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2001


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Biomimetic gaze stabilization based on feedback-error learning with nonparametric regression networks

Shibata, T., Schaal, S.

Neural Networks, 14(2):201-216, 2001, clmc (article)

Abstract
Oculomotor control in a humanoid robot faces similar problems as biological oculomotor systems, i.e. the stabilization of gaze in face of unknown perturbations of the body, selective attention, stereo vision, and dealing with large information processing delays. Given the nonlinearities of the geometry of binocular vision as well as the possible nonlinearities of the oculomotor plant, it is desirable to accomplish accurate control of these behaviors through learning approaches. This paper develops a learning control system for the phylogenetically oldest behaviors of oculomotor control, the stabilization reflexes of gaze. In a step-wise procedure, we demonstrate how control theoretic reasonable choices of control components result in an oculomotor control system that resembles the known functional anatomy of the primate oculomotor system. The core of the learning system is derived from the biologically inspired principle of feedback-error learning combined with a state-of-the-art non-parametric statistical learning network. With this circuitry, we demonstrate that our humanoid robot is able to acquire high performance visual stabilization reflexes after about 40 s of learning despite significant nonlinearities and processing delays in the system.

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link (url) [BibTex]


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Development of PZT and PZN-PT based unimorph actuators for micromechanical flapping mechanisms

Sitti, M., Campolo, D., Yan, J., Fearing, R. S.

In Robotics and Automation, 2001. Proceedings 2001 ICRA. IEEE International Conference on, 4, pages: 3839-3846, 2001 (inproceedings)

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[BibTex]

[BibTex]


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Thorax Design and Wing Control for a Micromechanical Flying Insect

Yan, J, Ayadhanula, S, Sitti, M, Wood, RJ, Fearing, RS

In PROCEEDINGS OF THE ANNUAL ALLERTON CONFERENCE ON COMMUNICATION CONTROL AND COMPUTING, 39(2):952-961, 2001 (inproceedings)

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[BibTex]

[BibTex]


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Interpretation of ab initio total energy results in a chemical language: II. Stability of TiAl3 and ScAl3

Bester, G., Fähnle, M.

{Journal of Physics-Condensed Matter}, 13(50):11551-11565, 2001 (article)

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[BibTex]

[BibTex]


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Atomic defects in FeCo: Stabilization of the B2 structure by magnetism

Neumayer, M., Fähnle, M.

{Physical Review B}, 64(13), 2001 (article)

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[BibTex]

[BibTex]


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Hydrogen desorption property of mechanically prepared nanostructured graphite

Orimo, S., Matsushima, T., Fujii, H., Fukunaga, T., Majer, G.

{Journal of Applied Physics}, 90(3):1545-1549, 2001 (article)

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[BibTex]

[BibTex]


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Positron annihilation in stable and supercooled metallic melts

Seeger, A., Siegle, A., Stoll, H.

{Zeitschrift f\"ur Metallkunde}, 92(7):632-644, 2001 (article)

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[BibTex]

[BibTex]


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Structural vacancies in B2 CoAl and NiAl

Meyer, B., Bester, G., Fähnle, M.

{Scripta Materialia}, 44(10):2485-2488, 2001 (article)

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[BibTex]

[BibTex]


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Nonlinear magnetoelastic effects in ultrathin epitaxial FCC Co(001) films: an ab initio study

Komelj, M., Fähnle, M.

{Journal of Magnetism and Magnetic Materials}, 224(1):L1-L4, 2001 (article)

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[BibTex]

[BibTex]


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First proof of slow trapping of positronium in polymers by an Age-Momentum-Correlation (AMOC) experiment

Dauwe, C., Balcaen, N., van Waeyenberge, B., van Petegem, S., Stoll, H.

In Positron Annihilation. Proceedings of the 12th International Conference on Positron Annihilation, 363/365, pages: 254-256, Materials Science Forum, Trans Tech Publications Ltd., München, 2001 (inproceedings)

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[BibTex]

[BibTex]


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Positron-age-momentum correlation

Stoll, H., Bandzuch, P., Siegle, A.

