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2012


Towards Multi-DOF model mediated teleoperation: Using vision to augment feedback
Towards Multi-DOF model mediated teleoperation: Using vision to augment feedback

Willaert, B., Bohg, J., Van Brussel, H., Niemeyer, G.

In IEEE International Workshop on Haptic Audio Visual Environments and Games (HAVE), pages: 25-31, October 2012 (inproceedings)

Abstract
In this paper, we address some of the challenges that arise as model-mediated teleoperation is applied to systems with multiple degrees of freedom and multiple sensors. Specifically we use a system with position, force, and vision sensors to explore an environment geometry in two degrees of freedom. The inclusion of vision is proposed to alleviate the difficulties of estimating an increasing number of environment properties. Vision can furthermore increase the predictive nature of model-mediated teleoperation, by effectively predicting touch feedback before the slave is even in contact with the environment. We focus on the case of estimating the location and orientation of a local surface patch at the contact point between the slave and the environment. We describe the various information sources with their respective limitations and create a combined model estimator as part of a multi-d.o.f. model-mediated controller. An experiment demonstrates the feasibility and benefits of utilizing vision sensors in teleoperation.

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DOI [BibTex]

2012


DOI [BibTex]


Failure Recovery with Shared Autonomy
Failure Recovery with Shared Autonomy

Sankaran, B., Pitzer, B., Osentoski, S.

In International Conference on Intelligent Robots and Systems, October 2012 (inproceedings)

Abstract
Building robots capable of long term autonomy has been a long standing goal of robotics research. Such systems must be capable of performing certain tasks with a high degree of robustness and repeatability. In the context of personal robotics, these tasks could range anywhere from retrieving items from a refrigerator, loading a dishwasher, to setting up a dinner table. Given the complexity of tasks there are a multitude of failure scenarios that the robot can encounter, irrespective of whether the environment is static or dynamic. For a robot to be successful in such situations, it would need to know how to recover from failures or when to ask a human for help. This paper, presents a novel shared autonomy behavioral executive to addresses these issues. We demonstrate how this executive combines generalized logic based recovery and human intervention to achieve continuous failure free operation. We tested the systems over 250 trials of two different use case experiments. Our current algorithm drastically reduced human intervention from 26% to 4% on the first experiment and 46% to 9% on the second experiment. This system provides a new dimension to robot autonomy, where robots can exhibit long term failure free operation with minimal human supervision. We also discuss how the system can be generalized.

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link (url) [BibTex]

link (url) [BibTex]


Task-Based Grasp Adaptation on a Humanoid Robot
Task-Based Grasp Adaptation on a Humanoid Robot

Bohg, J., Welke, K., León, B., Do, M., Song, D., Wohlkinger, W., Aldoma, A., Madry, M., Przybylski, M., Asfour, T., Marti, H., Kragic, D., Morales, A., Vincze, M.

In 10th IFAC Symposium on Robot Control, SyRoCo 2012, Dubrovnik, Croatia, September 5-7, 2012., pages: 779-786, September 2012 (inproceedings)

Abstract
In this paper, we present an approach towards autonomous grasping of objects according to their category and a given task. Recent advances in the field of object segmentation and categorization as well as task-based grasp inference have been leveraged by integrating them into one pipeline. This allows us to transfer task-specific grasp experience between objects of the same category. The effectiveness of the approach is demonstrated on the humanoid robot ARMAR-IIIa.

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Video pdf DOI [BibTex]

Video pdf DOI [BibTex]


Quasi-Newton Methods: A New Direction
Quasi-Newton Methods: A New Direction

Hennig, P., Kiefel, M.

In Proceedings of the 29th International Conference on Machine Learning, pages: 25-32, ICML ’12, (Editors: John Langford and Joelle Pineau), Omnipress, New York, NY, USA, ICML, July 2012 (inproceedings)

Abstract
Four decades after their invention, quasi- Newton methods are still state of the art in unconstrained numerical optimization. Although not usually interpreted thus, these are learning algorithms that fit a local quadratic approximation to the objective function. We show that many, including the most popular, quasi-Newton methods can be interpreted as approximations of Bayesian linear regression under varying prior assumptions. This new notion elucidates some shortcomings of classical algorithms, and lights the way to a novel nonparametric quasi-Newton method, which is able to make more efficient use of available information at computational cost similar to its predecessors.

