Transcript Haptics - CSE, IIT Bombay

Haptics
Courtesy:http://spacecollective.org/N8/4544/The-Next-Big-Sensation-Machines-that-touch-back
Prachur Goel
Ravikant Narayan
Kumar Lav
Sharjeel Imam
Haptics-Introduction
Haptics refers to sensing and manipulation through touch
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What is touch? What is haptics? How do they relate to each
other
'Haptics' - derived from the greek word meaning 'haptein'
which means 'hold'
Analogous to optics
Haptic Devices
Sensory information can be
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Tactile : presence of heat, pressure and texture.
Kinesthetic :position, body movements and the
forces which act on it
Devices are based on the theoretical results of
Human haptics.
Heat : gives the degree of hotness and coldness.
Texture : The roughness via friction measurement.
Two Primary Types of Haptic
Interfaces
Force-feedback (Force-reflecting)
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provides kinesthetic and temporal tactile
information
Tactile-Feedback
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used in master-slave systems.
relay contact information from the tip of a
remote tool or the jaws of a slave manipulator to
a human operator
Types
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Human Haptics -study of human sensing
through touch
Machine Haptics- machines used to simulate
human touch
Computer Haptics-Computational method to
generate and render touch
Human haptics
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"If you don't understand the capabilities and
limitations of humans, you can't design systems
that permit them to operate effectively on
remote environments whether they are real or
virtual". ----Susan J. Lederman
Study of sensorial,physiological and cognitive
components of human tactual sense
key terms
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Haptic communication: exchange information
and communicating via touching
Haptic perception: recognizing objects through
touch
somatosensation
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The following are grouped into
somatosensations
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Touch
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Temperature
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Proprioception
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Nociception
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Touch is actually a colloquial term
somatosensation contd
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Diverse system of receptors
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Thermoreceptors
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Chemoreceptors
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Mechanoreceptors
When a sensory neuron is triggered by some stimulus
this neuron passes to an area in brain.
physiology
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Two main sensory receptors related to touch-
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Tactile hairs and subcutaneous receptors
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The sensory receptors create physical
distortions in the membranes causing ion
channels to open and generating 'action
potential'
We will discuss mechanoreceptors in detail
mechanoreceptor classification
Courtesy: psy.ucsd.edu/~lshenk/Touch-Lecture6.pdf
somatosensory pathway
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Periphery-Detects stimuli through receptors
which is conveyed to central nervous system
through 'afferent neurons' .
Includes ascending pathways from the body to
the brain.
Brain-The primary somatosensory area is
located in the human cortex.
neural basis of somatosensation
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Medial Lemniscal Pathway
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Spinothalmic Pathway
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Large fibres carrying touch and proprioception
information
Small fibres carrying temperature and pain
information
Signals travel from thalamus to somatosensory
areas S1 and S2 as in the figure
neural basis of somatosensation
Courtesy: psy.ucsd.edu/~lshenk/Touch-Lecture6.pdf
Haptic perception
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Active exploration of 3D objects around us.
Humans use active touch rather than passive
touch .
How do we perceive-
Lateral motion
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Pressure
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Enclosure
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Contour following
illusions
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A research team induced a distortion of healthy
volunteers' sense of their own bodies.
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Tendon of right arm vibrated
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Feeling of right elbow rotating away
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If subjects held their left index finger with their
right hand , they felt their left index finger
getting longer
about neurons
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Neurons are electrically excitable cells generally
comprised of one or more dendrites, a single
soma, a single axon and one or more axon
terminals.
Courtesy: http://www.web-books.com/eLibrary/Medicine/Physiology/Nervous/Nervous.htm
neurons
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Skin when touched by an object causes the
neurons to fire
If the even pressure maintained the neurons
stop firing.
The neurons of the skin and muscles that are
responsive to pressure and vibration have
filtering accessory structures that aid their
function.
action potential
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A self-regenerating wave of electrochemical
activity that allows nerve cells to carry a signal
over a distance
Principal ions involved are sodium and
potassium
When the sodium current passes the the
threshold the cell 'fires' producing an active
potential.
flow of current
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In sensory neurons the external stimuli alter the
ionic permeabilities and thus the potential.
Axon hillock gets depolarized causing action
potential
Flow of currents through the axon is described
by the cable theory
parietal lobe
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http://www.cnn.com/fyi/interactive/news/11/brain/print.html
The parietal lobe integrates
sensory information and
determines spatial sense and
navigation.
