59,519 research outputs found
Joint Registration and Fusion of an Infra-Red Camera and Scanning Radar in a Maritime Context
The number of nodes in sensor networks is continually increasing, and maintaining accurate track estimates inside their common surveillance region is a critical necessity. Modern sensor platforms are likely to carry a range of different sensor modalities, all providing data at differing rates, and with varying degrees of uncertainty. These factors complicate the fusion problem as multiple observation models are required, along with a dynamic prediction model. However, the problem is exacerbated when sensors are not registered correctly with respect to each other, i.e. if they are subject to a static or dynamic bias. In this case, measurements from different sensors may correspond to the same target, but do not correlate with each other when in the same Frame of Reference (FoR), which decreases track accuracy. This paper presents a method to jointly estimate the state of multiple targets in a surveillance region, and to correctly register a radar and an Infrared Search and Track (IRST) system onto the same FoR to perform sensor fusion. Previous work using this type of parent-offspring process has been successful when calibrating a pair of cameras, but has never been attempted on a heterogeneous sensor network, nor in a maritime environment. This article presents results on both simulated scenarios and a segment of real data that show a significant increase in track quality in comparison to using incorrectly calibrated sensors or single-radar only
Factor Graphs for Heterogeneous Bayesian Decentralized Data Fusion
This paper explores the use of factor graphs as an inference and analysis
tool for Bayesian peer-to-peer decentralized data fusion. We propose a
framework by which agents can each use local factor graphs to represent
relevant partitions of a complex global joint probability distribution, thus
allowing them to avoid reasoning over the entirety of a more complex model and
saving communication as well as computation cost. This allows heterogeneous
multi-robot systems to cooperate on a variety of real world, task oriented
missions, where scalability and modularity are key. To develop the initial
theory and analyze the limits of this approach, we focus our attention on
static linear Gaussian systems in tree-structured networks and use Channel
Filters (also represented by factor graphs) to explicitly track common
information. We discuss how this representation can be used to describe various
multi-robot applications and to design and analyze new heterogeneous data
fusion algorithms. We validate our method in simulations of a multi-agent
multi-target tracking and cooperative multi-agent mapping problems, and discuss
the computation and communication gains of this approach.Comment: 8 pages, 6 figures, 1 table, submitted to the 24th International
Conference on Information Fusio
Collaborative signal and information processing for target detection with heterogeneous sensor networks
In this paper, an approach for target detection and acquisition with heterogeneous sensor networks through strategic resource allocation and coordination is presented. Based on sensor management and collaborative signal and information processing, low-capacity low-cost sensors are strategically deployed to guide and cue scarce high performance sensors in the network to improve the data quality, with which the mission is eventually completed more efficiently with lower cost. We focus on the problem of designing such a network system in which issues of resource selection and allocation, system behaviour and capacity, target behaviour and patterns, the environment, and multiple constraints such as the cost must be addressed simultaneously. Simulation results offer significant insight into sensor selection and network operation, and demonstrate the great benefits introduced by guided search in an application of hunting down and capturing hostile vehicles on the battlefield
Activity-dependence of synaptic vesicle dynamics
The proper function of synapses relies on efficient recycling of synaptic vesicles. The small size of synaptic boutons has hampered efforts to define the dynamical states of vesicles during recycling. Moreover, whether vesicle motion during recycling is regulated by neural activity remains largely unknown. We combined nanoscale-resolution tracking of individual synaptic vesicles in cultured hippocampal neurons from rats of both sexes with advanced motion analyses to demonstrate that the majority of recently endocytosed vesicles undergo sequences of transient dynamical states including epochs of directed, diffusional, and stalled motion. We observed that vesicle motion is modulated in an activity-dependent manner, with dynamical changes apparent in ∼20% of observed boutons. Within this subpopulation of boutons, 35% of observed vesicles exhibited acceleration and 65% exhibited