Header logo is


2011


Loose-limbed People: Estimating {3D} Human Pose and Motion Using Non-parametric Belief Propagation
Loose-limbed People: Estimating 3D Human Pose and Motion Using Non-parametric Belief Propagation

Sigal, L., Isard, M., Haussecker, H., Black, M. J.

International Journal of Computer Vision, 98(1):15-48, Springer Netherlands, May 2011 (article)

Abstract
We formulate the problem of 3D human pose estimation and tracking as one of inference in a graphical model. Unlike traditional kinematic tree representations, our model of the body is a collection of loosely-connected body-parts. In particular, we model the body using an undirected graphical model in which nodes correspond to parts and edges to kinematic, penetration, and temporal constraints imposed by the joints and the world. These constraints are encoded using pair-wise statistical distributions, that are learned from motion-capture training data. Human pose and motion estimation is formulated as inference in this graphical model and is solved using Particle Message Passing (PaMPas). PaMPas is a form of non-parametric belief propagation that uses a variation of particle filtering that can be applied over a general graphical model with loops. The loose-limbed model and decentralized graph structure allow us to incorporate information from "bottom-up" visual cues, such as limb and head detectors, into the inference process. These detectors enable automatic initialization and aid recovery from transient tracking failures. We illustrate the method by automatically tracking people in multi-view imagery using a set of calibrated cameras and present quantitative evaluation using the HumanEva dataset.

ps

pdf publisher's site link (url) Project Page Project Page [BibTex]

2011


pdf publisher's site link (url) Project Page Project Page [BibTex]


Point-and-Click Cursor Control With an Intracortical Neural Interface System by Humans With Tetraplegia
Point-and-Click Cursor Control With an Intracortical Neural Interface System by Humans With Tetraplegia

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

IEEE Transactions on Neural Systems and Rehabilitation Engineering, 19(2):193-203, April 2011 (article)

Abstract
We present a point-and-click intracortical neural interface system (NIS) that enables humans with tetraplegia to volitionally move a 2D computer cursor in any desired direction on a computer screen, hold it still and click on the area of interest. This direct brain-computer interface extracts both discrete (click) and continuous (cursor velocity) signals from a single small population of neurons in human motor cortex. A key component of this system is a multi-state probabilistic decoding algorithm that simultaneously decodes neural spiking activity and outputs either a click signal or the velocity of the cursor. The algorithm combines a linear classifier, which determines whether the user is intending to click or move the cursor, with a Kalman filter that translates the neural population activity into cursor velocity. We present a paradigm for training the multi-state decoding algorithm using neural activity observed during imagined actions. Two human participants with tetraplegia (paralysis of the four limbs) performed a closed-loop radial target acquisition task using the point-and-click NIS over multiple sessions. We quantified point-and-click performance using various human-computer interaction measurements for pointing devices. We found that participants were able to control the cursor motion accurately and click on specified targets with a small error rate (< 3% in one participant). This study suggests that signals from a small ensemble of motor cortical neurons (~40) can be used for natural point-and-click 2D cursor control of a personal computer.

ps

pdf publishers's site pub med link (url) Project Page [BibTex]

pdf publishers's site pub med link (url) Project Page [BibTex]


A Database and Evaluation Methodology for Optical Flow
A Database and Evaluation Methodology for Optical Flow

Baker, S., Scharstein, D., Lewis, J. P., Roth, S., Black, M. J., Szeliski, R.

International Journal of Computer Vision, 92(1):1-31, March 2011 (article)

