3,900 research outputs found
Gaussian-Process-based Robot Learning from Demonstration
Endowed with higher levels of autonomy, robots are required to perform
increasingly complex manipulation tasks. Learning from demonstration is arising
as a promising paradigm for transferring skills to robots. It allows to
implicitly learn task constraints from observing the motion executed by a human
teacher, which can enable adaptive behavior. We present a novel
Gaussian-Process-based learning from demonstration approach. This probabilistic
representation allows to generalize over multiple demonstrations, and encode
variability along the different phases of the task. In this paper, we address
how Gaussian Processes can be used to effectively learn a policy from
trajectories in task space. We also present a method to efficiently adapt the
policy to fulfill new requirements, and to modulate the robot behavior as a
function of task variability. This approach is illustrated through a real-world
application using the TIAGo robot.Comment: 8 pages, 10 figure
A multi-scale approach to the physics of ion beam cancer therapy
We propose a multi-scale approach to understanding physics related to the
ion/proton-beam cancer therapy and calculation of the probability of the DNA
damage as a result of irradiation of patients with energetic (up to 430 MeV/u)
ions. This approach is inclusive with respect to different scales starting from
the long scale defined by the ion stopping followed by a smaller scale defined
by secondary electrons and radicals ending with the shortest scale defined by
interactions of secondaries with the DNA. We present calculations of the
probabilities of single and double strand breaks of the DNA and suggest a way
of further elaboration of such calculations.Comment: submitted to RADAM2008 proceedings. 8 pages,5 Figures, class files
for AIP include
Physics of ion beam cancer therapy: a multi-scale approach
We propose a multi-scale approach to understand the physics related to
ion-beam cancer therapy. It allows the calculation of the probability of DNA
damage as a result of irradiation of tissues with energetic ions, up to 430
MeV/u. This approach covers different scales, starting from the large scale,
defined by the ion stopping, followed by a smaller scale, defined by secondary
electrons and radicals, and ending with the shortest scale, defined by
interactions of secondaries with the DNA. We present calculations of the
probabilities of single and double strand breaks of DNA, suggest a way to
further expand such calculations, and also make some estimates for glial cells
exposed to radiation.Comment: 18 pag,5 fig, submitted to PR
Learning to Prevent Monocular SLAM Failure using Reinforcement Learning
Monocular SLAM refers to using a single camera to estimate robot ego motion
while building a map of the environment. While Monocular SLAM is a well studied
problem, automating Monocular SLAM by integrating it with trajectory planning
frameworks is particularly challenging. This paper presents a novel formulation
based on Reinforcement Learning (RL) that generates fail safe trajectories
wherein the SLAM generated outputs do not deviate largely from their true
values. Quintessentially, the RL framework successfully learns the otherwise
complex relation between perceptual inputs and motor actions and uses this
knowledge to generate trajectories that do not cause failure of SLAM. We show
systematically in simulations how the quality of the SLAM dramatically improves
when trajectories are computed using RL. Our method scales effectively across
Monocular SLAM frameworks in both simulation and in real world experiments with
a mobile robot.Comment: Accepted at the 11th Indian Conference on Computer Vision, Graphics
and Image Processing (ICVGIP) 2018 More info can be found at the project page
at https://robotics.iiit.ac.in/people/vignesh.prasad/SLAMSafePlanner.html and
the supplementary video can be found at
https://www.youtube.com/watch?v=420QmM_Z8v
Measurements of the neutron electric to magnetic form factor ratio G_(En)/G_(Mn) via the ^2H(e, e'n)^1H reaction to Q^2 = 1.45 (GeV/c)^2
We report values for the neutron electric tomagnetic form factor ratio,G_(En)/G_(Mn), deduced frommeasurements
of the neutronâs recoil polarization in the quasielastic ^2H(e, e'n)^1H reaction, at three Q^2 values of 0.45, 1.13,
and 1.45 (GeV/c)^2. The data at Q^2 = 1.13 and 1.45 (GeV/c)^2 are the first direct experimental measurements of
G_(En) employing polarization degrees of freedom in the Q^2 > 1 (GeV/c)^2 region and stand as the most precise
determinations of G_(En) for all values of Q^2
Provably Safe Robot Navigation with Obstacle Uncertainty
As drones and autonomous cars become more widespread it is becoming
increasingly important that robots can operate safely under realistic
conditions. The noisy information fed into real systems means that robots must
use estimates of the environment to plan navigation. Efficiently guaranteeing
that the resulting motion plans are safe under these circumstances has proved
difficult. We examine how to guarantee that a trajectory or policy is safe with
only imperfect observations of the environment. We examine the implications of
various mathematical formalisms of safety and arrive at a mathematical notion
of safety of a long-term execution, even when conditioned on observational
information. We present efficient algorithms that can prove that trajectories
or policies are safe with much tighter bounds than in previous work. Notably,
the complexity of the environment does not affect our methods ability to
evaluate if a trajectory or policy is safe. We then use these safety checking
methods to design a safe variant of the RRT planning algorithm.Comment: RSS 201
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