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2002


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Forward models in visuomotor control

Mehta, B., Schaal, S.

J Neurophysiol, 88(2):942-53, August 2002, clmc (article)

Abstract
In recent years, an increasing number of research projects investigated whether the central nervous system employs internal models in motor control. While inverse models in the control loop can be identified more readily in both motor behavior and the firing of single neurons, providing direct evidence for the existence of forward models is more complicated. In this paper, we will discuss such an identification of forward models in the context of the visuomotor control of an unstable dynamic system, the balancing of a pole on a finger. Pole balancing imposes stringent constraints on the biological controller, as it needs to cope with the large delays of visual information processing while keeping the pole at an unstable equilibrium. We hypothesize various model-based and non-model-based control schemes of how visuomotor control can be accomplished in this task, including Smith Predictors, predictors with Kalman filters, tapped-delay line control, and delay-uncompensated control. Behavioral experiments with human participants allow exclusion of most of the hypothesized control schemes. In the end, our data support the existence of a forward model in the sensory preprocessing loop of control. As an important part of our research, we will provide a discussion of when and how forward models can be identified and also the possible pitfalls in the search for forward models in control.

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link (url) [BibTex]

2002


link (url) [BibTex]


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Kinetics of submonolayer epitaxial growth

Amar, J. G., Family, F., Popescu, M. N.

Computer Physics Communications, 146(1):1-8, 2002 (article)

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[BibTex]

[BibTex]


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Fluids of platelike particles near a hard wall

Harnau, L., Dietrich, S.

Physical Review E, 65(2), 2002 (article)

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[BibTex]

[BibTex]


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Fundamental measure theory for hard-sphere mixtures revisited: the White Bear version

Roth, R., Evans, R., Lang, A., Kahl, G.

Journal of Physics-Condensed Matter, 14(46):12063-12078, 2002 (article)

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[BibTex]

[BibTex]


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Microscopic theory of solvent-mediated long-range forces: Influence of wetting

Archer, A. J., Evans, R., Roth, R.

Europhysics Letters, 59(4):526-532, 2002 (article)

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[BibTex]

[BibTex]


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Colloid aggregation induced by oppositely charged polyions

Harnau, L., Hansen, J. P.

Journal of Chemical Physics, 116(20):9051-9057, 2002 (article)

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[BibTex]

[BibTex]


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Morphology of Condensed Matter - Physics and Geometry of Spatially Complex Systems
600, pages: 439 p., Lecture Notes in Physics, Springer, Berlin [et al.], 2002 (book)

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[BibTex]

[BibTex]


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Self-consistent rate equation theory of cluster size distribution in aggregation phenomena

Family, F., Popescu, M. N., Amar, J. G.

Physica A, 306(1-4):129-139, 2002 (article)

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[BibTex]

[BibTex]


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Wetting and capillary nematization of binary hard-platelet and hard-rod fluids

Harnau, L., Dietrich, S.

Physical Review E, 66(5), 2002 (article)

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[BibTex]


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Simulating stochastic geometries: morphology of overlapping grains

Brodatzki, U., Mecke, K.

Computer Physics Communications, 147(1-2):218-221, 2002 (article)

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[BibTex]

[BibTex]


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Nucleons as relativistic three-quark states

Oettel, M.

In Proceedings of the Workshop on Physics at the Japan Hadron Facility (JHF), pages: 203-211, World Scientific, Adelaide, Australia, 2002 (inproceedings)

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[BibTex]

[BibTex]


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Mark Correlations: Relating Physical Properties to Spatial Distributions

Beisbart, C., Kerscher, M., Mecke, K.

In Morphology of Condensed Matter, 600, pages: 358-390, Lecture Notes in Physics, Springer, Berlin [et al.], 2002 (incollection)

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[BibTex]

[BibTex]


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Thermodynamics and phase behavior of the lamellar Zwanzig model

Harnau, L., Rowan, D., Hansen, J. P.

Journal of Chemical Physics, 117(24):11359-11365, 2002 (article)

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[BibTex]

[BibTex]


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Renormierung der Minkowski-Funktionale im morphologischen Modell

Breidenbach, B.

