Haptic feedback

Haptic or kinesthetic communication recreates the sense of touch by applying forces, vibrations, or motions to the user. This mechanical stimulation can be used to assist in the creation of virtual objects in a computer simulation, to control such virtual objects, and to enhance the remote control of machines and devices (telerobotics). Haptic devices may incorporate tactile sensors that measure forces exerted by the user on the interface.

Most researchers distinguish three sensory systems related to sense of touch in humans: cutaneous, kinesthetic and haptic. All perceptions mediated by cutaneous and/or kinesthetic sensibility are referred to as tactual perception. The sense of touch may be classified as passive and active, and the term "haptic" is often associated with active touch to communicate or recognize objects.

Haptic technology has made it possible to investigate how the human sense of touch works by allowing the creation of carefully controlled haptic virtual objects.

The word , from the Greek: ἁπτικός (haptikos), means "pertaining to the sense of touch" and comes from the Greek verb ἅπτεσθαι haptesthai, meaning "to contact" or "to touch".

One of the earliest applications of haptic technology was in large aircraft that use servomechanism systems to operate control surfaces. Such systems tend to be "one-way", meaning external forces applied aerodynamically to the control surfaces are not perceived at the controls. Here, the missing normal forces are simulated with springs and weights. In lighter aircraft without servo systems, as the aircraft approached a stall the aerodynamic buffeting (vibrations) was felt in the pilot's controls. This was a useful warning of a dangerous flight condition. This control shake is not felt when servo control systems are used. To replace this missing sensory cue, the angle of attack is measured and when it approaches the critical stall point, a stick shaker is engaged which simulates the response of a simpler control system. Alternatively, the servo force may be measured and the signal directed to a servo system on the control, known as force feedback. Force feedback has been implemented experimentally in some excavators and is useful when excavating mixed material such as large rocks embedded in silt or clay. It allows the operator to "feel" and work around unseen obstacles, enabling significant increases in productivity and less risk of damage to the machine.

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