7,108 research outputs found
Factored Particles for Scalable Monitoring
Exact monitoring in dynamic Bayesian networks is intractable, so approximate
algorithms are necessary. This paper presents a new family of approximate
monitoring algorithms that combine the best qualities of the particle filtering
and Boyen-Koller methods. Our algorithms maintain an approximate representation
the belief state in the form of sets of factored particles, that correspond to
samples of clusters of state variables. Empirical results show that our
algorithms outperform both ordinary particle filtering and the Boyen-Koller
algorithm on large systems.Comment: Appears in Proceedings of the Eighteenth Conference on Uncertainty in
Artificial Intelligence (UAI2002
Distributed High Accuracy Peer-to-Peer Localization in Mobile Multipath Environments
In this paper we consider the problem of high accuracy localization of mobile
nodes in a multipath-rich environment where sub-meter accuracies are required.
We employ a peer to peer framework where the vehicles/nodes can get pairwise
multipath-degraded ranging estimates in local neighborhoods together with a
fixed number of anchor nodes. The challenge is to overcome the
multipath-barrier with redundancy in order to provide the desired accuracies
especially under severe multipath conditions when the fraction of received
signals corrupted by multipath is dominating. We invoke a message passing
analytical framework based on particle filtering and reveal its high accuracy
localization promise through simulations.Comment: 5 pages, 5 figures, Accepted at IEEE Globecom 2010, Miami, F
Regression with Linear Factored Functions
Many applications that use empirically estimated functions face a curse of
dimensionality, because the integrals over most function classes must be
approximated by sampling. This paper introduces a novel regression-algorithm
that learns linear factored functions (LFF). This class of functions has
structural properties that allow to analytically solve certain integrals and to
calculate point-wise products. Applications like belief propagation and
reinforcement learning can exploit these properties to break the curse and
speed up computation. We derive a regularized greedy optimization scheme, that
learns factored basis functions during training. The novel regression algorithm
performs competitively to Gaussian processes on benchmark tasks, and the
learned LFF functions are with 4-9 factored basis functions on average very
compact.Comment: Under review as conference paper at ECML/PKDD 201
PID control system analysis and design
With its three-term functionality offering treatment of both transient and steady-state responses,
proportional-integral-derivative (PID) control provides a generic and efficient solution to realworld
control problems. The wide application of PID control has stimulated and sustained
research and development to "get the best out of PID", and "the search is on to find
the next key technology or methodology for PID tuning".
This article presents remedies for problems involving the integral and derivative terms. PID design objectives,
methods, and future directions are discussed. Subsequently, a computerized, simulation-based approach
is presented, together with illustrative design results for first-order, higher order, and nonlinear plants. Finally,
we discuss differences between academic research and industrial practice, so as to motivate new research
directions in PID control
From Least Squares to Signal Processing and Particle Filtering
De Facto, signal processing is the interpolation and extrapolation of a
sequence of observations viewed as a realization of a stochastic process. Its
role in applied statistics ranges from scenarios in forecasting and time series
analysis, to image reconstruction, machine learning, and the degradation
modeling for reliability assessment. A general solution to the problem of
filtering and prediction entails some formidable mathematics. Efforts to
circumvent the mathematics has resulted in the need for introducing more
explicit descriptions of the underlying process. One such example, and a
noteworthy one, is the Kalman Filter Model, which is a special case of state
space models or what statisticians refer to as Dynamic Linear Models.
Implementing the Kalman Filter Model in the era of "big and high velocity
non-Gaussian data" can pose computational challenges with respect to efficiency
and timeliness. Particle filtering is a way to ease such computational burdens.
The purpose of this paper is to trace the historical evolution of this
development from its inception to its current state, with an expository focus
on two versions of the particle filter, namely, the propagate first-update next
and the update first-propagate next version. By way of going beyond a pure
review, this paper also makes transparent the importance and the role of a less
recognized principle, namely the principle of conditionalization, in filtering
and prediction based on Bayesian methods. Furthermore, the paper also
articulates the philosophical underpinnings of the filtering and prediction
set-up, a matter that needs to ne made explicit, and Yule's decomposition of a
random variable in terms of a sequence of innovations
Learning Partially Observable Deterministic Action Models
We present exact algorithms for identifying deterministic-actions effects and
preconditions in dynamic partially observable domains. They apply when one does
not know the action model(the way actions affect the world) of a domain and
must learn it from partial observations over time. Such scenarios are common in
real world applications. They are challenging for AI tasks because traditional
domain structures that underly tractability (e.g., conditional independence)
fail there (e.g., world features become correlated). Our work departs from
traditional assumptions about partial observations and action models. In
particular, it focuses on problems in which actions are deterministic of simple
logical structure and observation models have all features observed with some
frequency. We yield tractable algorithms for the modified problem for such
domains.
