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2008


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Learning to Move in Modular Robots using Central Pattern Generators and Online Optimization

Spröwitz, A., Moeckel, R., Maye, J., Ijspeert, A. J.

The International Journal of Robotics Research, 27(3-4):423-443, 2008 (article)

Abstract
This article addresses the problem of how modular robotics systems, i.e. systems composed of multiple modules that can be configured into different robotic structures, can learn to locomote. In particular, we tackle the problems of online learning, that is, learning while moving, and the problem of dealing with unknown arbitrary robotic structures. We propose a framework for learning locomotion controllers based on two components: a central pattern generator (CPG) and a gradient-free optimization algorithm referred to as Powell's method. The CPG is implemented as a system of coupled nonlinear oscillators in our YaMoR modular robotic system, with one oscillator per module. The nonlinear oscillators are coupled together across modules using Bluetooth communication to obtain specific gaits, i.e. synchronized patterns of oscillations among modules. Online learning involves running the Powell optimization algorithm in parallel with the CPG model, with the speed of locomotion being the criterion to be optimized. Interesting aspects of the optimization include the fact that it is carried out online, the robots do not require stopping or resetting and it is fast. We present results showing the interesting properties of this framework for a modular robotic system. In particular, our CPG model can readily be implemented in a distributed system, it is computationally cheap, it exhibits limit cycle behavior (temporary perturbations are rapidly forgotten), it produces smooth trajectories even when control parameters are abruptly changed and it is robust against imperfect communication among modules. We also present results of learning to move with three different robot structures. Interesting locomotion modes are obtained after running the optimization for less than 60 minutes.

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link (url) DOI [BibTex]

2008


link (url) DOI [BibTex]


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Active tails enhance arboreal acrobatics in geckos

Jusufi, A., Goldman, D., Revzen, S., Full, R.

PNAS, 105(11):4215-4219, 2008 (article)

bio

link (url) [BibTex]

link (url) [BibTex]


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Learning to control in operational space

Peters, J., Schaal, S.

International Journal of Robotics Research, 27, pages: 197-212, 2008, clmc (article)

Abstract
One of the most general frameworks for phrasing control problems for complex, redundant robots is operational space control. However, while this framework is of essential importance for robotics and well-understood from an analytical point of view, it can be prohibitively hard to achieve accurate control in face of modeling errors, which are inevitable in com- plex robots, e.g., humanoid robots. In this paper, we suggest a learning approach for opertional space control as a direct inverse model learning problem. A first important insight for this paper is that a physically cor- rect solution to the inverse problem with redundant degrees-of-freedom does exist when learning of the inverse map is performed in a suitable piecewise linear way. The second crucial component for our work is based on the insight that many operational space controllers can be understood in terms of a constrained optimal control problem. The cost function as- sociated with this optimal control problem allows us to formulate a learn- ing algorithm that automatically synthesizes a globally consistent desired resolution of redundancy while learning the operational space controller. From the machine learning point of view, this learning problem corre- sponds to a reinforcement learning problem that maximizes an immediate reward. We employ an expectation-maximization policy search algorithm in order to solve this problem. Evaluations on a three degrees of freedom robot arm are used to illustrate the suggested approach. The applica- tion to a physically realistic simulator of the anthropomorphic SARCOS Master arm demonstrates feasibility for complex high degree-of-freedom robots. We also show that the proposed method works in the setting of learning resolved motion rate control on real, physical Mitsubishi PA-10 medical robotics arm.

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link (url) DOI [BibTex]

link (url) DOI [BibTex]


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Hierarchical Reactive Control for Humanoid Soccer Robots

Behnke, S., Stueckler, J.

International Journal of Humanoid Robots (IJHR), 5(3):375-396, 2008 (article)

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link (url) [BibTex]

link (url) [BibTex]


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Passive compliant quadruped robot using central pattern generators for locomotion control

Rutishauser, S., Spröwitz, A., Righetti, L., Ijspeert, A. J.

In Proceedings of the 2008 2nd Biennial IEEE/RAS-EMBS International Conference on Biomedical Robotics and Biomechatronics, pages: 710-715, IEEE, Scottsdale, AZ, 2008 (inproceedings)

Abstract
We present a new quadruped robot, “Cheetah”, 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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DOI [BibTex]

DOI [BibTex]


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Graph signature for self-reconfiguration planning

Asadpour, M., Spröwitz, A., Billard, A., Dillenbourg, P., Ijspeert, A. J.

