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2011


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Electron theory of fast and ultrafast dissipative magnetization dynamics

Fähnle, M., Illg, C.

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

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DOI [BibTex]

2011


DOI [BibTex]


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Large-area hard magnetic L10-FePt nanopatterns by nanoimprint lithography

Bublat, T., Goll, D.

{Nanotechnology}, 22(31), 2011 (article)

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DOI [BibTex]

DOI [BibTex]


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Hydrogen storage by cryoadsorption in ultrahigh-porosity metal-organic frameworks

Hirscher, M.

{Angewandte Chemie International Edition}, 50(3):581-582, 2011 (article)

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DOI [BibTex]

DOI [BibTex]


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Amorphous grain boundary layers in the ferromagnetic nanograined ZnO films

Straumal, B. B., Mazilkin, A. A., Protasova, S. G., Myatiev, A. A., Straumal, P. B., Goering, E., Baretzky, B.

In 520, pages: 1192-1194, Hersonissos, Greece, 2011 (inproceedings)

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DOI [BibTex]

DOI [BibTex]


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Multilayer Fresnel zone plate for soft X-ray microscopy resolves sub-39 nm structures

Mayer, M., Grévent, C., Szeghalmi, A., Knez, M., Weigand, M., Rehbein, S., Schneider, G., Baretzky, B., Schütz, G.

{Ultramicroscopy}, 111, pages: 1706-1711, 2011 (article)

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DOI [BibTex]

DOI [BibTex]


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Generalized Gilbert equation including inertial damping: derivation from an extended breathing Fermi surface model

Fähnle, M., Steiauf, D., Illg, C.

{Physical Review B}, 84, 2011 (article)

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DOI [BibTex]


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Hydrogen physisorption in high SSA microporous materials - A comparison between AX-21\textunderscore33 and MOF-177 at cryogenic conditions

Schlichtenmayer, M., Streppel, B., Hirscher, M.

{International Journal of Hydrogen Energy}, 36, pages: 586-591, 2011 (article)

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DOI [BibTex]

DOI [BibTex]


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Inversed solid-phase grain boundary wetting in the Al-Zn system

Protasova, S. G., Kogtenkova, O. A., Straumal, B. B., Zieba, P., Baretzky, B.

In 46, pages: 4349-4353, Mie, Japan, 2011 (inproceedings)

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DOI [BibTex]

DOI [BibTex]


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Magnetic vortex core reversal by excitation of spin waves

Kammerer, M., Weigand, M., Curcic, M., Noske, M., Sproll, M., Vansteenkiste, A., Van Waeyenberge, B., Stoll, H., Woltersdorf, G., Back, C. H., Schütz, G.

{Nature Communications}, 2, pages: 279-284, 2011 (article)

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DOI [BibTex]

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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Teleoperation Based AFM Manipulation Control

Xie, H., Onal, C., Régnier, S., Sitti, M.

In Atomic Force Microscopy Based Nanorobotics, pages: 145-235, Springer Berlin Heidelberg, 2011 (incollection)

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[BibTex]

[BibTex]


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Descriptions and challenges of AFM based nanorobotic systems

Xie, H., Onal, C., Régnier, S., Sitti, M.

In Atomic Force Microscopy Based Nanorobotics, pages: 13-29, Springer Berlin Heidelberg, 2011 (incollection)

pi

[BibTex]

[BibTex]


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Control of multiple heterogeneous magnetic micro-robots on non-specialized surfaces

Diller, E., Floyd, S., Pawashe, C., Sitti, M.

In Robotics and Automation (ICRA), 2011 IEEE International Conference on, pages: 115-120, 2011 (inproceedings)

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[BibTex]

[BibTex]


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Tip based robotic precision micro/nanomanipulation systems

Onal, C., Sumer, B., Ozcan, O., Nain, A., Sitti, M.

In SPIE Defense, Security, and Sensing, pages: 80580M-80580M, 2011 (inproceedings)

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[BibTex]

[BibTex]


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Design of a miniature integrated multi-modal jumping and gliding robot

Woodward, M. A., Sitti, M.

