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2009


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Enhanced adhesion by gecko-inspired hierarchical fibrillar adhesives

Murphy, M. P., Kim, S., Sitti, M.

ACS applied materials \& interfaces, 1(4):849-855, American Chemical Society, 2009 (article)

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Project Page [BibTex]

2009


Project Page [BibTex]


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Miniature devices: Voyage of the microrobots

Sitti, M.

Nature, 458(7242):1121-1122, Nature Publishing Group, 2009 (article)

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[BibTex]

[BibTex]


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Dry spinning based spinneret based tunable engineered parameters (STEP) technique for controlled and aligned deposition of polymeric nanofibers

Nain, A. S., Sitti, M., Jacobson, A., Kowalewski, T., Amon, C.

Macromolecular rapid communications, 30(16):1406-1412, WILEY-VCH Verlag, 2009 (article)

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[BibTex]

[BibTex]


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Two-dimensional contact and noncontact micromanipulation in liquid using an untethered mobile magnetic microrobot

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

IEEE Transactions on Robotics, 25(6):1332-1342, IEEE, 2009 (article)

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[BibTex]

[BibTex]


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Mit Röntgenblitzen zu neuen Erkenntnissen

Hedderich, R., Weigand, M., Baretzky, B.

{Nanotechnik - Molek\"ule Materialien Mikrosysteme}, (6 (Beilage zu Photonik 41. 2009)), 2009 (article)

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[BibTex]

[BibTex]


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Second-order faceting-roughening of the tilt grain boundary in zinc

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

{International Journal of Materials Research}, 100(4):525-529, 2009 (article)

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DOI [BibTex]

DOI [BibTex]


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Improvement of interface structure and magnetic properties of Co on Si (100) by surfactant (Sb) mediated growth

Dash, S. P., Goll, D., Carstanjen, H. D.

{Applied Physics A}, 97(3):651-656, 2009 (article)

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DOI [BibTex]

DOI [BibTex]


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Effect of severe plastic deformation on the coercivity of Co-Cu alloys

Straumal, B. B., Protasova, S. G., Mazilkin, A. A., Baretzky, B., Goll, D., Gunderov, D. V., Valiev, R. Z.

{Philosophical Magazine Letters}, 89(10):649-654, 2009 (article)

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DOI [BibTex]

DOI [BibTex]


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Magnetic properties of cobalt-covered MgB2 films

Treiber, S., Stuhlhofer, B., Habermeier, H.-U., Albrecht, J.

{Superconductor Science and Technology}, 22, 2009 (article)

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DOI [BibTex]

DOI [BibTex]


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Reconstruction of historic alloys for pipe organs brings true Baroque music back to life

Baretzky, B., Friesel, M., Straumal, B.

{Japan Organist}, 36, pages: 29-38, 2009 (article)

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[BibTex]

[BibTex]


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Exchange-coupled L10-FePt/Fe composite patterns with perpendicular magnetization

Breitling, A., Bublat, T., Goll, D.

{Physica Status Solidi - Rapid Research Letters}, 3(5):130-132, 2009 (article)

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DOI [BibTex]

DOI [BibTex]


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Proton NMR studies of the NaAlH4 structure

Valiente-Banuet, L. E., Majer, G., Müller, K.

{Journal of Magnetic Resonance}, 200, pages: 280-284, 2009 (article)

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DOI [BibTex]

DOI [BibTex]


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A scaled bilateral control system for experimental one-dimensional teleoperated nanomanipulation

Onal, C. D., Sitti, M.

The International Journal of Robotics Research, 28(4):484-497, Sage Publications, 2009 (article)

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[BibTex]

[BibTex]


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A Swallowable Tethered Capsule Endoscope for Diagnosing Barrett’s Esophagus

Glass, P., Sitti, M., Pennathur, A., Appasamy, R.

Gastrointestinal Endoscopy, 69(5):AB106, Mosby, 2009 (article)

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Project Page [BibTex]

Project Page [BibTex]


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Adhesion of biologically inspired polymer microfibers on soft surfaces

Cheung, E., Sitti, M.

Langmuir, 25(12):6613-6616, ACS Publications, 2009 (article)

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[BibTex]

[BibTex]


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Dangling chain elastomers as repeatable fibrillar adhesives

Sitti, M., Cusick, B., Aksak, B., Nese, A., Lee, H., Dong, H., Kowalewski, T., Matyjaszewski, K.

ACS applied materials \& interfaces, 1(10):2277-2287, American Chemical Society, 2009 (article)

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[BibTex]

[BibTex]


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A Sensor-Based Learning Algorithm for the Self-Organization of Robot Behavior

Hesse, F., Martius, G., Der, R., Herrmann, J. M.

