23,701 research outputs found
Action for perception : active object recognition and pose estimation in cluttered environments
University of Technology Sydney. Faculty of Engineering and Information Technology.Object recognition and localisation are indispensable competency for service robots in everyday environments like offices and kitchens. Presence of similar objects that can only be differentiated from a small part of the surface together with clutter that leads to occlusions make it impossible to detect target objects accurately and reliably from a single observation. When the sensor observing the environment is mounted on a mobile platform, object detection and pose estimation can be facilitated by observing the environment from a series of different viewpoints. Computing Active perception strategies, with the aim of finding optimal actions to enhance object recognition and pose estimation performance is the focus of this thesis.
This thesis consists of two main parts:
In the first part, it focuses on object detection and pose estimation from a single frame of observation. Using an RGB-D sensor, we propose a modular 3D textured object detection and pose estimation framework which can recognise object under cluttered environment by taking advantage of the geometric information provided from the sensor. To handle less-textured objects and objects under severe illumination conditions, we propose a novel RGB-D feature which is robust to illumination, scale, rotation and viewpoint variations, and provides reliable feature matching results under challenging conditions. The proposed feature is validated for multiple applications including object detection and point cloud alignment. Parts of the above approaches are integrated with existing work to produce a practical and effective perception module for a warehouse automation task. The designed perception system can detect objects of different types and estimate their poses robustly thus guaranteeing a reliable object grasping and manipulation performances.
In the second part of the thesis, we investigate the problem of active object detection and pose estimation from two perspectives: with and without considering the uncertainties in the motion model and the observation model. First, we propose a model-driven active object recognition and pose estimation system via exploiting the feature association probability under scale and viewpoint variations. By explicitly modelling the feature association, the proposed system can predict future information more accurately thus laying the foundation of a successful active Next-Best-View planning system even with a naive greedy search technique. We also present a probabilistic framework which handles motion and observation uncertainties in the active object detection and pose estimation problem. We present an optimisation framework which computes the optimal control at each step, using an objective function which incorporates uncertainties in state estimation, feature coverage for better recognition confidence and control consumption. The proposed framework can handle various issues such as object initialisation, collision avoidance, occlusion and changing the object hypothesis. Validations based on a simulation environment are also presented
Deep Directional Statistics: Pose Estimation with Uncertainty Quantification
Modern deep learning systems successfully solve many perception tasks such as
object pose estimation when the input image is of high quality. However, in
challenging imaging conditions such as on low-resolution images or when the
image is corrupted by imaging artifacts, current systems degrade considerably
in accuracy. While a loss in performance is unavoidable, we would like our
models to quantify their uncertainty in order to achieve robustness against
images of varying quality. Probabilistic deep learning models combine the
expressive power of deep learning with uncertainty quantification. In this
paper, we propose a novel probabilistic deep learning model for the task of
angular regression. Our model uses von Mises distributions to predict a
distribution over object pose angle. Whereas a single von Mises distribution is
making strong assumptions about the shape of the distribution, we extend the
basic model to predict a mixture of von Mises distributions. We show how to
learn a mixture model using a finite and infinite number of mixture components.
