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2011


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Learning, planning, and control for quadruped locomotion over challenging terrain

Kalakrishnan, Mrinal, Buchli, Jonas, Pastor, Peter, Mistry, Michael, Schaal, S.

International Journal of Robotics Research, 30(2):236-258, February 2011 (article)

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[BibTex]

2011


[BibTex]


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Collective dynamics of colloids at fluid interfaces

Bleibel, J., Dominguez, A., Oettel, M., Dietrich, S.

European Physical Journal E, 34(11), 2011 (article)

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DOI [BibTex]

DOI [BibTex]


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Anomalous transport of a tracer on percolating clusters

Spanner, M., Höfling, F., Schröder-Turk, G. E., Mecke, K., Franosch, T.

Journal of Physics: Condensed Matter, 23(23), 2011 (article)

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DOI [BibTex]

DOI [BibTex]


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Dynamics of colloids in confined geometries

Almenar, L., Rauscher, M.

Journal of Physics: Condensed Matter, 23(18), 2011 (article)

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link (url) DOI [BibTex]

link (url) DOI [BibTex]


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The structure and melting transition of two-dimensional colloidal alloys

Law, A. D., Horozov, T. S., Buzza, D. M. A.

Soft Matter, 7(19):8923-8931, 2011 (article)

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DOI [BibTex]

DOI [BibTex]


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Second harmonic light scattering from spherical polyelectrolyte brushes

Schürer, B., Hoffmann, M., Wunderlich, S., Harnau, L., Peschel, U., Ballauff, M., Peukert, W.

Journal of Physical Chemistry C, 115, pages: 18302-18309, 2011 (article)

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DOI [BibTex]

DOI [BibTex]


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Solvation forces in Ising films with long-range boundary fields: density-matrix renormalization-group study

Drzewinski, A., Maciolek, A., Barasinski, A.

Molecular Physics, 109(7-10):1133-1141, 2011 (article)

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DOI [BibTex]

DOI [BibTex]


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Pulling and pushing a cargo with a catalytically active carrier

Popescu, M. N., Tasinkevych, M., Dietrich, S.

Europhysics Letters, 95(2), 2011 (article)

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DOI [BibTex]

DOI [BibTex]


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Critical Casimir forces for Ising films with variable boundary fields

Vasilyev, O., Maciolek, A., Dietrich, S.

Physical Review E, 84(4), 2011 (article)

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DOI [BibTex]


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Study of \pi\pi correlations at LHC and RHIC energies in pp collisions within the quark-gluon string model

Nilsson, M. S., Bravina, L. V., Zabrodin, E. E., Malinina, L. V., Bleibel, J.

Physical Review D, 84(5), 2011 (article)

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DOI [BibTex]

DOI [BibTex]


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Micro-rheology on (polymer-grafted) colloids using optical tweezers

Gutsche, C., Elmahdy, M. M., Kegler, K., Semenov, I., Stangner, T., Otto, O., Ueberschär, O., Keyser, U. F., Krüger, M., Rauscher, M., Weeber, R., Harting, J., Kim, Y. W., Lobaskin, V., Netz, R., Kremer, F.

Journal of Physics: Condensed Matter, 23(18), IOP Publishing, Bristol, 2011 (article)

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DOI [BibTex]

DOI [BibTex]


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Debye-Scherrer rings from block copolymer films with powder-like order

Busch, P., Rauscher, M., Moulin, J.-F., Müller-Buschbaum, P.

Journal of Applied Crystallography, 44(2):370-379, 2011 (article)

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DOI [BibTex]

DOI [BibTex]


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Effective interactions and equilibrium configurations of colloidal particles on a sessile droplet

Guzowski, J., Tasinkevych, M., Dietrich, S.

Soft Matter, 7(9):4189-4197, 2011 (article)

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DOI [BibTex]

DOI [BibTex]


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Capillary interactions in Pickering emulsions

Guzowski, J., Tasinkevych, M., Dietrich, S.

Physical Review E, 84(3), 2011 (article)

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DOI [BibTex]

DOI [BibTex]


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Critical Casimir forces steered by patterned substrates

Gambassi, A., Dietrich, S.

Soft Matter, 7(4):1247-1253, 2011 (article)

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DOI [BibTex]

DOI [BibTex]


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Interaction strength between proteins and polyelectrolyte brushes: A small angle X-ray scattering study

Henzler, K., Haupt, B., Rosenfeldt, S., Harnau, L., Narayanan, T., Ballauff, M.

