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2018


Gait learning for soft microrobots controlled by light fields
Gait learning for soft microrobots controlled by light fields

Rohr, A. V., Trimpe, S., Marco, A., Fischer, P., Palagi, S.

In International Conference on Intelligent Robots and Systems (IROS) 2018, pages: 6199-6206, International Conference on Intelligent Robots and Systems 2018, October 2018 (inproceedings)

Abstract
Soft microrobots based on photoresponsive materials and controlled by light fields can generate a variety of different gaits. This inherent flexibility can be exploited to maximize their locomotion performance in a given environment and used to adapt them to changing environments. However, because of the lack of accurate locomotion models, and given the intrinsic variability among microrobots, analytical control design is not possible. Common data-driven approaches, on the other hand, require running prohibitive numbers of experiments and lead to very sample-specific results. Here we propose a probabilistic learning approach for light-controlled soft microrobots based on Bayesian Optimization (BO) and Gaussian Processes (GPs). The proposed approach results in a learning scheme that is highly data-efficient, enabling gait optimization with a limited experimental budget, and robust against differences among microrobot samples. These features are obtained by designing the learning scheme through the comparison of different GP priors and BO settings on a semisynthetic data set. The developed learning scheme is validated in microrobot experiments, resulting in a 115% improvement in a microrobot’s locomotion performance with an experimental budget of only 20 tests. These encouraging results lead the way toward self-adaptive microrobotic systems based on lightcontrolled soft microrobots and probabilistic learning control.

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arXiv IEEE Xplore DOI Project Page [BibTex]

2018


arXiv IEEE Xplore DOI Project Page [BibTex]


Nanoscale robotic agents in biological fluids and tissues
Nanoscale robotic agents in biological fluids and tissues

Palagi, S., Walker, D. Q. T., Fischer, P.

In The Encyclopedia of Medical Robotics, 2, pages: 19-42, 2, (Editors: Desai, J. P. and Ferreira, A.), World Scientific, October 2018 (inbook)

Abstract
Nanorobots are untethered structures of sub-micron size that can be controlled in a non-trivial way. Such nanoscale robotic agents are envisioned to revolutionize medicine by enabling minimally invasive diagnostic and therapeutic procedures. To be useful, nanorobots must be operated in complex biological fluids and tissues, which are often difficult to penetrate. In this chapter, we first discuss potential medical applications of motile nanorobots. We briefly present the challenges related to swimming at such small scales and we survey the rheological properties of some biological fluids and tissues. We then review recent experimental results in the development of nanorobots and in particular their design, fabrication, actuation, and propulsion in complex biological fluids and tissues. Recent work shows that their nanoscale dimension is a clear asset for operation in biological tissues, since many biological tissues consist of networks of macromolecules that prevent the passage of larger micron-scale structures, but contain dynamic pores through which nanorobots can move.

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link (url) DOI [BibTex]

link (url) DOI [BibTex]


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Kernel Recursive ABC: Point Estimation with Intractable Likelihood

Kajihara, T., Kanagawa, M., Yamazaki, K., Fukumizu, K.

Proceedings of the 35th International Conference on Machine Learning, pages: 2405-2414, PMLR, July 2018 (conference)

Abstract
We propose a novel approach to parameter estimation for simulator-based statistical models with intractable likelihood. Our proposed method involves recursive application of kernel ABC and kernel herding to the same observed data. We provide a theoretical explanation regarding why the approach works, showing (for the population setting) that, under a certain assumption, point estimates obtained with this method converge to the true parameter, as recursion proceeds. We have conducted a variety of numerical experiments, including parameter estimation for a real-world pedestrian flow simulator, and show that in most cases our method outperforms existing approaches.

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Paper [BibTex]

Paper [BibTex]


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Counterfactual Mean Embedding: A Kernel Method for Nonparametric Causal Inference

Muandet, K., Kanagawa, M., Saengkyongam, S., Marukata, S.

Workshop on Machine Learning for Causal Inference, Counterfactual Prediction, and Autonomous Action (CausalML) at ICML, July 2018 (conference)

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[BibTex]

[BibTex]


Soft Miniaturized Linear Actuators Wirelessly Powered by Rotating Permanent Magnets
Soft Miniaturized Linear Actuators Wirelessly Powered by Rotating Permanent Magnets

Qiu, T., Palagi, S., Sachs, J., Fischer, P.