Universität Stuttgart, Stuttgart, 2002 (mastersthesis)

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[BibTex]

[BibTex]


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Capture-Numbers and Island Size-Distributions in Irreversible Homoepitaxial Growth: A Rate-Equation Approach

Popescu, M. N., Family, F., Amar, J. G.

In Atomistic Aspects of Epitaxial Growth, pages: 99-110, NATO Science Series: Series 2, Mathematics, Physics, and Chemistry, Kluwer Academic Publishers, Dassia [Korfu, Greece], 2002 (inproceedings)

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[BibTex]

[BibTex]


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Vector- und Tensor-Valued Descriptors for Spatial Patterns

Beisbart, C., Dahlke, R., Mecke, K., Wagner, H.

In Morphology of Condensed Matter, 600, pages: 238-260, Lecture Notes in Physics, Springer, Berlin [et al.], 2002 (incollection)

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[BibTex]


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Cluster-Computing and Computational Science mit der Wuppertaler Alpha-Linux-Cluster-Engine ALiCE

Arndt, H., Arnold, G., Eicker, N., Fliegner, D., Frommer, A., Hentschke, R., Isalia, F., Kabrede, H., Krech, M., Lippert, T. H., Neff, H., Orth, B., Schilling, K., Schroers, W., Tichy, W.

Praxis der Informationsverarbeitung und Kommunikation, 25(1):21-38, 2002 (article)

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[BibTex]


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Crossover between strong- and weak-field critical adsorption and the determination of the universal exponent η⊥

Nickel, B., Schlesener, F., Donner, W., Detlefs, C., Dosch, H.

Journal of Chemical Physics, 117(2):902-908, 2002 (article)

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[BibTex]

[BibTex]


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A novel technique for measuring diffusivities of short-lived radioisotopes in solids

Voss, T., Strohm, A., Matics, S., Scharwaechter, P., Frank, W.

Zeitschrift f\"ur Metallkunde, 93(10):1077-1082, 2002 (article)

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[BibTex]

[BibTex]


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The shape of parallel surface: porous media, fluctuating interfaces and complex fluids

Mecke, K. R.

Physica A-Statistical Mechanics and its Applications, 314(1-4):655-662, 2002 (article)

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[BibTex]

[BibTex]


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Diffusion in amorphen Vorstufen von Si-(B-)C-N-Keramiken und verwandten Materialien

Voss, L. T.

Universität Stuttgart, Stuttgart, 2002 (phdthesis)

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[BibTex]

[BibTex]


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Strong dependence of percolation thresholds on polydispersity

Mecke, K. R., Seyfried, A.

Europhysics Letters, 58(1):28-34, 2002 (article)

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[BibTex]

[BibTex]


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Characterizing the Morphology of Disordered Materials

Arns, C. H., Knackstedt, M. A., Mecke, K.

In Morphology of Condensed Matter, 600, pages: 37-74, Lecture Notes in Physics, Springer, Berlin [et al.], 2002 (incollection)

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[BibTex]

[BibTex]


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Selbstdiffusion in Silizium-Germanium-Legierungen

Strohm, A.

Universität Stuttgart, Stuttgart, 2002 (phdthesis)

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link (url) [BibTex]

link (url) [BibTex]


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Self-diffusion of 31Si and 71Ge in relaxed Si0.20Ge0.80 layers

Laitinen, P., Strohm, A., Huikari, J., Nieminen, A., Voss, T., Grodon, C., Riihimäki, I., Kummer, M., Äystö, J., Dendooven, P., Räisänen, J., Frank, W.

Physical Review Letters, 89(8), 2002 (article)

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[BibTex]

[BibTex]


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Self-diffusion of 71Ge and 31Si in Si-Ge alloys

Strohm, A., Voss, T., Frank, W., Laitinen, P., Räisänen, J.

Zeitschrift f\"ur Metallkunde, 93(7):737-744, 2002 (article)

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[BibTex]

[BibTex]


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Reconstruction of complex materials by integral geometric measures

Mecke, K. R.

Journal of Materials Science \& Technology, 18(2):155-158, 2002 (article)

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[BibTex]

[BibTex]


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Conformal map modeling of the pinning transition in Laplacian growth

Hentschel, H. G. E., Popescu, M. N., Family, F.