Physical Chemistry Chemical Physics, 13, pages: 17599-17605, 2011 (article)

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DOI [BibTex]

DOI [BibTex]


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Annealing of single lamella nanoparticles of polyethylene

Rochette, C. N., Rosenfeldt, S., Henzler, K., Polzer, F., Ballauff, M., Tong, Q., Mecking, S., Drechsler, M., Narayanan, T., Harnau, L.

Macromolecules, 44(12):4845-4851, 2011 (article)

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DOI [BibTex]

DOI [BibTex]


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Bayesian robot system identification with input and output noise

Ting, J., D’Souza, A., Schaal, S.

Neural Networks, 24(1):99-108, 2011, clmc (article)

Abstract
For complex robots such as humanoids, model-based control is highly beneficial for accurate tracking while keeping negative feedback gains low for compliance. However, in such multi degree-of-freedom lightweight systems, conventional identification of rigid body dynamics models using CAD data and actuator models is inaccurate due to unknown nonlinear robot dynamic effects. An alternative method is data-driven parameter estimation, but significant noise in measured and inferred variables affects it adversely. Moreover, standard estimation procedures may give physically inconsistent results due to unmodeled nonlinearities or insufficiently rich data. This paper addresses these problems, proposing a Bayesian system identification technique for linear or piecewise linear systems. Inspired by Factor Analysis regression, we develop a computationally efficient variational Bayesian regression algorithm that is robust to ill-conditioned data, automatically detects relevant features, and identifies input and output noise. We evaluate our approach on rigid body parameter estimation for various robotic systems, achieving an error of up to three times lower than other state-of-the-art machine learning methods

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link (url) [BibTex]

link (url) [BibTex]


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Trapping colloids near chemical stripes via critical Casimir forces

Tröndle, M., Zvyagolskaya, O., Gambassi, A., Vogt, D., Harnau, L., Bechinger, C., Dietrich, S.

Molecular Physics, 109, pages: 1169-1185, 2011 (article)

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DOI [BibTex]

DOI [BibTex]


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Electrostatic interactions in critical solvents

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

Europhysics Letters, 95, 2011 (article)

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DOI [BibTex]

DOI [BibTex]


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Structural investigation of thin diblock copolymer films using time-of-flight grazing-incidence small-angle neutron scattering

Metwalli, E., Moulin, J.-F., Rauscher, M., Kaune, G., Ruderer, M. A., Van Bürck, U., Haese-Seiller, M., Kampmann, R., Müller-Buschbaum, P.

Journal of Applied Crystallography, 44(1):84-92, 2011 (article)

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DOI [BibTex]

DOI [BibTex]


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Complexation of beta-lactoglobulin fibrils and sulfated polysaccharides

Jones, O. G., Handschin, S., Adamcik, J., Harnau, L., Bolisetty, S., Mezzenga, R.

Biomacromolecules, 12, pages: 3056-3065, 2011 (article)

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DOI [BibTex]

DOI [BibTex]


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Learning variable impedance control

Buchli, J., Stulp, F., Theodorou, E., Schaal, S.

International Journal of Robotics Research, 2011, clmc (article)

Abstract
One of the hallmarks of the performance, versatility, and robustness of biological motor control is the ability to adapt the impedance of the overall biomechanical system to different task requirements and stochastic disturbances. A transfer of this principle to robotics is desirable, for instance to enable robots to work robustly and safely in everyday human environments. It is, however, not trivial to derive variable impedance controllers for practical high degree-of-freedom (DOF) robotic tasks. In this contribution, we accomplish such variable impedance control with the reinforcement learning (RL) algorithm PISq ({f P}olicy {f I}mprovement with {f P}ath {f I}ntegrals). PISq is a model-free, sampling based learning method derived from first principles of stochastic optimal control. The PISq algorithm requires no tuning of algorithmic parameters besides the exploration noise. The designer can thus fully focus on cost function design to specify the task. From the viewpoint of robotics, a particular useful property of PISq is that it can scale to problems of many DOFs, so that reinforcement learning on real robotic systems becomes feasible. We sketch the PISq algorithm and its theoretical properties, and how it is applied to gain scheduling for variable impedance control. We evaluate our approach by presenting results on several simulated and real robots. We consider tasks involving accurate tracking through via-points, and manipulation tasks requiring physical contact with the environment. In these tasks, the optimal strategy requires both tuning of a reference trajectory emph{and} the impedance of the end-effector. The results show that we can use path integral based reinforcement learning not only for planning but also to derive variable gain feedback controllers in realistic scenarios. Thus, the power of variable impedance control is made available to a wide variety of robotic systems and practical applications.

