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2008


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Movement reproduction and obstacle avoidance with dynamic movement primitives and potential fields

Park, D., Hoffmann, H., Pastor, P., Schaal, S.

In IEEE International Conference on Humanoid Robots, 2008., 2008, clmc (inproceedings)

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PDF [BibTex]

2008


PDF [BibTex]


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Magnetism of amorphous and highly anisotropic multilayer systems on flat substrates and nanospheres

Amaladass, E. P.

Universität Stuttgart, Stuttgart, 2008 (phdthesis)

mms

link (url) [BibTex]


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Wetting and premelting of triple junctions and grain boundaries in the Al-Zn alloys

Straumal, B., Kogtenkova, O., Protasova, S., Mazilkin, A., Zieba, P., Czeppe, T., Wojewoda-Budka, J., Faryna, M.

In 495, pages: 126-131, Alicante, Spain, 2008 (inproceedings)

mms

DOI [BibTex]

DOI [BibTex]


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Interfaces in driven Ising models: shear enhances confinement

Smith, T. H. R., Vasilyev, O., Abraham, D. B., Maciolek, A., Schmidt, M.

{Physical Review Letters}, 101(6), 2008 (article)

mms

DOI [BibTex]

DOI [BibTex]


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Bose-Theorie der Dämpfung der Bewegung einer magnetischen Domänenwand

Hähnel, D.

Universität Stuttgart, Stuttgart, 2008 (mastersthesis)

mms

[BibTex]

[BibTex]


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Planar high-Tc superconducting quantum interference device gradiometer for simultaneous measurements of two magnetic field gradients

Steppke, A., Becker, C., Grosse, V., Dörrer, L., Schmidl, F., Seidel, P., Djupmyr, M., Albrecht, J.

{Applied Physics Letters}, 92, 2008 (article)

mms

DOI [BibTex]

DOI [BibTex]


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Terminal contact elements of insect attachment devices studied by transmission X-ray microscopy

Eimüller, T., Guttmann, P., Gorb, S. N.

{Journal of Experimental Biology}, 211, pages: 1958-1963, 2008 (article)

mms

[BibTex]

[BibTex]


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Increase of Co solubility with decreasing grain size in ZnO

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

{Acta Materialia}, 56, pages: 6246-6256, 2008 (article)

mms

DOI [BibTex]

DOI [BibTex]


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Hydrogen adsorption (Carbon, Zeolites, Nanocubes)

Hirscher, M., Panella, B.

In Hydrogen as a Future Energy Carrier, pages: 173-188, Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim, 2008 (incollection)

mms

[BibTex]

[BibTex]


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Uncompensated moments in the MnPd/Fe exchange bias system

Brück, S., Schütz, G., Goering, E., Ji, X., Krishnan, K. M.

{Physical Review Letters}, 101, 2008 (article)

mms

DOI [BibTex]

DOI [BibTex]


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Aqueous deposition of ultraviolet luminescent columnar tin-doped indium hydroxide films

Qiu, Y., Bellina, P., Jeurgens, L. P. H., Leineweber, A., Welzel, U., Gerstel, P., Jiang, L., van Aken, P. A., Bill, J., Aldinger, F.

{Advanced Functional Materials}, 18, pages: 2572-2583, 2008 (article)

mms

[BibTex]

[BibTex]


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Unified theory of near-adiabatic magnetization dynamics for collinear and noncollinear magnetization

Steiauf, D., Seib, J., Fähnle, M.

{Physical Review B}, 78, 2008 (article)

mms

DOI [BibTex]

DOI [BibTex]


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Hardmetals with nanograin reinforced binder: binder fine structure and hardness

Konyashin, I., Ries, B., Lachmann, F., Cooper, R., Mazilkin, A., Straumal, B., Aretz, A., Babaev, V.

{International Journal of Refractory Metals \& Hard Materials}, 26, pages: 583-588, 2008 (article)

mms

DOI [BibTex]

DOI [BibTex]


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The dual role of uncertainty in force field learning

Mistry, M., Theodorou, E., Hoffmann, H., Schaal, S.