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website+code pdf link (url) [BibTex]

website+code pdf link (url) [BibTex]


Entropy Search for Information-Efficient Global Optimization
Entropy Search for Information-Efficient Global Optimization

Hennig, P., Schuler, C.

Journal of Machine Learning Research, 13, pages: 1809-1837, -, June 2012 (article)

Abstract
Contemporary global optimization algorithms are based on local measures of utility, rather than a probability measure over location and value of the optimum. They thus attempt to collect low function values, not to learn about the optimum. The reason for the absence of probabilistic global optimizers is that the corresponding inference problem is intractable in several ways. This paper develops desiderata for probabilistic optimization algorithms, then presents a concrete algorithm which addresses each of the computational intractabilities with a sequence of approximations and explicitly adresses the decision problem of maximizing information gain from each evaluation.

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PDF Web Project Page [BibTex]

PDF Web Project Page [BibTex]


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Learning Tracking Control with Forward Models

Bócsi, B., Hennig, P., Csató, L., Peters, J.

In pages: 259 -264, IEEE International Conference on Robotics and Automation (ICRA), May 2012 (inproceedings)

Abstract
Performing task-space tracking control on redundant robot manipulators is a difficult problem. When the physical model of the robot is too complex or not available, standard methods fail and machine learning algorithms can have advantages. We propose an adaptive learning algorithm for tracking control of underactuated or non-rigid robots where the physical model of the robot is unavailable. The control method is based on the fact that forward models are relatively straightforward to learn and local inversions can be obtained via local optimization. We use sparse online Gaussian process inference to obtain a flexible probabilistic forward model and second order optimization to find the inverse mapping. Physical experiments indicate that this approach can outperform state-of-the-art tracking control algorithms in this context.

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PDF Web DOI [BibTex]

PDF Web DOI [BibTex]


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Movement Segmentation and Recognition for Imitation Learning

Meier, F., Theodorou, E., Schaal, S.

In Seventeenth International Conference on Artificial Intelligence and Statistics, La Palma, Canary Islands, Fifteenth International Conference on Artificial Intelligence and Statistics , April 2012 (inproceedings)

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link (url) [BibTex]

link (url) [BibTex]


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Approximate Gaussian Integration using Expectation Propagation

Cunningham, J., Hennig, P., Lacoste-Julien, S.

In pages: 1-11, -, January 2012 (inproceedings) Submitted

Abstract
While Gaussian probability densities are omnipresent in applied mathematics, Gaussian cumulative probabilities are hard to calculate in any but the univariate case. We offer here an empirical study of the utility of Expectation Propagation (EP) as an approximate integration method for this problem. For rectangular integration regions, the approximation is highly accurate. We also extend the derivations to the more general case of polyhedral integration regions. However, we find that in this polyhedral case, EP's answer, though often accurate, can be almost arbitrarily wrong. These unexpected results elucidate an interesting and non-obvious feature of EP not yet studied in detail, both for the problem of Gaussian probabilities and for EP more generally.

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Web [BibTex]

Web [BibTex]


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Kernel Topic Models

Hennig, P., Stern, D., Herbrich, R., Graepel, T.

In Fifteenth International Conference on Artificial Intelligence and Statistics, 22, pages: 511-519, JMLR Proceedings, (Editors: Lawrence, N. D. and Girolami, M.), JMLR.org, AISTATS , 2012 (inproceedings)

Abstract
Latent Dirichlet Allocation models discrete data as a mixture of discrete distributions, using Dirichlet beliefs over the mixture weights. We study a variation of this concept, in which the documents' mixture weight beliefs are replaced with squashed Gaussian distributions. This allows documents to be associated with elements of a Hilbert space, admitting kernel topic models (KTM), modelling temporal, spatial, hierarchical, social and other structure between documents. The main challenge is efficient approximate inference on the latent Gaussian. We present an approximate algorithm cast around a Laplace approximation in a transformed basis. The KTM can also be interpreted as a type of Gaussian process latent variable model, or as a topic model conditional on document features, uncovering links between earlier work in these areas.