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link (url) [BibTex]

link (url) [BibTex]


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Magnetization of multicomponent ferrofluids

Szalai, I., Dietrich, S.

Journal of Physics: Condensed Matter, 23(32), 2011 (article)

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DOI [BibTex]

DOI [BibTex]


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Space-resolved dynamics of a tracer in a disordered solid

Franosch, T., Spanner, M., Bauer, T., Schröder-Turk, G. E., Höfling, F.

Journal of Non-Crystalline Solids, 357(2):472-478, 2011 (article)

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DOI [BibTex]

DOI [BibTex]


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Long-wavelength anomalies in the asymptotic behavior of mode-coupling theory

Schnyder, S. K., Höfling, F., Franosch, T., Voigtmann, T.

Journal of Physics: Condensed Matter, 23(23), 2011 (article)

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DOI [BibTex]

DOI [BibTex]


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Toward simple control for complex, autonomous robotic applications: combining discrete and rhythmic motor primitives

Degallier, S., Righetti, L., Gay, S., Ijspeert, A.

Autonomous Robots, 31(2-3):155-181, October 2011 (article)

Abstract
Vertebrates are able to quickly adapt to new environments in a very robust, seemingly effortless way. To explain both this adaptivity and robustness, a very promising perspective in neurosciences is the modular approach to movement generation: Movements results from combinations of a finite set of stable motor primitives organized at the spinal level. In this article we apply this concept of modular generation of movements to the control of robots with a high number of degrees of freedom, an issue that is challenging notably because planning complex, multidimensional trajectories in time-varying environments is a laborious and costly process. We thus propose to decrease the complexity of the planning phase through the use of a combination of discrete and rhythmic motor primitives, leading to the decoupling of the planning phase (i.e. the choice of behavior) and the actual trajectory generation. Such implementation eases the control of, and the switch between, different behaviors by reducing the dimensionality of the high-level commands. Moreover, since the motor primitives are generated by dynamical systems, the trajectories can be smoothly modulated, either by high-level commands to change the current behavior or by sensory feedback information to adapt to environmental constraints. In order to show the generality of our approach, we apply the framework to interactive drumming and infant crawling in a humanoid robot. These experiments illustrate the simplicity of the control architecture in terms of planning, the integration of different types of feedback (vision and contact) and the capacity of autonomously switching between different behaviors (crawling and simple reaching).

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link (url) DOI [BibTex]

link (url) DOI [BibTex]


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Understanding haptics by evolving mechatronic systems

Loeb, G. E., Tsianos, G.A., Fishel, J.A., Wettels, N., Schaal, S.

Progress in Brain Research, 192, pages: 129, 2011 (article)

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[BibTex]

[BibTex]


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Intelligent Mobility—Autonomous Outdoor Robotics at the DFKI

Joyeux, S., Schwendner, J., Kirchner, F., Babu, A., Grimminger, F., Machowinski, J., Paranhos, P., Gaudig, C.

KI, 25(2):133-139, May 2011 (article)

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DOI [BibTex]

DOI [BibTex]

2010


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Policy learning algorithmis for motor learning (Algorithmen zum automatischen Erlernen von Motorfähigkigkeiten)

Peters, J., Kober, J., Schaal, S.

Automatisierungstechnik, 58(12):688-694, 2010, clmc (article)

Abstract
Robot learning methods which allow au- tonomous robots to adapt to novel situations have been a long standing vision of robotics, artificial intelligence, and cognitive sciences. However, to date, learning techniques have yet to ful- fill this promise as only few methods manage to scale into the high-dimensional domains of manipulator robotics, or even the new upcoming trend of humanoid robotics. If possible, scaling was usually only achieved in precisely pre-structured domains. In this paper, we investigate the ingredients for a general ap- proach policy learning with the goal of an application to motor skill refinement in order to get one step closer towards human- like performance. For doing so, we study two major components for such an approach, i. e., firstly, we study policy learning algo- rithms which can be applied in the general setting of motor skill learning, and, secondly, we study a theoretically well-founded general approach to representing the required control structu- res for task representation and execution.

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link (url) [BibTex]


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Comment on biomimetic ultrathin whitening by capillary-force-induced random clustering of hydrogel micropillar arrays

Bernardino, N. R., Dietrich, S.