In Abstracts of the Eighteenth Annual Meeting of Neural Control of Movement (NCM), Naples, Florida, April 29-May 4, 2008, clmc (inproceedings)

Abstract
Force field experiments have been a successful paradigm for studying the principles of planning, execution, and learning in human arm movements. Subjects have been shown to cope with the disturbances generated by force fields by learning internal models of the underlying dynamics to predict disturbance effects or by increasing arm impedance (via co-contraction) if a predictive approach becomes infeasible. Several studies have addressed the issue uncertainty in force field learning. Scheidt et al. demonstrated that subjects exposed to a viscous force field of fixed structure but varying strength (randomly changing from trial to trial), learn to adapt to the mean disturbance, regardless of the statistical distribution. Takahashi et al. additionally show a decrease in strength of after-effects after learning in the randomly varying environment. Thus they suggest that the nervous system adopts a dual strategy: learning an internal model of the mean of the random environment, while simultaneously increasing arm impedance to minimize the consequence of errors. In this study, we examine what role variance plays in the learning of uncertain force fields. We use a 7 degree-of-freedom exoskeleton robot as a manipulandum (Sarcos Master Arm, Sarcos, Inc.), and apply a 3D viscous force field of fixed structure and strength randomly selected from trial to trial. Additionally, in separate blocks of trials, we alter the variance of the randomly selected strength multiplier (while keeping a constant mean). In each block, after sufficient learning has occurred, we apply catch trials with no force field and measure the strength of after-effects. As expected in higher variance cases, results show increasingly smaller levels of after-effects as the variance is increased, thus implying subjects choose the robust strategy of increasing arm impedance to cope with higher levels of uncertainty. Interestingly, however, subjects show an increase in after-effect strength with a small amount of variance as compared to the deterministic (zero variance) case. This result implies that a small amount of variability aides in internal model formation, presumably a consequence of the additional amount of exploration conducted in the workspace of the task.

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[BibTex]

[BibTex]


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Dynamic movement primitives for movement generation motivated by convergent force fields in frog

Hoffmann, H., Pastor, P., Schaal, S.

In Adaptive Motion of Animals and Machines (AMAM), 2008, clmc (inproceedings)

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PDF [BibTex]

PDF [BibTex]


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Adhesion of biologically inspired oil-coated polymer micropillars

Cheung, E., Sitti, M.

Journal of Adhesion Science and Technology, 22(5-6):569-589, Taylor & Francis Group, 2008 (article)

pi

[BibTex]

[BibTex]


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Polymeric Micro/Nanofiber Manufacturing and Mechanical Characterization

Nain, A. S., Sitti, M., Amon, C.

In ASME 2008 International Mechanical Engineering Congress and Exposition, pages: 295-303, 2008 (inproceedings)

pi

[BibTex]

[BibTex]


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An untethered magnetically actuated micro-robot capable of motion on arbitrary surfaces

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

In Robotics and Automation, 2008. ICRA 2008. IEEE International Conference on, pages: 419-424, 2008 (inproceedings)

pi

[BibTex]

[BibTex]


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Fabrication of bio-inspired elastomer nanofiber arrays with spatulate tips using notching effect

Kim, S., Sitti, M., Jang, J., Thomas, E. L.

In Nanotechnology, 2008. NANO’08. 8th IEEE Conference on, pages: 780-782, 2008 (inproceedings)

pi

[BibTex]

[BibTex]


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A motorized anchoring mechanism for a tethered capsule robot using fibrillar adhesives for interventions in the esophagus

Glass, P., Cheung, E., Wang, H., Appasamy, R., Sitti, M.

In Biomedical Robotics and Biomechatronics, 2008. BioRob 2008. 2nd IEEE RAS & EMBS International Conference on, pages: 758-764, 2008 (inproceedings)

pi

[BibTex]

[BibTex]


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Vision-based feedback strategy for controlled pushing of microparticles

Lynch, N. A., Onal, C. D., Schuster, E., Sitti, M.

