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2003


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Surface adsorbed atoms suppressing hydrogen permeation of Pd membranes

Yamakawa, K., Ege, M., Ludescher, B., Hirscher, M.

{Journal of Alloys and Compounds}, 352, pages: 57-59, 2003 (article)

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[BibTex]

2003


[BibTex]


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Experiment with a crystal-assisted positron source using 6 and 10 GeV electrons

Artru, X., Baier, V., Beloborodov, K., Bochek, G., Bogdanov, A., Bozhenok, A., Bukin, A., Burdin, S., Chehab, R., Chevallier, M., Cizeron, R., Dauvergne, D., Dimova, T., Drozdetsky, A., Druzhinin, V., Dubrovin, M., Gatignon, L., Golubev, V., Jejcic, A., Keppler, P., Kirsch, R., Kulibaba, V., Lautesse, P., Major, J., Maslov, N., Poizat, J. C., Potylitsin, A., Remillieux, J., Serednyakov, S., Shary, V., Strakhovenko, V., Sylvia, C., Vnukov, I.

{Nuclear Instruments and Methods in Physics Research B}, 201, pages: 243-252, 2003 (article)

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[BibTex]

[BibTex]


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Surface patterning of SrTiO3 by 30 keV ion irradiation

Albrecht, J., Leonhardt, S., Spolenak, R., Täffner, U., Habermeier, H. U., Schütz, G.

{Surface Science Letters}, 547, pages: L847-L852, 2003 (article)

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[BibTex]

[BibTex]


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Evolution of Fault-tolerant Self-replicating Structures

Righetti, L., Shokur, S., Capcarre, M.

In Advances in Artificial Life, pages: 278-288, Lecture Notes in Computer Science, Springer Berlin Heidelberg, 2003 (inproceedings)

Abstract
Designed and evolved self-replicating structures in cellular automata have been extensively studied in the past as models of Artificial Life. However, CAs, unlike their biological counterpart, are very brittle: any faulty cell usually leads to the complete destruction of any emerging structures, let alone self-replicating structures. A way to design fault-tolerant structures based on error-correcting-code has been presented recently [1], but it required a cumbersome work to be put into practice. In this paper, we get back to the original inspiration for these works, nature, and propose a way to evolve self-replicating structures, faults here being only an idiosyncracy of the environment.

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link (url) DOI [BibTex]

link (url) DOI [BibTex]


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Learning from demonstration and adaptation of biped locomotion with dynamical movement primitives

Nakanishi, J., Morimoto, J., Endo, G., Schaal, S., Kawato, M.

In Workshop on Robot Learning by Demonstration, IEEE International Conference on Intelligent Robots and Systems (IROS 2003), Las Vegas, NV, Oct. 27-31, 2003, clmc (inproceedings)

Abstract
In this paper, we report on our research for learning biped locomotion from human demonstration. Our ultimate goal is to establish a design principle of a controller in order to achieve natural human-like locomotion. We suggest dynamical movement primitives as a CPG of a biped robot, an approach we have previously proposed for learning and encoding complex human movements. Demonstrated trajectories are learned through the movement primitives by locally weighted regression, and the frequency of the learned trajectories is adjusted automatically by a novel frequency adaptation algorithm based on phase resetting and entrainment of oscillators. Numerical simulations demonstrate the effectiveness of the proposed locomotion controller.

am

link (url) [BibTex]

link (url) [BibTex]


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Movement planning and imitation by shaping nonlinear attractors

Schaal, S.