ACS Applied Materials \& Interfaces, 2(3):603-604, 2010 (article)

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DOI [BibTex]

DOI [BibTex]


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Wetting of surfaces covered by elastic hairs

Bernardino, N. R., Blickle, V., Dietrich, S.

Langmuir, 26(10):7233-7241, 2010 (article)

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DOI [BibTex]

DOI [BibTex]


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Phase diagrams of binary mixtures of oppositely charged colloids

Bier, M., van Roij, R., Dijkstra, M.

Journal of Chemical Physics, 133(12), 2010 (article)

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DOI [BibTex]

DOI [BibTex]


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Narrow-escape times for diffusion in microdomains with a particle-surface affinity: mean-field results

Oshanin, G., Tamm, M., Vasilyev, O.

Journal of Chemical Physics, 132(23), 2010 (article)

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DOI [BibTex]

DOI [BibTex]


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The localization transition of the two-dimensional Lorentz model

Bauer, T., Höfling, Felix, Munk, T., Frey, E., Franosch, T.

European Physical Journal - Special Topics, 189(1):103-118, 2010 (article)

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DOI [BibTex]

DOI [BibTex]


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DDFT for Brownian particles and hydrodynamics

Rauscher, M.

Journal of Physics: Condensed Matter, 22(36), 2010 (article)

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link (url) DOI [BibTex]

link (url) DOI [BibTex]


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Colloidal particles in liquid crystal films and at interfaces

Tasinkevych, M., Andrienko, D.

Condensed Matter Physics, 13(3), 2010 (article)

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[BibTex]

[BibTex]


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Phase behavior of ionic liquid crystals

Kondrat, S., Bier, M., Harnau, L.

The Journal of Chemical Physics, 132, 2010 (article)

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DOI [BibTex]

DOI [BibTex]


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Nanoindentation studies on crosslinking and curing effects of PDMS

Deuschle, J. K., de Souza, E. J., Arzt, E., Enders, S.

International Journal of Materials Research, 101(8):1014-1023, 2010 (article)

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DOI [BibTex]

DOI [BibTex]


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Fundamental measure theory for hard-sphere mixtures: a review

Roth, R.

Journal of Physics: Condensed Matter, 22(6), 2010 (article)

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DOI [BibTex]

DOI [BibTex]


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Universality of the glassy transitions in the two-dimensional \pmJ Ising model

Parisen Toldin, F., Pelissetto, A, Vicari, E.

Physical Review E, 82(2), 2010 (article)

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DOI [BibTex]

DOI [BibTex]


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Phoretic motion of spheroidal particles due to self-generated solute gradients

Popescu, M. N., Dietrich, S., Tasinkevych, M., Ralston, J.

European Physical Journal E, 31(04):351-367, 2010 (article)

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DOI [BibTex]

DOI [BibTex]


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Vapor pressure of ionic liquids

Bier, M., Dietrich, S.

Molecular Physics, 108(2):211-214, 2010 (article)

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DOI [BibTex]

DOI [BibTex]


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Colloidal aggregation and critical Casimir forces

Gambassi, A., Dietrich, S.

Physical Review Letters, 105(5), 2010 (article)

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DOI [BibTex]

DOI [BibTex]


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Localization phenomena in models of ion-conduction glass formers

Horbach, J., Voigtmann, T., Höfling, F., Franosch, T.

European Physical Journal - Special Topics, 189(1):141-145, 2010 (article)

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DOI [BibTex]

DOI [BibTex]


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Tensorial density functional theory for non-spherical hard-body fluids

Hansen-Goos, H., Mecke, K.

Journal of Physics: Condensed Matter, 22(36), 2010 (article)

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DOI [BibTex]

DOI [BibTex]


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Thermoresponsive colloidal molecules

Hoffmann, M., Siebenbürger, M., Harnau, L., Hund, M., Hanske, C., Wagner, C. S., Drechsler, M., Ballauff, M.

Soft Matter, 6, pages: 1125-1128, 2010 (article)

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DOI [BibTex]

DOI [BibTex]


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Critical Casimir forces and adsorption profiles in the presence of a chemically structured substrate

Parisen Toldin, F., Dietrich, S.

Journal of Statistical Mechanics: Theory and Experiment, (Nov.), 2010 (article)

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DOI [BibTex]

DOI [BibTex]


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Free energy of colloidal particles at the surface of sessile drops

Guzowski, J., Tasinkevych, M., Dietrich, S.

European Physical Journal, 33(3):219-242, 2010 (article)

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DOI [BibTex]

DOI [BibTex]