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2005


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On the imaging of the flux-line lattice of a type-II superconductor by soft X-ray absorption spectroscopy

Fähnle, M., Albrecht, J., Eimüller, T., Fisher, P., Goering, E., Steiauf, D., Schütz, G.

{Journal of Synchrotron Radiation}, 12, pages: 251-253, 2005 (article)

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[BibTex]

2005


[BibTex]


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Grain-boundary melting phase transition in the Cu-Bi system

Divinski, S., Lohmann, M., Herzig, C., Straumal, B., Baretzky, B., Gust, W.

{Physical Review B}, 71, 2005 (article)

mms

[BibTex]

[BibTex]


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A fast ab initio approach to the simulation of spin dynamics

Fähnle, M., Drautz, R., Singer, R., Steiauf, D., Berkov, D. V.

{Computational Materials Science}, 32, pages: 118-122, 2005 (article)

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[BibTex]

[BibTex]


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Hydrogen adsorption in different carbon nanostructures

Panella, B., Hirscher, M., Roth, S.

{Carbon}, 43, pages: 2209-2214, 2005 (article)

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[BibTex]

[BibTex]


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A dynamical systems approach to learning: a frequency-adaptive hopper robot

Buchli, J., Righetti, L., Ijspeert, A.

In Proceedings of the VIIIth European Conference on Artificial Life ECAL 2005, pages: 210-220, Springer Verlag, 2005 (inproceedings)

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[BibTex]

[BibTex]


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From Dynamic Hebbian Learning for Oscillators to Adaptive Central Pattern Generators

Righetti, L., Buchli, J., Ijspeert, A.

In Proceedings of 3rd International Symposium on Adaptive Motion in Animals and Machines – AMAM 2005, Verlag ISLE, Ilmenau, 2005 (inproceedings)

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[BibTex]

[BibTex]


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A new methodology for robot control design

Peters, J., Mistry, M., Udwadia, F. E., Schaal, S.

In The 5th ASME International Conference on Multibody Systems, Nonlinear Dynamics, and Control (MSNDC 2005), Long Beach, CA, Sept. 24-28, 2005, clmc (inproceedings)

Abstract
Gauss principle of least constraint and its generalizations have provided a useful insights for the development of tracking controllers for mechanical systems (Udwadia,2003). Using this concept, we present a novel methodology for the design of a specific class of robot controllers. With our new framework, we demonstrate that well-known and also several novel nonlinear robot control laws can be derived from this generic framework, and show experimental verifications on a Sarcos Master Arm robot for some of these controllers. We believe that the suggested approach unifies and simplifies the design of optimal nonlinear control laws for robots obeying rigid body dynamics equations, both with or without external constraints, holonomic or nonholonomic constraints, with over-actuation or underactuation, as well as open-chain and closed-chain kinematics.

am

link (url) [BibTex]

link (url) [BibTex]


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Fusion of biomedical microcapsule endoscope and microsystem technology

Kim, Tae Song, Kim, Byungkyu, Cho, Dongil Dan, Song, Si Young, Dario, P, Sitti, M

In Solid-State Sensors, Actuators and Microsystems, 2005. Digest of Technical Papers. TRANSDUCERS’05. The 13th International Conference on, 1, pages: 9-14, 2005 (inproceedings)

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[BibTex]

[BibTex]


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Atomic force microscope based two-dimensional assembly of micro/nanoparticles

Tafazzoli, A., Pawashe, C., Sitti, M.

In Assembly and Task Planning: From Nano to Macro Assembly and Manufacturing, 2005.(ISATP 2005). The 6th IEEE International Symposium on, pages: 230-235, 2005 (inproceedings)

pi

[BibTex]

[BibTex]


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Synthesis of the nanocrystalline MgS and its interaction with hydrogen

Goo, N. H., Hirscher, M.

{Journal of Alloys and Compounds}, 404, pages: 503-506, 2005 (article)

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[BibTex]

[BibTex]


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Time-scales of electronic processes in Fe3O4 - An attempt to resolve a recently accentuated controversy

Fähnle, M., Kronmüller, H., Walz, F.