The postcentral gyrus of the
parietal lobe is the main sensory
receptive area for the sense of
touch
neural basis of somatosensation
Courtesy: psy.ucsd.edu/~lshenk/Touch-Lecture6.pdf
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Postcentral gyrus maps to certain areas of the
body
Computer haptics
The ability to touch and feel virtual objects
"Haptic Rendering is vital in haptics
development. Human Haptic gave the
theory, Machine Haptic built devices,
but Computer Haptic connected them,
Computer Haptic is the heart."
http://electronics.howstuffworks.com/gadgets/othergadgets/haptic-technology1.htm
“What You See Is What You Feel”
Haptic Rendering
provide a right performance to haptic devices.
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Courtesy: http://hapticshistory.chc61.uci.cu/haptic/site/pages/Computer-Haptic.php
Collision detection and response force computation are the most
important phases.
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Interaction
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From virtual to real world
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Real world to virtual world
Two way of interaction with the surface are :
Point-based: only the end point of the haptic device interacts with
the objects.Collision algorithm checks for the point and calculate the
force.
Ray-based : collisions are checked between the ray and objects.
Force is calulated as F=kx, k is stiffness of the object and x is the depth of
indentation.
If the point penterates into a region which is shared by multiple sub-spaces,
then superposition of surface normals is used to calculate the direction of
resultant force vector.
Texture Rendering:
Modeling of the haptic textures requires an
understanding of textures that exists in nature
and their interaction with humans sensory
system.
Two approahes :
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Image-based
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Procedural based
Image-based
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Gray scale 2d image is constructed.
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Gray-scale is used as the height indicators.
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Then generate the haptic texture field.
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2d co-ordinates are mapped with the coordinate of each vertex using the force vector
direction.
Procedural-based
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Generates synthetic texture fields using
mathematical functions for height fields.
The gradient is then calculated.
Applied to the force to update the forec vector
at each point.
Friction ....
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Makes the situation more realistic.
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Without it we cannot survive.
Two approach to add friction rendering:
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columb friction: It has static and dynamic
components and it is applied in a direction
tangential to the normal force.
Viscous friction: It depends on the velocity of the
object.
Rendering friction changes the dynamics of the
object and changes the force vector.
Applications
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Games: Gaming experience can be greatly
enhanced by applying force feedback
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Multi-media publishing: Currently include text,
sound, images and video.
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Tennis with Wii controller
'Mechanical Documents' could be transmitted
conveying material properties
Scientific Discovery: Data display
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Remote sensing, mining in geology (oil and gas
prospecting)
Applications (contd.)
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Other fields of application
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Arts and Creation: Artists and musicians, virtual
exhibitions of paintings and sculpture
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Vehicle operation: iDrive in BMW and Rolls Royce
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Engineering: CAD
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Education and Training: surgical training, pilot
training
Current activity
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Virtual Reality:
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Force producing elements act on discrete areas
inside a user's hand. Portable.
Image: google
Current activity
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Point interaction:
Phantom
Courtesy: http://www.sensable.com/documents/images/FFSystemShot_right_Large.jpg
Current activity
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TapTap is a wearable haptic interface that can
record and play back patterns of tactile
information so that people can experience the
emotional and physical benefits of human touch
in different times and places.
Future Vision
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Can touch be distributed over space and time,
recorded and broadcast like streaming data?
Courtesy: TapTap: A haptic wearable for asynchronous distributed touch therapy
Conclusion
Haptics plays an important role in constructing
an autonomous robot.
Although haptic interface devices are available,
further improvements are needed to match the
performance of the human user.
Tactile display is one of the most challenging
technologies that needs to be developed in
moving towards realistic haptic displays.
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References
M Srinivasan,C. Basdogan, Haptics Display in Virtual Environment,Computer &
Graphics,Vol. 2, 1997
http://hapticshistory.chc61.uci.cu/haptic/site/pages/Introduction.php
psy.ucsd.edu/~lshenk/Touch-Lecture6.pdf
http://www.newworldencyclopedia.org/entry/Touch
http://en.wikipedia.org/wiki/Somatosensation
http://spacecollective.org/N8/4544/The-Next-Big-Sensation-Machines-that-touch-back
http://www.docstoc.com/docs/2685206/Introduction-to-Computer-Haptics
V. Hayward, O. Astley, M.C. Hernandez, D Grant, G. Torre, Haptic Interfaces and
devices, Sensor Review, Vol.24. 2004.
Mandayam A Srinivasan, What is Haptics?, Laboratory for Human and Machine
Haptics: The Touch Lab, Massachusetts Institute of Technology.
L. Bonanni, J Lieberman, C Vaucelle, O Zuckerman, TapTap: A haptic wearable for
asynchronous distributed touch therapy, Proc CHI 2006.