In Proceedings of the 12th Yale Workshop on Adaptive and Learning Systems, Yale University, New Haven, CT, 2003, clmc (inproceedings)

Abstract
Given the continuous stream of movements that biological systems exhibit in their daily activities, an account for such versatility and creativity has to assume that movement sequences consist of segments, executed either in sequence or with partial or complete overlap. Therefore, a fundamental question that has pervaded research in motor control both in artificial and biological systems revolves around identifying movement primitives (a.k.a. units of actions, basis behaviors, motor schemas, etc.). What are the fundamental building blocks that are strung together, adapted to, and created for ever new behaviors? This paper summarizes results that led to the hypothesis of Dynamic Movement Primitives (DMP). DMPs are units of action that are formalized as stable nonlinear attractor systems. They are useful for autonomous robotics as they are highly flexible in creating complex rhythmic (e.g., locomotion) and discrete (e.g., a tennis swing) behaviors that can quickly be adapted to the inevitable perturbations of a dy-namically changing, stochastic environment. Moreover, DMPs provide a formal framework that also lends itself to investigations in computational neuroscience. A recent finding that allows creating DMPs with the help of well-understood statistical learning methods has elevated DMPs from a more heuristic to a principled modeling approach, and, moreover, created a new foundation for imitation learning. Theoretical insights, evaluations on a humanoid robot, and behavioral and brain imaging data will serve to outline the framework of DMPs for a general approach to motor control and imitation in robotics and biology.

am

link (url) [BibTex]

link (url) [BibTex]


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Computational approaches to motor learning by imitation

Schaal, S., Ijspeert, A., Billard, A.

Philosophical Transaction of the Royal Society of London: Series B, Biological Sciences, 358(1431):537-547, 2003, clmc (article)

Abstract
Movement imitation requires a complex set of mechanisms that map an observed movement of a teacher onto one's own movement apparatus. Relevant problems include movement recognition, pose estimation, pose tracking, body correspondence, coordinate transformation from external to egocentric space, matching of observed against previously learned movement, resolution of redundant degrees-of-freedom that are unconstrained by the observation, suitable movement representations for imitation, modularization of motor control, etc. All of these topics by themselves are active research problems in computational and neurobiological sciences, such that their combination into a complete imitation system remains a daunting undertaking - indeed, one could argue that we need to understand the complete perception-action loop. As a strategy to untangle the complexity of imitation, this paper will examine imitation purely from a computational point of view, i.e. we will review statistical and mathematical approaches that have been suggested for tackling parts of the imitation problem, and discuss their merits, disadvantages and underlying principles. Given the focus on action recognition of other contributions in this special issue, this paper will primarily emphasize the motor side of imitation, assuming that a perceptual system has already identified important features of a demonstrated movement and created their corresponding spatial information. Based on the formalization of motor control in terms of control policies and their associated performance criteria, useful taxonomies of imitation learning can be generated that clarify different approaches and future research directions.

am

link (url) [BibTex]

link (url) [BibTex]


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Efficient charge recovery method for driving piezoelectric actuators with quasi-square waves

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

IEEE transactions on ultrasonics, ferroelectrics, and frequency control, 50(3):237-244, IEEE, 2003 (article)

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[BibTex]

[BibTex]


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Synthetic gecko foot-hair micro/nano-structures for future wall-climbing robots

Sitti, M., Fearing, R. S.

In Robotics and Automation, 2003. Proceedings. ICRA’03. IEEE International Conference on, 1, pages: 1164-1170, 2003 (inproceedings)

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[BibTex]

[BibTex]


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Magnetization reversal study of CoCrPt alloy thin films on a nanogranular-length scale using magnetic transmission soft x-ray microscopy

Im, M. Y., Fischer, P., Eimüller, T., Denbeaux, G., Shin, S. C.

{Applied Physics Letters}, 83(22):4589-4591, 2003 (article)

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[BibTex]

[BibTex]


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XANES und MEXAFS an magnetischen Übergangsmetalloxiden: Entwicklung eines digitalen Lock-In XMCD Experimentes mit Phasenschieber

Weigand, F.

Bayerische Julius-Maximilians-Universität Würzburg, Würzburg, 2003 (phdthesis)

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[BibTex]

[BibTex]


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Temperature-dependent pinning of vortices in low-angle grain boundaries in YBa2Cu3O7-δ

Albrecht, J.

