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24
MCMCbased particle filtering for tracking a variable number of interacting targets
 IEEE Transactions on Pattern Analysis and Machine Intelligence
, 2005
"... We describe a particle filter that effectively deals with interacting targets targets that are influenced by the proximity and/or behavior of other targets. The particle filter includes a Markov random field (MRF) motion prior that helps maintain the identity of targets throughout an interaction, s ..."
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Cited by 117 (6 self)
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We describe a particle filter that effectively deals with interacting targets targets that are influenced by the proximity and/or behavior of other targets. The particle filter includes a Markov random field (MRF) motion prior that helps maintain the identity of targets throughout an interaction, significantly reducing tracker failures. We show that this MRF prior can be easily implemented by including an additional interaction factor in the importance weights of the particle filter. However, the computational requirements of the resulting multitarget filter render it unusable for large numbers of targets. Consequently, we replace the traditional importance sampling step in the particle filter with a novel Markov chain Monte Carlo (MCMC) sampling step to obtain a more efficient MCMCbased multitarget filter. We also show how to extend this MCMCbased filter to address a variable number of interacting targets. Finally, we present both qualitative and quantitative experimental results, demonstrating that the resulting particle filters deal efficiently and effectively with complicated target interactions.
On Contrastive Divergence Learning
"... Maximumlikelihood (ML) learning of Markov random fields is challenging because it requires estimates of averages that have an exponential number of terms. Markov chain Monte Carlo methods typically take a long time to converge on unbiased estimates, but Hinton (2002) showed that if the Markov ..."
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Cited by 82 (15 self)
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Maximumlikelihood (ML) learning of Markov random fields is challenging because it requires estimates of averages that have an exponential number of terms. Markov chain Monte Carlo methods typically take a long time to converge on unbiased estimates, but Hinton (2002) showed that if the Markov chain is only run for a few steps, the learning can still work well and it approximately minimizes a di#erent function called "contrastive divergence" (CD). CD learning has been successfully applied to various types of random fields. Here, we study the properties of CD learning and show that it provides biased estimates in general, but that the bias is typically very small. Fast CD learning can therefore be used to get close to an ML solution and slow ML learning can then be used to finetune the CD solution.
Tracking many objects with many sensors
 In IJCAI99
, 1999
"... Keeping track of multiple objects over time is a problem that arises in many realworld domains. The problem is often complicated by noisy sensors and unpredictable dynamics. Previous work by Huang and Russell, drawing on the data association literature, provided a probabilistic analysis and a thres ..."
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Cited by 80 (5 self)
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Keeping track of multiple objects over time is a problem that arises in many realworld domains. The problem is often complicated by noisy sensors and unpredictable dynamics. Previous work by Huang and Russell, drawing on the data association literature, provided a probabilistic analysis and a thresholdbased approximation algorithm for the case of multiple objects detected by two spatially separated sensors. This paper analyses the case in which large numbers of sensors are involved. We show that the approach taken by Huang and Russell, who used pairwise sensorbased appearance probabilities as the elementary probabilistic model, does not scale. When more than two observations are made, the objects ' intrinsic properties must be estimated. These provide the necessary conditional independencies to allow a spatial decomposition of the global probability model. We also replace Huang and Russell's threshold algorithm for object identification with a polynomialtime approximation scheme based on Markov chain Monte Carlo simulation. Using sensor data from a freeway traffic simulation, we show that this allows accurate estimation of longrange origin/destination information even when the individual links in the sensor chain are highly unreliable. 1
Bayesian inference in the space of topological maps
 IEEE Transactions on Robotics
, 2006
"... Abstract—While probabilistic techniques have previously been investigated extensively for performing inference over the space of metric maps, no corresponding generalpurpose methods exist for topological maps. We present the concept of probabilistic topological maps (PTMs), a samplebased represent ..."
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Cited by 27 (1 self)
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Abstract—While probabilistic techniques have previously been investigated extensively for performing inference over the space of metric maps, no corresponding generalpurpose methods exist for topological maps. We present the concept of probabilistic topological maps (PTMs), a samplebased representation that approximates the posterior distribution over topologies, given available sensor measurements. We show that the space of topologies is equivalent to the intractably large space of set partitions on the set of available measurements. The combinatorial nature of the problem is overcome by computing an approximate, samplebased representation of the posterior. The PTM is obtained by performing Bayesian inference over the space of all possible topologies, and provides a systematic solution to the problem of perceptual aliasing in the domain of topological mapping. In this paper, we describe a general framework for modeling measurements, and the use of a Markovchain Monte Carlo algorithm that uses specific instances of these models for odometry and appearance measurements to estimate the posterior distribution. We present experimental results that validate our technique and generate good maps when using odometry and appearance, derived from panoramic images, as sensor measurements. Index Terms—Bayesian inference, Markovchain Monte Carlo (MCMC), mobile robots, perceptual aliasing, probability distributions, samplebased representations, topological maps. I.