In Proceedings of the 2008 IEEE/RSJ International Conference on Intelligent Robots and Systems, pages: 863-869, IEEE, Nice, 2008 (inproceedings)

Abstract
This project incorporates modular robots as build- ing blocks for furniture that moves and self-reconfigures. The reconfiguration is done using dynamic connection / disconnection of modules and rotations of the degrees of freedom. This paper introduces a new approach to self-reconfiguration planning for modular robots based on the graph signature and the graph edit-distance. The method has been tested in simulation on two type of modules: YaMoR and M-TRAN. The simulation results shows interesting features of the approach, namely rapidly finding a near-optimal solution.

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DOI [BibTex]

DOI [BibTex]


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Voltage-Controllable Magnetic Composite Based on Multifunctional Polyethylene Microparticles

Ghosh, A., Sheridon, N. K., Fischer, P.

SMALL, 4(11):1956-1958, 2008 (article)

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DOI [BibTex]


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An active connection mechanism for modular self-reconfigurable robotic systems based on physical latching

Spröwitz, A., Asadpour, M., Bourquin, Y., Ijspeert, A. J.

In Proceedings on the 2008 IEEE International Conference on Robotics and Automation (ICRA), 2008, pages: 3508-3513, IEEE, Pasadena, CA, 2008 (inproceedings)

Abstract
This article presents a robust and heavy duty physical latching connection mechanism, which can be actuated with DC motors to actively connect and disconnect modular robot units. The special requirements include a lightweight and simple construction providing an active, strong, hermaphrodite, completely retractable connection mechanism with a 90 degree symmetry and a no-energy consumption in the locked state. The mechanism volume is kept small to fit multiple copies into a single modular robot unit and to be used on as many faces of the robot unit as possible. This way several different lattice like modular robot structures are possible. The large selection for dock-able connection positions will likely simplify self-reconfiguration strategies. Tests with the implemented mechanism demonstrate its applicative potential for self-reconfiguring modular robots.

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DOI [BibTex]

DOI [BibTex]


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Neural control of computer cursor velocity by decoding motor cortical spiking activity in humans with tetraplegia

(J. Neural Engineering Highlights of 2008 Collection)

Kim, S., Simeral, J., Hochberg, L., Donoghue, J. P., Black, M. J.

J. Neural Engineering, 5, pages: 455–476, 2008 (article)

Abstract
Computer-mediated connections between human motor cortical neurons and assistive devices promise to improve or restore lost function in people with paralysis. Recently, a pilot clinical study of an intracortical neural interface system demonstrated that a tetraplegic human was able to obtain continuous two-dimensional control of a computer cursor using neural activity recorded from his motor cortex. This control, however, was not sufficiently accurate for reliable use in many common computer control tasks. Here, we studied several central design choices for such a system including the kinematic representation for cursor movement, the decoding method that translates neuronal ensemble spiking activity into a control signal and the cursor control task used during training for optimizing the parameters of the decoding method. In two tetraplegic participants, we found that controlling a cursor’s velocity resulted in more accurate closed-loop control than controlling its position directly and that cursor velocity control was achieved more rapidly than position control. Control quality was further improved over conventional linear filters by using a probabilistic method, the Kalman filter, to decode human motor cortical activity. Performance assessment based on standard metrics used for the evaluation of a wide range of pointing devices demonstrated significantly improved cursor control with velocity rather than position decoding.

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pdf preprint pdf from publisher [BibTex]

pdf preprint pdf from publisher [BibTex]


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ENHANCED ADHESION OF PDMS SURFACES FUNCTIONALIZED BY POLY (n-BUTYL ACRYLATE) BRUSHES INSPIRED BY GECKO FOOT HAIRS

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

Polymer Preprints, 49(2):107, 2008 (article)

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[BibTex]

[BibTex]


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Design and development of the lifting and propulsion mechanism for a biologically inspired water runner robot

Floyd, S., Sitti, M.

IEEE transactions on robotics, 24(3):698-709, IEEE, 2008 (article)

pi

[BibTex]

[BibTex]


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Control of Cell Behavior by Aligned Micro/Nanofibrous Biomaterial Scaffolds Fabricated by Spinneret-Based Tunable Engineered Parameters (STEP) Technique

Nain, A. S., Phillippi, J. A., Sitti, M., MacKrell, J., Campbell, P. G., Amon, C.

