Header logo is


2019


no image
Hierarchical Task-Parameterized Learning from Demonstration for Collaborative Object Movement

Hu, S., Kuchenbecker, K. J.

Applied Bionics and Biomechanics, (9765383), December 2019 (article)

Abstract
Learning from demonstration (LfD) enables a robot to emulate natural human movement instead of merely executing preprogrammed behaviors. This article presents a hierarchical LfD structure of task-parameterized models for object movement tasks, which are ubiquitous in everyday life and could benefit from robotic support. Our approach uses the task-parameterized Gaussian mixture model (TP-GMM) algorithm to encode sets of demonstrations in separate models that each correspond to a different task situation. The robot then maximizes its expected performance in a new situation by either selecting a good existing model or requesting new demonstrations. Compared to a standard implementation that encodes all demonstrations together for all test situations, the proposed approach offers four advantages. First, a simply defined distance function can be used to estimate test performance by calculating the similarity between a test situation and the existing models. Second, the proposed approach can improve generalization, e.g., better satisfying the demonstrated task constraints and speeding up task execution. Third, because the hierarchical structure encodes each demonstrated situation individually, a wider range of task situations can be modeled in the same framework without deteriorating performance. Last, adding or removing demonstrations incurs low computational load, and thus, the robot’s skill library can be built incrementally. We first instantiate the proposed approach in a simulated task to validate these advantages. We then show that the advantages transfer to real hardware for a task where naive participants collaborated with a Willow Garage PR2 robot to move a handheld object. For most tested scenarios, our hierarchical method achieved significantly better task performance and subjective ratings than both a passive model with only gravity compensation and a single TP-GMM encoding all demonstrations.

hi

DOI [BibTex]


Series Elastic Behavior of Biarticular Muscle-Tendon Structure in a Robotic Leg
Series Elastic Behavior of Biarticular Muscle-Tendon Structure in a Robotic Leg

Ruppert, F., Badri-Spröwitz, A.

Frontiers in Neurorobotics, 64, pages: 13, 13, August 2019 (article)

dlg

Frontiers YouTube link (url) DOI [BibTex]

Frontiers YouTube link (url) DOI [BibTex]


no image
Low-Hysteresis and Low-Interference Soft Tactile Sensor Using a Conductive Coated Porous Elastomer and a Structure for Interference Reduction

Park, K., Kim, S., Lee, H., Park, I., Kim, J.

Sensors and Actuators A: Physical, 295, pages: 541-550, August 2019 (article)

Abstract
The need for soft whole-body tactile sensors is emerging. Piezoresistive materials are advantageous in terms of making large tactile sensors, but the hysteresis of piezoresistive materials is a major drawback. The hysteresis of a piezoresistive material should be attenuated to make a practical piezoresistive soft tactile sensor. In this paper, we introduce a low-hysteresis and low-interference soft tactile sensor using a conductive coated porous elastomer and a structure to reduce interference (grooves). The developed sensor exhibits low hysteresis because the transduction mechanism of the sensor is dominated by the contact between the conductive coated surface. In a cyclic loading experiment with different loading frequencies, the mechanical and piezoresistive hysteresis values of the sensor are less than 21.7% and 6.8%, respectively. The initial resistance change is found to be within 4% after the first loading cycle. To reduce the interference among the sensing points, we also propose a structure where the grooves are inserted between the adjacent electrodes. This structure is implemented during the molding process, which is adopted to extend the porous tactile sensor to large-scale and facile fabrication. The effects of the structure are investigated with respect to the normalized design parameters ΘD, ΘW, and ΘT in a simulation, and the result is validated for samples with the same design parameters. An indentation experiment also shows that the structure designed for interference reduction effectively attenuates the interference of the sensor array, indicating that the spatial resolution of the sensor array is improved. As a result, the sensor can exhibit low hysteresis and low interference simultaneously. This research can be used for many applications, such as robotic skin, grippers, and wearable devices.

hi

DOI [BibTex]

DOI [BibTex]


Beyond Basins of Attraction: Quantifying Robustness of Natural Dynamics
Beyond Basins of Attraction: Quantifying Robustness of Natural Dynamics

Steve Heim, , Spröwitz, A.