In Positron Annihilation: Proceedings of the 12th International Conference on Positron Annihilation, 363-365, pages: 547-551, Materials Science Forum, Trans Tech Publications Ltd., München, 2001 (inproceedings)

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[BibTex]

[BibTex]


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X-ray magnetic circular dichroism - a universal tool for magnetic investigations

Goering, E., Will, J., Geissler, J., Justen, M., Weigand, F., Schütz, G.

{Journal of Alloys and Compounds}, 328, pages: 14-19, 2001 (article)

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DOI [BibTex]

DOI [BibTex]


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Nanocrystalline and nanostructured high-performance permanent magnets

Goll, D., Hadjipanayis, G. C., Kronmüller, H.

In Applications of Ferromagnetic and Optical Materials, Storage and Magnetoelectronics, 674, pages: U2.4.1-U2.4.12, Materials Research Society Symposium Proceedings, MRS, San Francisco, Calif., 2001 (inproceedings)

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[BibTex]

[BibTex]


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Ion beam analysis with monolayer depth resolution using the electrostatic spectrometer at the MPI Stuttgart

Plachke, D., Blohm, G., Fischer, T., Khellaf, A., Kruse, O., Stoll, H., Carstanjen, H. D.

In Proceedings of the 16th International Conference on Applications of Accelerators in Research and Industry, 576, pages: 458-462, American Institute of Physics Conference Proceedings, AIP, Denton, Texas, 2001 (inproceedings)

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[BibTex]

[BibTex]


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A full field transmission X-ray microscope as a tool for high-resolution magnetic imaging

Denbeaux, G., Fischer, P., Kusinski, G., Le Gros, M., Pearson, A., Attwood, D.

{IEEE Transactions on Magnetics}, 37, pages: 2764-2766, 2001 (article)

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[BibTex]

[BibTex]


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The six-jump diffusion cycles in B2-compounds

Drautz, R., Meyer, B., Fähnle, M.

{Defect and Diffusion Forum}, 194-199, pages: 417-422, 2001 (article)

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[BibTex]

[BibTex]


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From the electronic structure to the macroscopiy behavior: A multi-scale analysis of plasticity in intermetallic compounds

Fähnle, M., Kohlhammer, S., Bester, G.

In Influences of Interface and Dislocation Behavior on Microstructure Evolution, 652, pages: Y4.5.1.-Y4.5.12, Materials Research Society Symposium Proceedings, MRS, Boston, Mass., USA, 2001 (inproceedings)

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[BibTex]

[BibTex]


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Influence of the microstructure on the magnetic properties of giant-magnetostrictive TbDyFe films

Hirscher, M., Winzek, B., Fischer, S. F., Kronmüller, H.

In Smart Materials. Proceedings of the 1st Caesarium, pages: 23-37, Springer, Bonn, 2001 (inproceedings)

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[BibTex]

[BibTex]


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Atomic defects and electronic structure of B2FeAl, CoAl and NiAl

Fähnle, M., Meyer, B., Bester, G., Majer, J., Börnsen, N.

{Defect and Diffusion Forum}, 194-199, pages: 279-285, 2001 (article)

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[BibTex]

[BibTex]


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Fast learning of biomimetic oculomotor control with nonparametric regression networks (in Japanese)

Shibata, T., Schaal, S.

Journal of the Robotics Society of Japan, 19(4):468-479, 2001, clmc (article)

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[BibTex]

[BibTex]


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Bouncing a ball: Tuning into dynamic stability

Sternad, D., Duarte, M., Katsumata, H., Schaal, S.

Journal of Experimental Psychology: Human Perception and Performance, 27(5):1163-1184, 2001, clmc (article)

Abstract
Rhythmically bouncing a ball with a racket was investigated and modeled with a nonlinear map. Model analyses provided a variable defining a dynamically stable solution that obviates computationally expensive corrections. Three experiments evaluated whether dynamic stability is optimized and what perceptual support is necessary for stable behavior. Two hypotheses were tested: (a) Performance is stable if racket acceleration is negative at impact, and (b) variability is lowest at an impact acceleration between -4 and -1 m/s2. In Experiment 1 participants performed the task, eyes open or closed, bouncing a ball confined to a 1-dimensional trajectory. Experiment 2 eliminated constraints on racket and ball trajectory. Experiment 3 excluded visual or haptic information. Movements were performed with negative racket accelerations in the range of highest stability. Performance with eyes closed was more variable, leaving acceleration unaffected. With haptic information, performance was more stable than with visual information alone.