{Physica B}, 369, pages: 177-180, 2005 (article)

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[BibTex]

[BibTex]


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Bending of magnetic avalanches in MgB2 thin films

Albrecht, J., Matveev, A., Djupmyr, M., Schütz, G., Stuhlhofer, B., Habermeier, H.

{Applied Physics Letters}, 87, 2005 (article)

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[BibTex]

[BibTex]


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Magnetic pinning of flux lines in heterostructures of cuprates and manganites

Albrecht, J., Soltan, S., Habermeier, H.-U.

{Physical Review B}, 72, 2005 (article)

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[BibTex]

[BibTex]


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On the pair-potential modelling of alloy surfaces

Drautz, R., Fähnle, M.

{Surface Science}, 585, pages: 108-112, 2005 (article)

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[BibTex]

[BibTex]


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Crystal field parameters at the (0001) surface of rare-earth metals: an ab initio study

Welsch, F., Fähnle, M., Jensen, P. J.

{Journal of Physics: Condensed Matter}, 17, pages: 2061-2072, 2005 (article)

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[BibTex]

[BibTex]


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Spatially resolved ferromagnetic resonance: Imaging of ferromagnetic eigenmodes

Puzic, A., Van Waeyenberge, B., Chou, K. W., Fischer, P., Stoll, H., Schütz, G., Tyliszczak, T., Rott, K., Brückl, H., Reiss, G., Neudecker, I., Haug, T., Buess, M., Back, C. H.

{Journal of Applied Physics}, 97, 2005 (article)

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DOI [BibTex]

DOI [BibTex]


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Defects distribution of Pr2Fe14B hard magnetic magnet from amorphous to nanostructures characterized by positron annihilation spectroscopy

Wu, Y. C., Sprengel, W., Reimann, K., Reichle, K. J., Goll, D., Würschum, R., Schaefer, H. E.

In PRICM 5. Proceedings of the Fifth Pacific RIM International Conference on Advanced Materials and Processing, 475-479, pages: 2123-2126, Materials Science Forum, Trans Tech, Beijing, China, 2005 (inproceedings)

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[BibTex]

[BibTex]


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Implementing sub-ns time resolution into magnetic X-ray microscopies

Puzic, A., Stoll, H., Fischer, P., Van Waeyenberge, B., Raabe, J., Denbeaux, G., Haug, T., Weiss, D., Schütz, G.

In T115, pages: 1029-1031, Malmö/Lund, Sweden, 2005 (inproceedings)

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[BibTex]

[BibTex]


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Proton magnetic resonance spectra of YH3 and LuH3

Brady, S. K., Conradi, M. S., Majer, G., Barnes, R. G.

{Physical Review B}, 72, 2005 (article)

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[BibTex]

[BibTex]


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Hydrogen storage in spherical nanoporous carbons

Terres, E., Panella, B., Hayashi, T., Kim, Y. A., Endo, M., Dominguez, J. M., Hirscher, M., Terrones, H., Terrones, H.

{Chemical Physics Letters}, 403(4-6):363-366, 2005 (article)

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[BibTex]

[BibTex]


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Faceting and migration of twin grain boundaries in zinc

Straumal, B. B., Rabkin, E., Sursaeva, V. G., Goruakova, A. S.

{Zeitschrift f\"ur Metallkunde}, 96(2):161-166, 2005 (article)

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[BibTex]

[BibTex]


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Arm movement experiments with joint space force fields using an exoskeleton robot

Mistry, M., Mohajerian, P., Schaal, S.