Algorithms, 2(1):398-409, 2009 (article)

Abstract
Ideally, sensory information forms the only source of information to a robot. We consider an algorithm for the self-organization of a controller. At short timescales the controller is merely reactive but the parameter dynamics and the acquisition of knowledge by an internal model lead to seemingly purposeful behavior on longer timescales. As a paradigmatic example, we study the simulation of an underactuated snake-like robot. By interacting with the real physical system formed by the robotic hardware and the environment, the controller achieves a sensitive and body-specific actuation of the robot.

al

link (url) [BibTex]

link (url) [BibTex]


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Magnetism of FePt surface alloys

Honolka, J., Lee, T. Y., Kuhnke, K., Enders, A., Skomski, R., Bornemann, S., Mankovsky, S., Minár, J., Staunton, J., Ebert, H., Hessler, M., Fauth, K., Schütz, G., Buchsbaum, A., Schmid, M., Varga, P., Kern, K.

{Physical Review Letters}, 102(6), 2009 (article)

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DOI [BibTex]

DOI [BibTex]


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Enhanced 95Zr diffusion in grain boundaries of nano-crystalline ZrO2 \mbox⋅ 9.5 mol\textpercent Y2O3

Drings, H., Brossmann, U., Carstanjen, H. D., Szökefalvi-Nagy, A., Noll, C., Schaefer, H.-E.

{Physica Status Solidi (A)}, 206(1):54-58, 2009 (article)

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DOI [BibTex]

DOI [BibTex]


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Magnetism of nanostructured materials for advanced magnetic recording

Goll, D.

{International Journal of Materials Research}, 100, pages: 652-662, 2009 (article)

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DOI [BibTex]

DOI [BibTex]


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Vortex core switching by coherent excitation with single in-plane magnetic field pulses

Weigand, M., van Waeyenberge, B., Vansteenkiste, A., Curcic, M., Sackmann, V., Stoll, H., Tyliszczak, T., Kaznatcheev, K., Bertwistle, D., Woltersdorf, G., Back, C. H., Schütz, G.

{Physical Review Letters}, 102, 2009 (article)

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DOI [BibTex]

DOI [BibTex]


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Increase of Mn solubility with decreasing grain size in ZnO

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

{Journal of the European Ceramic Society}, 29(10):1963-1970, 2009 (article)

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DOI [BibTex]

DOI [BibTex]


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Fe-C nanograined alloys obtained by high-pressure torsion: Structure and magnetic properties

Straumal, B. B., Mazilkin, A. A., Protasova, S. G., Dobatkin, S. V., Rodin, A. O., Baretzky, B., Goll, D., Schütz, G.

{Materials Science and Engineering A}, 503, pages: 185-189, 2009 (article)

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DOI [BibTex]

DOI [BibTex]


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Chiral symmetry breaking of magnetic vortices by sample roughness

Vansteenkiste, A., Weigand, M., Curcic, M., Stoll, H., Schütz, G., Van Waeyenberge, B.

{New Journal of Physics}, 11, 2009 (article)

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DOI [BibTex]

DOI [BibTex]


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Extended s-d model for magnetization dynamics of strongly noncollinear configurations

De Angeli, L., Steiauf, D., Singer, R., Köberle, I., Dietermann, F., Fähnle, M.

{Physical Review B}, 79, 2009 (article)

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DOI [BibTex]

DOI [BibTex]


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Incorporating Muscle Activation-Contraction dynamics to an optimal control framework for finger movements

Theodorou, Evangelos A., Valero-Cuevas, Francisco J.

Abstracts of Neural Control of Movement Conference (NCM 2009), 2009, clmc (article)

Abstract
Recent experimental and theoretical work [1] investigated the neural control of contact transition between motion and force during tapping with the index finger as a nonlinear optimization problem. Such transitions from motion to well-directed contact force are a fundamental part of dexterous manipulation. There are 3 alternative hypotheses of how this transition could be accomplished by the nervous system as a function of changes in direction and magnitude of the torque vector controlling the finger. These hypotheses are 1) an initial change in direction with a subsequent change in magnitude of the torque vector; 2) an initial change in magnitude with a subsequent directional change of the torque vector; and 3) a simultaneous and proportionally equal change of both direction and magnitude of the torque vector. Experimental work in [2] shows that the nervous system selects the first strategy, and in [1] we suggest that this may in fact be the optimal strategy. In [4] the framework of Iterative Linear Quadratic Optimal Regulator (ILQR) was extended to incorporate motion and force control. However, our prior simulation work assumed direct and instantaneous control of joint torques, which ignores the known delays and filtering properties of skeletal muscle. In this study, we implement an ILQR controller for a more biologically plausible biomechanical model of the index finger than [4], and add activation-contraction dynamics to the system to simulate muscle function. The planar biomechanical model includes the kinematics of the 3 joints while the applied torques are driven by activation?contraction dynamics with biologically plausible time constants [3]. In agreement with our experimental work [2], the task is to, within 500 ms, move the finger from a given resting configuration to target configuration with a desired terminal velocity. ILQR does not only stabilize the finger dynamics according to the objective function, but it also generates smooth joint space trajectories with minimal tuning and without an a-priori initial control policy (which is difficult to find for highly dimensional biomechanical systems). Furthemore, the use of this optimal control framework and the addition of activation-contraction dynamics considers the full nonlinear dynamics of the index finger and produces a sequence of postures which are compatible with experimental motion data [2]. These simulations combined with prior experimental results suggest that optimal control is a strong candidate for the generation of finger movements prior to abrupt motion-to-force transitions. This work is funded in part by grants NIH R01 0505520 and NSF EFRI-0836042 to Dr. Francisco J. Valero- Cuevas 1 Venkadesan M, Valero-Cuevas FJ. 
Effects of neuromuscular lags on controlling contact transitions. 
Philosophical Transactions of the Royal Society A: 2008. 2 Venkadesan M, Valero-Cuevas FJ. 
Neural Control of Motion-to-Force Transitions with the Fingertip. 
J. Neurosci., Feb 2008; 28: 1366 - 1373; 3 Zajac. Muscle and tendon: properties, models, scaling, and application to biomechanics and motor control. Crit Rev Biomed Eng, 17 4. Weiwei Li., Francisco Valero Cuevas: ?Linear Quadratic Optimal Control of Contact Transition with Fingertip ? ACC 2009