Journal of Micro-Nano Mechatronics, 4(1-2):73-83, Springer-Verlag, 2008 (article)

pi

[BibTex]

[BibTex]


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Effect of quantity and configuration of attached bacteria on bacterial propulsion of microbeads

Behkam, B., Sitti, M.

Applied Physics Letters, 93(22):223901, AIP, 2008 (article)

pi

[BibTex]

[BibTex]


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Emergence of Interaction Among Adaptive Agents

Martius, G., Nolfi, S., Herrmann, J. M.

In Proc. From Animals to Animats 10 (SAB 2008), 5040, pages: 457-466, LNCS, Springer, 2008 (inproceedings)

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DOI [BibTex]

DOI [BibTex]


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Interfaces in confined Ising models: Kawasaki, Glauber and sheared dynamics

Smith, T. H. R., Vasilyev, O., Abraham, D. B., Maciolek, A., Schmidt, M.

{Journal of Physics: Condensed Matter}, 20(49), 2008 (article)

mms

DOI [BibTex]

DOI [BibTex]


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Critical fields of an exchange coupled two-layer composite particle

Goll, D., Kronmüller, H.

{Physica B}, 403, pages: 1854-1859, 2008 (article)

mms

DOI [BibTex]

DOI [BibTex]


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Coercivity and domain structure of nanograined Fe-C alloys after high-pressure torsion

Protasova, S. G., Straumal, B., Dobatkin, S. V., Goll, D., Schütz, G., Baretzky, B., Mazilkin, A. A., Nebrasov, A. N.

{Journal of Materials Science}, 43, pages: 3775-3781, 2008 (article)

mms

DOI [BibTex]

DOI [BibTex]


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Epitaxial growth and properties of (001)-oriented TbBaCo2O6-αfilms

Kasper, N. V., Wochner, P., Vigliante, A., Dosch, H., Jakob, G., Carstanjen, H. D., Kremer, R. K.

{Journal of Applied Physics}, 103, 2008 (article)

mms

DOI [BibTex]

DOI [BibTex]


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Magnetic properties of exchange-coupled L10-FePt/Fe composite elements

Goll, D., Breitling, A., Macke, S.

{IEEE Transactions on Magnetics}, 44(11):3472-3475, 2008 (article)

mms

DOI [BibTex]

DOI [BibTex]


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Colloidal cobalt-doped ZnO nanorods: synthesis, structural, and magnetic properties

Büsgen, T., Hilgendorff, M., Irsen, S., Wilhelm, F., Rogalev, A., Goll, D., Giersig, M.

{Journal of Physical Chemistry C}, 112(7):2412-2417, 2008 (article)

mms

DOI [BibTex]

DOI [BibTex]


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Raman studies of hydrogen adsorbed on nanostructured porous materials

Panella, B., Hirscher, M.

{Physical Chemistry Chemical Physics}, 10, pages: 2910-2917, 2008 (article)

mms

DOI [BibTex]

DOI [BibTex]


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Thermal evolution and grain boundary phase transformations in severely deformed nanograined Al-Zn alloys

Straumal, B., Valiev, R., Kogtenkova, O., Zieba, P., Czeppe, T., Bielanska, E., Faryna, M.

{Acta Materialia}, 56(20):6123-6131, 2008 (article)

mms

DOI [BibTex]

DOI [BibTex]


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Hydrogen storage properties of Pd nanoparticle/carbon template composites

Campesi, R., Cuevas, F., Gadiou, R., Leroy, E., Hirscher, M., Vix-Guterl, C., Latroche, M.

{Carbon}, 46, pages: 206-214, 2008 (article)

mms

DOI [BibTex]

DOI [BibTex]


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Reversible transformation of a grain-boundary facet into a rough-to-rough ridge in zinc

Straumal, B. B., Gornakova, A. S., Sursaeva, V. G.

{Philosophical Magazine Letters}, 88(1):27-36, 2008 (article)

mms

DOI [BibTex]

DOI [BibTex]


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A Dynamical System for Online Learning of Periodic Movements of Unknown Waveform and Frequency

Gams, A., Righetti, L., Ijspeert, A., Lenarčič, J.