Small, 4(8):1153-1159, Wiley Online Library, 2008 (article)

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[BibTex]

[BibTex]


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Simulation and analysis of a passive pitch reversal flapping wing mechanism for an aerial robotic platform

Arabagi, V., Sitti, M.

In Intelligent Robots and Systems, 2008. IROS 2008. IEEE/RSJ International Conference on, pages: 1260-1265, 2008 (inproceedings)

pi

Project Page [BibTex]

Project Page [BibTex]


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Adaptation to a sub-optimal desired trajectory

M. Mistry, E. A. G. L. T. Y. S. S. M. K.

Advances in Computational Motor Control VII, Symposium at the Society for Neuroscience Meeting, Washington DC, 2008, 2008, clmc (article)

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PDF [BibTex]

PDF [BibTex]


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Human movement generation based on convergent flow fields: A computational model and a behavioral experiment

Hoffmann, H., Schaal, S.

In Advances in Computational Motor Control VII, Symposium at the Society for Neuroscience Meeting, Washington DC, 2008, 2008, clmc (inproceedings)

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link (url) [BibTex]

link (url) [BibTex]


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Brownian Warps for Non-Rigid Registration

Mads Nielsen, Peter Johansen, Andrew Jackson, Benny Lautrup, Soren Hauberg

Journal of Mathematical Imaging and Vision, 31, pages: 221-231, Springer Netherlands, 2008 (article)

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Publishers site PDF [BibTex]

Publishers site PDF [BibTex]


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Simultaneous Visual Recognition of Manipulation Actions and Manipulated Objects

Kjellström, H., Romero, J., Martinez, D., Kragic, D.

In European Conference on Computer Vision, ECCV, pages: 336-349, 2008 (inproceedings)

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Pdf [BibTex]

Pdf [BibTex]


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Tuning analysis of motor cortical neurons in a person with paralysis during performance of visually instructed cursor control tasks

Kim, S., Simeral, J. D., Hochberg, L. R., Truccolo, W., Donoghue, J., Friehs, G. M., Black, M. J.

2008 Abstract Viewer and Itinerary Planner, Society for Neuroscience, Washington, DC, 2008, Online (conference)

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[BibTex]

[BibTex]


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Texture, microstructure and mechanical properties of equiaxed ultrafine-grained Zr fabricated by accumulative roll bonding

Jiang, L., Perez-Prado, M. T., Gruber, P. A., Arzt, E., Ruano, O. A., Kassner, M. E.

{Acta Materialia}, 56(6):1228-1242, 2008 (article)

mms

[BibTex]

[BibTex]


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Theory of size mismatched alloy systems: many-body Kanzaki forces

Shchyglo, O., Diaz-Ortiz, A., Udyansky, A., Bugaev, V. N., Reichert, H., Dosch, H., Drautz, R.

{Journal of Physics: Condensed Matter}, 20, pages: 1-9, 2008 (article)

mms

[BibTex]

[BibTex]


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Pinning of domain walls in composite particles

Kronmüller, H., Goll, D.

{Physica B}, 403, pages: 237-241, 2008 (article)

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DOI [BibTex]

DOI [BibTex]


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Chaotic vortex dynamics and low current phases in the remanent state of MgB2 thin films

Albrecht, J., Audehm, P., Djupmyr, M.

{Superconductor Science and Technology}, 21, 2008 (article)

mms

DOI [BibTex]

DOI [BibTex]


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Continuous and discontinuous grain-boundary wetting in ZnxAl1-x

Straumal, B. B., Gornakova, A. S., Kogtenkova, O. A., Protasova, S. G., Sursaeva, V. G., Baretzky, B.

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

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DOI [BibTex]

DOI [BibTex]


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Magnetic circular dichroism in two-photon absorption and depth-resolved magnetic microscopy

Seib, J., Fähnle, M.

{Physical Review B}, 77, 2008 (article)

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DOI [BibTex]

DOI [BibTex]


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Heat of adsorption for hydrogen in microporous high-surface-area materials

Schmitz, B., Müller, U., Trukhan, N., Schubert, M., Férey, G., Hirscher, M.

{ChemPhysChem}, 9, 2008 (article)

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DOI [BibTex]

DOI [BibTex]


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Untersuchungen der Desorption von Wasserstoff in metall-organischen Gerüsten

Panella, B., Hönes, K., Müller, U., Trukhan, N., Schubert, M., Pütter, H., Hirscher, M.