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PDF [BibTex]

PDF [BibTex]


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On-line learning and modulation of periodic movements with nonlinear dynamical systems

Gams, A., Ijspeert, A., Schaal, S., Lenarčič, J.

Autonomous Robots, 27(1):3-23, 2009, clmc (article)

Abstract
Abstract  The paper presents a two-layered system for (1) learning and encoding a periodic signal without any knowledge on its frequency and waveform, and (2) modulating the learned periodic trajectory in response to external events. The system is used to learn periodic tasks on a humanoid HOAP-2 robot. The first layer of the system is a dynamical system responsible for extracting the fundamental frequency of the input signal, based on adaptive frequency oscillators. The second layer is a dynamical system responsible for learning of the waveform based on a built-in learning algorithm. By combining the two dynamical systems into one system we can rapidly teach new trajectories to robots without any knowledge of the frequency of the demonstration signal. The system extracts and learns only one period of the demonstration signal. Furthermore, the trajectories are robust to perturbations and can be modulated to cope with a dynamic environment. The system is computationally inexpensive, works on-line for any periodic signal, requires no additional signal processing to determine the frequency of the input signal and can be applied in parallel to multiple dimensions. Additionally, it can adapt to changes in frequency and shape, e.g. to non-stationary signals, such as hand-generated signals and human demonstrations.

am

link (url) [BibTex]

link (url) [BibTex]


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Reversible dry micro-fibrillar adhesives with thermally controllable adhesion

Kim, S., Sitti, M., Xie, T., Xiao, X.

Soft Matter, 5(19):3689-3693, Royal Society of Chemistry, 2009 (article)

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Project Page [BibTex]

Project Page [BibTex]


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Enhanced reversible adhesion of dopamine methacrylamide-coated elastomer microfibrillar structures under wet conditions

Glass, P., Chung, H., Washburn, N. R., Sitti, M.

Langmuir, 25(12):6607-6612, ACS Publications, 2009 (article)

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Project Page [BibTex]

Project Page [BibTex]


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Superconducting phase formation in random neck syntheses: a study of the Y-Ba-Cu-O system by magneto-optics and magnetometry

Willems, J. B., Albrecht, J., Landau, I. L., Hulliger, J.

{Superconductor Science and Technology}, 22, 2009 (article)

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DOI [BibTex]

DOI [BibTex]


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Determination of spin moments from magnetic EXAFS

Popescu, V., Gü\ssmann, M., Fähnle, M., Schütz, G.

{Physical Review B}, 79, 2009 (article)

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DOI [BibTex]

DOI [BibTex]


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Linewidth of ferromagnetic resonance for systems with anisotropic damping

Seib, J., Steiauf, D., Fähnle, M.

{Physical Review B}, 79, 2009 (article)

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DOI [BibTex]

DOI [BibTex]


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Structural and magnetic deconvolution of FePt/FeOx-nanoparticles using x-ray magnetic circular dichroism

Nolle, D., Goering, E., Tietze, T., Schütz, G., Figuerola, A., Manna, L.

{New Journal of Physics}, 11, 2009 (article)

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DOI [BibTex]

DOI [BibTex]


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Magnetic imaging with femtosecond temporal resolution

Li, J., Lee, M.-S., He, W., Redeker, B., Remhof, A., Amaladass, E., Hassel, C., Eimüller, T.

{Review of Scientific Instruments}, 80(7), 2009 (article)

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DOI [BibTex]

DOI [BibTex]


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Elliott-Yafet mechanism and the discussion of femtosecond magnetization dynamics

Steiauf, D., Fähnle, M.

{Physical Review B}, 79, 2009 (article)

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DOI [BibTex]

DOI [BibTex]


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Investigation of the stability of Mn12 single molecule magnets

Voss, S., Fonin, M., Burova, L., Burgert, M., Dedkov, Y. S., Preobrajenski, A. B., Goering, E., Groth, U., Kaul, A. R., Ruediger, U.

{Applied Physics A}, 94(3):491-495, 2009 (article)

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DOI [BibTex]

DOI [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]