159 research outputs found
Measurements by A LEAP-Based Virtual Glove for the hand rehabilitation
Hand rehabilitation is fundamental after stroke or surgery. Traditional rehabilitation
requires a therapist and implies high costs, stress for the patient, and subjective evaluation of
the therapy effectiveness. Alternative approaches, based on mechanical and tracking-based gloves,
can be really effective when used in virtual reality (VR) environments. Mechanical devices are often
expensive, cumbersome, patient specific and hand specific, while tracking-based devices are not
affected by these limitations but, especially if based on a single tracking sensor, could suffer from
occlusions. In this paper, the implementation of a multi-sensors approach, the Virtual Glove (VG),
based on the simultaneous use of two orthogonal LEAP motion controllers, is described. The VG is
calibrated and static positioning measurements are compared with those collected with an accurate
spatial positioning system. The positioning error is lower than 6 mm in a cylindrical region of interest
of radius 10 cm and height 21 cm. Real-time hand tracking measurements are also performed, analysed
and reported. Hand tracking measurements show that VG operated in real-time (60 fps), reduced
occlusions, and managed two LEAP sensors correctly, without any temporal and spatial discontinuity
when skipping from one sensor to the other. A video demonstrating the good performance of VG
is also collected and presented in the Supplementary Materials. Results are promising but further
work must be done to allow the calculation of the forces exerted by each finger when constrained by
mechanical tools (e.g., peg-boards) and for reducing occlusions when grasping these tools. Although
the VG is proposed for rehabilitation purposes, it could also be used for tele-operation of tools and
robots, and for other VR applications
A real time classification algorithm for EEG-based BCI driven by self-induced emotions
Background and objective: The aim of this paper is to provide an efficient, parametric, general, and completely automatic real time classification method of electroencephalography (EEG) signals obtained from self-induced emotions. The particular characteristics of the considered low-amplitude signals (a self-induced emotion produces a signal whose amplitude is about 15% of a really experienced emotion) require exploring and adapting strategies like the Wavelet Transform, the Principal Component Analysis (PCA) and the Support Vector Machine (SVM) for signal processing, analysis and classification. Moreover, the method is thought to be used in a multi-emotions based Brain Computer Interface (BCI) and, for this reason, an ad hoc shrewdness is assumed. Method: The peculiarity of the brain activation requires ad-hoc signal processing by wavelet decomposition, and the definition of a set of features for signal characterization in order to discriminate different self-induced emotions. The proposed method is a two stages algorithm, completely parameterized, aiming at a multi-class classification and may be considered in the framework of machine learning. The first stage, the calibration, is off-line and is devoted at the signal processing, the determination of the features and at the training of a classifier. The second stage, the real-time one, is the test on new data. The PCA theory is applied to avoid redundancy in the set of features whereas the classification of the selected features, and therefore of the signals, is obtained by the SVM. Results: Some experimental tests have been conducted on EEG signals proposing a binary BCI, based on the self-induced disgust produced by remembering an unpleasant odor. Since in literature it has been shown that this emotion mainly involves the right hemisphere and in particular the T8 channel, the classification procedure is tested by using just T8, though the average accuracy is calculated and reported also for the whole set of the measured channels. Conclusions: The obtained classification results are encouraging with percentage of success that is, in the average for the whole set of the examined subjects, above 90%. An ongoing work is the application of the proposed procedure to map a large set of emotions with EEG and to establish the EEG headset with the minimal number of channels to allow the recognition of a significant range of emotions both in the field of affective computing and in the development of auxiliary communication tools for subjects affected by severe disabilities
Wave propagation in relaxed micromorphic continua: modelling metamaterials with frequency band-gaps
In this paper the relaxed micromorphic model proposed in [Patrizio Neff,
Ionel-Dumitrel Ghiba, Angela Madeo, Luca Placidi, Giuseppe Rosi. A unifying
perspective: the relaxed linear micromorphic continuum, submitted, 2013,
arXiv:1308.3219; and Ionel-Dumitrel Ghiba, Patrizio Neff, Angela Madeo, Luca
Placidi, Giuseppe Rosi. The relaxed linear micromorphic continuum: existence,
uniqueness and continuous dependence in dynamics, submitted, 2013,
arXiv:1308.3762] has been used to study wave propagation in unbounded continua
with microstructure. By studying dispersion relations for the considered
relaxed medium, we are able to disclose precise frequency ranges (band-gaps)
for which propagation of waves cannot occur. These dispersion relations are
strongly nonlinear so giving rise to a macroscopic dispersive behavior of the
considered medium. We prove that the presence of band-gaps is related to a
unique elastic coefficient, the so-called Cosserat couple modulus ,
which is also responsible for the loss of symmetry of the Cauchy force stress
tensor. This parameter can be seen as the trigger of a bifurcation phenomenon
since the fact of slightly changing its value around a given threshold
drastically changes the observed response of the material with respect to wave
propagation. We finally show that band-gaps cannot be accounted for by
classical micromorphic models as well as by Cosserat and second gradient ones.
The potential fields of application of the proposed relaxed model are manifold,
above all for what concerns the conception of new engineering materials to be
used for vibration control and stealth technology
The relaxed linear micromorphic continuum: existence, uniqueness and continuous dependence in dynamics
We study well-posedness for the relaxed linear elastic micromorphic continuum
model with symmetric Cauchy force-stresses and curvature contribution depending
only on the micro-dislocation tensor. In contrast to classical micromorphic
models our free energy is not uniformly pointwise positive definite in the
control of the independent constitutive variables. Another interesting feature
concerns the prescription of boundary values for the micro-distortion field:
only tangential traces may be determined which are weaker than the usual strong
anchoring boundary condition. There, decisive use is made of new coercive
inequalities recently proved by Neff, Pauly and Witsch and by Bauer, Neff,
Pauly and Starke. The new relaxed micromorphic formulation can be related to
dislocation dynamics, gradient plasticity and seismic processes of earthquakes.Comment: arXiv admin note: substantial text overlap with arXiv:1308.321
A unifying perspective: the relaxed linear micromorphic continuum
We formulate a relaxed linear elastic micromorphic continuum model with
symmetric Cauchy force-stresses and curvature contribution depending only on
the micro-dislocation tensor. Our relaxed model is still able to fully describe
rotation of the microstructure and to predict non-polar size-effects. It is
intended for the homogenized description of highly heterogeneous, but non polar
materials with microstructure liable to slip and fracture. In contrast to
classical linear micromorphic models our free energy is not uniformly pointwise
positive definite in the control of the independent constitutive variables. The
new relaxed micromorphic model supports well-posedness results for the dynamic
and static case. There, decisive use is made of new coercive inequalities
recently proved by Neff, Pauly and Witsch and by Bauer, Neff, Pauly and Starke.
The new relaxed micromorphic formulation can be related to dislocation
dynamics, gradient plasticity and seismic processes of earthquakes. It unifies
and simplifies the understanding of the linear micromorphic models
A Virtual Glove System for the Hand Rehabilitation based on Two Orthogonal LEAP Motion Controllers
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