Half-day workshop on “Contact Mechanics for Electrovibration”
with Dr. Bo Persson
appearing as special guest speaker, a well-known expert on sliding
friction.
Introduction:
When an alternating voltage is
applied to the conductive layer of a capacitive touch screen, a uniform and
attractive electrostatic force field is generated between finger pad and the
touch screen in the direction normal to the its surface. Although the magnitude
of this electrostatic force is small relative to the normal force applied by
the finger, it results in a perceivable frictional force in tangential
direction when the finger pad slides on the touch screen. This frictional force
can be modulated by altering the magnitude, frequency, and phase of the voltage
signal applied to the conductive layer of the touch screen. This technology has
exciting potential applications in mobile computing in the areas such as online
shopping, gaming, interfaces for blind, education, and data visualization.
Problem Statement:
While the technology for
generating tactile feedback on a touch screen via electrovibration
(i.e. electroadhesion under an oscillating electric
field) is already in
place and straightforward to implement, our knowledge on contact mechanics for electrovibration is highly limited. In particular, we still
do not know the exact mechanism leading to an increase in tangential frictional
forces under electrovibration. Analytical models for
estimating the electrostatic forces in normal direction and the friction forces
acting on the finger in tangential direction are insufficient and the
simulations produced by those models do not match well with the experimental
data. This workshop aims to bring the experts working in the areas of contact
mechanics, sliding friction, mechanical and electrical modeling of human
finger, and electrovibration to discuss in depth the
reasons behind this mismatch.
Audience:
The workshop is open to any student, researcher as well as developer and end user interested in the design, development, and use of electrovibration for various applications in mobile computing. Although the focus of the workshop will be on contact mechanics and friction between finger and a touch surface, the basic concepts of contact mechanics and electrovibration will be covered for the beginners. We also plan to have a Q&A session where the participants can ask questions to the speakers and the audiance can discuss the next greatest challenges in electrovibration.
Tentative program:
8.30 – 8.45 Welcome by the organizer
8.45 – 9.30 Guest Speaker: Dr. Bo N.J. Persson, “Electroadhesion and Contact Mechanics for the Human Skin”
9.30 – 10.00 Dr. Vincent
Hayward, “Tactual Curiosities”
10.00 – 10.30 Coffee Break
10.30 – 11.00 Dr. Ed Colgate, “The Mechanics of Electroadhesion”
11.00 – 11.30 Dr. Cagatay Basdogan, “Experimental
Investigation of Contact Mechanics for Electrovibration”
11.30 – 12.00 Panel discussion
Organizer:
Cagatay Basdogan (http://portal.ku.edu.tr/~cbasdogan)
Robotics and Mechatronics
Laboratory (http://rml.ku.edu.tr/)
College of Engineering, Room:
ENG-247
Koc University (http://www.ku.edu.tr)
Sariyer, Istanbul, TURKEY 34450
Speakers:
Special Guest Speaker: Bo N.J. Persson Research Center Juelich,
Germany. |
Dr. Persson is a
research scientist at Research Center Juelich. He is also the founder and CEO
of MultiscaleConsulting, which is helping companies (e.g., tire and medical
companies) to understand and solve contact mechanics problems involving friction,
adhesion, leakage of seals, the electric and thermal contact resistance, and
related problems. During 1983-1984 Persson worked at IBM research lab in
Yorktown Height, New York, and 1986-1987 at the IBM Zurich research lab. His
early interest was in ultra high vacuum surface science (e.g. theories for
surface spectroscopy's, and studies of dynamical processes at surfaces) but
starting ~ 1995 his main research activity is in tribology (adhesion,
friction, contact mechanics). He is author of~ 400 articles published in
internationals Journals, and of two books on tribology, and a book on the
electromagnetic fluctuations at the nanoscale. |
Title: Electroadhesion
and contact mechanics for the human skin All solids have surface
roughness. When two elastic solids are squeezed into contact, the area of
real contact is usually only a small fraction of the nominal contact area.
This is true even for elastically soft solids such as rubber or the human
skin. Thus, for example, the contact area between a tire on a passenger car
and an asphalt road surface may be only 1cm x 1cm (or less). I have developed
a contact mechanics theory which is valid under very general conditions,
e.g., for layered and viscoelastic materials and including plastic
deformations. In this presentation, I will briefly describe this theory and
present applications to the contact between the human skin and a smooth glass
surface. I will discuss how adhesion, in particular due to capillary
bridges or an applied electric voltage (electroadhesion), affect the
skin-glass contact area and the sliding friction. |
Vincent Hayward Professor of
Tactile Perception and Technologies, Leverhulme Fellow School of Advanced
Study, University of London http://philosophy.sas.ac.uk/about/people Chief Scientific
Officer, Actronika SAS, Paris Professeur des
Universités (on leave) |
Vincent Hayward is a
Professor at the Sorbonne Université in Paris, presently on leave. Before, he
was with the Department of Electrical and Computer Engineering at McGill University,
Montréal, Canada, where he became a full Professor in 2006 and was the
Director of the McGill Centre for Intelligent Machines from 2001 to 2004.