In 2008 2nd IEEE RAS & EMBS International Conference on Biomedical Robotics and Biomechatronics, pages: 85-90, IEEE, Scottsdale, USA, October 2008 (inproceedings)

Abstract
The paper presents a two-layered system for learning and encoding a periodic signal onto a limit cycle without any knowledge on the waveform and the frequency of the signal, and without any signal processing. The first dynamical system is responsible for extracting the main frequency of the input signal. It is based on adaptive frequency phase oscillators in a feedback structure, enabling us to extract separate frequency components without any signal processing, as all of the processing is embedded in the dynamics of the system itself. The second dynamical system is responsible for learning of the waveform. It has a built-in learning algorithm based on locally weighted regression, which adjusts the weights according to the amplitude of the input signal. By combining the output of the first system with the input of the second system we can rapidly teach new trajectories to robots. The systems works online for any periodic signal and can be applied in parallel to multiple dimensions. Furthermore, it can adapt to changes in frequency and shape, e.g. to non-stationary signals, and is computationally inexpensive. Results using simulated and hand-generated input signals, along with applying the algorithm to a HOAP-2 humanoid robot are presented.

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link (url) DOI [BibTex]

link (url) DOI [BibTex]


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Passive compliant quadruped robot using central pattern generators for locomotion control

Rutishauser, S., Sproewitz, A., Righetti, L., Ijspeert, A.

In 2008 IEEE International Conference on Biomedical Robotics and Biomechatronics, pages: 710-715, IEEE, Scottsdale, USA, October 2008 (inproceedings)

Abstract
We present a new quadruped robot, ldquoCheetahrdquo, featuring three-segment pantographic legs with passive compliant knee joints. Each leg has two degrees of freedom - knee and hip joint can be actuated using proximal mounted RC servo motors, force transmission to the knee is achieved by means of a bowden cable mechanism. Simple electronics to command the actuators from a desktop computer have been designed in order to test the robot. A Central Pattern Generator (CPG) network has been implemented to generate different gaits. A parameter space search was performed and tested on the robot to optimize forward velocity.

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link (url) DOI [BibTex]

link (url) DOI [BibTex]


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Efficient inverse kinematics algorithms for highdimensional movement systems

Tevatia, G., Schaal, S.

CLMC Technical Report: TR-CLMC-2008-1, 2008, clmc (techreport)

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 methods of resolved motion rate control (RMRC) that employ optimization criteria to resolve kinematic redundancies. In particular we focus on two established techniques, the pseudo inverse with explicit optimization and the extended Jacobian method. We prove that the extended Jacobian method includes pseudo-inverse methods as a special solution. In terms of computational complexity, however, pseudo-inverse and extended Jacobian differ significantly in favor of pseudo-inverse methods. Employing numerical estimation techniques, we introduce a computationally efficient version of the extended Jacobian with performance comparable to the original version. Our results are illustrated in simulation studies with a multiple degree-offreedom robot, and were evaluated on an actual 30 degree-of-freedom full-body humanoid robot.

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link (url) [BibTex]

link (url) [BibTex]


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Behavioral experiments on reinforcement learning in human motor control

Hoffmann, H., Theodorou, E., Schaal, S.

In Abstracts of the Eighteenth Annual Meeting of Neural Control of Movement (NCM), Naples, Florida, April 29-May 4, 2008, clmc (inproceedings)