IEEE Transactions on Robotics (T-RO) , 35(4), pages: 939-952, August 2019 (article)

Abstract
Properly designing a system to exhibit favorable natural dynamics can greatly simplify designing or learning the control policy. However, it is still unclear what constitutes favorable natural dynamics and how to quantify its effect. Most studies of simple walking and running models have focused on the basins of attraction of passive limit cycles and the notion of self-stability. We instead emphasize the importance of stepping beyond basins of attraction. In this paper, we show an approach based on viability theory to quantify robust sets in state-action space. These sets are valid for the family of all robust control policies, which allows us to quantify the robustness inherent to the natural dynamics before designing the control policy or specifying a control objective. We illustrate our formulation using spring-mass models, simple low-dimensional models of running systems. We then show an example application by optimizing robustness of a simulated planar monoped, using a gradient-free optimization scheme. Both case studies result in a nonlinear effective stiffness providing more robustness.

dlg

arXiv preprint arXiv:1806.08081 T-RO link (url) DOI Project Page [BibTex]

arXiv preprint arXiv:1806.08081 T-RO link (url) DOI Project Page [BibTex]


no image
Physical activity in non-ambulatory toddlers with cerebral palsy

M.Orlando, J., Pierce, S., Mohan, M., Skorup, J., Paremski, A., Bochnak, M., Prosser, L. A.

Research in Developmental Disabilities, 90, pages: 51-58, July 2019 (article)

Abstract
Background: Children with cerebral palsy are less likely to be physically active than their peers, however there is limited evidence regarding self-initiated physical activity in toddlers who are not able, or who may never be able, to walk. Aims: The aim of this study was to measure self-initiated physical activity and its relationship to gross motor function and participation in non-ambulatory toddlers with cerebral palsy. Methods and procedures: Participants were between the ages of 1–3 years. Physical activity during independent floor-play at home was recorded using a wearable tri-axial accelerometer worn on the child’s thigh. The Gross Motor Function Measure-66 and the Child Engagement in Daily Life, a parent-reported questionnaire of participation, were administered. Outcomes and results: Data were analyzed from the twenty participants who recorded at least 90 min of floor-play (mean: 229 min), resulting in 4598 total floor-play minutes. The relationship between physical activity and gross motor function was not statistically significant (r = 0.20; p = 0.39), nor were the relationships between physical activity and participation (r = 0.05−0.09; p = 0.71−0.84). Conclusions and implications: The results suggest physical activity during floor-play is not related to gross motor function or participation in non-ambulatory toddlers with cerebral palsy. Clinicians and researchers should independently measure physical activity, gross motor function, and participation.

hi

DOI [BibTex]

DOI [BibTex]


Implementation of a 6-{DOF} Parallel Continuum Manipulator for Delivering Fingertip Tactile Cues
Implementation of a 6-DOF Parallel Continuum Manipulator for Delivering Fingertip Tactile Cues

Young, E. M., Kuchenbecker, K. J.

IEEE Transactions on Haptics, 12(3):295-306, June 2019 (article)

Abstract
Existing fingertip haptic devices can deliver different subsets of tactile cues in a compact package, but we have not yet seen a wearable six-degree-of-freedom (6-DOF) display. This paper presents the Fuppeteer (short for Fingertip Puppeteer), a device that is capable of controlling the position and orientation of a flat platform, such that any combination of normal and shear force can be delivered at any location on any human fingertip. We build on our previous work of designing a parallel continuum manipulator for fingertip haptics by presenting a motorized version in which six flexible Nitinol wires are actuated via independent roller mechanisms and proportional-derivative controllers. We evaluate the settling time and end-effector vibrations observed during system responses to step inputs. After creating a six-dimensional lookup table and adjusting simulated inputs using measured Jacobians, we show that the device can make contact with all parts of the fingertip with a mean error of 1.42 mm. Finally, we present results from a human-subject study. A total of 24 users discerned 9 evenly distributed contact locations with an average accuracy of 80.5%. Translational and rotational shear cues were identified reasonably well near the center of the fingertip and more poorly around the edges.

hi

DOI Project Page [BibTex]


no image
How Does It Feel to Clap Hands with a Robot?

Fitter, N. T., Kuchenbecker, K. J.