In Intelligent Robots and Systems (IROS), 2011 IEEE/RSJ International Conference on, pages: 556-561, 2011 (inproceedings)

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Project Page [BibTex]

Project Page [BibTex]


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Assembly and disassembly of magnetic mobile micro-robots towards deterministic 2-D reconfigurable micro-systems

Diller, E., Pawashe, C., Floyd, S., Sitti, M.

The International Journal of Robotics Research, 30(14):1667-1680, SAGE Publications Sage UK: London, England, 2011 (article)

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[BibTex]

[BibTex]


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Tipping the Scales: Guidance and Intrinsically Motivated Behavior

Martius, G., Herrmann, J. M.

In Advances in Artificial Life, ECAL 2011, pages: 506-513, (Editors: Tom Lenaerts and Mario Giacobini and Hugues Bersini and Paul Bourgine and Marco Dorigo and René Doursat), MIT Press, 2011 (incollection)

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[BibTex]

[BibTex]


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Movement segmentation using a primitive library

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

In IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS 2011), Sept. 25-30, San Francisco, CA, 2011, clmc (inproceedings)

Abstract
Segmenting complex movements into a sequence of primitives remains a difficult problem with many applications in the robotics and vision communities. In this work, we show how the movement segmentation problem can be reduced to a sequential movement recognition problem. To this end, we reformulate the orig-inal Dynamic Movement Primitive (DMP) formulation as a linear dynamical sys-tem with control inputs. Based on this new formulation, we develop an Expecta-tion-Maximization algorithm to estimate the duration and goal position of a par-tially observed trajectory. With the help of this algorithm and the assumption that a library of movement primitives is present, we present a movement seg-mentation framework. We illustrate the usefulness of the new DMP formulation on the two applications of online movement recognition and movement segmen-tation.

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link (url) [BibTex]

link (url) [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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Learning Force Control Policies for Compliant Manipulation

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

In 2011 IEEE/RSJ International Conference on Intelligent Robots and Systems, pages: 4639-4644, IEEE, San Francisco, USA, sep 2011 (inproceedings)

Abstract
Developing robots capable of fine manipulation skills is of major importance in order to build truly assistive robots. These robots need to be compliant in their actuation and control in order to operate safely in human environments. Manipulation tasks imply complex contact interactions with the external world, and involve reasoning about the forces and torques to be applied. Planning under contact conditions is usually impractical due to computational complexity, and a lack of precise dynamics models of the environment. We present an approach to acquiring manipulation skills on compliant robots through reinforcement learning. The initial position control policy for manipulation is initialized through kinesthetic demonstration. We augment this policy with a force/torque profile to be controlled in combination with the position trajectories. We use the Policy Improvement with Path Integrals (PI2) algorithm to learn these force/torque profiles by optimizing a cost function that measures task success. We demonstrate our approach on the Barrett WAM robot arm equipped with a 6-DOF force/torque sensor on two different manipulation tasks: opening a door with a lever door handle, and picking up a pen off the table. We show that the learnt force control policies allow successful, robust execution of the tasks.

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link (url) DOI [BibTex]

link (url) DOI [BibTex]


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Control of legged robots with optimal distribution of contact forces

Righetti, L., Buchli, J., Mistry, M., Schaal, S.

In 2011 11th IEEE-RAS International Conference on Humanoid Robots, pages: 318-324, IEEE, Bled, Slovenia, 2011 (inproceedings)

Abstract
The development of agile and safe humanoid robots require controllers that guarantee both high tracking performance and compliance with the environment. More specifically, the control of contact interaction is of crucial importance for robots that will actively interact with their environment. Model-based controllers such as inverse dynamics or operational space control are very appealing as they offer both high tracking performance and compliance. However, while widely used for fully actuated systems such as manipulators, they are not yet standard controllers for legged robots such as humanoids. Indeed such robots are fundamentally different from manipulators as they are underactuated due to their floating-base and subject to switching contact constraints. In this paper we present an inverse dynamics controller for legged robots that use torque redundancy to create an optimal distribution of contact constraints. The resulting controller is able to minimize, given a desired motion, any quadratic cost of the contact constraints at each instant of time. In particular we show how this can be used to minimize tangential forces during locomotion, therefore significantly improving the locomotion of legged robots on difficult terrains. In addition to the theoretical result, we present simulations of a humanoid and a quadruped robot, as well as experiments on a real quadruped robot that demonstrate the advantages of the controller.