Our model allows for likelihood-based training and efficient inference at test
time. We demonstrate on a number of challenging pose estimation datasets that
our model produces calibrated probability predictions and competitive or
superior point estimates compared to the current state-of-the-art
Hybrid Bayesian Eigenobjects: Combining Linear Subspace and Deep Network Methods for 3D Robot Vision
We introduce Hybrid Bayesian Eigenobjects (HBEOs), a novel representation for
3D objects designed to allow a robot to jointly estimate the pose, class, and
full 3D geometry of a novel object observed from a single viewpoint in a single
practical framework. By combining both linear subspace methods and deep
convolutional prediction, HBEOs efficiently learn nonlinear object
representations without directly regressing into high-dimensional space. HBEOs
also remove the onerous and generally impractical necessity of input data
voxelization prior to inference. We experimentally evaluate the suitability of
HBEOs to the challenging task of joint pose, class, and shape inference on
novel objects and show that, compared to preceding work, HBEOs offer
dramatically improved performance in all three tasks along with several orders
of magnitude faster runtime performance.Comment: To appear in the International Conference on Intelligent Robots
(IROS) - Madrid, 201
Learning Analysis-by-Synthesis for 6D Pose Estimation in RGB-D Images
Analysis-by-synthesis has been a successful approach for many tasks in
computer vision, such as 6D pose estimation of an object in an RGB-D image
which is the topic of this work. The idea is to compare the observation with
the output of a forward process, such as a rendered image of the object of
interest in a particular pose. Due to occlusion or complicated sensor noise, it
can be difficult to perform this comparison in a meaningful way. We propose an
approach that "learns to compare", while taking these difficulties into
account. This is done by describing the posterior density of a particular
object pose with a convolutional neural network (CNN) that compares an observed
and rendered image. The network is trained with the maximum likelihood
paradigm. We observe empirically that the CNN does not specialize to the
geometry or appearance of specific objects, and it can be used with objects of
vastly different shapes and appearances, and in different backgrounds. Compared
to state-of-the-art, we demonstrate a significant improvement on two different
datasets which include a total of eleven objects, cluttered background, and
heavy occlusion.Comment: 16 pages, 8 figure
Event-based Vision: A Survey
Event cameras are bio-inspired sensors that differ from conventional frame
cameras: Instead of capturing images at a fixed rate, they asynchronously
measure per-pixel brightness changes, and output a stream of events that encode
the time, location and sign of the brightness changes. Event cameras offer
attractive properties compared to traditional cameras: high temporal resolution
(in the order of microseconds), very high dynamic range (140 dB vs. 60 dB), low
power consumption, and high pixel bandwidth (on the order of kHz) resulting in
reduced motion blur. Hence, event cameras have a large potential for robotics
and computer vision in challenging scenarios for traditional cameras, such as
low-latency, high speed, and high dynamic range. However, novel methods are
required to process the unconventional output of these sensors in order to
unlock their potential. This paper provides a comprehensive overview of the
emerging field of event-based vision, with a focus on the applications and the
algorithms developed to unlock the outstanding properties of event cameras. We
present event cameras from their working principle, the actual sensors that are
available and the tasks that they have been used for, from low-level vision
(feature detection and tracking, optic flow, etc.) to high-level vision
(reconstruction, segmentation, recognition). We also discuss the techniques
developed to process events, including learning-based techniques, as well as
specialized processors for these novel sensors, such as spiking neural
networks. Additionally, we highlight the challenges that remain to be tackled
and the opportunities that lie ahead in the search for a more efficient,
bio-inspired way for machines to perceive and interact with the world
Graph-based classification of multiple observation sets
We consider the problem of classification of an object given multiple
observations that possibly include different transformations. The possible
transformations of the object generally span a low-dimensional manifold in the
original signal space. We propose to take advantage of this manifold structure
for the effective classification of the object represented by the observation
set. In particular, we design a low complexity solution that is able to exploit
the properties of the data manifolds with a graph-based algorithm. Hence, we
formulate the computation of the unknown label matrix as a smoothing process on
the manifold under the constraint that all observations represent an object of
one single class. It results into a discrete optimization problem, which can be
solved by an efficient and low complexity algorithm. We demonstrate the
performance of the proposed graph-based algorithm in the classification of sets
of multiple images. Moreover, we show its high potential in video-based face
recognition, where it outperforms state-of-the-art solutions that fall short of
exploiting the manifold structure of the face image data sets.Comment: New content adde
Deep Single-View 3D Object Reconstruction with Visual Hull Embedding
3D object reconstruction is a fundamental task of many robotics and AI
problems. With the aid of deep convolutional neural networks (CNNs), 3D object
reconstruction has witnessed a significant progress in recent years. However,
possibly due to the prohibitively high dimension of the 3D object space, the
results from deep CNNs are often prone to missing some shape details. In this
paper, we present an approach which aims to preserve more shape details and
improve the reconstruction quality. The key idea of our method is to leverage
object mask and pose estimation from CNNs to assist the 3D shape learning by
constructing a probabilistic single-view visual hull inside of the network. Our
method works by first predicting a coarse shape as well as the object pose and
silhouette using CNNs, followed by a novel 3D refinement CNN which refines the
coarse shapes using the constructed probabilistic visual hulls. Experiment on
both synthetic data and real images show that embedding a single-view visual
hull for shape refinement can significantly improve the reconstruction quality
by recovering more shapes details and improving shape consistency with the
input image.Comment: 11 page
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