Abstract
The quantitative evaluation of optical flow algorithms by Barron et al. (1994) led to significant advances in performance. The challenges for optical flow algorithms today go beyond the datasets and evaluation methods proposed in that paper. Instead, they center on problems associated with complex natural scenes, including nonrigid motion, real sensor noise, and motion discontinuities. We propose a new set of benchmarks and evaluation methods for the next generation of optical flow algorithms. To that end, we contribute four types of data to test different aspects of optical flow algorithms: (1) sequences with nonrigid motion where the ground-truth flow is determined by tracking hidden fluorescent texture, (2) realistic synthetic sequences, (3) high frame-rate video used to study interpolation error, and (4) modified stereo sequences of static scenes. In addition to the average angular error used by Barron et al., we compute the absolute flow endpoint error, measures for frame interpolation error, improved statistics, and results at motion discontinuities and in textureless regions. In October 2007, we published the performance of several well-known methods on a preliminary version of our data to establish the current state of the art. We also made the data freely available on the web at http://vision.middlebury.edu/flow/ . Subsequently a number of researchers have uploaded their results to our website and published papers using the data. A significant improvement in performance has already been achieved. In this paper we analyze the results obtained to date and draw a large number of conclusions from them.

ps

pdf pdf from publisher Middlebury Flow Evaluation Website [BibTex]

pdf pdf from publisher Middlebury Flow Evaluation Website [BibTex]


no image
Design and application of a wire-driven bidirectional telescopic mechanism for workspace expansion with a focus on shipbuilding tasks

Lee, D., Chang, D., Shin, Y., Son, D., Kim, T., Lee, K., Kim, J.

Advanced Robotics, 25, 2011 (article)

pi

[BibTex]

[BibTex]


no image
Waalbot II: Adhesion recovery and improved performance of a climbing robot using fibrillar adhesives

Murphy, M. P., Kute, C., Mengüç, Y., Sitti, M.

The International Journal of Robotics Research, 30(1):118-133, SAGE Publications Sage UK: London, England, 2011 (article)

pi

Project Page [BibTex]

Project Page [BibTex]


no image
Automated 2-D nanoparticle manipulation using atomic force microscopy

Onal, C. D., Ozcan, O., Sitti, M.

IEEE Transactions on Nanotechnology, 10(3):472-481, IEEE, 2011 (article)

pi

[BibTex]

[BibTex]


no image
Biaxial mechanical modeling of the small intestine

Bellini, C., Glass, P., Sitti, M., Di Martino, E. S.

Journal of the mechanical behavior of biomedical materials, 4(8):1727-1740, Elsevier, 2011 (article)

pi

Project Page [BibTex]

Project Page [BibTex]


Neural control of cursor trajectory and click by a human with tetraplegia 1000 days after implant of an intracortical microelectrode array
Neural control of cursor trajectory and click by a human with tetraplegia 1000 days after implant of an intracortical microelectrode array

(J. Neural Engineering Highlights of 2011 Collection. JNE top 10 cited papers of 2010-2011.)

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

J. of Neural Engineering, 8(2):025027, 2011 (article)

Abstract
The ongoing pilot clinical trial of the BrainGate neural interface system aims in part to assess the feasibility of using neural activity obtained from a small-scale, chronically implanted, intracortical microelectrode array to provide control signals for a neural prosthesis system. Critical questions include how long implanted microelectrodes will record useful neural signals, how reliably those signals can be acquired and decoded, and how effectively they can be used to control various assistive technologies such as computers and robotic assistive devices, or to enable functional electrical stimulation of paralyzed muscles. Here we examined these questions by assessing neural cursor control and BrainGate system characteristics on five consecutive days 1000 days after implant of a 4 × 4 mm array of 100 microelectrodes in the motor cortex of a human with longstanding tetraplegia subsequent to a brainstem stroke. On each of five prospectively-selected days we performed time-amplitude sorting of neuronal spiking activity, trained a population-based Kalman velocity decoding filter combined with a linear discriminant click state classifier, and then assessed closed-loop point-and-click cursor control. The participant performed both an eight-target center-out task and a random target Fitts metric task which was adapted from a human-computer interaction ISO standard used to quantify performance of computer input devices. The neural interface system was further characterized by daily measurement of electrode impedances, unit waveforms and local field potentials. Across the five days, spiking signals were obtained from 41 of 96 electrodes and were successfully decoded to provide neural cursor point-and-click control with a mean task performance of 91.3% ± 0.1% (mean ± s.d.) correct target acquisition. Results across five consecutive days demonstrate that a neural interface system based on an intracortical microelectrode array can provide repeatable, accurate point-and-click control of a computer interface to an individual with tetraplegia 1000 days after implantation of this sensor.