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[BibTex]

[BibTex]


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Overt visual attention for a humanoid robot

Vijayakumar, S., Conradt, J., Shibata, T., Schaal, S.

In IEEE International Conference on Intelligent Robots and Systems (IROS 2001), 2001, clmc (inproceedings)

Abstract
The goal of our research is to investigate the interplay between oculomotor control, visual processing, and limb control in humans and primates by exploring the computational issues of these processes with a biologically inspired artificial oculomotor system on an anthropomorphic robot. In this paper, we investigate the computational mechanisms for visual attention in such a system. Stimuli in the environment excite a dynamical neural network that implements a saliency map, i.e., a winner-take-all competition between stimuli while simultenously smoothing out noise and suppressing irrelevant inputs. In real-time, this system computes new targets for the shift of gaze, executed by the head-eye system of the robot. The redundant degrees-of- freedom of the head-eye system are resolved through a learned inverse kinematics with optimization criterion. We also address important issues how to ensure that the coordinate system of the saliency map remains correct after movement of the robot. The presented attention system is built on principled modules and generally applicable for any sensory modality.

am

link (url) [BibTex]

link (url) [BibTex]


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PZT actuated four-bar mechanism with two flexible links for micromechanical flying insect thorax

Sitti, M.

In Robotics and Automation, 2001. Proceedings 2001 ICRA. IEEE International Conference on, 4, pages: 3893-3900, 2001 (inproceedings)

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[BibTex]

[BibTex]


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Wing transmission for a micromechanical flying insect

Yan, J., Avadhanula, S., Birch, J., Dickinson, M., Sitti, M., Su, T., Fearing, R.

Journal of Micromechatronics, 1(3):221-237, Brill, 2001 (article)

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[BibTex]

[BibTex]


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Spontaneous L12 order at Ni90Al10(110) surfaces: An X-ray and first-principles-calculation study

Drautz, R., Reichert, H., Fähnle, M., Dosch, H., Sanchez, J. M.

{Physical Review Letters}, 87(23), 2001 (article)

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[BibTex]

[BibTex]


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Magnetic viscosity and demagnetization behaviour in isotropic nanocrystalline Pr12Fe82B6 ribbons

Zhang, H. W., Zhang, S. Y., Shen, B. G., Goll, D., Kronmüller, H.

{Chinese Physics}, 10(12):1169-1171, 2001 (article)

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[BibTex]

[BibTex]


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Materials analysis with monolayer depth resolution using MeV ion beams

Carstanjen, H. D.

In 117, Las Vegas, USA, 2001 (inproceedings)

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[BibTex]

[BibTex]


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Strain relaxation and internal friction in the range of the glass transition

Ege, M., Ulfert, W., Kronmüller, H.

{Zeitschrift f\"ur Metallkunde}, 92(7):690-694, 2001 (article)

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[BibTex]

[BibTex]


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Hardness-depth profiling on nanometer scale

Kunert, M., Baretzky, B., Baker, S. P., Mittemeijer, E. J.

{Metallurgical and Materials Transactions A-Physical Metallurgy and Materials Science}, 32(5):1201-1209, 2001 (article)

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[BibTex]

[BibTex]


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Compound formation and abrasion resistance of ion-implanted Ti6Al4V

Schmidt, H., Schminke, A., Schmiedgen, M., Baretzky, B.

{Acta Materialia}, 49(3):487-495, 2001 (article)

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[BibTex]

[BibTex]


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Influence of vortex-vortex interaction on critical currents across low-angle grain boundaries in YBa2Cu3O7-δthin films

Albrecht, J., Leonhardt, S., Kronmüller, H.

{Physical Review B}, 63, 2001 (article)

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[BibTex]

[BibTex]


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Structure of superconducting [BaCuOx]2/[CaCuO2]n superlattices on SrTiO3(001) investigated by x-ray scattering

Aruta, C., Zegenhagen, J., Cowie, B., Balestrino, G., Pasquini, G., Medaglia, P. G., Ricci, F., Luebbert, D., Baumbach, T., Riedo, E., Ortega, L., Kremer, R., Albrecht, J.