In IEEE Ninth International Conference on Rehabilitation Robotics, pages: 408-413, Chicago, Illinois, June 28-July 1, 2005, clmc (inproceedings)

Abstract
A new experimental platform permits us to study a novel variety of issues of human motor control, particularly full 3-D movements involving the major seven degrees-of-freedom (DOF) of the human arm. We incorporate a seven DOF robot exoskeleton, and can minimize weight and inertia through gravity, Coriolis, and inertia compensation, such that subjects' arm movements are largely unaffected by the manipulandum. Torque perturbations can be individually applied to any or all seven joints of the human arm, thus creating novel dynamic environments, or force fields, for subjects to respond and adapt to. Our first study investigates a joint space force field where the shoulder velocity drives a disturbing force in the elbow joint. Results demonstrate that subjects learn to compensate for the force field within about 100 trials, and from the strong presence of aftereffects when removing the field in some randomized catch trials, that an inverse dynamics, or internal model, of the force field is formed by the nervous system. Interestingly, while post-learning hand trajectories return to baseline, joint space trajectories remained changed in response to the field, indicating that besides learning a model of the force field, the nervous system also chose to exploit the space to minimize the effects of the force field on the realization of the endpoint trajectory plan. Further applications for our apparatus include studies in motor system redundancy resolution and inverse kinematics, as well as rehabilitation.

am

link (url) [BibTex]

link (url) [BibTex]


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A unifying framework for the control of robotics systems

Peters, J., Mistry, M., Udwadia, F. E., Cory, R., Nakanishi, J., Schaal, S.

In IEEE International Conference on Intelligent Robots and Systems (IROS 2005), pages: 1824-1831, Edmonton, Alberta, Canada, Aug. 2-6, 2005, clmc (inproceedings)

Abstract
Recently, [1] suggested to derive tracking controllers for mechanical systems using a generalization of GaussÕ principle of least constraint. This method al-lows us to reformulate control problems as a special class of optimal control. We take this line of reasoning one step further and demonstrate that well-known and also several novel nonlinear robot control laws can be derived from this generic methodology. We show experimental verifications on a Sar-cos Master Arm robot for some of the the derived controllers.We believe that the suggested approach offers a promising unification and simplification of nonlinear control law design for robots obeying rigid body dynamics equa-tions, both with or without external constraints, with over-actuation or under-actuation, as well as open-chain and closed-chain kinematics.

am

link (url) [BibTex]

link (url) [BibTex]


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A new endoscopic microcapsule robot using beetle inspired microfibrillar adhesives

Cheung, E., Karagozler, M. E., Park, S., Kim, B., Sitti, M.

In Advanced Intelligent Mechatronics. Proceedings, 2005 IEEE/ASME International Conference on, pages: 551-557, 2005 (inproceedings)

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Project Page [BibTex]

Project Page [BibTex]


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Learning to Feel the Physics of a Body

Der, R., Hesse, F., Martius, G.

In Computational Intelligence for Modelling, Control and Automation, CIMCA 2005 , 2, pages: 252-257, Washington, DC, USA, 2005 (inproceedings)

Abstract
Despite the tremendous progress in robotic hardware and in both sensorial and computing efficiencies the performance of contemporary autonomous robots is still far below that of simple animals. This has triggered an intensive search for alternative approaches to the control of robots. The present paper exemplifies a general approach to the self-organization of behavior which has been developed and tested in various examples in recent years. We apply this approach to an underactuated snake like artifact with a complex physical behavior which is not known to the controller. Due to the weak forces available, the controller so to say has to develop a kind of feeling for the body which is seen to emerge from our approach in a natural way with meandering and rotational collective modes being observed in computer simulation experiments.

al

[BibTex]

[BibTex]


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Nanostructures with high surface area for hydrogen storage

Hirscher, M., Panella, B.

{Journal of Alloys and Compounds}, 404, pages: 399-401, 2005 (article)

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[BibTex]

[BibTex]


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Timescale settling and nature of electron transport in magnetite - General considerations in view of new magnetic after-effect results on dilutely Ti4+-doped Fe3O4

Walz, F., Brabers, V. A. M., Brabers, J. H. V. J., Kronmüller, H.

{Journal of Physics: Condensed Matter}, 17(42):6763-6781, 2005 (article)

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[BibTex]

[BibTex]


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Topological k-space refinement of the configurational energy of alloys

Shchyglo, O., Bugaev, V. N., Drautz, R., Udyansky, A., Reichert, H., Dosch, H.