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PDF Web [BibTex]

PDF Web [BibTex]


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From Dynamic Movement Primitives to Associative Skill Memories

Pastor, P., Kalakrishnan, M., Meier, F., Stulp, F., Buchli, J., Theodorou, E., Schaal, S.

Robotics and Autonomous Systems, 2012 (article)

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Project Page [BibTex]

Project Page [BibTex]


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Structure and aggregation of colloids immersed in critical solvents

Mohry, T. F., Maciolek, A., Dietrich, S.

Journal of Chemical Physics, 136(22), 2012 (article)

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DOI [BibTex]

DOI [BibTex]


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Ewald sum for hydrodynamic interactions with periodicity in two dimensions

Bleibel, J.

Journal of Physics A: Mathematical and Theoretical, 45(22), 2012 (article)

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DOI [BibTex]

DOI [BibTex]


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Nanodroplets at topographic steps

Bartsch, H.

Universität Stuttgart, Stuttgart, 2012 (mastersthesis)

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[BibTex]

[BibTex]


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Patchy worm-like micelles: solution structure studied by small-angle neutron scattering

Rosenfeldt, S., Luedel, F., Schulreich, C., Hellweg, T., Radulescu, A., Schmelz, J., Schmalz, H., Harnau, L.

Physical Chemistry Chemical Physics, 14, pages: 12750-12756, 2012 (article)

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DOI [BibTex]

DOI [BibTex]


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Time correlations and persistence probability of a Brownian particle in a shear flow

Chakraborty, D.

European Physical Journal B, 85(8), Springer-Verlag Heidelberg, Heidelberg, 2012 (article)

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DOI [BibTex]

DOI [BibTex]


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Local theory for ions in binary liquid mixtures

Bier, M., Gambassi, A., Dietrich, S.

The Journal of Chemical Physics, 137(3), American Institute of Physics, Woodbury, N.Y., 2012 (article)

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DOI [BibTex]

DOI [BibTex]


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Effect of ions on confined near-critical binary aqueous mixture

Pousaneh, F., Ciach, A., Maciolek, A.

Soft Matter, 8(29):7567-7581, 2012 (article)

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DOI [BibTex]

DOI [BibTex]


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Janus particles in critical liquids

Labbe-Laurent, M.

Universität Stuttgart, Stuttgart, 2012 (mastersthesis)

icm

[BibTex]

[BibTex]


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Surface integration approach: a new technique for evaluating geometry dependent forces between objects of various geometry and a plate

Dantchev, D., Valchev, G.

Journal of Colloid and Interface Science, 372(1):148-163, 2012 (article)

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DOI [BibTex]

DOI [BibTex]


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Phase equilibria of binary liquid crystals

Klöss, Hans-Christian

Universität Stuttgart, Stuttgart, 2012 (mastersthesis)

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[BibTex]

[BibTex]


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Pinning of drops at superhydrophobic surfaces

Daschke, Lena

Universität Stuttgart, Stuttgart, 2012 (mastersthesis)

icm

[BibTex]

[BibTex]


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Stability of thin wetting films on chemically nanostructured surfaces

Checco, A., Ocko, B. M., Tasinkevych, M., Dietrich, S.

Physical Review Letters, 109(16), American Physical Society., Woodbury, N.Y., etc., 2012 (article)

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DOI [BibTex]

DOI [BibTex]


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The structure of fluids with impurities

Bier, M., Harnau, L.

Zeitschrift f\"ur physikalische Chemie, 226(7-8):807-814, Akademische Verlagsgesellschaft, Frankfurt am Main, 2012 (article)

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DOI [BibTex]

DOI [BibTex]


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Impedance spectroscopy of ions at interfaces

Reindl, A.

