HAPTICS

Introduction Haptics is the study of how to couple the human sense of touch with a computer generated world. Haptic refers to the sensing and manipulation through touch Haptics is derived from the greek word ‘haptien’ which means ‘hold’. In combination with visual display ,haptics technology can be used to train people for tasks requiring hand-eye coordination.

Contd.. The study of Haptics emerged from advances in virtual reality. Virtual reality is a form of human - computer interaction providing a virtual enviornment that one can explore through direct interaction with our senses. To be able to interact with virtual enviornment there must be some feedback and this type of feedback is called Haptic feedback. Haptic interface:device for touch interaction in real and virtual world.

Types Machine Haptics :machines used to simulate human touch. Human Haptics:study of human sensing through touch. Computer Haptics:Computational method to generate and render touch.

Two primary types of Haptic interfaces 1.Force feedback(Force reflecting) It deals with devices that interact with the muscles and tendon that give the human a sensation of force being applied. These devices mainly consist of robotic manipulators.

Contd… 2.Tactile feedback It deals with devices that interact with the nerve endings in the skin which indicate heat ,pressure and texture. These devices typically have been to indicate whether or not the user is in contact with a virtual object.

Tactile feedback Force feedback display

Haptic interaction Haptic interaction uses haptic interfaces. Haptic interface devices behave like small robots that exchange mechanical energy with a user. We use the term device-body interaction to highlight the physical connection between the operator and device The interaction can be in contact with any part of operator’s body.

Contd.. An avatar is created which is the the virtual representation of haptic interface. User physically interacts with virtual enviornment through the avatar. The operator controls the avatar’s position in virtual enviornment. Contact between the avatar and the virtual enviornment sets off the action and reaction force.

Contd… From real world to virtual world and vice versa. Two methods of interaction Point based:only the end point of the haptic device interacts with the objects. Ray based:collision are checked between the ray and objects

Point based Model the haptic probe as a single point. Each time the user moves the haptic probe the collision is detected. If so then appropriate forces are reflected back to the user.

Ray based The generic probe of haptic device is modeled as a line segment . Collisions are checked between the finite line and virtual objects. This approach enables users to touch multiple objects simultaneously.

Potential benefits Reduction in fatigue. Increase in productivity and comfort. Decreased learning times. Reduction in manipulation errors.

Commercially available Haptic interfaces 3DOF omega haptic device Haptic master The freedom s7 • Pantograph The novint falcon

Haptic devices Sensory information in haptic devices include: Tactile:presence of heat,texture and pressure. Kinesthetic:position,body movements and the forces which act on it. Haptic devices can also be classified according to the no:of degrees of freedom of the force or motion at the haptic interface device. DOF is the no:of dimensions characterizing the possible movements of forces exchanged b/w the user and device.

Computer haptics Haptic technology:technology that interfaces with the user through touch. Haptic rendering:process of displaying synthetically generated 2D/3D stimuli to the user. Computer haptics is the heart of haptics.

Haptic rendering Haptic rendering has two main parts: Collision detection Collision response Collision detection: As a user manipulates the probe of a haptic device,the new position and orientation of the probe are acquired and collisions are detected. If no collision has occurred,then the device remains passive and no force is reflected.

Contd.. collision response If collision is detected ,interaction forces are calculated and conveyed to the user through the haptic device which provides tactual information. Haptic loop updates the forces around 1khz. The opposing force acting on the user during interaction is F=k*x. The direction of force will be normal to the surface.

illusions 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.

Applications Games: Gaming experience can be greatly enhanced by applying force feedback 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 TapTap is a wearable haptic interface. It 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. Actuators are present to provide the various touch sensations.

Downsides of Haptics Haptic applications can be extremely complex requiring specialized hardware and processing power. Many haptic projects rely on fixed installations and they are not easily portable. Cost is high .

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 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. M Srinivasan,C. Basdogan, Haptics Display in Virtual Environment,Computer & Graphics,Vol. 2, 1997

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