{Angewandte Chemie}, 120, pages: 2169-2173, 2008 (article)

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DOI [BibTex]

DOI [BibTex]


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Influence of domain wall pinning on the dynamic behavior of magnetic vortex structures: Time-resolved scanning x-ray transmission microscopy in NiFe thin film structures

Vansteenkiste, A., De Baerdemaeker, J., Chou, K. W., Stoll, H., Curcic, M., Tyliszczak, T., Woltersdorf, G., Back, C. H., Schütz, G., Van Waeyenberge, B.

{Physical Review B}, 77, 2008 (article)

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DOI [BibTex]

DOI [BibTex]


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Temperature dependence of mechanical properties in ultrathin Au films with and without passivation

Gruber, P. A., Olliges, S., Arzt, E., Spolenak, R.

{Journal of Materials Research}, 23(9):2406-2419, 2008 (article)

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DOI [BibTex]

DOI [BibTex]


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Structure, phase composition, and microhardness of carbon steels after high-pressure torsion

Mazilkin, A. A., Straumal, B., Protasova, S. G., Dobatkin, S. V., Baretzky, B.

{Journal of Materials Science}, 43, pages: 3800-3805, 2008 (article)

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DOI [BibTex]

DOI [BibTex]


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Pattern generators with sensory feedback for the control of quadruped locomotion

Righetti, L., Ijspeert, A.

In 2008 IEEE International Conference on Robotics and Automation, pages: 819-824, IEEE, Pasadena, USA, 2008 (inproceedings)

Abstract
Central pattern generators (CPGs) are becoming a popular model for the control of locomotion of legged robots. Biological CPGs are neural networks responsible for the generation of rhythmic movements, especially locomotion. In robotics, a systematic way of designing such CPGs as artificial neural networks or systems of coupled oscillators with sensory feedback inclusion is still missing. In this contribution, we present a way of designing CPGs with coupled oscillators in which we can independently control the ascending and descending phases of the oscillations (i.e. the swing and stance phases of the limbs). Using insights from dynamical system theory, we construct generic networks of oscillators able to generate several gaits under simple parameter changes. Then we introduce a systematic way of adding sensory feedback from touch sensors in the CPG such that the controller is strongly coupled with the mechanical system it controls. Finally we control three different simulated robots (iCub, Aibo and Ghostdog) using the same controller to show the effectiveness of the approach. Our simulations prove the importance of independent control of swing and stance duration. The strong mutual coupling between the CPG and the robot allows for more robust locomotion, even under non precise parameters and non-flat environment.

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link (url) DOI [BibTex]

link (url) DOI [BibTex]


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Experimental Study of Limit Cycle and Chaotic Controllers for the Locomotion of Centipede Robots

Matthey, L., Righetti, L., Ijspeert, A.

In 2008 IEEE/RSJ International Conference on Intelligent Robots and Systems, pages: 1860-1865, IEEE, Nice, France, sep 2008 (inproceedings)

Abstract
In this contribution we present a CPG (central pattern generator) controller based on coupled Rossler systems. It is able to generate both limit cycle and chaotic behaviors through bifurcation. We develop an experimental test bench to measure quantitatively the performance of different controllers on unknown terrains of increasing difficulty. First, we show that for flat terrains, open loop limit cycle systems are the most efficient (in terms of speed of locomotion) but that they are quite sensitive to environmental changes. Second, we show that sensory feedback is a crucial addition for unknown terrains. Third, we show that the chaotic controller with sensory feedback outperforms the other controllers in very difficult terrains and actually promotes the emergence of short synchronized movement patterns. All that is done using an unified framework for the generation of limit cycle and chaotic behaviors, where a simple parameter change can switch from one behavior to the other through bifurcation. Such flexibility would allow the automatic adaptation of the robot locomotion strategy to the terrain uncertainty.

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link (url) DOI [BibTex]

link (url) DOI [BibTex]


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Rolling and spinning friction characterization of fine particles using lateral force microscopy based contact pushing

Sümer, B., Sitti, M.

Journal of Adhesion Science and Technology, 22(5-6):481-506, Taylor & Francis Group, 2008 (article)

pi

[BibTex]

[BibTex]


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Fabrication and Characterization of Biologically Inspired Mushroom-Shaped Elastomer Microfiber Arrays

Kim, S., Sitti, M.

In ASME 2008 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, pages: 839-847, 2008 (inproceedings)

pi

Project Page [BibTex]

Project Page [BibTex]


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Gecko inspired micro-fibrillar adhesives for wall climbing robots on micro/nanoscale rough surfaces

Aksak, B., Murphy, M. P., Sitti, M.