Universität Stuttgart, Stuttgart, 2012 (mastersthesis)

icm

[BibTex]

[BibTex]


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Stepwise swelling of a thin film of lamellae-forming poly(styrene-b-butadiene) in cyclohexane vapor

Di, Zhenyu, Posselt, Dorthe, Smilgies, Detlef-M., Li, Ruipeng, Rauscher, Markus, Potemkin, Igor I., Papadakis, Christine M.

Macromolecules, 45(12):5185-5195, 2012 (article)

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link (url) DOI [BibTex]

link (url) DOI [BibTex]


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A close look at proteins: submolecular resolution of two- and three-dimensionally folded cytochrome c at surfaces

Deng, Z., Thontasen, N., Malinowski, N., Rinke, G., Harnau, L., Rauschenbach, S., Kern, K.

Nano Letters, 12, pages: 2452-2458, 2012 (article)

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DOI [BibTex]

DOI [BibTex]


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Field-induced breakup of emulsion droplets stabilized by colloidal particles

Kim, E. G., Stratford, K., Clegg, P. S., Cates, M. E.

Physical Review E, 85(2), 2012 (article)

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DOI [BibTex]

DOI [BibTex]


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Surface of an evaporating liquid

Arnold, Daniel

Universität Stuttgart, Stuttgart, 2012 (mastersthesis)

icm

[BibTex]

[BibTex]


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Precursor films in wetting phenomena

Popescu, M. N., Oshanin, G., Dietrich, S., Cazabat, A. M.

Journal of Physics: Condensed Matter, 24, 2012 (article)

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DOI [BibTex]

DOI [BibTex]


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Statics and dynamics of critical Casimir forces

Tröndle, M.

Universität Stuttgart, Stuttgart, 2012 (phdthesis)

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link (url) [BibTex]

link (url) [BibTex]


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First passages in bounded domains: When is the mean first passage time meaningful?

Mattos, Thiago G., Mejia-Monasterio, Carlos, Metzler, Ralf, Oshanin, Gleb

Physical Review E, 86(3), Published by the American Physical Society through the American Institute of Physics, Melville, NY, 2012 (article)

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DOI [BibTex]

DOI [BibTex]


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Gelation, phase behavior, and dynamics of beta-lactoglobulin amyloid fibrils at varying concentrations and ionic strengths

Bolisetty, S., Harnau, L., Jung, J., Mezzenga, R.

Biomacromolecules, 13, pages: 3241-3252, 2012 (article)

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DOI [BibTex]

DOI [BibTex]


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Interactions of distinct quadrupolar nematic colloids

Eskandari, Z., Silvestre, N. M., Tasinkevych, M., Telo da Gama, M. M.

Soft Matter, 8(39):10100-10106, Royal Society of Chemistry, Cambridge, UK, 2012 (article)

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DOI [BibTex]

DOI [BibTex]


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Critical Casimir forces beyond the Derjaguin approximation

Brunner, Niklas

Universität Stuttgart, Stuttgart, 2012 (mastersthesis)

icm

[BibTex]

[BibTex]


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Inverse dynamics with optimal distribution of contact forces for the control of legged robots

Righetti, L., Schaal, S.

In Dynamic Walking 2012, Pensacola, 2012 (inproceedings)

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[BibTex]

[BibTex]


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Transport of cargo by catalytic Janus micro-motors

Baraban, L., Tasinkevych, M., Popescu, M. N., Sanchez, S., Dietrich, S., Schmidt, O. G.

Soft Matter, 8(1):48-52, 2012 (article)

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DOI [BibTex]

DOI [BibTex]


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Mesoscopic analysis of Gibbs’criterion for sessile nanodroplets on trapezoidal substrates

Dutka, F., Napiorkowski, M., Dietrich, S.

Journal of Chemical Physics, 136(6), 2012 (article)

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DOI [BibTex]

DOI [BibTex]


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Complete wetting of elastically responsive substrates

Bernardino, N. R., Dietrich, S.