Physical Review E, 65(3), 2002 (article)

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[BibTex]

[BibTex]


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Geometrically-controlled twist transitions in nematic cells

Patricio, P., Telo da Gama, M. M., Dietrich, S.

Physical Review Letters, 88(24), 2002 (article)

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[BibTex]

[BibTex]


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Entropic torque

Roth, R., van Roij, R., Andrienko, D., Mecke, K. R., Dietrich, S.

Physical Review Letters, 89(8), 2002 (article)

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[BibTex]

[BibTex]


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Non-Gaussian morphology of galaxy-cluster distribution: Minkowski functionals of the REFLEX catalogue

Kerscher, M., Mecke, K., Schücker, P., Reflex Collaboration

In Tracing Cosmic Evolution with Galaxy Clusters. Proceedings of the Sesto-2001 Workshop, 268, pages: 60-62, Astronomical Society Pacific Conference Series, Alto Adige/Südtirol, 2002 (inproceedings)

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[BibTex]

[BibTex]


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Effective forces in colloidal mixtures: From depletion attraction to accumulation repulsion

Louis, A. A., Allahyarov, E., Löwen, H., Roth, R.

Physical Review E, 65(6), 2002 (article)

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[BibTex]

[BibTex]


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Nucleon mass and pion loops: Renormalization

Oettel, M., Thomas, A. W.

Physical Review C, 66(6), 2002 (article)

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[BibTex]

[BibTex]


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Learning rhythmic movements by demonstration using nonlinear oscillators

Ijspeert, J. A., Nakanishi, J., Schaal, S.

In IEEE International Conference on Intelligent Robots and Systems (IROS 2002), pages: 958-963, Piscataway, NJ: IEEE, Lausanne, Sept.30-Oct.4 2002, 2002, clmc (inproceedings)

Abstract
Locally weighted learning (LWL) is a class of statistical learning techniques that provides useful representations and training algorithms for learning about complex phenomena during autonomous adaptive control of robotic systems. This paper introduces several LWL algorithms that have been tested successfully in real-time learning of complex robot tasks. We discuss two major classes of LWL, memory-based LWL and purely incremental LWL that does not need to remember any data explicitly. In contrast to the traditional beliefs that LWL methods cannot work well in high-dimensional spaces, we provide new algorithms that have been tested in up to 50 dimensional learning problems. The applicability of our LWL algorithms is demonstrated in various robot learning examples, including the learning of devil-sticking, pole-balancing of a humanoid robot arm, and inverse-dynamics learning for a seven degree-of-freedom robot.

am

link (url) [BibTex]

link (url) [BibTex]


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Learning robot control

Schaal, S.

In The handbook of brain theory and neural networks, 2nd Edition, pages: 983-987, 2, (Editors: Arbib, M. A.), MIT Press, Cambridge, MA, 2002, clmc (inbook)

Abstract
This is a review article on learning control in robots.

am

link (url) [BibTex]

link (url) [BibTex]


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Arm and hand movement control

Schaal, S.

In The handbook of brain theory and neural networks, 2nd Edition, pages: 110-113, 2, (Editors: Arbib, M. A.), MIT Press, Cambridge, MA, 2002, clmc (inbook)

Abstract
This is a review article on computational and biological research on arm and hand control.

am

link (url) [BibTex]

link (url) [BibTex]


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Scalable techniques from nonparameteric statistics for real-time robot learning

Schaal, S., Atkeson, C. G., Vijayakumar, S.

Applied Intelligence, 17(1):49-60, 2002, clmc (article)

Abstract
Locally weighted learning (LWL) is a class of techniques from nonparametric statistics that provides useful representations and training algorithms for learning about complex phenomena during autonomous adaptive control of robotic systems. This paper introduces several LWL algorithms that have been tested successfully in real-time learning of complex robot tasks. We discuss two major classes of LWL, memory-based LWL and purely incremental LWL that does not need to remember any data explicitly. In contrast to the traditional belief that LWL methods cannot work well in high-dimensional spaces, we provide new algorithms that have been tested on up to 90 dimensional learning problems. The applicability of our LWL algorithms is demonstrated in various robot learning examples, including the learning of devil-sticking, pole-balancing by a humanoid robot arm, and inverse-dynamics learning for a seven and a 30 degree-of-freedom robot. In all these examples, the application of our statistical neural networks techniques allowed either faster or more accurate acquisition of motor control than classical control engineering.

am

link (url) [BibTex]

link (url) [BibTex]


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A micromechanical flying insect thorax

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

Neurotechnology for Biomimetic Robots, pages: 469-480, The MIT Press Cambridge, MA, 2002 (article)

pi

[BibTex]

[BibTex]


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Reliable stair climbing in the simple hexapod ’RHex’

Moore, E. Z., Campbell, D., Grimminger, F., Buehler, M.