In Robotics and Automation, 2008. ICRA 2008. IEEE International Conference on, pages: 3058-3063, 2008 (inproceedings)

pi

Project Page [BibTex]

Project Page [BibTex]


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Modeling the soft backing layer thickness effect on adhesion of elastic microfiber arrays

Long, R., Hui, C., Kim, S., Sitti, M.

Journal of Applied Physics, 104(4):044301, AIP, 2008 (article)

pi

Project Page [BibTex]

Project Page [BibTex]


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Cross-talk compensation in atomic force microscopy

Onal, C. D., Sümer, B., Sitti, M.

Review of scientific instruments, 79(10):103706, AIP, 2008 (article)

pi

[BibTex]

[BibTex]


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Miniature Mobile Robots Down to Micron Scale

Sitti, M.

In Micro-NanoMechatronics and Human Science, 2008. MHS 2008. International Symposium on, pages: 525-525, 2008 (inproceedings)

pi

[BibTex]

[BibTex]


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Operational space control: A theoretical and emprical comparison

Nakanishi, J., Cory, R., Mistry, M., Peters, J., Schaal, S.

International Journal of Robotics Research, 27(6):737-757, 2008, clmc (article)

Abstract
Dexterous manipulation with a highly redundant movement system is one of the hallmarks of hu- man motor skills. From numerous behavioral studies, there is strong evidence that humans employ compliant task space control, i.e., they focus control only on task variables while keeping redundant degrees-of-freedom as compliant as possible. This strategy is robust towards unknown disturbances and simultaneously safe for the operator and the environment. The theory of operational space con- trol in robotics aims to achieve similar performance properties. However, despite various compelling theoretical lines of research, advanced operational space control is hardly found in actual robotics imple- mentations, in particular new kinds of robots like humanoids and service robots, which would strongly profit from compliant dexterous manipulation. To analyze the pros and cons of different approaches to operational space control, this paper focuses on a theoretical and empirical evaluation of different methods that have been suggested in the literature, but also some new variants of operational space controllers. We address formulations at the velocity, acceleration and force levels. First, we formulate all controllers in a common notational framework, including quaternion-based orientation control, and discuss some of their theoretical properties. Second, we present experimental comparisons of these approaches on a seven-degree-of-freedom anthropomorphic robot arm with several benchmark tasks. As an aside, we also introduce a novel parameter estimation algorithm for rigid body dynamics, which ensures physical consistency, as this issue was crucial for our successful robot implementations. Our extensive empirical results demonstrate that one of the simplified acceleration-based approaches can be advantageous in terms of task performance, ease of parameter tuning, and general robustness and compliance in face of inevitable modeling errors.

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link (url) [BibTex]

link (url) [BibTex]


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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)

am

PDF [BibTex]

PDF [BibTex]


Thumb xl screen shot 2012 06 06 at 11.28.04 am
Infinite Kernel Learning

Gehler, P., Nowozin, S.

In Proceedings of NIPS 2008 Workshop on "Kernel Learning: Automatic Selection of Optimal Kernels", 2008 (inproceedings)

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project page pdf [BibTex]

project page pdf [BibTex]


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An Efficient Algorithm for Modelling Duration in Hidden Markov Models, with a Dramatic Application

Soren Hauberg, Jakob Sloth

Journal of Mathematical Imaging and Vision, 31, pages: 165-170, Springer Netherlands, 2008 (article)

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Publishers site Paper site PDF [BibTex]

Publishers site Paper site PDF [BibTex]


Thumb xl thumb screen shot 2012 10 06 at 12.29.08 pm
Visual Recognition of Grasps for Human-to-Robot Mapping

Kjellström, H., Romero, J., Kragic, D.

In IEEE/RSJ International Conference on Intelligent Robots and Systems, IROS, pages: 3192-3199, 2008 (inproceedings)

ps

Pdf [BibTex]

Pdf [BibTex]


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More than two years of intracortically-based cursor control via a neural interface system

Hochberg, L. R., Simeral, J. D., Kim, S., Stein, J., Friehs, G. M., Black, M. J., Donoghue, J. P.

2008 Abstract Viewer and Itinerary Planner, Society for Neuroscience, Washington, DC, 2008, Online (conference)

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[BibTex]

[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)

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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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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)

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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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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]