{Physica Status Solidi (A)}, 183, pages: 353-364, 2001 (article)

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[BibTex]

[BibTex]


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Flux-line pinning in low-angle grain boundaries.

Albrecht, J., Leonhardt, S., Kronmüller, H.

In Proceedings 10th International Workshop on Critical Currents (IWCC 2001), pages: 41-43, Göttingen, Germany, 2001 (inproceedings)

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[BibTex]

[BibTex]


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Transmission X-ray microscopy using X-MCD

Eimüller, T., Fischer, P., Köhler, M., Scholz, M., Guttmann, P., Denbeaux, G., Glück, S., Bayreuther, G., Schmahl, G., Attwood, D., Schütz, G.

{Applied Physics A}, 73, pages: 697-701, 2001 (article)

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[BibTex]

[BibTex]


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Soft X-ray microscopy to 25 nm with applications to biology and magnetic materials

Denbeaux, G., Anderson, E., Chao, W., Eimüller, T., Johnson, L., Köhler, M., Larabell, C., Legros, M., Fischer, P., Pearson, A., Schütz, G., Yager, D., Attwood, D.

{Nuclear Instruments and Methods in Physics Research A}, 467-468, pages: 841-844, 2001 (article)

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[BibTex]

[BibTex]


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Study of in-plane magnetic domains with magnetic transmission X-ray microscopy

Fischer, P., Eimüller, T., Schütz, G., Köhler, M., Bayreuther, G., Denbeaux, G., Attwood, D.

{Journal of Applied Physics}, 89, pages: 7159-7161, 2001 (article)

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[BibTex]

[BibTex]


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Influence of vortex-vortex interaction on critical currents across low-angle grain boundaries in YBa2Cu3O7-δthin films

Albrecht, J., Leonhardt, S., Kronmüller, H.

{Physical Review B}, 63, 2001 (article)

mms

[BibTex]

[BibTex]


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Non-symmetric influences in the total electron yield X-ray magnetic circular dichroism signal in applied magnetic fields

Goering, E., Gold, S., Bayer, A., Schütz, G.

{Journal of Synchrotron Radiation}, 8, pages: 434-436, 2001 (article)

mms

DOI [BibTex]

DOI [BibTex]


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Effect of Ga substitution on the magnetocrystalline anisotropy of arc-melted Sm2Co17-xGax (x\textequals5,6) compounds

Liang, B., Kleinschroth, I., Kronmüller, H.

{Journal of Applied Physics}, 89(1):488-491, 2001 (article)

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[BibTex]

[BibTex]


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Influence of grain boundary phase transitions on the properties of Cu-Bi polycrystals

Straumal, B. B., Sluchanko, N.E., Gust, W.

In Defects and Diffusion in Metals III: An Annual Retrospective III, 188-1, pages: 185-194, Defect and Diffusion Forum, 2001 (incollection)

mms

[BibTex]

[BibTex]


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Learning inverse kinematics

D’Souza, A., Vijayakumar, S., Schaal, S.

In IEEE International Conference on Intelligent Robots and Systems (IROS 2001), Piscataway, NJ: IEEE, Maui, Hawaii, Oct.29-Nov.3, 2001, clmc (inproceedings)

Abstract
Real-time control of the endeffector of a humanoid robot in external coordinates requires computationally efficient solutions of the inverse kinematics problem. In this context, this paper investigates learning of inverse kinematics for resolved motion rate control (RMRC) employing an optimization criterion to resolve kinematic redundancies. Our learning approach is based on the key observations that learning an inverse of a non uniquely invertible function can be accomplished by augmenting the input representation to the inverse model and by using a spatially localized learning approach. We apply this strategy to inverse kinematics learning and demonstrate how a recently developed statistical learning algorithm, Locally Weighted Projection Regression, allows efficient learning of inverse kinematic mappings in an incremental fashion even when input spaces become rather high dimensional. The resulting performance of the inverse kinematics is comparable to Liegeois ([1]) analytical pseudo inverse with optimization. Our results are illustrated with a 30 degree-of-freedom humanoid robot.

