89 research outputs found
Bayesian Nonparametric Hidden Semi-Markov Models
There is much interest in the Hierarchical Dirichlet Process Hidden Markov
Model (HDP-HMM) as a natural Bayesian nonparametric extension of the ubiquitous
Hidden Markov Model for learning from sequential and time-series data. However,
in many settings the HDP-HMM's strict Markovian constraints are undesirable,
particularly if we wish to learn or encode non-geometric state durations. We
can extend the HDP-HMM to capture such structure by drawing upon
explicit-duration semi-Markovianity, which has been developed mainly in the
parametric frequentist setting, to allow construction of highly interpretable
models that admit natural prior information on state durations.
In this paper we introduce the explicit-duration Hierarchical Dirichlet
Process Hidden semi-Markov Model (HDP-HSMM) and develop sampling algorithms for
efficient posterior inference. The methods we introduce also provide new
methods for sampling inference in the finite Bayesian HSMM. Our modular Gibbs
sampling methods can be embedded in samplers for larger hierarchical Bayesian
models, adding semi-Markov chain modeling as another tool in the Bayesian
inference toolbox. We demonstrate the utility of the HDP-HSMM and our inference
methods on both synthetic and real experiments
Nonparametric Bayesian Double Articulation Analyzer for Direct Language Acquisition from Continuous Speech Signals
Human infants can discover words directly from unsegmented speech signals
without any explicitly labeled data. In this paper, we develop a novel machine
learning method called nonparametric Bayesian double articulation analyzer
(NPB-DAA) that can directly acquire language and acoustic models from observed
continuous speech signals. For this purpose, we propose an integrative
generative model that combines a language model and an acoustic model into a
single generative model called the "hierarchical Dirichlet process hidden
language model" (HDP-HLM). The HDP-HLM is obtained by extending the
hierarchical Dirichlet process hidden semi-Markov model (HDP-HSMM) proposed by
Johnson et al. An inference procedure for the HDP-HLM is derived using the
blocked Gibbs sampler originally proposed for the HDP-HSMM. This procedure
enables the simultaneous and direct inference of language and acoustic models
from continuous speech signals. Based on the HDP-HLM and its inference
procedure, we developed a novel double articulation analyzer. By assuming
HDP-HLM as a generative model of observed time series data, and by inferring
latent variables of the model, the method can analyze latent double
articulation structure, i.e., hierarchically organized latent words and
phonemes, of the data in an unsupervised manner. The novel unsupervised double
articulation analyzer is called NPB-DAA.
The NPB-DAA can automatically estimate double articulation structure embedded
in speech signals. We also carried out two evaluation experiments using
synthetic data and actual human continuous speech signals representing Japanese
vowel sequences. In the word acquisition and phoneme categorization tasks, the
NPB-DAA outperformed a conventional double articulation analyzer (DAA) and
baseline automatic speech recognition system whose acoustic model was trained
in a supervised manner.Comment: 15 pages, 7 figures, Draft submitted to IEEE Transactions on
Autonomous Mental Development (TAMD
Energy Efficiency and Emission Testing for Connected and Automated Vehicles Using Real-World Driving Data
By using the onboard sensing and external connectivity technology, connected
and automated vehicles (CAV) could lead to improved energy efficiency, better
routing, and lower traffic congestion. With the rapid development of the
technology and adaptation of CAV, it is more critical to develop the universal
evaluation method and the testing standard which could evaluate the impacts on
energy consumption and environmental pollution of CAV fairly, especially under
the various traffic conditions. In this paper, we proposed a new method and
framework to evaluate the energy efficiency and emission of the vehicle based
on the unsupervised learning methods. Both the real-world driving data of the
evaluated vehicle and the large naturalistic driving dataset are used to
perform the driving primitive analysis and coupling. Then the linear weighted
estimation method could be used to calculate the testing result of the
evaluated vehicle. The results show that this method can successfully identify
the typical driving primitives. The couples of the driving primitives from the
evaluated vehicle and the typical driving primitives from the large real-world
driving dataset coincide with each other very well. This new method could
enhance the standard development of the energy efficiency and emission testing
of CAV and other off-cycle credits
Automatic Identification of Driving Maneuver Patterns using a Robust Hidden Semi-Markov Models
There is an increase in interest to model driving maneuver patterns via the
automatic unsupervised clustering of naturalistic sequential kinematic driving
data. The patterns learned are often used in transportation research areas such
as eco-driving, road safety, and intelligent vehicles. One such model capable
of modeling these patterns is the Hierarchical Dirichlet Process Hidden
Semi-Markov Model (HDP-HSMM), as it is often used to estimate data
segmentation, state duration, and transition probabilities. While this model is
a powerful tool for automatically clustering observed sequential data, the
existing HDP-HSMM estimation suffers from an inherent tendency to overestimate
the number of states. This can result in poor estimation, which can potentially
impact impact transportation research through incorrect inference of driving
patterns. In this paper, a new robust HDP-HSMM (rHDP-HSMM) method is proposed
to reduce the number of redundant states and improve the consistency of the
model's estimation. Both a simulation study and a case study using naturalistic
driving data are presented to demonstrate the effectiveness of the proposed
rHDP-HSMM in identifying and inference of driving maneuver patterns
The Hierarchical Dirichlet Process Hidden Semi-Markov Model
There is much interest in the Hierarchical Dirichlet Process Hidden Markov Model (HDP-HMM) as a natural Bayesian nonparametric extension of the traditional HMM. However, in many settings the HDP-HMM's strict Markovian constraints are undesirable, particularly if we wish to learn or encode non-geometric state durations. We can extend the HDP-HMM to capture such structure by drawing upon explicit-duration semi- Markovianity, which has been developed in the parametric setting to allow construction of highly interpretable models that admit natural prior information on state durations. In this paper we introduce the explicitduration HDP-HSMM and develop posterior sampling algorithms for efficient inference in both the direct-assignment and weak-limit approximation settings. We demonstrate the utility of the model and our inference methods on synthetic data as well as experiments on a speaker diarization problem and an example of learning the patterns in Morse code
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