{Physical Review B}, 72(14), 2005 (article)

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[BibTex]

[BibTex]


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Large surface area nanostructures for hydrogen storage

Hirscher, M., Panella, B.

{Annales de Chimie}, 30(5):519-529, 2005 (article)

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[BibTex]

[BibTex]


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Electronic and magnetic properties of ligand-free FePt nanoparticles

Boyen, H., Fauth, K., Stahl, B., Ziemann, P., Kästle, G., Weigl, F., Banhart, F., He\ssler, M., Schütz, G., Gajbhiye, N. S., Ellrich, J., Hahn, H., Büttner, M., Garnier, M. G., Oelhafen, P.

{Advanced Materials}, 17(5):574-578, 2005 (article)

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DOI [BibTex]

DOI [BibTex]


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Identification of extrinsic Mn contributions in Ga1-xMnxAs by field-dependent magnetic circular X-ray dichroism

Rader, O., Fauth, K., Gould, C., Rüster, C., Schott, G. M., Schmidt, G., Brunner, K., Molenkamp, L. W., Schütz, G., Kronast, F., Dürr, H. A., Eberhardt, W., Gudat, W.

{Journal of Electron Spectroscopy and Related Phenomena}, 144(Sp. issue):789-792, 2005 (article)

mms

DOI [BibTex]

DOI [BibTex]


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Fundamentals of interface phenomena in advanced bulk nanoscale materials

Baretzky, B., Baró, M. D., Grabovetskaya, G. P., Gubicza, J., Ivanov, M. B., Kolobov, Y. R., Langdon, T. G., Lendvai, J., Lipnitskii, A. G., Mazilkin, A. A., Nazarov, A. A., Nogués, J., Ovidko, I. A., Protasova, S. G., Raab, G. I., Révész, Á., Skiba, N. V., Sort, J., Starink, M. J., Straumal, B. B., Suriñach, S., Ungár, T., Zhilyaev, A. P.

{Reviews on Advanced Materials Science}, 9(1):45-108, 2005 (article)

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[BibTex]

[BibTex]


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Formation of nanostructure during high-pressure torsion of Al-Zn, Al-Mg and Al-Zn-Mg alloys

Mazilkin, A. A., Kogtenkova, O. A., Straumal, B. B., Ruslan, Z, Valiev, Z., Baretzky, B.

{Defect and Diffusion Forum}, 237-240, pages: 739-744, 2005 (article)

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[BibTex]

[BibTex]


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Micromagnetic simulation as a bridge between magnetic-force and magnetic-transmission X-ray microscopy

Bolte, M., Eiselt, R., Eimüller, T.

{Journal of Magnetism and Magnetic Materials}, 290, pages: 723-726, 2005 (article)

mms

[BibTex]

[BibTex]


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Grain-boundary melting phase transition in the Cu-Bi system

Divinski, S., Lohmann, M., Herzig, C., Straumal, B., Baretzky, B., Gust, W.

{Physical Review B}, 71, 2005 (article)

mms

[BibTex]

[BibTex]

1994


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Robot juggling: An implementation of memory-based learning

Schaal, S., Atkeson, C. G.

Control Systems Magazine, 14(1):57-71, 1994, clmc (article)

Abstract
This paper explores issues involved in implementing robot learning for a challenging dynamic task, using a case study from robot juggling. We use a memory-based local modeling approach (locally weighted regression) to represent a learned model of the task to be performed. Statistical tests are given to examine the uncertainty of a model, to optimize its prediction quality, and to deal with noisy and corrupted data. We develop an exploration algorithm that explicitly deals with prediction accuracy requirements during exploration. Using all these ingredients in combination with methods from optimal control, our robot achieves fast real-time learning of the task within 40 to 100 trials.

am

link (url) [BibTex]

1994


link (url) [BibTex]


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Robot learning by nonparametric regression

Schaal, S., Atkeson, C. G.