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link (url) [BibTex]

link (url) [BibTex]


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Biomimetic smooth pursuit based on fast learning of the target dynamics

Shibata, T., Schaal, S.

In IEEE International Conference on Intelligent Robots and Systems (IROS 2001), 2001, clmc (inproceedings)

Abstract
Following a moving target with a narrow-view foveal vision system is one of the essential oculomotor behaviors of humans and humanoids. This oculomotor behavior, called ``Smooth Pursuit'', requires accurate tracking control which cannot be achieved by a simple visual negative feedback controller due to the significant delays in visual information processing. In this paper, we present a biologically inspired and control theoretically sound smooth pursuit controller consisting of two cascaded subsystems. One is an inverse model controller for the oculomotor system, and the other is a learning controller for the dynamics of the visual target. The latter controller learns how to predict the target's motion in head coordinates such that tracking performance can be improved. We investigate our smooth pursuit system in simulations and experiments on a humanoid robot. By using a fast on-line statistical learning network, our humanoid oculomotor system is able to acquire high performance smooth pursuit after about 5 seconds of learning despite significant processing delays in the syste

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link (url) [BibTex]

link (url) [BibTex]


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Biomimetic oculomotor control

Shibata, T., Vijayakumar, S., Conradt, J., Schaal, S.

Adaptive Behavior, 9(3/4):189-207, 2001, clmc (article)

Abstract
Oculomotor control in a humanoid robot faces similar problems as biological oculomotor systems, i.e., capturing targets accurately on a very narrow fovea, dealing with large delays in the control system, the stabilization of gaze in face of unknown perturbations of the body, selective attention, and the complexity of stereo vision. In this paper, we suggest control circuits to realize three of the most basic oculomotor behaviors and their integration - the vestibulo-ocular and optokinetic reflex (VOR-OKR) for gaze stabilization, smooth pursuit for tracking moving objects, and saccades for overt visual attention. Each of these behaviors and the mechanism for their integration was derived with inspiration from computational theories as well as behavioral and physiological data in neuroscience. Our implementations on a humanoid robot demonstrate good performance of the oculomotor behaviors, which proves to be a viable strategy to explore novel control mechanisms for humanoid robotics. Conversely, insights gained from our models have been able to directly influence views and provide new directions for computational neuroscience research.

am

link (url) [BibTex]

link (url) [BibTex]


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Development of a scaled teleoperation system for nano scale interaction and manipulation

Sitti, M., Aruk, B., Shintani, H., Hashimoto, H.

In Robotics and Automation, 2001. Proceedings 2001 ICRA. IEEE International Conference on, 1, pages: 860-867, 2001 (inproceedings)

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[BibTex]

[BibTex]


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Irradiation-induced electron tunnelling and small-polaron hopping in single-crystalline YIG

Walz, F., Brabers, J. H. V. J., Torres, L., Kronmüller, H.

{Physica Status Solidi B-Basic Research}, 228(3):717-730, 2001 (article)

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[BibTex]

[BibTex]


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Kernspinresonanzuntersuchungen zur Diffusion von Wasserstoff in den Di- und Trihydriden der Übergangsmetalle

Gottwald, J.

Universität Stuttgart, Stuttgart, 2001 (phdthesis)

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[BibTex]


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Hexagonally ordered 100 nm period nickel nanowire arrays

Nielsch, K., Wehrspohn, R. B., Barthel, J., Kirschner, J., Gösele, U., Fischer, S. F., Kronmüller, H.

{Applied Physics Letters}, 79(9):1360-1362, 2001 (article)

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[BibTex]

[BibTex]


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Magnetization processes in isotropic and textured Nd2Fe14B- films

Melsheimer, A., Kronmüller, H.

{Physica B}, 299(3-4):251-259, 2001 (article)

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[BibTex]

[BibTex]


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Critical magnetic properties of disordered Cr-rich FeCr alloys

Fischer, S. F., Kaul, S. N., Kronmüller, H.

{Journal of Magnetism and Magnetic Materials}, 226(Sp. Iss. SI):540-541, 2001 (article)

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[BibTex]

[BibTex]