Our algorithms take sequences of partial observations over time as input, and
output deterministic action models that could have lead to those observations.
The algorithms output all or one of those models (depending on our choice), and
are exact in that no model is misclassified given the observations. Our
algorithms take polynomial time in the number of time steps and state features
for some traditional action classes examined in the AI-planning literature,
e.g., STRIPS actions. In contrast, traditional approaches for HMMs and
Reinforcement Learning are inexact and exponentially intractable for such
domains. Our experiments verify the theoretical tractability guarantees, and
show that we identify action models exactly. Several applications in planning,
autonomous exploration, and adventure-game playing already use these results.
They are also promising for probabilistic settings, partially observable
reinforcement learning, and diagnosis
Deep Variational Reinforcement Learning for POMDPs
Many real-world sequential decision making problems are partially observable
by nature, and the environment model is typically unknown. Consequently, there
is great need for reinforcement learning methods that can tackle such problems
given only a stream of incomplete and noisy observations. In this paper, we
propose deep variational reinforcement learning (DVRL), which introduces an
inductive bias that allows an agent to learn a generative model of the
environment and perform inference in that model to effectively aggregate the
available information. We develop an n-step approximation to the evidence lower
bound (ELBO), allowing the model to be trained jointly with the policy. This
ensures that the latent state representation is suitable for the control task.
In experiments on Mountain Hike and flickering Atari we show that our method
outperforms previous approaches relying on recurrent neural networks to encode
the past
Probabilistic Receiver Architecture Combining BP, MF, and EP for Multi-Signal Detection
Receiver algorithms which combine belief propagation (BP) with the mean field
(MF) approximation are well-suited for inference of both continuous and
discrete random variables. In wireless scenarios involving detection of
multiple signals, the standard construction of the combined BP-MF framework
includes the equalization or multi-user detection functions within the MF
subgraph. In this paper, we show that the MF approximation is not particularly
effective for multi-signal detection. We develop a new factor graph
construction for application of the BP-MF framework to problems involving the
detection of multiple signals. We then develop a low-complexity variant to the
proposed construction in which Gaussian BP is applied to the equalization
factors. In this case, the factor graph of the joint probability distribution
is divided into three subgraphs: (i) a MF subgraph comprised of the observation
factors and channel estimation, (ii) a Gaussian BP subgraph which is applied to
multi-signal detection, and (iii) a discrete BP subgraph which is applied to
demodulation and decoding. Expectation propagation is used to approximate
discrete distributions with a Gaussian distribution and links the discrete BP
and Gaussian BP subgraphs. The result is a probabilistic receiver architecture
with strong theoretical justification which can be applied to multi-signal
detection.Comment: 30 pages, 9 figure
Continuous-Time Gaussian Process Motion Planning via Probabilistic Inference
We introduce a novel formulation of motion planning, for continuous-time
trajectories, as probabilistic inference. We first show how smooth
continuous-time trajectories can be represented by a small number of states
using sparse Gaussian process (GP) models. We next develop an efficient
gradient-based optimization algorithm that exploits this sparsity and GP
interpolation. We call this algorithm the Gaussian Process Motion Planner
(GPMP). We then detail how motion planning problems can be formulated as
probabilistic inference on a factor graph. This forms the basis for GPMP2, a
very efficient algorithm that combines GP representations of trajectories with
fast, structure-exploiting inference via numerical optimization. Finally, we
extend GPMP2 to an incremental algorithm, iGPMP2, that can efficiently replan
when conditions change. We benchmark our algorithms against several
sampling-based and trajectory optimization-based motion planning algorithms on
planning problems in multiple environments. Our evaluation reveals that GPMP2
is several times faster than previous algorithms while retaining robustness. We
also benchmark iGPMP2 on replanning problems, and show that it can find
successful solutions in a fraction of the time required by GPMP2 to replan from
scratch.Comment: The International Journal of Robotics Research (IJRR), 2018, Volume
37, Issue 1
Gibbs Sampling in Factorized Continuous-Time Markov Processes
A central task in many applications is reasoning about processes that change
over continuous time. Continuous-Time Bayesian Networks is a general compact
representation language for multi-component continuous-time processes. However,
exact inference in such processes is exponential in the number of components,
and thus infeasible for most models of interest. Here we develop a novel Gibbs
sampling procedure for multi-component processes. This procedure iteratively
samples a trajectory for one of the components given the remaining ones. We
show how to perform exact sampling that adapts to the natural time scale of the
sampled process. Moreover, we show that this sampling procedure naturally
exploits the structure of the network to reduce the computational cost of each
step. This procedure is the first that can provide asymptotically unbiased
approximation in such processes.Comment: Appears in Proceedings of the Twenty-Fourth Conference on Uncertainty
in Artificial Intelligence (UAI2008
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