International Journal of Social Robotics, 12(1):113-127, April 2019 (article)

Abstract
Future robots may need lighthearted physical interaction capabilities to connect with people in meaningful ways. To begin exploring how users perceive playful human–robot hand-to-hand interaction, we conducted a study with 20 participants. Each user played simple hand-clapping games with the Rethink Robotics Baxter Research Robot during a 1-h-long session involving 24 randomly ordered conditions that varied in facial reactivity, physical reactivity, arm stiffness, and clapping tempo. Survey data and experiment recordings demonstrate that this interaction is viable: all users successfully completed the experiment and mentioned enjoying at least one game without prompting. Hand-clapping tempo was highly salient to users, and human-like robot errors were more widely accepted than mechanical errors. Furthermore, perceptions of Baxter varied in the following statistically significant ways: facial reactivity increased the robot’s perceived pleasantness and energeticness; physical reactivity decreased pleasantness, energeticness, and dominance; higher arm stiffness increased safety and decreased dominance; and faster tempo increased energeticness and increased dominance. These findings can motivate and guide roboticists who want to design social–physical human–robot interactions.

hi

DOI [BibTex]

DOI [BibTex]


Tailored Magnetic Springs for Shape-Memory Alloy Actuated Mechanisms in Miniature Robots
Tailored Magnetic Springs for Shape-Memory Alloy Actuated Mechanisms in Miniature Robots

Woodward, M. A., Sitti, M.

IEEE Transactions on Robotics, 35, 2019 (article)

Abstract
Animals can incorporate large numbers of actuators because of the characteristics of muscles; whereas, robots cannot, as typical motors tend to be large, heavy, and inefficient. However, shape-memory alloys (SMA), materials that contract during heating because of change in their crystal structure, provide another option. SMA, though, is unidirectional and therefore requires an additional force to reset (extend) the actuator, which is typically provided by springs or antagonistic actuation. These strategies, however, tend to limit the actuator's work output and functionality as their force-displacement relationships typically produce increasing resistive force with limited variability. In contrast, magnetic springs-composed of permanent magnets, where the interaction force between magnets mimics a spring force-have much more variable force-displacement relationships and scale well with SMA. However, as of yet, no method for designing magnetic springs for SMA-actuators has been demonstrated. Therefore, in this paper, we present a new methodology to tailor magnetic springs to the characteristics of these actuators, with experimental results both for the device and robot-integrated SMA-actuators. We found magnetic building blocks, based on sets of permanent magnets, which are well-suited to SMAs and have the potential to incorporate features such as holding force, state transitioning, friction minimization, auto-alignment, and self-mounting. We show magnetic springs that vary by more than 3 N in 750 $\mu$m and two SMA-actuated devices that allow the MultiMo-Bat to reach heights of up to 4.5 m without, and 3.6 m with, integrated gliding airfoils. Our results demonstrate the potential of this methodology to add previously impossible functionality to smart material actuators. We anticipate this methodology will inspire broader consideration of the use of magnetic springs in miniature robots and further study of the potential of tailored magnetic springs throughout mechanical systems.

pi

DOI [BibTex]


Thrust and Hydrodynamic Efficiency of the Bundled Flagella
Thrust and Hydrodynamic Efficiency of the Bundled Flagella

Danis, U., Rasooli, R., Chen, C., Dur, O., Sitti, M., Pekkan, K.

Micromachines, 10, 2019 (article)

pi

[BibTex]

[BibTex]


Microrobotics and Microorganisms: Biohybrid Autonomous Cellular Robots
Microrobotics and Microorganisms: Biohybrid Autonomous Cellular Robots

Alapan, Y., Yasa, O., Yigit, B., Yasa, I. C., Erkoc, P., Sitti, M.

Annual Review of Control, Robotics, and Autonomous Systems, 2019 (article)

pi

[BibTex]

[BibTex]


no image
X-ray Optics Fabrication Using Unorthodox Approaches

Sanli, U., Baluktsian, M., Ceylan, H., Sitti, M., Weigand, M., Schütz, G., Keskinbora, K.

Bulletin of the American Physical Society, APS, 2019 (article)

mms pi

[BibTex]

[BibTex]


no image
Response of active Brownian particles to shear flow

Asheichyk, K., Solon, A., Rohwer, C. M., Krüger, M.

The Journal of Chemical Physics, 150(14), American Institute of Physics, Woodbury, N.Y., 2019 (article)

icm

DOI [BibTex]

DOI [BibTex]


no image
Vortex Mass in the Three-Dimensional O(2) Scalar Theory

Delfino, G., Selke, W., Squarcini, A.

Physical Review Letters, 122(5), American Physical Society, Woodbury, N.Y., 2019 (article)

icm

DOI [BibTex]

DOI [BibTex]


no image
Ferromagnetic colloids in liquid crystal solvents

Zarubin, G.