{Physical Review B}, 68, 2003 (article)

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[BibTex]


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Magnetic soft X-ray transmission microscopy

Fischer, P.

{Current Opinion in Solid State \& Materials Science}, 7(2):173-179, 2003 (article)

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[BibTex]

[BibTex]


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The magnetic transmission X-ray microscopy project at BESSY II

Eimüller, T., Niemann, B., Guttmann, P., Fischer, P., Englisch, U., Vatter, R., Wolter, C., Seiffert, S., Schmahl, G., Schütz, G.

{Journal de Physique IV}, 104, pages: 91-94, 2003 (article)

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[BibTex]

[BibTex]


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Ab-initio statistical mechanics for ordered compounds: single-defect theory vs. cluster-expansion techniques

Drautz, R., Schultz, I., Lechermann, F., Fähnle, M.

{Physica Status Solidi B}, 240(1):37-44, 2003 (article)

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[BibTex]

[BibTex]


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Magnetic imaging with soft x-ray microscopies

Fischer, P., Denbeaux, G., Stoll, H., Puzic, A., Raabe, J., Nolting, F., Eimüller, T., Schütz, G.

{Journal de Physique IV}, 104, pages: 471-476, 2003 (article)

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[BibTex]

[BibTex]


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Hydrogen storage in carbon nanotubes

Hirscher, M., Becher, M.

{Journal of Nanoscience and Nanotechnology}, 3(1/2):3-17, 2003 (article)

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[BibTex]

[BibTex]


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Grain boundary faceting phase transition and thermal grooving in Cu

Straumal, B. B., Polyakov, S. A., Bischoff, E., Mittemeijer, E. J., Gust, W.

In Proceedings of the International Conference on Diffusion, Segregation and Stresses in Materials, 216/217, pages: 93-100, Diffusion and Defect Data, Pt. A, Defect and Diffusion Forum, Scitec Publ., Moscow, 2003 (inproceedings)

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[BibTex]

[BibTex]


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AMOC in positron and positronium chemistry

Stoll, H., Castellaz, P., Siegle, A.

In Principles and Applications of Positron and Positronium Chemistry, pages: 344-366, World Scientific Publishers, Singapore, 2003 (incollection)

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[BibTex]

[BibTex]


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Strong influence on the electronic structure of Pt adatoms and clusters on graphite

Fauth, K., He\ssler, M., Batchelor, D., Schütz, G.

{Surface Science}, 529(3):397-402, 2003 (article)

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[BibTex]

[BibTex]


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NMR studies of hydrogen diffusion in the dihydrides of hafnium

Gottwald, J., Majer, G., Peterson, D. T., Barnes, R. G.

{Journal of Alloys and Compounds}, 356-357, pages: 274-278, 2003 (article)

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[BibTex]

[BibTex]


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The +/-45 degrees correlation interferometer as a means to measure phase noise of parametric origin

Rubiola, E., Giordano, V., Stoll, H.

{IEEE Transactions on Instrumentation and Measurement}, 52, pages: 182-188, 2003 (article)

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[BibTex]

[BibTex]


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

Sitti, M.

IEEE/ASME transactions on mechatronics, 8(1):26-36, IEEE, 2003 (article)

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[BibTex]


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Biomimetic propulsion for a swimming surgical micro-robot

Edd, J., Payen, S., Rubinsky, B., Stoller, M. L., Sitti, M.

In Intelligent Robots and Systems, 2003.(IROS 2003). Proceedings. 2003 IEEE/RSJ International Conference on, 3, pages: 2583-2588, 2003 (inproceedings)

pi

Project Page [BibTex]

Project Page [BibTex]


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Slow removal of vacancies in B2-Ni52Al48 upon long-term low-temperature annealing

Zhang, X. Y., Sprengel, W., Reichle, K. J., Blaurock, K., Henes, R., Schaefer, H. E.

