4,048 research outputs found
The Design and Implementation of a Bayesian CAD Modeler for Robotic Applications
We present a Bayesian CAD modeler for robotic applications. We address the problem of taking into account the propagation of geometric uncertainties when solving inverse geometric problems. The proposed method may be seen as a generalization of constraint-based approaches in which we explicitly model geometric uncertainties. Using our methodology, a geometric constraint is expressed as a probability distribution on the system parameters and the sensor measurements, instead of a simple equality or inequality. To solve geometric problems in this framework, we propose an original resolution method able to adapt to problem complexity.
Using two examples, we show how to apply our approach by providing simulation results using our modeler
Micro-Doppler Based Human-Robot Classification Using Ensemble and Deep Learning Approaches
Radar sensors can be used for analyzing the induced frequency shifts due to
micro-motions in both range and velocity dimensions identified as micro-Doppler
(-D) and micro-Range (-R), respectively.
Different moving targets will have unique -D and
-R signatures that can be used for target classification.
Such classification can be used in numerous fields, such as gait recognition,
safety and surveillance. In this paper, a 25 GHz FMCW Single-Input
Single-Output (SISO) radar is used in industrial safety for real-time
human-robot identification. Due to the real-time constraint, joint
Range-Doppler (R-D) maps are directly analyzed for our classification problem.
Furthermore, a comparison between the conventional classical learning
approaches with handcrafted extracted features, ensemble classifiers and deep
learning approaches is presented. For ensemble classifiers, restructured range
and velocity profiles are passed directly to ensemble trees, such as gradient
boosting and random forest without feature extraction. Finally, a Deep
Convolutional Neural Network (DCNN) is used and raw R-D images are directly fed
into the constructed network. DCNN shows a superior performance of 99\%
accuracy in identifying humans from robots on a single R-D map.Comment: 6 pages, accepted in IEEE Radar Conference 201
Combination of Annealing Particle Filter and Belief Propagation for 3D Upper Body Tracking
3D upper body pose estimation is a topic greatly studied by the computer vision society because it is useful in a great number of applications, mainly for human robots interactions including communications with companion robots. However there is a challenging problem: the complexity of classical algorithms that increases exponentially with the dimension of the vectors’ state becomes too difficult to handle. To tackle this problem, we propose a new approach that combines several annealing particle filters defined independently for each limb and belief propagation method to add geometrical constraints between individual filters. Experimental results on a real human gestures sequence will show that this combined approach leads to reliable results
Toward Abstraction from Multi-modal Data: Empirical Studies on Multiple Time-scale Recurrent Models
The abstraction tasks are challenging for multi- modal sequences as they
require a deeper semantic understanding and a novel text generation for the
data. Although the recurrent neural networks (RNN) can be used to model the
context of the time-sequences, in most cases the long-term dependencies of
multi-modal data make the back-propagation through time training of RNN tend to
vanish in the time domain. Recently, inspired from Multiple Time-scale
Recurrent Neural Network (MTRNN), an extension of Gated Recurrent Unit (GRU),
called Multiple Time-scale Gated Recurrent Unit (MTGRU), has been proposed to
learn the long-term dependencies in natural language processing. Particularly
it is also able to accomplish the abstraction task for paragraphs given that
the time constants are well defined. In this paper, we compare the MTRNN and
MTGRU in terms of its learning performances as well as their abstraction
representation on higher level (with a slower neural activation). This was done
by conducting two studies based on a smaller data- set (two-dimension time
sequences from non-linear functions) and a relatively large data-set
(43-dimension time sequences from iCub manipulation tasks with multi-modal
data). We conclude that gated recurrent mechanisms may be necessary for
learning long-term dependencies in large dimension multi-modal data-sets (e.g.
learning of robot manipulation), even when natural language commands was not
involved. But for smaller learning tasks with simple time-sequences, generic
version of recurrent models, such as MTRNN, were sufficient to accomplish the
abstraction task.Comment: Accepted by IJCNN 201
A Novel Predictive-Coding-Inspired Variational RNN Model for Online Prediction and Recognition
This study introduces PV-RNN, a novel variational RNN inspired by the
predictive-coding ideas. The model learns to extract the probabilistic
structures hidden in fluctuating temporal patterns by dynamically changing the
stochasticity of its latent states. Its architecture attempts to address two
major concerns of variational Bayes RNNs: how can latent variables learn
meaningful representations and how can the inference model transfer future
observations to the latent variables. PV-RNN does both by introducing adaptive
vectors mirroring the training data, whose values can then be adapted
differently during evaluation. Moreover, prediction errors during
backpropagation, rather than external inputs during the forward computation,
are used to convey information to the network about the external data. For
testing, we introduce error regression for predicting unseen sequences as
inspired by predictive coding that leverages those mechanisms. The model
introduces a weighting parameter, the meta-prior, to balance the optimization
pressure placed on two terms of a lower bound on the marginal likelihood of the
sequential data. We test the model on two datasets with probabilistic
structures and show that with high values of the meta-prior the network
develops deterministic chaos through which the data's randomness is imitated.
For low values, the model behaves as a random process. The network performs
best on intermediate values, and is able to capture the latent probabilistic
structure with good generalization. Analyzing the meta-prior's impact on the
network allows to precisely study the theoretical value and practical benefits
of incorporating stochastic dynamics in our model. We demonstrate better
prediction performance on a robot imitation task with our model using error
regression compared to a standard variational Bayes model lacking such a
procedure.Comment: The paper is accepted in Neural Computatio
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