ps

pdf pdf from publisher link (url) Project Page [BibTex]


no image
Assembly and disassembly of magnetic mobile micro-robots towards deterministic 2-D reconfigurable micro-systems

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

The International Journal of Robotics Research, 30(14):1667-1680, SAGE Publications Sage UK: London, England, 2011 (article)

pi

[BibTex]

[BibTex]


no image
Toward simple control for complex, autonomous robotic applications: combining discrete and rhythmic motor primitives

Degallier, S., Righetti, L., Gay, S., Ijspeert, A.

Autonomous Robots, 31(2-3):155-181, October 2011 (article)

Abstract
Vertebrates are able to quickly adapt to new environments in a very robust, seemingly effortless way. To explain both this adaptivity and robustness, a very promising perspective in neurosciences is the modular approach to movement generation: Movements results from combinations of a finite set of stable motor primitives organized at the spinal level. In this article we apply this concept of modular generation of movements to the control of robots with a high number of degrees of freedom, an issue that is challenging notably because planning complex, multidimensional trajectories in time-varying environments is a laborious and costly process. We thus propose to decrease the complexity of the planning phase through the use of a combination of discrete and rhythmic motor primitives, leading to the decoupling of the planning phase (i.e. the choice of behavior) and the actual trajectory generation. Such implementation eases the control of, and the switch between, different behaviors by reducing the dimensionality of the high-level commands. Moreover, since the motor primitives are generated by dynamical systems, the trajectories can be smoothly modulated, either by high-level commands to change the current behavior or by sensory feedback information to adapt to environmental constraints. In order to show the generality of our approach, we apply the framework to interactive drumming and infant crawling in a humanoid robot. These experiments illustrate the simplicity of the control architecture in terms of planning, the integration of different types of feedback (vision and contact) and the capacity of autonomously switching between different behaviors (crawling and simple reaching).

mg

link (url) DOI [BibTex]

link (url) DOI [BibTex]


no image
Modeling of stochastic motion of bacteria propelled spherical microbeads

Arabagi, V., Behkam, B., Cheung, E., Sitti, M.

Journal of Applied Physics, 109(11):114702, AIP, 2011 (article)

pi

Project Page [BibTex]

Project Page [BibTex]


no image
The effect of aspect ratio on adhesion and stiffness for soft elastic fibres

Aksak, B., Hui, C., Sitti, M.

Journal of The Royal Society Interface, 8(61):1166-1175, The Royal Society, 2011 (article)

pi

Project Page [BibTex]

Project Page [BibTex]


no image
Enhancing adhesion of biologically inspired polymer microfibers with a viscous oil coating

Cheung, E., Sitti, M.

The Journal of Adhesion, 87(6):547-557, Taylor & Francis Group, 2011 (article)

pi

Project Page [BibTex]

Project Page [BibTex]


no image
Piezoelectric polymer fiber arrays for tactile sensing applications

Sümer, B., Aksak, B., Şsahin, K., Chuengsatiansup, K., Sitti, M.

Sensor Letters, 9(2):457-463, American Scientific Publishers, 2011 (article)

pi

Project Page [BibTex]

Project Page [BibTex]


no image
Control methodologies for a heterogeneous group of untethered magnetic micro-robots

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

The International Journal of Robotics Research, 30(13):1553-1565, SAGE Publications, 2011 (article)

pi

[BibTex]

[BibTex]

2008


no image
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)

pi

[BibTex]

2008


[BibTex]


no image
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]


no image
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)

pi

[BibTex]

[BibTex]


no image
Biologically Inspired Polymer Micro-Patterned Adhesives

Cheung, E., Sitti, M.