In Proceedings of the International Conference on Intelligent Robots and Systems (IROS’94), pages: 478-485, Munich Germany, 1994, clmc (inproceedings)

Abstract
We present an approach to robot learning grounded on a nonparametric regression technique, locally weighted regression. The model of the task to be performed is represented by infinitely many local linear models, i.e., the (hyper-) tangent planes at every query point. Such a model, however, is only generated when a query is performed and is not retained. This is in contrast to other methods using a finite set of linear models to accomplish a piecewise linear model. Architectural parameters of our approach, such as distance metrics, are also a function of the current query point instead of being global. Statistical tests are presented for when a local model is good enough such that it can be reliably used to build a local controller. These statistical measures also direct the exploration of the robot. We explicitly deal with the case where prediction accuracy requirements exist during exploration: By gradually shifting a center of exploration and controlling the speed of the shift with local prediction accuracy, a goal-directed exploration of state space takes place along the fringes of the current data support until the task goal is achieved. We illustrate this approach by describing how it has been used to enable a robot to learn a challenging juggling task: Within 40 to 100 trials the robot accomplished the task goal starting out with no initial experiences.

am

[BibTex]

[BibTex]


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Assessing the quality of learned local models

Schaal, S., Atkeson, C. G.

In Advances in Neural Information Processing Systems 6, pages: 160-167, (Editors: Cowan, J.;Tesauro, G.;Alspector, J.), Morgan Kaufmann, San Mateo, CA, 1994, clmc (inproceedings)

Abstract
An approach is presented to learning high dimensional functions in the case where the learning algorithm can affect the generation of new data. A local modeling algorithm, locally weighted regression, is used to represent the learned function. Architectural parameters of the approach, such as distance metrics, are also localized and become a function of the query point instead of being global. Statistical tests are given for when a local model is good enough and sampling should be moved to a new area. Our methods explicitly deal with the case where prediction accuracy requirements exist during exploration: By gradually shifting a "center of exploration" and controlling the speed of the shift with local prediction accuracy, a goal-directed exploration of state space takes place along the fringes of the current data support until the task goal is achieved. We illustrate this approach with simulation results and results from a real robot learning a complex juggling task.

am

link (url) [BibTex]

link (url) [BibTex]


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Memory-based robot learning

Schaal, S., Atkeson, C. G.

In IEEE International Conference on Robotics and Automation, 3, pages: 2928-2933, San Diego, CA, 1994, clmc (inproceedings)

Abstract
We present a memory-based local modeling approach to robot learning using a nonparametric regression technique, locally weighted regression. The model of the task to be performed is represented by infinitely many local linear models, the (hyper-) tangent planes at every query point. This is in contrast to other methods using a finite set of linear models to accomplish a piece-wise linear model. Architectural parameters of our approach, such as distance metrics, are a function of the current query point instead of being global. Statistical tests are presented for when a local model is good enough such that it can be reliably used to build a local controller. These statistical measures also direct the exploration of the robot. We explicitly deal with the case where prediction accuracy requirements exist during exploration: By gradually shifting a center of exploration and controlling the speed of the shift with local prediction accuracy, a goal-directed exploration of state space takes place along the fringes of the current data support until the task goal is achieved. We illustrate this approach by describing how it has been used to enable a robot to learn a challenging juggling task: within 40 to 100 trials the robot accomplished the task goal starting out with no initial experiences.

am

[BibTex]

[BibTex]


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Nonparametric regression for learning

Schaal, S.

In Conference on Adaptive Behavior and Learning, Center of Interdisciplinary Research (ZIF) Bielefeld Germany, also technical report TR-H-098 of the ATR Human Information Processing Research Laboratories, 1994, clmc (inproceedings)

Abstract
In recent years, learning theory has been increasingly influenced by the fact that many learning algorithms have at least in part a comprehensive interpretation in terms of well established statistical theories. Furthermore, with little modification, several statistical methods can be directly cast into learning algorithms. One family of such methods stems from nonparametric regression. This paper compares nonparametric learning with the more widely used parametric counterparts and investigates how these two families differ in their properties and their applicability. 

am

link (url) [BibTex]

link (url) [BibTex]