In 2018 IEEE International Conference on Robotics and Automation (ICRA), pages: 3595-3600, May 2018 (inproceedings)

Abstract
Wireless actuation by magnetic fields allows for the operation of untethered miniaturized devices, e.g. in biomedical applications. Nevertheless, generating large controlled forces over relatively large distances is challenging. Magnetic torques are easier to generate and control, but they are not always suitable for the tasks at hand. Moreover, strong magnetic fields are required to generate a sufficient torque, which are difficult to achieve with electromagnets. Here, we demonstrate a soft miniaturized actuator that transforms an externally applied magnetic torque into a controlled linear force. We report the design, fabrication and characterization of both the actuator and the magnetic field generator. We show that the magnet assembly, which is based on a set of rotating permanent magnets, can generate strong controlled oscillating fields over a relatively large workspace. The actuator, which is 3D-printed, can lift a load of more than 40 times its weight. Finally, we show that the actuator can be further miniaturized, paving the way towards strong, wirelessly powered microactuators.

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link (url) DOI [BibTex]

link (url) DOI [BibTex]


Dissecting Adam: The Sign, Magnitude and Variance of Stochastic Gradients
Dissecting Adam: The Sign, Magnitude and Variance of Stochastic Gradients

Balles, L., Hennig, P.

In Proceedings of the 35th International Conference on Machine Learning (ICML), 2018 (inproceedings) Accepted

Abstract
The ADAM optimizer is exceedingly popular in the deep learning community. Often it works very well, sometimes it doesn't. Why? We interpret ADAM as a combination of two aspects: for each weight, the update direction is determined by the sign of stochastic gradients, whereas the update magnitude is determined by an estimate of their relative variance. We disentangle these two aspects and analyze them in isolation, gaining insight into the mechanisms underlying ADAM. This analysis also extends recent results on adverse effects of ADAM on generalization, isolating the sign aspect as the problematic one. Transferring the variance adaptation to SGD gives rise to a novel method, completing the practitioner's toolbox for problems where ADAM fails.

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link (url) Project Page [BibTex]

link (url) Project Page [BibTex]

2013


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The Randomized Dependence Coefficient

Lopez-Paz, D., Hennig, P., Schölkopf, B.

In Advances in Neural Information Processing Systems 26, pages: 1-9, (Editors: C.J.C. Burges, L. Bottou, M. Welling, Z. Ghahramani, and K.Q. Weinberger), 27th Annual Conference on Neural Information Processing Systems (NIPS), 2013 (inproceedings)

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PDF [BibTex]

2013


PDF [BibTex]


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Fast Probabilistic Optimization from Noisy Gradients

Hennig, P.

In Proceedings of The 30th International Conference on Machine Learning, JMLR W&CP 28(1), pages: 62–70, (Editors: S Dasgupta and D McAllester), ICML, 2013 (inproceedings)

ei pn

PDF [BibTex]

PDF [BibTex]


Nonparametric dynamics estimation for time periodic systems
Nonparametric dynamics estimation for time periodic systems

Klenske, E., Zeilinger, M., Schölkopf, B., Hennig, P.

In Proceedings of the 51st Annual Allerton Conference on Communication, Control, and Computing, pages: 486-493 , 2013 (inproceedings)

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PDF DOI [BibTex]

PDF DOI [BibTex]


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Analytical probabilistic proton dose calculation and range uncertainties

Bangert, M., Hennig, P., Oelfke, U.

In 17th International Conference on the Use of Computers in Radiation Therapy, pages: 6-11, (Editors: A. Haworth and T. Kron), ICCR, 2013 (inproceedings)

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[BibTex]

[BibTex]


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Dynamics of nanodroplets on structured surfaces

Rauscher, M.

In Nanodroplets, 18, pages: 143-167, Lecture Notes in Nanoscale Science and Technology, Springer, New York, 2013 (incollection)

Abstract
Editors:Zhiming M. Wang

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DOI [BibTex]

DOI [BibTex]


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Wetting Phenomena on the Nanometer Scale

Rauscher, M., Dietrich, S., Napiórkowski, M.

In Nanoscale Liquid Interfaces - Wetting, Patterning and Force Microscopy at the Molecular Scale, pages: 83-154, Pan Stanford Publishing Pte. Ltd., Singapore, 2013 (incollection)

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DOI [BibTex]

DOI [BibTex]

2003


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Diffusion in quasicrystals

Mehrer, H., Galler, R., Frank, W., Blüher, R., Strohm, A.

In Quasicrystals - Structure and Physical Properties, pages: 312-337, Wiley-VCH, Weinheim, 2003 (incollection)

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[BibTex]

2003


[BibTex]

2002


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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]

2002


[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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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]

[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)

icm

[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]