EDGEWOOD CHEMICAL BIOLOGICAL CENTER ABERDEEN PROVING GROUND MD, 2008 (techreport)

pi

[BibTex]

[BibTex]


no image
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]


no image
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]


no image
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]


no image
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]


no image
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]


no image
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]


no image
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]


no image
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]


no image
Dynamic modeling of stick slip motion in an untethered magnetic microrobot

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

Proceedings of Robotics: Science and Systems IV, Zurich, Switzerland, 2008 (article)

pi

[BibTex]

[BibTex]


no image
Frequency analysis with coupled nonlinear oscillators

Buchli, J., Righetti, L., Ijspeert, A.

Physica D: Nonlinear Phenomena, 237(13):1705-1718, August 2008 (article)

Abstract
We present a method to obtain the frequency spectrum of a signal with a nonlinear dynamical system. The dynamical system is composed of a pool of adaptive frequency oscillators with negative mean-field coupling. For the frequency analysis, the synchronization and adaptation properties of the component oscillators are exploited. The frequency spectrum of the signal is reflected in the statistics of the intrinsic frequencies of the oscillators. The frequency analysis is completely embedded in the dynamics of the system. Thus, no pre-processing or additional parameters, such as time windows, are needed. Representative results of the numerical integration of the system are presented. It is shown, that the oscillators tune to the correct frequencies for both discrete and continuous spectra. Due to its dynamic nature the system is also capable to track non-stationary spectra. Further, we show that the system can be modeled in a probabilistic manner by means of a nonlinear Fokker–Planck equation. The probabilistic treatment is in good agreement with the numerical results, and provides a useful tool to understand the underlying mechanisms leading to convergence.

mg

link (url) DOI [BibTex]

link (url) DOI [BibTex]

2007


no image
Bacterial flagella-based propulsion and on/off motion control of microscale objects

Behkam, B., Sitti, M.

Applied Physics Letters, 90(2):023902, AIP, 2007 (article)

pi

[BibTex]

2007


[BibTex]


no image
Friction of partially embedded vertically aligned carbon nanofibers inside elastomers

Aksak, B., Sitti, M., Cassell, A., Li, J., Meyyappan, M., Callen, P.

Applied Physics Letters, 91(6):061906, AIP, 2007 (article)

pi

[BibTex]

[BibTex]


no image
Enhanced friction of elastomer microfiber adhesives with spatulate tips

Kim, S., Aksak, B., Sitti, M.

Applied Physics Letters, 91(22):221913, AIP, 2007 (article)

pi

Project Page [BibTex]

Project Page [BibTex]


no image
Microscale and nanoscale robotics systems [grand challenges of robotics]

Sitti, M.

IEEE Robotics \& Automation Magazine, 14(1):53-60, IEEE, 2007 (article)

pi

[BibTex]

[BibTex]


no image
A new biomimetic adhesive for therapeutic capsule endoscope applications in the gastrointestinal tract

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

Gastrointestinal Endoscopy, 65(5):AB91, Mosby, 2007 (article)

pi

[BibTex]

[BibTex]


no image
Visual servoing-based autonomous 2-D manipulation of microparticles using a nanoprobe

Onal, C. D., Sitti, M.

IEEE Transactions on control systems technology, 15(5):842-852, IEEE, 2007 (article)

pi

[BibTex]

[BibTex]


no image
Adhesion of biologically inspired vertical and angled polymer microfiber arrays

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

Langmuir, 23(6):3322-3332, ACS Publications, 2007 (article)

pi

Project Page [BibTex]

Project Page [BibTex]


no image
Waalbot: An agile small-scale wall-climbing robot utilizing dry elastomer adhesives

Murphy, M. P., Sitti, M.

IEEE/ASME transactions on Mechatronics, 12(3):330-338, IEEE, 2007 (article)

pi

[BibTex]

[BibTex]


no image
iCub - The Design and Realization of an Open Humanoid Platform for Cognitive and Neuroscience Research

Tsagarakis, N., Metta, G., Sandini, G., Vernon, D., Beira, R., Becchi, F., Righetti, L., Santos-Victor, J., Ijspeert, A., Carrozza, M., Caldwell, D.