Universität Stuttgart, Stuttgart, 2019 (phdthesis)

icm

link (url) DOI [BibTex]

link (url) DOI [BibTex]


no image
Fluctuating interface with a pinning potential

Pranjić, Daniel

Universität Stuttgart, Stuttgart, 2019 (mastersthesis)

icm

[BibTex]

[BibTex]


no image
Dynamics near planar walls for various model self-phoretic particles

Bayati, P., Popescu, M. N., Uspal, W. E., Dietrich, S., Najafi, A.

Soft Matter, 15(28):5644-5672, Royal Society of Chemistry, Cambridge, UK, 2019 (article)

icm

DOI [BibTex]

DOI [BibTex]


no image
Glucose Oxidase Micropumps: Multi-Faceted Effects of Chemical Activity on Tracer Particles Near the Solid-Liquid Interface

Munteanu, R. E., Popescu, M. N., Gáspár, S.

Condensed Matter, 4(3), MDPI, Basel, 2019 (article)

icm

DOI [BibTex]


no image
Criticality senses topology

Vasilyev, O. A., Maciolek, A., Dietrich, S.

EPL, 128(2), EDP Science, Les-Ulis, 2019 (article)

icm

DOI [BibTex]

DOI [BibTex]


no image
On the positivity and magnitudes of Bayesian quadrature weights

Karvonen, T., Kanagawa, M., Särkä, S.

Statistics and Computing, 29, pages: 1317-1333, 2019 (article)

pn

DOI [BibTex]

DOI [BibTex]


Multifarious Transit Gates for Programmable Delivery of Bio‐functionalized Matters
Multifarious Transit Gates for Programmable Delivery of Bio‐functionalized Matters

Hu, X., Torati, S. R., Kim, H., Yoon, J., Lim, B., Kim, K., Sitti, M., Kim, C.

Small, Wiley Online Library, 2019 (article)

pi

[BibTex]

[BibTex]


Multi-functional soft-bodied jellyfish-like swimming
Multi-functional soft-bodied jellyfish-like swimming

Ren, Z., Hu, W., Dong, X., Sitti, M.

Nature communications, 10, 2019 (article)

pi

[BibTex]


no image
Welcome to Progress in Biomedical Engineering

Sitti, M.

Progress in Biomedical Engineering, 1, IOP Publishing, 2019 (article)

pi

[BibTex]

[BibTex]


no image
Drag Force for Asymmetrically Grafted Colloids in Polymer Solutions

Werner, M., Malgaretti, P., Maciolek, A.

Frontiers in Physics, 7, Frontiers Media, Lausanne, 2019 (article)

icm

DOI [BibTex]

DOI [BibTex]


no image
Feeling Your Neighbors across the Walls: How Interpore Ionic Interactions Affect Capacitive Energy Storage

Kondrat, S., Vasilyev, O., Kornyshev, A. A.

The Journal of Physical Chemistry Letters, 10(16):4523-4527, American Chemical Society, Washington, DC, 2019 (article)

icm

DOI [BibTex]

DOI [BibTex]


no image
Active Janus colloids at chemically structured surfaces

Uspal, W. E., Popescu, M. N., Dietrich, S., Tasinkevych, M.

The Journal of Chemical Physics, 150(20), American Institute of Physics, Woodbury, N.Y., 2019 (article)

icm

DOI [BibTex]

DOI [BibTex]


no image
Illumination-induced motion of a Janus nanoparticle in binary solvents

Araki, T., Maciolek, A.

Soft Matter, 15(26):5243-5254, Royal Society of Chemistry, Cambridge, UK, 2019 (article)

icm

DOI [BibTex]

DOI [BibTex]


no image
Transient response of an electrolyte to a thermal quench

Janssen, M., Bier, M.

Physical Review E, 99(4), American Physical Society, Melville, NY, 2019 (article)

icm

DOI [BibTex]

DOI [BibTex]


The near and far of a pair of magnetic capillary disks
The near and far of a pair of magnetic capillary disks

Koens, L., Wang, W., Sitti, M., Lauga, E.

Soft Matter, 2019 (article)

pi

DOI [BibTex]

DOI [BibTex]


Mechanics of a pressure-controlled adhesive membrane for soft robotic gripping on curved surfaces
Mechanics of a pressure-controlled adhesive membrane for soft robotic gripping on curved surfaces

Song, S., Drotlef, D., Paik, J., Majidi, C., Sitti, M.

Extreme Mechanics Letters, Elsevier, 2019 (article)

pi

[BibTex]


Multifunctional and biodegradable self-propelled protein motors
Multifunctional and biodegradable self-propelled protein motors

Pena-Francesch, A., Giltinan, J., Sitti, M.