Abstract
Reinforcement learning (RL) - learning solely based on reward or cost feedback - is widespread in robotics control and has been also suggested as computational model for human motor control. In human motor control, however, hardly any experiment studied reinforcement learning. Here, we study learning based on visual cost feedback in a reaching task and did three experiments: (1) to establish a simple enough experiment for RL, (2) to study spatial localization of RL, and (3) to study the dependence of RL on the cost function. In experiment (1), subjects sit in front of a drawing tablet and look at a screen onto which the drawing pen's position is projected. Beginning from a start point, their task is to move with the pen through a target point presented on screen. Visual feedback about the pen's position is given only before movement onset. At the end of a movement, subjects get visual feedback only about the cost of this trial. We choose as cost the squared distance between target and virtual pen position at the target line. Above a threshold value, the cost was fixed at this value. In the mapping of the pen's position onto the screen, we added a bias (unknown to subject) and Gaussian noise. As result, subjects could learn the bias, and thus, showed reinforcement learning. In experiment (2), we randomly altered the target position between three different locations (three different directions from start point: -45, 0, 45). For each direction, we chose a different bias. As result, subjects learned all three bias values simultaneously. Thus, RL can be spatially localized. In experiment (3), we varied the sensitivity of the cost function by multiplying the squared distance with a constant value C, while keeping the same cut-off threshold. As in experiment (2), we had three target locations. We assigned to each location a different C value (this assignment was randomized between subjects). Since subjects learned the three locations simultaneously, we could directly compare the effect of the different cost functions. As result, we found an optimal C value; if C was too small (insensitive cost), learning was slow; if C was too large (narrow cost valley), the exploration time was longer and learning delayed. Thus, reinforcement learning in human motor control appears to be sen

am

[BibTex]

[BibTex]


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Movement generation by learning from demonstration and generalization to new targets

Pastor, P., Hoffmann, H., Schaal, S.

In Adaptive Motion of Animals and Machines (AMAM), 2008, clmc (inproceedings)

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PDF [BibTex]

PDF [BibTex]


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Combining dynamic movement primitives and potential fields for online obstacle avoidance

Park, D., Hoffmann, H., Schaal, S.

In Adaptive Motion of Animals and Machines (AMAM), Cleveland, Ohio, 2008, 2008, clmc (inproceedings)

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link (url) [BibTex]

link (url) [BibTex]


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A library for locally weighted projection regression

Klanke, S., Vijayakumar, S., Schaal, S.

Journal of Machine Learning Research, 9, pages: 623-626, 2008, clmc (article)

Abstract
In this paper we introduce an improved implementation of locally weighted projection regression (LWPR), a supervised learning algorithm that is capable of handling high-dimensional input data. As the key features, our code supports multi-threading, is available for multiple platforms, and provides wrappers for several programming languages.

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link (url) [BibTex]

link (url) [BibTex]


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Fabrication of Single and Multi-Layer Fibrous Biomaterial Scaffolds for Tissue Engineering

Nain, A. S., Miller, E., Sitti, M., Campbell, P., Amon, C.

In ASME 2008 International Mechanical Engineering Congress and Exposition, pages: 231-238, 2008 (inproceedings)

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[BibTex]

[BibTex]


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Performance of different foot designs for a water running robot

Floyd, S., Adilak, S., Ramirez, S., Rogman, R., Sitti, M.

In Robotics and Automation, 2008. ICRA 2008. IEEE International Conference on, pages: 244-250, 2008 (inproceedings)

pi

[BibTex]

[BibTex]


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Dynamic modeling of a basilisk lizard inspired quadruped robot running on water

Park, H. S., Floyd, S., Sitti, M.

In Intelligent Robots and Systems, 2008. IROS 2008. IEEE/RSJ International Conference on, pages: 3101-3107, 2008 (inproceedings)

pi

[BibTex]

[BibTex]


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Bacterial propulsion of chemically patterned micro-cylinders

Behkam, B., Sitti, M.

In Biomedical Robotics and Biomechatronics, 2008. BioRob 2008. 2nd IEEE RAS & EMBS International Conference on, pages: 753-757, 2008 (inproceedings)

pi

[BibTex]

[BibTex]


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Preface to the Journal of Micro-Nano Mechatronics

Dario, P., Fukuda, T., Sitti, M.

Journal of Micro-Nano Mechatronics, 4(1-2):1-1, Springer-Verlag, 2008 (article)

pi

[BibTex]

[BibTex]


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A legged anchoring mechanism for capsule endoscopes using micropatterned adhesives

Glass, P., Cheung, E., Sitti, M.

IEEE Transactions on Biomedical Engineering, 55(12):2759-2767, IEEE, 2008 (article)

pi

Project Page [BibTex]

Project Page [BibTex]