Haptic Technology

1. 1 What is *Haptics*? Haptics refers to sensing and manipulation through touch. The word comes from the Greek haptesthai, meaning to touch. The history of the haptic port dates moxie to the 1950s, when a master-slave system was proposed by Goertz (1952). Haptic interfaces were established out of the field of tele- operation, which was then employed in the remote manipulation of radioactive materials. The crowning(prenominal) goal of the tele-operation system was transp arncy.That is, an user interacting with the master twirl in a master-slave pair should not be able to distinguish between victimisation the master makeler and manipulating the actual tool itself. Early haptic interface systems were therefore developed purely for telerobotic applications. draw skeleton drawframe Fig. 2. 1Basic architecture for a virtual reality application incorporating visual, auditory, and haptic feedback. Simulation engine Visual, auditory, and haptic rendering algorithms Compute the virtua l environments graphic, sound, and force responses toward the user. Transducers transfer visual, sound, and force signals from the computer into a form the operator trick perceive. The human operator typically holds or wears the haptic interface device and perceives audiovisual feedback from audio (computer speakers, headphones, and so on) and visual displays (a computer screen or head-mounted display, for example). 2. 2 System architecture for *haptic* rendering drawrect drawrect drawrect drawframe drawframe Fig 2. 2Haptic rendering divided into main three blocks S- contacts* occurring between an avatar at position X and objects in the virtual environment. Fd- * takings* the ideal interaction force between avatar and virtual objects. Fr- Force to the user 1. Collision-detection algorithms detect collisions between objects and avatars in the virtual environment and yield training about where, when, and ideally to what extent collisions (penetrations, indentations, contact area, a nd so on) have occurred. 2. Force-response algorithms compute the interaction force between avatars and virtual objects when a collision is detected.This force approximates as closely as possible the contact forces that would prescriptly arise during contact between real objects. Hardware coiffeations nix haptic devices from applying the exact force computed by the force-response algorithms to the user. 3. Control algorithms command the haptic device in such a way that minimizes the error between ideal and applicable forces. The discrete-time nature of the haptic- rendering algorithms much makes this difficult.The force response algorithms return values are the actual force and torque vectors that will be commanded to the haptic device. Existing haptic rendering techniques are currently based upon two main principles depute-interaction or ray-based. In point interactions, a single point, usually the distal point of a probe, thimble or stylus employed for direct interaction with the user, is employed in the simulation of collisions. The point penetrates the virtual objects, and the depth of indentation is calculated between the current point and a point on the surface of the object.Forces are then generated according to physical models, such as spring stiffness or a spring-damper model. In ray-based rendering, the user interface mechanism, for example, a probe, is modeled in the virtual environment as a finite ray. Orientation is thus taken into account, and collisions are stubborn between the simulated probe and virtual objects. Collision detection algorithms return the intersection point between the ray and the surface of the simulated object. *2. 2. 1 deliberation contact-response forces*Humans perceive contact with real objects through sensors (mechanoreceptors) located in their skin, joints, tendons, and muscles. We make a simple distinction between the information these two typewrites of sensors can acquire. 1. Tactile information refers to the in formation acquired through sensors in the skin with particular reference to the spatial distribution of pressure, or more generally, tractions, across the contact area. To oversee flexible materials like fabric and paper, we sense the pressure variation across the fingertip.Tactile sensing is also the basis of complex perceptual tasks like medical checkup palpation, where physicians locate hidden anatomical structures and evaluate tissue properties using their hands. 2. Kinesthetic information refers to the information acquired through the sensors in the joints. Interaction forces are normally perceived through a combination of these two. To provide a haptic simulation experience, systems are designed to recreate the contact forces a user would perceive when sense of touch a real object. There are two types of forces . Forces due to object geometry. 2. Forces due to object surface properties, such as texture and friction. The first type of force-rendering algorithms aspires to re create the force interaction a user would feel when touching a frictionless and textureless object. Force-rendering algorithms are also grouped by the number of Degrees-of-freedom (DOF) requisite to describe the interaction force being rendered. 2. 2. 3 Surface property-dependent force-rendering algorithms All real surfaces contain tiny irregularities or indentations.Higher accuracy, however, sacrifices speed, a critical mover in real-time applications. Any choice of modeling technique must consider this tradeoff. Keeping this trade-off in mind, researchers have developed more high-fidelity haptic-rendering algorithms for friction. In computer graphics, texture mapping adds realism to computer-generated scenes by projecting a bitmap image onto surfaces being rendered. The same can be make haptically. 2. 3 Controlling forces delivered through *haptic* interfaces Once such forces have been computed, they must be applied to the user.Limitations of haptic device technology, however, have sometimes do applying the forces exact value as computed by force-rendering algorithms impossible. They are as follows Haptic interfaces can only exert forces with limited magnitude and not equally well in all directions Haptic devices arent ideal force transducers. An ideal haptic device would render zero impedance when simulating dejection in free space, and any finite impedance when simulating contact with an object featuring such impedance characteristics.The friction, inertia, and backlash present in most haptic devices prevent them from meeting this ideal. A third issue is that haptic-rendering algorithms operate in discrete time whereas users operate in continuous time. drawframe ?Finally, haptic device position sensors have finite resolution. Consequently, attempting to determine where and when contact occurs always results in a quantization error. It can create stability problems. All of these issues can limit a haptic applications realism. High servo rates (or l ow servo rate periods) are a key issue for invariable haptic interaction.There are two main types of haptic devices Devices that allow users to touch and manipulate 3-dimentional virtual objects. Devices that allow users to feel textures of 2-dementional objects. 3. 1 LOGITECH WINGMAN FORCE FEEDBACK purloin drawframe fig. 3. 1 logitech mouse Fig. 3. 1 shows a Logitech mouse which is attached to a base that replaces the mouse mat and contains the motors used to provide forces back to the user. drawframe Fig. 3. 2 Phantom Used in surgical simulations and remote operation of robotics in hazardous environments drawframeFig3. 3 Cyber mitt Cyber Glove can sense the position and movement of the fingers and wrist. drawg The basic Cyber Glove system includes one CyberGlove, its instrumentation unit, serial cable to interrelate to your host computer, and an executable version of VirtualHand graphic hand model display and calibration software. The firm introduced haptic technology for th e X-by-Wire system and was showcased at the Alps channelize 2005 in Tokyo. The system consisted of a cockpit with steering, a gearshift lever and pedals that embed haptic technology, and a remote-control car.Visitors could control a remote control car by operating the steering, gearshift lever and pedals in the cockpit seeing the screen in front of the cockpit, which is projected via a camera equipped on the remote control car. With many new haptic devices being sold to industrial companies, haptics will soon be a part of a persons normal computer interaction. REFERENCES http//www. sensable. com/products/datafiles/phantom_ghost/Salisbury_Haptics95. pdf http//www. wam. umd. edu/prmartin/3degrees/HAPTIC%20TECHNOLOGY1. doc http//www. sensable. com http//www. logitech. com http//www. technologyreview. com