Bayesian Structure From Motion
"... We formulate structure from motion as a Bayesian inference problem, and use a Markov chain Monte Carlo sampler to sample the posterior on this problem. This results in a method that can identify both small and large tracker errors, and yields reconstructions that are stable in the presence of these ..."
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Cited by 24 (1 self)
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We formulate structure from motion as a Bayesian inference problem, and use a Markov chain Monte Carlo sampler to sample the posterior on this problem. This results in a method that can identify both small and large tracker errors, and yields reconstructions that are stable in the presence of these errors. Furthermore, the method gives detailed information on the range of ambiguities in structure given a particular dataset, and requires no special geometric formulation to cope with degenerate situations. Motion segmentation is obtained by a layer of discrete variables associating a point with an object. We demonstrate a sampler that successfully samples an approximation to the marginal on this domain, producing a relatively unambiguous segmentation.
Finding People by Sampling
 Proc. Int'l Conf. on Computer Vision
, 1999
"... We show how to use a sampling method to find sparsely clad people in static images. People are modeled as an assembly of nine cylindrical segments. Segments are found using an EM algorithm, and then assembled into hypotheses incrementally, using a learned likelihood model. Each assembly step passes ..."
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Cited by 17 (1 self)
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We show how to use a sampling method to find sparsely clad people in static images. People are modeled as an assembly of nine cylindrical segments. Segments are found using an EM algorithm, and then assembled into hypotheses incrementally, using a learned likelihood model. Each assembly step passes on a set of samples of its likelihood to the next; this yields effective pruning of the space of hypotheses. The collection of available ninesegment hypotheses is then represented by a set of equivalence classes, which yield an efficient pruning process. The posterior for the number of people is obtained from the class representatives. People are counted quite accurately in images of real scenes using an MAP estimate. We show the method allows topdown as well as bottom up reasoning. While the method can be overwhelmed by very large numbers of segments, we show that this problem can be avoided by quite simple pruning steps.
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 In In'ogress Ilindle, D
, 2005
"... Probabilistic techniques have become the mainstay of robotic mapping, particularly for generating metric maps. In previous work, we have presented a hitherto nonexistent general purpose probabilistic framework for dealing with topological mapping. This involves the creation of Probabilistic Topologi ..."
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Cited by 10 (1 self)
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Probabilistic techniques have become the mainstay of robotic mapping, particularly for generating metric maps. In previous work, we have presented a hitherto nonexistent general purpose probabilistic framework for dealing with topological mapping. This involves the creation of Probabilistic Topological Maps (PTMs), a samplebased representation that approximates the posterior distribution over topologies given available sensor measurements. The PTM is inferred using Markov Chain Monte Carlo (MCMC) that overcomes the combinatorial nature of the problem. In this paper, we address the problem of integrating appearance measurements into the PTM framework. Specifically, we consider appearance measurements in the form of panoramic images obtained from a camera rig mounted on a robot. We also propose improvements to the efficiency of the MCMC algorithm through the use of an intelligent datadriven proposal distribution. We present experiments that illustrate the robustness and wide applicability of our algorithm. 1
Bayesian Modelling Of Harmonic Signals For Polyphonic Music Tracking
, 1999
"... Musical signals can be well represented as a sum of harmonically related sinusoids motivated by consideration of the sound generation mechanisms of many musical instruments. We consider the problem of estimating the harmonic model parameters in a Bayesian framework which has the potential to incorpo ..."
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Cited by 6 (1 self)
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Musical signals can be well represented as a sum of harmonically related sinusoids motivated by consideration of the sound generation mechanisms of many musical instruments. We consider the problem of estimating the harmonic model parameters in a Bayesian framework which has the potential to incorporate a priori knowledge about the structure of the data and of its parameters. Constraints can be imposed upon the timedomain variation of model parameters to reflect the high correlation of frequency and harmonic structure over time. Hierarchical model structure is represented using graphical models which allows a flexible approach to the specification of the model. 1 Introduction There are two largely distinct approaches to the analysis of signals  loosely categorised as parametric and nonparametric methods. Nonparametric methods generally apply some manner of filtering and transformation of the raw data such that features which represent a desired characteristic can be obtained. P...