1. Haptics Prachur Goel Ravikant Narayan Kumar Lav Sharjeel Imam 1
Courtesy: 1

2. Haptics-Introduction
Haptics refers to sensing and manipulation through touch
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 2

3. 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. 3

4. 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 4

5. 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 5

6. 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 6

7. key terms
Haptic communication: exchange information and communicating via touching
Haptic perception: recognizing objects through touch 7

8. somatosensation The following are grouped into somatosensations Touch
Temperature
Proprioception
Nociception
Touch is actually a colloquial term 8

9. 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. 9

10. 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 10

11. mechanoreceptor classification
Courtesy: psy.ucsd.edu/~lshenk/Touch-Lecture6.pdf 11

12. 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. 12

13. 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 13

14. neural basis of somatosensation
Courtesy: psy.ucsd.edu/~lshenk/Touch-Lecture6.pdf 14

15. 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 15

16. 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 16

17. 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.
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18. 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. 18

19. 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. 19

20. 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 20

21. 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 21

22. neural basis of somatosensation
Courtesy: psy.ucsd.edu/~lshenk/Touch-Lecture6.pdf
Postcentral gyrus maps to certain areas of the body 22

23. “What You See Is What You Feel”
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."
“What You See Is What You Feel” 23

24. Haptic Rendering provide a right performance to haptic devices.
Courtesy:
Collision detection and response force computation are the most important phases. 24

25. 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. 25

26. 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 26

27. 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. 27

28. 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. 28

29. 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. 29

30. 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)‏ 30

31. 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 31

32. Current activity Virtual Reality:
Force producing elements act on discrete areas inside a user's hand. Portable.
Image: google 32

33. Current activity Point interaction: Phantom 33
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34. 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. 34

35. 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 35

36. 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. 36

37. References
M Srinivasan,C. Basdogan, Haptics Display in Virtual Environment,Computer & Graphics,Vol. 2, 1997
psy.ucsd.edu/~lshenk/Touch-Lecture6.pdf
V. Hayward, O. Astley, M.C. Hernandez, D Grant, G. Torre, Haptic Interfaces and devices, Sensor Review, Vol
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. 37