Haptic

Overview

 * This article is about haptic technology. For the study of touching behaviour in humans, see Haptic communication. For the biology of sensory receptors, see Somatosensory system. For object perception via touch, see Haptic perception.

Haptic, from the Greek (Haphe), means pertaining to the sense of touch (or possibly from the Greek word  haptesthai meaning “contact” or “touch”).

Haptic technology refers to technology which interfaces the user via the sense of touch by applying forces, vibrations and/or motions to the user. This mechanical stimulation may be used to assist in the creation of virtual objects (objects existing only in a computer simulation), for control of such virtual objects, and to enhance the remote control of machines and devices (teleoperators). This emerging technology promises to have wide reaching applications. In some fields, it already has. For example, haptic technology has made it possible to investigate in detail how the human sense of touch works, by allowing the creation of carefully-controlled haptic virtual objects. These objects are used to systematically probe human haptic capabilities. This is very difficult to achieve otherwise. These new research tools contribute to our understanding of how touch and its underlying brain functions work (See References below).

Although haptic devices are capable of measuring bulk or reactive forces that are applied by the user it should not to be confused with touch or tactile sensors that measure the pressure or force exerted by the user to the interface.

History
One of the earliest forms of haptic devices is used in large modern aircraft that use servo systems to operate control systems. Such systems tend to be "one-way" in that forces applied aerodynamically to the control surfaces are not perceived at the controls, with the missing normal forces simulated with springs and weights. In earlier, lighter aircraft without servo systems, as the aircraft approached a stall the aerodynamic buffeting was felt in the pilot's controls, a useful warning to the pilot of a dangerous flight condition. This control shake is not felt when servo control systems are used. To replace this missing cue, the angle of attack is measured, and when it approaches the critical stall point a "stick shaker" (an unbalanced rotating mass) is engaged, simulating the effects of a simpler control system. This is known as haptic feedback. Alternatively the servo force may be measured and this signal directed to a servo system on the control. This method is known as force feedback. Force feedback has been implemented experimentally in some excavators. This is useful when excavating mixed materials such as large rocks embedded in silt or clay, as it allows the operator to "feel" and work around unseen obstacles, enabling significant increases in productivity.

Teleoperators and simulators
Teleoperators are remote controlled robotic tools, and when contact forces are reproduced to the operator, it is called "haptic teleoperation". The first electrically actuated teleoperators were built in the 1950's at the Argonne National Lab, USA, by Dr. Raymond C. Goertz, to remotely handle radioactive substances. Since then, the use of "force feedback" has become more widespread in all kinds of teleoperators such as underwater exploration devices controlled from a remote location.

In 1988 researchers at Cybernet Systems first developed devices that generated arbitrary forces from computer models or simulations in lieu of actual physical slave devices. When such devices are simulated using a computer (as they are in operator training devices) it is useful to provide the force feedback that would be felt in actual operations. Since the objects being manipulated do not exist in a physical sense, the forces are generated using haptic (force generating) operator controls. Data representing touch sensations may be saved or played back using such haptic technologies. Cybernet licensed its force feedback patents to Immersion Corporation in 1998 and Immersion licensed Logitech, Microsoft, Sony and others to manufacture Force Feedback joysticks, wheels, and other devices worldwide.

Haptic simulators are currently used in medical simulators and flight simulators for pilot training (2004).

Games
Some low-end haptic devices are already common in the form game controllers, in particular of joysticks and steering wheels. At first, such features and/or devices used to be optional components (like the Nintendo 64 controller's Rumble Pak). Now many of the newer generation console controllers and some joysticks feature built in devices. An example of this feature would be the simulated automobile steering wheels that are programmed to provide a "feel" of the road. As the user makes a turn or accelerates, the steering wheel responds by resisting turns or slipping out of control. Another concept of force feedback was that of the ability to change the temperature of the controlling device. This would prove especially efficient for prolonged usage of the device. However, due to the high cost of such a technology (not to mention the power drainage of such a component) the closest many manufacturers have come to realizing this concept has been to install air holes or small fans into the device to provide the user's hands with ventilation while operating the device.