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link (url) DOI [BibTex]

link (url) DOI [BibTex]


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Learning Motion Primitive Goals for Robust Manipulation

Stulp, F., Theodorou, E., Kalakrishnan, M., Pastor, P., Righetti, L., Schaal, S.

In IEEE/RSJ International Conference on Intelligent Robots and Systems, pages: 325-331, IEEE, San Francisco, USA, sep 2011 (inproceedings)

Abstract
Applying model-free reinforcement learning to manipulation remains challenging for several reasons. First, manipulation involves physical contact, which causes discontinuous cost functions. Second, in manipulation, the end-point of the movement must be chosen carefully, as it represents a grasp which must be adapted to the pose and shape of the object. Finally, there is uncertainty in the object pose, and even the most carefully planned movement may fail if the object is not at the expected position. To address these challenges we 1) present a simplified, computationally more efficient version of our model-free reinforcement learning algorithm PI2; 2) extend PI2 so that it simultaneously learns shape parameters and goal parameters of motion primitives; 3) use shape and goal learning to acquire motion primitives that are robust to object pose uncertainty. We evaluate these contributions on a manipulation platform consisting of a 7-DOF arm with a 4-DOF hand.

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link (url) DOI [BibTex]

link (url) DOI [BibTex]


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Inverse Dynamics Control of Floating-Base Robots with External Constraints: a Unified View

Righetti, L., Buchli, J., Mistry, M., Schaal, S.

In 2011 IEEE International Conference on Robotics and Automation, pages: 1085-1090, IEEE, Shanghai, China, 2011 (inproceedings)

Abstract
Inverse dynamics controllers and operational space controllers have proved to be very efficient for compliant control of fully actuated robots such as fixed base manipulators. However legged robots such as humanoids are inherently different as they are underactuated and subject to switching external contact constraints. Recently several methods have been proposed to create inverse dynamics controllers and operational space controllers for these robots. In an attempt to compare these different approaches, we develop a general framework for inverse dynamics control and show that these methods lead to very similar controllers. We are then able to greatly simplify recent whole-body controllers based on operational space approaches using kinematic projections, bringing them closer to efficient practical implementations. We also generalize these controllers such that they can be optimal under an arbitrary quadratic cost in the commands.

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link (url) DOI [BibTex]

link (url) DOI [BibTex]


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Benchmark datasets for pose estimation and tracking

Andriluka, M., Sigal, L., Black, M. J.

In Visual Analysis of Humans: Looking at People, pages: 253-274, (Editors: Moesland and Hilton and Kr"uger and Sigal), Springer-Verlag, London, 2011 (incollection)

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publisher's site Project Page [BibTex]

publisher's site Project Page [BibTex]


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Piezo driven strain effects on magneto-crystalline anisotropy

Badr, E.

Universität Stuttgart, Stuttgart, 2011 (mastersthesis)

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[BibTex]

[BibTex]


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Magnetooptische Untersuchungen an granularen und beschichteten MgB2 Filmen

Stahl, C.

Universität Stuttgart, Stuttgart, 2011 (mastersthesis)

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[BibTex]

[BibTex]


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Mikromagnetismus der Wechselwirkung von Spinwellen mit Domänenwänden in Ferromagneten

Macke, S.

Universität Stuttgart, Stuttgart, 2011 (phdthesis)

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[BibTex]

[BibTex]


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Magnetism studied with circularly polarized X-rays

Schütz, G., Goering, E., Stoll, H.

{International Journal of Materials Research}, 102(7):773-783, 2011 (article)

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DOI [BibTex]

DOI [BibTex]


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Coupled vortex oscillations in spatially separated permalloy squares

Vogel, A., Kamionka, T., Martens, M., Drews, A., Chou, K., Tyliszczak, T., Stoll, H., Van Waeyenberge, B., Meier, G.