{Physical Review B}, 68(22), 2003 (article)

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[BibTex]

[BibTex]


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Magnetic domain structure in SmCo 2 : 17 permanent magnets

Zhang, Y., Tang, W., Hadjipanayis, G. C., Chen, C. H., Goll, D., Kronmüller, H.

{IEEE Transactions on Magnetics}, 39(5):2905-2907, 2003 (article)

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[BibTex]

[BibTex]


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Energy loss and charge state dependency of swift Nq+ ions scattered off a Pt(110)(1 x 2) surface

Robin, A., Hatke, N., Jensen, J., Plachke, D., Carstanjen, H. D., Heiland, W.

{Nuclear Instruments \& Methods in Physics Research B-Beam Interactions with Materials and Atoms}, 209, pages: 259-264, 2003 (article)

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[BibTex]

[BibTex]


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Preparation and properties of [NdFeBx/Nbz]n multi-layer films

Tsai, J. L., Chin, T. S., Yao, Y. D., Melsheimer, A., Fischer, S. F., Dragon, T., Kelsch, M., Kronmüller, H.

{Physica B-Condensed Matter}, 327(2-4):283-286, 2003 (article)

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[BibTex]

[BibTex]


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Multilayered magnetic nanostrips studied by transmission X-ray microscopy

Eimüller, T., Fischer, P., Guttmann, P., Denbeaux, G., Scholz, M., Köhler, M., Schmahl, G., Bayreuther, G., Schütz, G.

{Journal de Physique IV}, 104, pages: 483-486, 2003 (article)

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[BibTex]

[BibTex]


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Imaging magnetic domain structures with soft X-ray microscopy

Fischer, P., Eimüller, T., Schütz, G., Denbeaux, G.

{Structural Chemistry}, 14(1):39-47, 2003 (article)

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[BibTex]

[BibTex]


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Hydrogen solubility and diffusivity in amorphous La14Ni86 films

Cuevas, F., Hirscher, M.

{Acta Materialia}, 51, pages: 701-712, 2003 (article)

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[BibTex]

[BibTex]


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Coercivity mechanism in nanocrystalline and bonded magnets

Goll, D., Kronmüller, H.

In Bonded Magnets. Proceedings of the NATO Advanced Research Workshop on Science and Technology of Bonded Magnets, 118, pages: 115-127, NATO Science Series: Series 2, Mathematics, Physics and Chemistry, Kluwer Acad. Publ., Newark, USA, 2003 (inproceedings)

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[BibTex]

[BibTex]


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Hydrogen interaction with carbon nanostructures - current situation and future prospects

Orimo, S., Züttel, A., Schlapbach, L., Majer, G., Fukunaga, T., Fujii, H.

{Journal of Alloys and Compounds}, 356-357, pages: 716-719, 2003 (article)

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[BibTex]

[BibTex]


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Desorption of hydrogen from blowing agents used for foaming metals

von Zeppelin, F., Hirscher, M., Stanzick, H., Banhart, J.

{Composites Science and Technology}, 63, pages: 2293-2300, 2003 (article)

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[BibTex]

[BibTex]


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Investigation of Electromigration in Copper Interconnects by Noise Measurements

Emelianov, V., Ganesan, G., Puzic, A., Schulz, S., Eizenberg, M., Habermeier, H., Stoll, H.

In Noise as a Tool for Studying Materials, pages: 271-281, Proceedings of SPIE, Santa Fe, New Mexico, 2003 (inproceedings)

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[BibTex]

[BibTex]


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Entropic wetting of a colloidal rod-sphere mixture

Roth, R., Brader, J. M., Schmidt, M.

{Europhysics Letters}, 63(4):549-555, 2003 (article)

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[BibTex]

[BibTex]

1993


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Learning passive motor control strategies with genetic algorithms

Schaal, S., Sternad, D.