Vincent Hayward is an elected a Fellow of the IEEE. Since January 2017, he is
Professor of Tactile Perception and Technology at the School of Advanced
Studies of the University of London, supported by a Leverhulme Trust
Fellowship. Over the past decade Vincent developed a computational theory of
tactile perception that is grounded in the physics of mechanical
interactions. During his tenure at the University of London’s School of
Advanced Study, Vincent relates this theory to the cognitive and
metacognitive functions of the brain: i.e. how judgments about objects are
made through touch. He spends part of his time contributing to the
development of a start-up company in Paris, Actronika SAS, dedicated to
lowering the accessibility barrier of haptic technology and also helps
develop a tactile communication technology for use by the Deafblind. |
Title: Tactual
Curiosities The astonishing variety
of phenomena resulting from the contact between fingers and objects can be
regarded as a formidable trove of information that can be extracted by
organisms and robots to learn about the nature and the properties of objects.
This richness is likely to have fashioned our somatosensory system at all
levels of its organisation, from early mechanics to cognition. The talk will
illustrate this idea through examples that show how the physics of mechanical
interactions shape the messages that are sent to the brain, providing new
opportunities for applications to robotics and human machines interfaces. |
J. Edward Colgate Breed University
Professor of Design Department of Mechanical
Engineering Northwestern University Evanston, Illinois, USA |
J. Edward Colgate is the
Breed University Design Professor and a member of the Department of
Mechanical Engineering at Northwestern University. Dr. Colgate’s principal
research interest is haptic interface.
He is the co-inventor of a class of collaborative robots known as
“cobots” and a suite of technologies for bringing programmable haptic
feedback to touch surfaces. He served as the founding Editor-in-Chief of the
IEEE Transactions on Haptics and is a Fellow of the IEEE and the National
Academy of Inventors. Dr. Colgate has
founded three startup companies the most recent of which, Tanvas Inc., is
commercializing haptic technologies. |
Title: The Mechanics of Electroadhesion Electroadhesion is a
promising approach to surface haptics:
it is solid state, requires modest power, exhibits high bandwidth, and
is compatible with modern touchscreen manufacture. Yet, the underlying mechanics of
electroadhesion are poorly understood, leaving engineers little basis for
selecting parameters such as surface layer thickness, dielectric constant,
roughness, and so on. In this talk,
I’ll present a picture of electroadhesion which is emerging as the result of
extensive experimentation and modeling in our laboratory. Certain factors that were once routinely
ignored are now known to be critical.
These include the nanoscale roughness of skin, the high elastic
modulus of the outermost layers of stratum corneum, and the crucial role of
the air gap, especially during motion. |
Cagatay Basdogan Robotics and
Mechatronics Laboratory (http://rml.ku.edu.tr/) College of Engineering,
Room: ENG-247 Koc University Sariyer, Istanbul,
TURKEY 34450 Phone: +90 212 338 1721 Fax: +90 212 338 1548 e-mail: cbasdogan@ku.edu.tr |
Prof. Basdogan is a
member of faculty in College of Engineering at Koc University since 2002.
Before joining to Koc University, he was a senior member of technical staff
at Information and Computer Science Division of NASA-Jet Propulsion
Laboratory of California Institute of Technology (Caltech) from 1999 to 2002.
At JPL, he worked on 3D reconstruction of Martian models from stereo images
captured by a rover and their haptic visualization on Earth. He moved to JPL
from Massachusetts Institute of Technology (MIT) where he was a research
scientist and principal investigator at MIT Research Laboratory of
Electronics and a member of the MIT Touch Lab from 1996 to 1999. At MIT, he
was involved in the development of algorithms that enable a user to touch and
feel virtual objects through a haptic device. He received his Ph.D. degree
from Southern Methodist University in 1994 and worked on medical simulation
and robotics for Musculographics Inc. at Northwestern University Research
Park for two years before moving to MIT. Prof.Basdogan is currently the
associate editor in chief (AEiC) of the IEEE Transactions on Haptics and
serves in the editorial boards of IEEE Transactions on Mechatronics,
Presence: Teleoperators and Virtual Worlds (MIT Press), and Computer Animation
and Virtual Worlds (Wiley) journals. In addition to serving in the program
and organizational committees of several conferences, he also chaired the
IEEE World Haptics Conference in 2011. |
Title: Experimental Investigation of Contact Mechanics for Electrovibration Allthough the
technology for generating tactile feedback on a touch screen via
electrovibration is already in place and straightforward to implement, our
knowledge on contact mechanics for electrovibration is highly limited. In
particular, we still do not know the exact mechanism leading to an increase
in tangential frictional forces under electrovibration. Based on the results
of our experimental studies, we speculate that the main cause in increase in
tangential frictional force under electrovibration during full slip is due to
an increase in real contact area. We argue that the increase in frictional
forces under electrovibration causes a further reduction in apparent contact
area due to nonlinear stiffening of finger in tangential direction, which
results in an increase in real contact area due to the rounded geometry of
fingerpad and existence of its asperities. |