{Physical Review Letters}, 106, 2011 (article)

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DOI [BibTex]

DOI [BibTex]


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Contruction of basis functions with crystal symmetry for the spin-cluster expansion of the magnetic energy on the atomic scale

Dietermann, F., Singer, R., Fähnle, M.

{Journal of Mathematical Physics}, 52, 2011 (article)

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DOI [BibTex]

DOI [BibTex]


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Magnetic patterning perpendicular anisotropy FePd alloy films by masked ion irradiation

Merkel, D. G., Bottyán, L., Tanczikó, F., Zolnai, Z., Nagy, N., Vértesy, G., Waizinger, J., Bommer, L.

{Journal of Applied Physics}, 109(12), 2011 (article)

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DOI [BibTex]

DOI [BibTex]


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Characterization of hydrogen/deuterium adsorption sites in nanoporous Cu-BTC by low-temperature thermal-desorption mass spectroscopy

Krkljus, I., Hirscher, M.

{Microporous and Mesoporous Materials}, 142, pages: 725-729, 2011 (article)

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DOI [BibTex]


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Stability of the current-carrying state in nonhomogeneous MgB2 films

Treiber, S., Stahl, C., Schütz, G., Albrecht, J.

{Physical Review B}, 84, 2011 (article)

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DOI [BibTex]

DOI [BibTex]


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First measurement of the heat effect of the grain boundary wetting phase transition

Straumal, B. B., Kogtenkova, O. A., Protasova, S. G., Zieba, P., Czeppe, T., Baretzky, B., Valiev, R. Z.

In 46, pages: 4243, Mie, Japan, 2011 (inproceedings)

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DOI [BibTex]

DOI [BibTex]


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Orbital reflectometry of oxide heterostructures

Benckiser, E., Haverkort, M. W., Brück, S., Goering, E., Macke, S., Fraño, A., Yang, X., Andersen, O. K., Cristiani, G., Habermeier, H., Boris, A. V., Zegkinoglou, I., Wochner, P., Kim, H., Hinkov, V., Keimer, B.

{Nature Materials}, 10(3):189-193, 2011 (article)

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DOI [BibTex]

DOI [BibTex]


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Potential explanation of charge response of magnetization in nanoporous systems

Subkow, S., Fähnle, M.

{Physical Review B}, 84, 2011 (article)

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DOI [BibTex]

DOI [BibTex]


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Applications of AFM Based Nanorobotic Systems

Xie, H., Onal, C., Régnier, S., Sitti, M.

In Atomic Force Microscopy Based Nanorobotics, pages: 313-342, Springer Berlin Heidelberg, 2011 (incollection)

pi

[BibTex]

[BibTex]


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Free flight simulations and pitch and roll control experiments of a sub-gram flapping-flight micro aerial vehicle

Hines, L. L., Arabagi, V., Sitti, M.

In Robotics and Automation (ICRA), 2011 IEEE International Conference on, pages: 1-7, 2011 (inproceedings)

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Project Page [BibTex]

Project Page [BibTex]


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Modeling of stochastic motion of bacteria propelled spherical microbeads

Arabagi, V., Behkam, B., Cheung, E., Sitti, M.

Journal of Applied Physics, 109(11):114702, AIP, 2011 (article)

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Project Page [BibTex]

Project Page [BibTex]


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The effect of aspect ratio on adhesion and stiffness for soft elastic fibres

Aksak, B., Hui, C., Sitti, M.

Journal of The Royal Society Interface, 8(61):1166-1175, The Royal Society, 2011 (article)

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Project Page [BibTex]

Project Page [BibTex]


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Chemotactic behavior and dynamics of bacteria propelled microbeads

Kim, Dongwook, Liu, Albert, Stitti, Metin

In Intelligent Robots and Systems (IROS), 2011 IEEE/RSJ International Conference on, pages: 1674-1679, 2011 (inproceedings)

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Project Page [BibTex]

Project Page [BibTex]


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Shape and pose-invariant correspondences using probabilistic geodesic surface embedding

Tsoli, A., Black, M. J.