Advanced Robotics, 21(10):1151-1175, 2007 (article)

Abstract
The development of robotic cognition and the advancement of understanding of human cognition form two of the current greatest challenges in robotics and neuroscience, respectively. The RobotCub project aims to develop an embodied robotic child (iCub) with the physical (height 90 cm and mass less than 23 kg) and ultimately cognitive abilities of a 2.5-year-old human child. The iCub will be a freely available open system which can be used by scientists in all cognate disciplines from developmental psychology to epigenetic robotics to enhance understanding of cognitive systems through the study of cognitive development. The iCub will be open both in software, but more importantly in all aspects of the hardware and mechanical design. In this paper the design of the mechanisms and structures forming the basic 'body' of the iCub are described. The papers considers kinematic structures dynamic design criteria, actuator specification and selection, and detailed mechanical and electronic design. The paper concludes with tests of the performance of sample joints, and comparison of these results with the design requirements and simulation projects.

mg

link (url) DOI [BibTex]

link (url) DOI [BibTex]


no image
Subfeature patterning of organic and inorganic materials using robotic assembly

Tafazzoli, A., Cheng, C., Pawashe, C., Sabo, E. K., Trofin, L., Sitti, M., LeDuc, P. R.

Journal of materials research, 22(06):1601-1608, Cambridge University Press, 2007 (article)

pi

[BibTex]

[BibTex]


no image
Effect of backing layer thickness on adhesion of single-level elastomer fiber arrays

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

Applied Physics Letters, 91(16):161905, AIP, 2007 (article)

pi

[BibTex]

[BibTex]


no image
Adhesion and anisotropic friction enhancements of angled heterogeneous micro-fiber arrays with spherical and spatula tips

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

Journal of Adhesion Science and Technology, 21(12-13):1281-1296, Taylor & Francis Group, 2007 (article)

pi

Project Page [BibTex]

Project Page [BibTex]


no image
Surface-tension-driven biologically inspired water strider robots: Theory and experiments

Song, Y. S., Sitti, M.

IEEE Transactions on robotics, 23(3):578-589, IEEE, 2007 (article)

pi

[BibTex]

[BibTex]

2004


no image
E. Coli Inspired Propulsion for Swimming Microrobots

Behkam, Bahareh, Sitti, Metin

pages: 1037–1041, 2004 (article)

Abstract
Medical applications are among the most fascinating areas of microrobotics. For long, scientists have dreamed of miniature smart devices that can travel inside the human body and carry out a host of complex operations such as minimally invasive surgery (MIS), highly localized drug delivery, and screening for diseases that are in their very early stages. Still a distant dream, significant progress in micro and nanotechnology brings us closer to materializing it. For such a miniature device to be injected into the body, it has to be 800 μm or smaller in diameter. Miniature, safe and energy efficient propulsion systems hold the key to maturing this technology but they pose significant challenges. Scaling the macroscale natation mechanisms to micro/nano length scales is unfeasible. It has been estimated that a vibrating-fin driven swimming robot shorter than 6 mm can not overcome the viscous drag forces in water. In this paper, the authors propose a new type of propulsion inspired by the motility mechanism of bacteria with peritrichous flagellation, such as Escherichia coli, Salmonella typhimurium and Serratia marcescens. The perfomance of the propulsive mechanism is estimated by modeling the dynamics of the motion. The motion of the moving organelle is simulated and key parameters such as velocity, distribution of force and power requirments for different configurations of the tail are determined theoretically. In order to validate the theoretical result, a scaled up model of the swimming robot is fabricated and characterized in silicone oil using the Buckingham PI theorem for scaling. The results are compared with the theoretically computed values. These robots are intended to swim in stagnation/low velocity biofluid and reach currently inaccessible areas of the human body for disease inspection and possibly treatment. Potential target regions to use these robots include eyeball cavity, cerebrospinal fluid and the urinary system.

pi

link (url) DOI [BibTex]

2004


link (url) DOI [BibTex]


no image
Atomic force microscope probe based controlled pushing for nanotribological characterization

Sitti, M.

IEEE/ASME Transactions on mechatronics, 9(2):343-349, IEEE, 2004 (article)

pi

[BibTex]

[BibTex]