In Proceedings 2002 IEEE International Conference on Robotics and Automation (Cat. No.02CH37292), 3, pages: 2222-2227 vol.3, May 2002 (inproceedings)

am

DOI [BibTex]

DOI [BibTex]


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Nanomolding based fabrication of synthetic gecko foot-hairs

Sitti, M., Fearing, R. S.

In Nanotechnology, 2002. IEEE-NANO 2002. Proceedings of the 2002 2nd IEEE Conference on, pages: 137-140, 2002 (inproceedings)

pi

Project Page [BibTex]

Project Page [BibTex]


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Evidence for van der Waals adhesion in gecko setae

Autumn, K., Sitti, M., Liang, Y. A., Peattie, A. M., Hansen, W. R., Sponberg, S., Kenny, T. W., Fearing, R., Israelachvili, J. N., Full, R. J.

Proceedings of the National Academy of Sciences, 99(19):12252-12256, National Acad Sciences, 2002 (article)

pi

Project Page [BibTex]

Project Page [BibTex]


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Movement imitation with nonlinear dynamical systems in humanoid robots

Ijspeert, J. A., Nakanishi, J., Schaal, S.

In International Conference on Robotics and Automation (ICRA2002), Washinton, May 11-15 2002, 2002, clmc (inproceedings)

Abstract
Locally weighted learning (LWL) is a class of statistical learning techniques that provides useful representations and training algorithms for learning about complex phenomena during autonomous adaptive control of robotic systems. This paper introduces several LWL algorithms that have been tested successfully in real-time learning of complex robot tasks. We discuss two major classes of LWL, memory-based LWL and purely incremental LWL that does not need to remember any data explicitly. In contrast to the traditional beliefs that LWL methods cannot work well in high-dimensional spaces, we provide new algorithms that have been tested in up to 50 dimensional learning problems. The applicability of our LWL algorithms is demonstrated in various robot learning examples, including the learning of devil-sticking, pole-balancing of a humanoid robot arm, and inverse-dynamics learning for a seven degree-of-freedom robot.

am

link (url) [BibTex]

link (url) [BibTex]


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A locally weighted learning composite adaptive controller with structure adaptation

Nakanishi, J., Farrell, J. A., Schaal, S.

In IEEE International Conference on Intelligent Robots and Systems (IROS 2002), Lausanne, Sept.30-Oct.4 2002, 2002, clmc (inproceedings)

Abstract
This paper introduces a provably stable adaptive learning controller which employs nonlinear function approximation with automatic growth of the learning network according to the nonlinearities and the working domain of the control system. The unknown function in the dynamical system is approximated by piecewise linear models using a nonparametric regression technique. Local models are allocated as necessary and their parameters are optimized on-line. Inspired by composite adaptive control methods, the pro-posed learning adaptive control algorithm uses both the tracking error and the estimation error to up-date the parameters. We provide Lyapunov analyses that demonstrate the stability properties of the learning controller. Numerical simulations illustrate rapid convergence of the tracking error and the automatic structure adaptation capability of the function approximator. This paper introduces a provably stable adaptive learning controller which employs nonlinear function approximation with automatic growth of the learning network according to the nonlinearities and the working domain of the control system. The unknown function in the dynamical system is approximated by piecewise linear models using a nonparametric regression technique. Local models are allocated as necessary and their parameters are optimized on-line. Inspired by composite adaptive control methods, the pro-posed learning adaptive control algorithm uses both the tracking error and the estimation error to up-date the parameters. We provide Lyapunov analyses that demonstrate the stability properties of the learning controller. Numerical simulations illustrate rapid convergence of the tracking error and the automatic structure adaptation capability of the function approximator

am

link (url) [BibTex]

link (url) [BibTex]