Haptics in virtual reality
Haptics is gaining widespread acceptance as a key part of virtual reality systems, adding the sense of touch to previously visual-only solutions. Most of these solutions use stylus-based haptic rendering, where the user interfaces to the virtual world via a tool or stylus, giving a form of interaction that is computationally realistic on today's hardware

Research
Some research has been done into simulating the different kinds of tactition by means of high-speed vibrations or other stimuli. One device of this type uses a pad array of pins, where the pins vibrate to simulate a surface being touched. While this does not have a realistic feel, it does provide useful feedback, allowing discrimination between various shapes, textures, and resiliencies.

Several haptics API's have been developed for research applications, such as Chai3D, OpenHaptics and H3DAPI (Open Source).

Medicine
Various haptic interfaces for medical simulation may prove especially useful for training of minimally invasive procedures (laparoscopy/interventional radiology) and remote surgery using teleoperators. In the future, expert surgeons may work from a central workstation, performing operations in various locations, with machine setup and patient preparation performed by local nursing staff. Rather than traveling to an operating room, the surgeon instead becomes a telepresence. A particular advantage of this type of work is that the surgeon can perform many more operations of a similar type, and with less fatigue. It is well documented that a surgeon who performs more procedures of a given kind will have statistically better outcomes for his patients.

In ophthalmology, "haptic" refers to a supporting spring, two of which hold an artificial lens within the lens capsule (after surgical removal of cataracts).

A 'Virtual Haptic Back' (VHB) is being successfully integrated in the curriculum of students at the Ohio University College of Osteopathic Medicine. Research indicates that VHB is a significant teaching aid in palpatory diagnosis (detection of medical problems via touch). The VHB simulates the contour and compliance (reciprocal of stiffness) properties of human backs, which are palpated with two haptic interfaces (SensAble Technologies, PHANToM 3.0).

Literature
The use of haptic devices in entertainment appeared in the 1932 futurist fiction book Brave New World by Aldous Huxley. The author described a future entertainment theater where the arm rests of the seats had positions for the hands to rest that gave haptic stimulation. The programs exhibited were of an erotic nature and rather than "the movies" these theaters and shows were called "the feelies". Haptic devices, including self-propelled haptics, feature prominently in Vernor Vinge's 2006 novel Rainbows End.

Robotics
The Shadow Dextrous Robot Hand uses the sense of touch, pressure, and position to reproduce the human grip in all its strength, delicacy, and complexity. The SDRH was first developed by Richard Greenhill and his team of engineers in Islington, London, as part of The Shadow Project, (now known as the Shadow Robot Company) an ongoing research and development program whose goal is to complete the first convincing humanoid. An early prototype can be seen in NASA's collection of humanoid robots, or robonauts. The Dextrous Hand has haptic sensors embedded in every joint and in every finger pad which relay information to a central computer for processing and analysis. Carnegie Mellon University in Pennsylvania and Bielefeld University in Germany in particular have found The Dextrous Hand is an invaluable tool in progressing our understanding of haptic awareness and are currently involved (2006) in research with wide ranging implications.

Arts
Touching is not limited to a feeling, but it allows interactivity in real-time with virtual objects. Thus haptics are commonly used in virtual arts, such as sound synthesis or graphic design/animation. The haptic device allows the artist to have direct contact with a virtual instrument which is able to produce real-time sound or images. We can quote the physical modelling synthesis which is an efficient modelling theory to implement cross-play interaction between sound, image, and physical objects. For instance, the simulation of a violin string produces real-time vibrations of this string under the pressure and expressivity of the bow (haptic device) held by the artist.

Design
Designers and modellers may use high-degree of freedom input devices which give touch feedback relating to the "surface" they are sculpting or creating, allowing faster and more natural workflow than with traditional methods.