In 33rd Annual Symposium of the German Association for Pattern Recognition (DAGM), 6835, pages: 256-265, Lecture Notes in Computer Science, (Editors: Mester, Rudolf and Felsberg, Michael), Springer, 2011 (inproceedings)

Abstract
Correspondence between non-rigid deformable 3D objects provides a foundation for object matching and retrieval, recognition, and 3D alignment. Establishing 3D correspondence is challenging when there are non-rigid deformations or articulations between instances of a class. We present a method for automatically finding such correspondences that deals with significant variations in pose, shape and resolution between pairs of objects.We represent objects as triangular meshes and consider normalized geodesic distances as representing their intrinsic characteristics. Geodesic distances are invariant to pose variations and nearly invariant to shape variations when properly normalized. The proposed method registers two objects by optimizing a joint probabilistic model over a subset of vertex pairs between the objects. The model enforces preservation of geodesic distances between corresponding vertex pairs and inference is performed using loopy belief propagation in a hierarchical scheme. Additionally our method prefers solutions in which local shape information is consistent at matching vertices. We quantitatively evaluate our method and show that is is more accurate than a state of the art method.

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pdf talk Project Page [BibTex]

pdf talk Project Page [BibTex]


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Steerable random fields for image restoration and inpainting

Roth, S., Black, M. J.

In Markov Random Fields for Vision and Image Processing, pages: 377-387, (Editors: Blake, A. and Kohli, P. and Rother, C.), MIT Press, 2011 (incollection)

Abstract
This chapter introduces the concept of a Steerable Random Field (SRF). In contrast to traditional Markov random field (MRF) models in low-level vision, the random field potentials of a SRF are defined in terms of filter responses that are steered to the local image structure. This steering uses the structure tensor to obtain derivative responses that are either aligned with, or orthogonal to, the predominant local image structure. Analysis of the statistics of these steered filter responses in natural images leads to the model proposed here. Clique potentials are defined over steered filter responses using a Gaussian scale mixture model and are learned from training data. The SRF model connects random fields with anisotropic regularization and provides a statistical motivation for the latter. Steering the random field to the local image structure improves image denoising and inpainting performance compared with traditional pairwise MRFs.

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publisher site [BibTex]

publisher site [BibTex]


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Herstellung und Qualifizierung gesputterter Magnesiumdiboridschichten

Breyer, F.

Hochschule Aalen, Aalen, 2011 (mastersthesis)

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[BibTex]

[BibTex]


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Large hidden orbital moments in magnetite

Goering, E.

{Physica Status Solidi B}, 248(10):2345-2351, 2011 (article)

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DOI [BibTex]

DOI [BibTex]


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Cr magnetization reversal at the CrO2/RuO2 interface: Origin of the reduced GMR effect

Zafar, K., Audehm, P., Schütz, G., Goering, E., Pathak, M., Chetry, K. B., LeClair, P. R., Gupta, A.

{Physical Review B}, 84, 2011 (article)

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DOI [BibTex]

DOI [BibTex]


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Magnetocaloric effect, magnetic domain structure and spin-reorientation transitios in HoCo5 single crystals

Skokov, K. P., Pastushenkov, Y. G., Koshkid\textquotesingleko, Y. S., Schütz, G., Goll, D., Ivanova, T. I., Nikitin, S. A., Semenova, E. M., Petrenko, A. V.

{Journal of Magnetism and Magnetic Materials}, 323(5):447-450, 2011 (article)

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DOI [BibTex]

DOI [BibTex]


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Elucidating gating effects for hydrogen sorption in MFU-4-type triazolate-based metal-organic frameworks featuring different pore sizes

Denysenko, D., Grzywa, M., Tonigold, M., Streppel, B., Krkljus, I., Hirscher, M., Mugnaioli, E., Kolb, U., Hanss, J., Volkmer, D.

{Chemistry - A European Journal}, 17(6):1837-1848, 2011 (article)

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DOI [BibTex]

DOI [BibTex]


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BET specific surface area and pore structure of MOFs determined by hydrogen adsorption at 20 K

Streppel, B., Hirscher, M.

{Physical Chemistry Chemical Physics}, 13(8):3220-3222, 2011 (article)

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DOI [BibTex]

DOI [BibTex]