Haptics Prachur Goel Ravikant Narayan Kumar Lav Sharjeel Imam Courtesy:http://spacecollective.org/N8/4544/The-Next-Big-Sensation-Machines-that-touch-back
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
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 'afferentneurons' . • 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 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/other-gadgets/haptic-technology1.htm “What You See Is What You Feel”
Haptic Rendering • provide a right performance to haptic devices. Courtesy: http://hapticshistory.chc61.uci.cu/haptic/site/pages/Computer-Haptic.php • Collision detection and response force computation are the most important phases.
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.