deceleration, accompanied by corresponding changes in directed motion. Individual vesicles observed in the remaining ∼80% of boutons did not exhibit apparent dynamical changes in response to stimulation. More quantitative transient motion analyses revealed that the overall reduction of vesicle mobility, and specifically of the directed motion component, is the predominant activity-evoked change across the entire bouton population. Activity-dependent modulation of vesicle mobility may represent an important mechanism controlling vesicle availability and neurotransmitter release.SIGNIFICANCE STATEMENTMechanisms governing synaptic vesicle dynamics during recycling remain poorly understood. Using nanoscale resolution tracking of individual synaptic vesicles in hippocampal synapses and advanced motion analysis tools we demonstrate that synaptic vesicles undergo complex sets of dynamical states that include epochs of directed, diffusive, and stalled motion. Most importantly, our analyses revealed that vesicle motion is modulated in an activity-dependent manner apparent as the reduction in overall vesicle mobility in response to stimulation. These results define the vesicle dynamical states during recycling and reveal their activity-dependent modulation. Our study thus provides fundamental new insights into the principles governing synaptic function
A decentralized motion coordination strategy for dynamic target tracking
This paper presents a decentralized motion planning
algorithm for the distributed sensing of a noisy dynamical
process by multiple cooperating mobile sensor agents. This
problem is motivated by localization and tracking tasks of
dynamic targets. Our gradient-descent method is based on a
cost function that measures the overall quality of sensing. We
also investigate the role of imperfect communication between
sensor agents in this framework, and examine the trade-offs in
performance between sensing and communication. Simulations
illustrate the basic characteristics of the algorithms
Inferring diffusion in single live cells at the single molecule level
The movement of molecules inside living cells is a fundamental feature of
biological processes. The ability to both observe and analyse the details of
molecular diffusion in vivo at the single molecule and single cell level can
add significant insight into understanding molecular architectures of diffusing
molecules and the nanoscale environment in which the molecules diffuse. The
tool of choice for monitoring dynamic molecular localization in live cells is
fluorescence microscopy, especially so combining total internal reflection
fluorescence (TIRF) with the use of fluorescent protein (FP) reporters in
offering exceptional imaging contrast for dynamic processes in the cell
membrane under relatively physiological conditions compared to competing single
molecule techniques. There exist several different complex modes of diffusion,
and discriminating these from each other is challenging at the molecular level
due to underlying stochastic behaviour. Analysis is traditionally performed
using mean square displacements of tracked particles, however, this generally
requires more data points than is typical for single FP tracks due to
photophysical instability. Presented here is a novel approach allowing robust
Bayesian ranking of diffusion processes (BARD) to discriminate multiple complex
modes probabilistically. It is a computational approach which biologists can
use to understand single molecule features in live cells.Comment: combined ms (1-37 pages, 8 figures) and SI (38-55, 3 figures
People tracking by cooperative fusion of RADAR and camera sensors
Accurate 3D tracking of objects from monocular camera poses challenges due to the loss of depth during projection. Although ranging by RADAR has proven effective in highway environments, people tracking remains beyond the capability of single sensor systems. In this paper, we propose a cooperative RADAR-camera fusion method for people tracking on the ground plane. Using average person height, joint detection likelihood is calculated by back-projecting detections from the camera onto the RADAR Range-Azimuth data. Peaks in the joint likelihood, representing candidate targets, are fed into a Particle Filter tracker. Depending on the association outcome, particles are updated using the associated detections (Tracking by Detection), or by sampling the raw likelihood itself (Tracking Before Detection). Utilizing the raw likelihood data has the advantage that lost targets are continuously tracked even if the camera or RADAR signal is below the detection threshold. We show that in single target, uncluttered environments, the proposed method entirely outperforms camera-only tracking. Experiments in a real-world urban environment also confirm that the cooperative fusion tracker produces significantly better estimates, even in difficult and ambiguous situations
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