Haptics

Prachur GoelPrachur GoelRavikant NarayanRavikant NarayanKumar LavKumar LavSharjeel ImamSharjeel Imam

Courtesy:http://spacecollective.org/N8/4544/The-Next-Big-Sensation-Machines-that-touch-back

Haptics-Introduction

What is touch? What is haptics? How do they relate to each What is touch? What is haptics? How do they relate to each otherother

'Haptics' - derived from the greek word meaning 'haptein' 'Haptics' - derived from the greek word meaning 'haptein' which means 'hold'which means 'hold'

Analogous to opticsAnalogous to optics

Haptics refers to sensing and manipulation through touchHaptics refers to sensing and manipulation through touch

Haptic Devices

Sensory information can be 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)

provides kinesthetic and temporal tactile information

Tactile-Feedback

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

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

"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

Haptic communication: exchange information and communicating via touching

Haptic perception: recognizing objects through touch

somatosensation

The following are grouped into somatosensations

Touch

Temperature

Proprioception

Nociception

Touch is actually a colloquial term

somatosensation contd

Diverse system of receptors Thermoreceptors Chemoreceptors Mechanoreceptors 

When a sensory neuron is triggered by some stimulus this neuron passes to an area in brain.

physiology

Two main sensory receptors related to touch-

Tactile hairs and subcutaneous receptors

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

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

Medial Lemniscal Pathway Large fibres carrying touch and proprioception

information

Spinothalmic Pathway 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

Active exploration of 3D objects around us.

Humans use active touch rather than passive touch .

How do we perceive-- Lateral motion Pressure Enclosure Contour following

illusions

A research team induced a distortion of healthy volunteers' sense of their own bodies.

Tendon of right arm vibrated

Feeling of right elbow rotating away

If subjects held their left index finger with their right hand , they felt their left index finger getting longer

about neurons

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

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

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

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

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

http://www.cnn.com/fyi/interactive/news/11/brain/print.html

neural basis of somatosensation

Courtesy: psy.ucsd.edu/~lshenk/Touch-Lecture6.pdf

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 "Haptic Rendering is vital in haptics development. Human Haptic gave the development. Human Haptic gave the theory, Machine Haptic built devices, theory, Machine Haptic built devices, but Computer Haptic connected them, but Computer Haptic connected them, Computer Haptic is the heart."Computer Haptic is the heart."

““What You See Is What You Feel”What You See Is What You Feel”

http://electronics.howstuffworks.com/gadgets/other-

gadgets/haptic-technology1.htm

Haptic Rendering

Collision detection and response force computation are the most important phases.

provide a right performance to haptic devices. provide a right performance to haptic devices.

Courtesy: http://hapticshistory.chc61.uci.cu/haptic/site/pages/Computer-Haptic.php

Interaction

From virtual to real world 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 :

Image-based

Procedural based

Image-based

Gray scale 2d image is constructed.

Gray-scale is used as the height indicators.

Then generate the haptic texture field.

2d co-ordinates are mapped with the co-ordinate of each vertex using the force vector direction.

Procedural-based

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 ....

Makes the situation more realistic. Without it we cannot survive.

Two approach to add friction rendering: 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

Games: Gaming experience can be greatly enhanced by applying force feedback

Tennis with Wii controller

Multi-media publishing: Currently include text, sound, images and video.

'Mechanical Documents' could be transmitted conveying material properties

Scientific Discovery: Data display Remote sensing, mining in geology (oil and gas

prospecting)

Applications (contd.)

Other fields of application Arts and Creation: Artists and musicians, virtual

exhibitions of paintings and sculpture Vehicle operation: iDrive in BMW and Rolls Royce Engineering: CAD Education and Training: surgical training, pilot

training

Current activity

Virtual Reality: Force producing elements act on discrete areas

inside a user's hand. Portable.

Image: google

Current activity

Point interaction: Phantom

Courtesy: http://www.sensable.com/documents/images/FFSystemShot_right_Large.jpg

Current activity

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

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.

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.