8,151 research outputs found
A probabilistic data-driven model for planar pushing
This paper presents a data-driven approach to model planar pushing
interaction to predict both the most likely outcome of a push and its expected
variability. The learned models rely on a variation of Gaussian processes with
input-dependent noise called Variational Heteroscedastic Gaussian processes
(VHGP) that capture the mean and variance of a stochastic function. We show
that we can learn accurate models that outperform analytical models after less
than 100 samples and saturate in performance with less than 1000 samples. We
validate the results against a collected dataset of repeated trajectories, and
use the learned models to study questions such as the nature of the variability
in pushing, and the validity of the quasi-static assumption.Comment: 8 pages, 11 figures, ICRA 201
Friction Variability in Planar Pushing Data: Anisotropic Friction and Data-collection Bias
Friction plays a key role in manipulating objects. Most of what we do with
our hands, and most of what robots do with their grippers, is based on the
ability to control frictional forces. This paper aims to better understand the
variability and predictability of planar friction. In particular, we focus on
the analysis of a recent dataset on planar pushing by Yu et al. [1] devised to
create a data-driven footprint of planar friction.
We show in this paper how we can explain a significant fraction of the
observed unconventional phenomena, e.g., stochasticity and multi-modality, by
combining the effects of material non-homogeneity, anisotropy of friction and
biases due to data collection dynamics, hinting that the variability is
explainable but inevitable in practice.
We introduce an anisotropic friction model and conduct simulation experiments
comparing with more standard isotropic friction models. The anisotropic
friction between object and supporting surface results in convergence of
initial condition during the automated data collection. Numerical results
confirm that the anisotropic friction model explains the bias in the dataset
and the apparent stochasticity in the outcome of a push. The fact that the data
collection process itself can originate biases in the collected datasets,
resulting in deterioration of trained models, calls attention to the data
collection dynamics.Comment: 8 pages, 13 figure
Simple model for a Quantum Wire II. Correlations
In a previous paper (Eur. Phys. J. B 30, 239-251 (2002)) we have presented
the main features and properties of a simple model which -in spite of its
simplicity- describes quite accurately the qualitative behaviour of a quantum
wire. The model was composed of N distinct deltas each one carrying a different
coupling. We were able to diagonalize the Hamiltonian in the periodic case and
yield a complete and analytic description of the subsequent band structure.
Furthermore the random case was also analyzed and we were able to describe
Anderson localization and fractal structure of the conductance. In the present
paper we go one step further and show how to introduce correlations among the
sites of the wire. The presence of a correlated disorder manifests itself by
altering the distribution of states and the localization of the electrons
within the systemComment: RevTex, 7 pages, 9 figures (3 greyscale, 6 coloured
Infinite chain of N different deltas: a simple model for a Quantum Wire
We present the exact diagonalization of the Schrodinger operator
corresponding to a periodic potential with N deltas of different couplings, for
arbitrary N. This basic structure can repeat itself an infinite number of
times. Calculations of band structure can be performed with a high degree of
accuracy for an infinite chain and of the correspondent eigenlevels in the case
of a random chain. The main physical motivation is to modelate quantum wire
band structure and the calculation of the associated density of states. These
quantities show the fundamental properties we expect for periodic structures
although for low energy the band gaps follow unpredictable patterns. In the
case of random chains we find Anderson localization; we analize also the role
of the eigenstates in the localization patterns and find clear signals of
fractality in the conductance. In spite of the simplicity of the model many of
the salient features expected in a quantum wire are well reproduced.Comment: 28 pages, LaTeX, 13 eps figures (3 color
Realtime State Estimation with Tactile and Visual sensing. Application to Planar Manipulation
Accurate and robust object state estimation enables successful object
manipulation. Visual sensing is widely used to estimate object poses. However,
in a cluttered scene or in a tight workspace, the robot's end-effector often
occludes the object from the visual sensor. The robot then loses visual
feedback and must fall back on open-loop execution.
In this paper, we integrate both tactile and visual input using a framework
for solving the SLAM problem, incremental smoothing and mapping (iSAM), to
provide a fast and flexible solution. Visual sensing provides global pose
information but is noisy in general, whereas contact sensing is local, but its
measurements are more accurate relative to the end-effector. By combining them,
we aim to exploit their advantages and overcome their limitations. We explore
the technique in the context of a pusher-slider system. We adapt iSAM's
measurement cost and motion cost to the pushing scenario, and use an
instrumented setup to evaluate the estimation quality with different object
shapes, on different surface materials, and under different contact modes
Stable Prehensile Pushing: In-Hand Manipulation with Alternating Sticking Contacts
This paper presents an approach to in-hand manipulation planning that
exploits the mechanics of alternating sticking contact. Particularly, we
consider the problem of manipulating a grasped object using external pushes for
which the pusher sticks to the object. Given the physical properties of the
object, frictional coefficients at contacts and a desired regrasp on the
object, we propose a sampling-based planning framework that builds a pushing
strategy concatenating different feasible stable pushes to achieve the desired
regrasp. An efficient dynamics formulation allows us to plan in-hand
manipulations 100-1000 times faster than our previous work which builds upon a
complementarity formulation. Experimental observations for the generated plans
show that the object precisely moves in the grasp as expected by the planner.
Video Summary -- youtu.be/qOTKRJMx6HoComment: IEEE International Conference on Robotics and Automation 201
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