowered by the algorithmic innovation,
UrbanFly outperforms competing baselines in metrics such as collision rate,
trajectory length, etc., on a high fidelity AirSim simulator augmented with
synthetic and real-world dataset scenes.Comment: Submitted to IROS 2022, Code available at
https://github.com/sudarshan-s-harithas/UrbanFl
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
View generated database
This document represents the final report for the View Generated Database (VGD) project, NAS7-1066. It documents the work done on the project up to the point at which all project work was terminated due to lack of project funds. The VGD was to provide the capability to accurately represent any real-world object or scene as a computer model. Such models include both an accurate spatial/geometric representation of surfaces of the object or scene, as well as any surface detail present on the object. Applications of such models are numerous, including acquisition and maintenance of work models for tele-autonomous systems, generation of accurate 3-D geometric/photometric models for various 3-D vision systems, and graphical models for realistic rendering of 3-D scenes via computer graphics
Evaluating the boundary and covering degree of planar Minkowski sums and other geometrical convolutions
AbstractAlgorithms are developed, based on topological principles, to evaluate the boundary and “internal structure” of the Minkowski sum of two planar curves. A graph isotopic to the envelope curve is constructed by computing its characteristic points. The edges of this graph are in one-to-one correspondence with a set of monotone envelope segments. A simple formula allows a degree to be assigned to each face defined by the graph, indicating the number of times its points are covered by the Minkowski sum. The boundary can then be identified with the set of edges that separate faces of zero and non-zero degree, and the boundary segments corresponding to these edges can be approximated to any desired geometrical accuracy. For applications that require only the Minkowski sum boundary, the algorithm minimizes geometrical computations on the “internal” envelope edges, that do not contribute to the final boundary. In other applications, this internal structure is of interest, and the algorithm provides comprehensive information on the covering degree for different regions within the Minkowski sum. Extensions of the algorithm to the computation of Minkowski sums in R3, and other forms of geometrical convolution, are briefly discussed
Automated 3D model generation for urban environments [online]
Abstract
In this thesis, we present a fast approach to automated
generation of textured 3D city models with both high details at
ground level and complete coverage for birds-eye view.
A ground-based facade model is acquired by driving a vehicle
equipped with two 2D laser scanners and a digital camera under
normal traffic conditions on public roads. One scanner is
mounted horizontally and is used to determine the approximate
component of relative motion along the movement of the
acquisition vehicle via scan matching; the obtained relative
motion estimates are concatenated to form an initial path.
Assuming that features such as buildings are visible from both
ground-based and airborne view, this initial path is globally
corrected by Monte-Carlo Localization techniques using an aerial
photograph or a Digital Surface Model as a global map. The
second scanner is mounted vertically and is used to capture the
3D shape of the building facades. Applying a series of automated
processing steps, a texture-mapped 3D facade model is
reconstructed from the vertical laser scans and the camera
images. In order to obtain an airborne model containing the roof
and terrain shape complementary to the facade model, a Digital
Surface Model is created from airborne laser scans, then
triangulated, and finally texturemapped with aerial imagery.
Finally, the facade model and the airborne model are fused
to one single model usable for both walk- and fly-thrus. The
developed algorithms are evaluated on a large data set acquired
in downtown Berkeley, and the results are shown and discussed
Past, Present, and Future of Simultaneous Localization And Mapping: Towards the Robust-Perception Age
Simultaneous Localization and Mapping (SLAM)consists in the concurrent
construction of a model of the environment (the map), and the estimation of the
state of the robot moving within it. The SLAM community has made astonishing
progress over the last 30 years, enabling large-scale real-world applications,
and witnessing a steady transition of this technology to industry. We survey
the current state of SLAM. We start by presenting what is now the de-facto
standard formulation for SLAM. We then review related work, covering a broad
set of topics including robustness and scalability in long-term mapping, metric
and semantic representations for mapping, theoretical performance guarantees,
active SLAM and exploration, and other new frontiers. This paper simultaneously
serves as a position paper and tutorial to those who are users of SLAM. By
looking at the published research with a critical eye, we delineate open
challenges and new research issues, that still deserve careful scientific
investigation. The paper also contains the authors' take on two questions that
often animate discussions during robotics conferences: Do robots need SLAM? and
Is SLAM solved
Constructing Binary Space Partitions for Orthogonal Rectangles in Practice
The original publication is available at www.springerlink.comIn this paper, we develop a simple technique for constructing
a I3inary Space Partition (nSP) for a set of orthogonal rectangles in IR3.
OUf algorithm has the novel feature that it tunes its performance to the
geometric properties of the rectangles, e.g., their aspect ratios.
"Fe have implemented our algorithm and tested its performance on real
data scti). V\.Tc have also systematically compared the performance of our
algorithm with that of other techniques presented in the literature. Our
studies show that our algorithm constructs nsps of near-linear size and
small height in practice, has fast running times, and answers queries
efficiently. It is a method of choice for constructing BSPs for orthogonal
rectangles
Using an anisotropic diffusion scale-space for the detection and delineation of shacks in informal settlement imagery
PhD, Faculty of Engineering and the Built Environment, University of the Witwatersrand, 2010Informal settlements are a growing world-wide phenomenon. Up-to-date spatial
information mapping settlements is essential for a variety of end-user applications
from planning settlement upgrading to monitoring expansion and infill. One method
of gathering this information is through the analysis of nadir-view aerial imagery and
the automated or semi-automated extraction of individual shacks. The problem of
shack detection and delineation in, particularly South African, informal settlements
is a unique and difficult one. This is primarily due to the inhomogeneous appearance
of shack roofs, which are constructed from a variety of disparate materials, and
the density of shacks. Previous research has focused mostly on the use of height
data in conjunction with optical images to perform automated or semi-automated
shack extraction. In this thesis, a novel approach to automating shack extraction is
presented and prototyped, in which the appearance of shack roofs is homogenised,
facilitating their detection. The main features of this strategy are: construction of
an anisotropic scale-space from a single source image and detection of hypotheses
at multiple scales; simplification of hypotheses' boundaries through discrete curve
evolution and regularisation of boundaries in accordance with an assumed shack
model - a 4-6 sided, compact, rectilinear shape; selection of hypotheses competing
across scales using fuzzy rules; grouping of hypotheses based on their support
for one another, and localisation and re-regularisation of boundaries through the
incorporation of image edges. The prototype's performance is evaluated in terms of
standard metrics and is analysed for four different images, having three different sets
of imaging conditions, and containing well over a hundred shacks. Detection rates in
terms of building counts vary from 83% to 100% and, in terms of roof area coverage,
from 55% to 84%. These results, each derived from a single source image, compare
favourably with those of existing shack detection systems, especially automated ones
which make use of richer source data. Integrating this scale-space approach with
height data offers the promise of even better results
Automatic Reconstruction of Textured 3D Models
Three dimensional modeling and visualization of environments is an increasingly important problem. This work addresses the problem of automatic 3D reconstruction and we present a system for unsupervised reconstruction of textured 3D models in the context of modeling indoor environments. We present solutions to all aspects of the modeling process and an integrated system for the automatic creation of large scale 3D models
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