In 1992 Lectures in complex systems, pages: 913-918, (Editors: Nadel, L.;Stein, D.), Addison-Wesley, Redwood City, CA, 1993, clmc (inbook)

Abstract
This study investigates learning passive motor control strategies. Passive control is understood as control without active error correction; the movement is stabilized by particular properties of the controlling dynamics. We analyze the task of juggling a ball on a racket. An approximation to the optimal solution of the task is derived by means of optimization theory. In order to model the learning process, the problem is coded for a genetic algorithm in representations without sensory or with sensory information. For all representations the genetic algorithm is able to find passive control strategies, but learning speed and the quality of the outcome are significantly different. A comparison with data from human subjects shows that humans seem to apply yet different movement strategies to the ones proposed. For the feedback representation some implications arise for learning from demonstration.

am

link (url) [BibTex]

1993


link (url) [BibTex]


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A genetic algorithm for evolution from an ecological perspective

Sternad, D., Schaal, S.

In 1992 Lectures in Complex Systems, pages: 223-231, (Editors: Nadel, L.;Stein, D.), Addison-Wesley, Redwood City, CA, 1993, clmc (inbook)

Abstract
In the population model presented, an evolutionary dynamic is explored which is based on the operator characteristics of genetic algorithms. An essential modification in the genetic algorithms is the inclusion of a constraint in the mixing of the gene pool. The pairing for the crossover is governed by a selection principle based on a complementarity criterion derived from the theoretical tenet of perception-action (P-A) mutuality of ecological psychology. According to Swenson and Turvey [37] P-A mutuality underlies evolution and is an integral part of its thermodynamics. The present simulation tested the contribution of P-A-cycles in evolutionary dynamics. A numerical experiment compares the population's evolution with and without this intentional component. The effect is measured in the difference of the rate of energy dissipation, as well as in three operationalized aspects of complexity. The results support the predicted increase in the rate of energy dissipation, paralleled by an increase in the average heterogeneity of the population. Furthermore, the spatio-temporal evolution of the system is tested for the characteristic power-law relations of a nonlinear system poised in a critical state. The frequency distribution of consecutive increases in population size shows a significantly different exponent in functional relationship.

am

[BibTex]

[BibTex]


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Roles for memory-based learning in robotics

Atkeson, C. G., Schaal, S.

In Proceedings of the Sixth International Symposium on Robotics Research, pages: 503-521, Hidden Valley, PA, 1993, clmc (inproceedings)

am

[BibTex]

[BibTex]


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Design concurrent calculation: A CAD- and data-integrated approach

Schaal, S., Ehrlenspiel, K.

Journal of Engineering Design, 4, pages: 71-85, 1993, clmc (article)

Abstract
Besides functional regards, product design demands increasingly more for further reaching considerations. Quality alone cannot suffice anymore to compete in the market; design for manufacturability, for assembly, for recycling, etc., are well-known keywords. Those can largely be reduced to the necessity of design for costs. This paper focuses on a CAD-based approach to design concurrent calculation. It will discuss how, in the meantime well-established, tools like feature technology, knowledge-based systems, and relational databases can be blended into one coherent concept to achieve an entirely CAD- and data-integrated cost information tool. This system is able to extract data from the CAD-system, combine it with data about the company specific manufacturing environment, and subsequently autonomously evaluate manufacturability aspects and costs of the given CAD-model. Within minutes the designer gets quantitative in-formation about the major cost sources of his/her design. Additionally, some alternative methods for approximating manu-facturing times from empirical data, namely neural networks and local weighted regression, are introduced.

am

[BibTex]

[BibTex]


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Open loop stable control strategies for robot juggling

Schaal, S., Atkeson, C. G.

In IEEE International Conference on Robotics and Automation, 3, pages: 913-918, Piscataway, NJ: IEEE, Georgia, Atlanta, May 2-6, 1993, clmc (inproceedings)

Abstract
In a series of case studies out of the field of dynamic manipulation (Mason, 1992), different principles for open loop stable control are introduced and analyzed. This investigation may provide some insight into how open loop control can serve as a useful foundation for closed loop control and, particularly, what to focus on in learning control. 

am

link (url) [BibTex]

link (url) [BibTex]