Virtual Fixtures

A virtual fixture is an overlay of augmented sensory information on a workspace in order to improve human performance in direct and remotely manipulated tasks. Developed in the early 1990s by Louis Rosenberg at the US Air Force, virtual fixtures was a pioneering platform in virtual reality and augmented reality technologies.

Virtual Fixtures was first developed by Louis Rosenberg in 1992 at the USAF Armstrong Labs, resulting in the first immersive Augmented Reality system ever built. Because 3D graphics were too slow in the early 1990s to present a photorealistic and spatially-registered augmented reality, Virtual Fixtures used two real physical robots, controlled by a full upper-body exoskeleton worn by the user. To create the immersive experience for the user, a unique optics configuration was employed that involved a pair of binocular magnifiers aligned so that the user’s view of the robot arms were brought forward so as to appear registered in the exact location of the user’s real physical arms. The result was a spatially-registered immersive experience in which the user moved his or her arms, while seeing robot arms in the place where his or her arms should be. The system also employed computer-generated virtual overlays in the form of simulated physical barriers, fields, and guides, designed to assist in the user while performing real physical tasks.Fitts Law performance testing was conducted on batteries of human test subjects, demonstrating for the first time, that a significant enhancement in human performance of real-world dexterous tasks could be achieved by providing immersive Augmented Reality overlays to users.

The concept of virtual fixtures was first introduced in (Rosenberg, 1992) as an overlay of virtual sensory information on a workspace in order to improve human performance in direct and remotely manipulated tasks. The virtual sensory overlays can be presented as physically realistic structures, registered in space such that they are perceived by the user to be fully present in the real workspace environment. The virtual sensory overlays can also be abstractions that have properties not possible of real physical structures. The concept of sensory overlays is difficult to visualize and talk about, as a consequence the virtual fixture metaphor was introduced. To understand what a virtual fixture is an analogy with a real physical fixture such as a ruler is often used. A simple task such as drawing a straight line on a piece of paper on free-hand is a task that most humans are unable to perform with good accuracy and high speed. However, the use of a simple device such as a ruler allows the task to be carried out fast and with good accuracy. The use of a ruler helps the user by guiding the pen along the ruler reducing the tremor and mental load of the user, thus increasing the quality of the task.

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