Nature communications, 10, Nature Publishing Group, 2019 (article)

pi

[BibTex]

[BibTex]


Review of emerging concepts in nanotoxicology: opportunities and challenges for safer nanomaterial design
Review of emerging concepts in nanotoxicology: opportunities and challenges for safer nanomaterial design

Singh, A. V., Laux, P., Luch, A., Sudrik, C., Wiehr, S., Wild, A., Santamauro, G., Bill, J., Sitti, M.

Toxicology Mechanisms and Methods, 2019 (article)

pi

[BibTex]

[BibTex]


Graphene oxide synergistically enhances antibiotic efficacy in Vancomycin resistance Staphylococcus aureus
Graphene oxide synergistically enhances antibiotic efficacy in Vancomycin resistance Staphylococcus aureus

Singh, V., Kumar, V., Kashyap, S., Singh, A. V., Kishore, V., Sitti, M., Saxena, P. S., Srivastava, A.

ACS Applied Bio Materials, ACS Publications, 2019 (article)

pi

[BibTex]

[BibTex]


no image
Aging phenomena during phase separation in fluids: decay of autocorrelation for vapor\textendashliquid transitions

Roy, Sutapa, Bera, Arabinda, Majumder, Suman, Das, Subir K.

Soft Matter, 15(23):4743-4750, Royal Society of Chemistry, Cambridge, UK, 2019 (article)

icm

DOI [BibTex]

DOI [BibTex]


no image
Controlling pattern formation in the confined Schnakenberg model

Beyer, David Bernhard

Universität Stuttgart, Stuttgart, 2019 (mastersthesis)

icm

[BibTex]

[BibTex]


no image
Flux and storage of energy in nonequilibrium stationary states

Holyst, R., Maciolek, A., Zhang, Y., Litniewski, M., Knycha\la, P., Kasprzak, M., Banaszak, M.

Physical Review E, 99(4), American Physical Society, Melville, NY, 2019 (article)

icm

DOI [BibTex]

DOI [BibTex]


no image
Correlations and forces in sheared fluids with or without quenching

Rohwer, C. M., Maciolek, A., Dietrich, S., Krüger, M.

New Journal of Physics, 21, IOP Publishing, Bristol, 2019 (article)

icm

DOI [BibTex]


no image
Ensemble dependence of critical Casimir forces in films with Dirichlet boundary conditions

Rohwer, C. M., Squarcini, A., Vasilyev, O., Dietrich, S., Gross, M.

Physical Review E, 99(6), American Physical Society, Melville, NY, 2019 (article)

icm

DOI [BibTex]

DOI [BibTex]


no image
Controlling the dynamics of colloidal particles by critical Casimir forces

Magazzù, A., Callegari, A., Staforelli, J. P., Gambassi, A., Dietrich, S., Volpe, G.

Soft Matter, 15(10):2152-2162, Royal Society of Chemistry, Cambridge, UK, 2019 (article)

icm

DOI [BibTex]

DOI [BibTex]


no image
Charge regulation radically modifies electrostatics in membrane stacks

Majee, A., Bier, M., Blossey, R., Podgornik, R.

Physical Review E, 100(5), American Physical Society, Melville, NY, 2019 (article)

icm

DOI [BibTex]

DOI [BibTex]


ENGINEERING Bio-inspired robotic collectives
ENGINEERING Bio-inspired robotic collectives

Sitti, M.

Nature, 567, pages: 314-315, Macmillan Publishers Ltd., London, England, 2019 (article)

pi

[BibTex]

[BibTex]


Shape-encoded dynamic assembly of mobile micromachines
Shape-encoded dynamic assembly of mobile micromachines

Alapan, Y., Yigit, B., Beker, O., Demirörs, A. F., Sitti, M.

Nature, 18, 2019 (article)

pi

[BibTex]

[BibTex]


Peptide-Induced Biomineralization of Tin Oxide (SnO2) Nanoparticles for Antibacterial Applications
Peptide-Induced Biomineralization of Tin Oxide (SnO2) Nanoparticles for Antibacterial Applications

Singh, A. V., Jahnke, T., Xiao, Y., Wang, S., Yu, Y., David, H., Richter, G., Laux, P., Luch, A., Srivastava, A., Saxena, P. S., Bill, J., Sitti, M.

Journal of nanoscience and nanotechnology, 19, American Scientific Publishers, 2019 (article)

pi

[BibTex]

[BibTex]