Physical Review E, 85(5), 2012 (article)

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DOI [BibTex]

DOI [BibTex]


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GPU-accelerated simulation of colloidal suspensions with direct hydrodynamic interactions

Kopp, M., Höfling, F.

The European Physical Journal - Special Topics, 210(1):101-117, 2012 (article)

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DOI [BibTex]

DOI [BibTex]


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Liquid crystal boojum-colloids

Tasinkevych, M., Silvestre, N. M., da Gama, M. M. Telo

New Journal of Physics, 14, Institute of Physics Pub., Bristol, UK, 2012 (article)

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DOI [BibTex]

DOI [BibTex]


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Crystalline inverted membrane grown on surfaces by electrospray ion beam deposition in vacuum

Rauschenbach, S., Rinke, G., Malinowski, N., Weitz, R., Dinnebier, R., Thontasen, N., Deng, Z., Lutz, T., Rollo, P., Costantini, G., Harnau, L., Kern, K.

Advanced Materials, 24, pages: 2761-2767, 2012 (article)

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DOI [BibTex]

DOI [BibTex]


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Crystallization of flexible molecules

Held, Felix

Universität Stuttgart, Stuttgart, 2012 (mastersthesis)

icm

[BibTex]

[BibTex]


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Encoding of Periodic and their Transient Motions by a Single Dynamic Movement Primitive

Ernesti, J., Righetti, L., Do, M., Asfour, T., Schaal, S.

In 2012 12th IEEE-RAS International Conference on Humanoid Robots (Humanoids 2012), pages: 57-64, IEEE, Osaka, Japan, November 2012 (inproceedings)

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link (url) DOI [BibTex]

link (url) DOI [BibTex]


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An adaptive sensor foot for a bipedal and quadrupedal robot

Fondahl, K., Kuehn, D., Beinersdorf, F., Bernhard, F., Grimminger, F., Schilling, M., Stark, T., Kirchner, F.

In 2012 4th IEEE RAS EMBS International Conference on Biomedical Robotics and Biomechatronics (BioRob), pages: 270-275, June 2012 (inproceedings)

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DOI [BibTex]

DOI [BibTex]


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Learning Force Control Policies for Compliant Robotic Manipulation

Kalakrishnan, M., Righetti, L., Pastor, P., Schaal, S.

In ICML’12 Proceedings of the 29th International Coference on International Conference on Machine Learning, pages: 49-50, Edinburgh, Scotland, 2012 (inproceedings)

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[BibTex]

[BibTex]


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Quadratic programming for inverse dynamics with optimal distribution of contact forces

Righetti, L., Schaal, S.

In 2012 12th IEEE-RAS International Conference on Humanoid Robots (Humanoids 2012), pages: 538-543, IEEE, Osaka, Japan, November 2012 (inproceedings)

Abstract
In this contribution we propose an inverse dynamics controller for a humanoid robot that exploits torque redundancy to minimize any combination of linear and quadratic costs in the contact forces and the commands. In addition the controller satisfies linear equality and inequality constraints in the contact forces and the commands such as torque limits, unilateral contacts or friction cones limits. The originality of our approach resides in the formulation of the problem as a quadratic program where we only need to solve for the control commands and where the contact forces are optimized implicitly. Furthermore, we do not need a structured representation of the dynamics of the robot (i.e. an explicit computation of the inertia matrix). It is in contrast with existing methods based on quadratic programs. The controller is then robust to uncertainty in the estimation of the dynamics model and the optimization is fast enough to be implemented in high bandwidth torque control loops that are increasingly available on humanoid platforms. We demonstrate properties of our controller with simulations of a human size humanoid robot.

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link (url) DOI [BibTex]

link (url) DOI [BibTex]


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Model-free reinforcement learning of impedance control in stochastic environments

Stulp, Freek, Buchli, Jonas, Ellmer, Alice, Mistry, Michael, Theodorou, Evangelos A., Schaal, S.

Autonomous Mental Development, IEEE Transactions on, 4(4):330-341, 2012 (article)

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[BibTex]

[BibTex]