Disney Research's gloveless REVEL system adds virtual textures to physical objects
By Brian Dodson
August 13, 2012
Having long been successful with "talkies," Disney has developed technology that could allow the creation of "feelies." While designed more for touchscreens than the silver screen, the REVEL system developed at Disney Research uses reverse electrovibration to bring computerized control over the sense of touch, thereby allowing programmers to change the feel of real-world surfaces and objects without requiring users to wear special gloves or use force-feedback devices.
One obstacle to attaining immersive augmented reality is that certain senses are difficult to fool into accepting virtual information. Touch, in particular, has many facets, each of which must be tricked into experiencing a virtual reality. If you squeeze a virtual tennis ball in your hand, you must not only feel the mass and compressibility of the ball, but also feel the texture of the ball's surface.
Feeling the first two properties can be achieved by simply providing resistance to the motion of your fingers, perhaps through the exoskeleton of a virtual reality (VR) glove. If you apply force and your fingers discover that a given level of pressure causes only so much motion, the feel of squeezing a ball is reproduced. Textures, however, are felt as a set of high-frequency and small scale touches and are much more difficult to reproduce.
In moving your finger over a sheet of sandpaper, for example, you feel not only the high friction of the surface, but you also feel the changing pattern of the abrasive grains as your finger moves over the surface. The size of the grit on 120 sandpaper is roughly 4 mils (0.1 mm), so the sensation of feeling the roughness involves sensory signals having frequencies from a few tens of Hz to a few hundred Hz. The small physical length scale makes brute force simulation extraordinarily difficult – a glove with an inner surface literally paved with thousands of sub-millimeter MEMS sensors and actuators and their control electronics would be required.
Fortunately, Disney researchers have discovered an approach to fool our sense of touch into believing that an object has a texture far different than what it actually is. It relies on reverse electrovibration, a new technique that creates the illusion of a range of textures as the user's fingers sweep across a surface, without the need for actuators. A weak electrical signal, which can be applied imperceptibly anywhere on the user's body, creates an oscillating electrical field around the user's fingers that is responsible for the tactile feedback.
The electrovibration effect was first reported in the early 1950s. It's a sensation that people sometimes feel when they slide a finger across a smooth metal surface of an ungrounded electrical appliance, such as an older model of toaster. With the dry, outer layer of skin serving as an insulator, a small alternating current on the metal surface generates an attractive force between the surface and the tissues of the finger. No current actually passes through the skin, but the result is the perception that the surface is rubbery.
The Disney researchers discovered that the same sensation could be created by applying the small alternating current anywhere on the user's body instead of the surface – reverse electrovibration, or REVEL. REVEL could be used to add tactile feedback to games, add the perception of texture to projected images on surfaces of any size and shape, provide customized directions on walls for people with visual disabilities and enhance other applications of augmented reality. By tracking the finger's position with external sensors, REVEL can manipulate the reverse electrovibration to make the user feel bumps, edges or changes in texture corresponding to particular locations on the surface.
The surfaces to which computerized textures are to be applied need to be coated with an insulator-covered electrode, or "REVEL skin." Anodized aluminum objects or capacitive touch-screens can be used without any modification, while a REVEL skin can be manufactured on walls or other surfaces using off-the-shelf materials. One simple method is to coat a surface with a conductive paint and add a coat of conventional household paint as an insulating layer.
The surfaces must also share a common electrical ground with the REVEL signal generator carried on the person experiencing the induced textures. This can be accomplished by a variety of methods, including holding a grounded cane containing the REVEL oscillator, having a conducting plate and a REVEL oscillator in one's shoe, and placing a REVEL contact next to an object with induced texture and touching one in each hand. For immersive reality, of course, there will be many intimate contacts which can be used to connect the user to a REVEL oscillator.
One of the early uses of REVEL technology is likely to be a new form of representational artwork, as it is applicable to both paintings and sculpture. Realistic art may include induced textures appropriate for the subject, impressionistic art may include textures having some intended relation to the subject, and revolutionary art may include extremely discordant textures to suit the artist's vision. In addition to enhancing the experience of art, REVEL technology may spark a type of participatory art, in which the viewer is able to change the induced textures, resulting in a more pleasant overall experience which can be shared with others, or public art which remembers new and popular induced textures contributed by passers-by.
Both immersive reality and augmented reality techniques are in their early stages. Yet the building blocks of future technologies are rapidly appearing owing to the efforts of teams of multi-skilled researchers dedicated to this goal. Disney appears keen to be at the forefront of next generation haptics technology with REVEL joining Surround Haptics, a haptic feedback system that uses a low-resolution grid of vibrating actuators to generate high-resolution, continuous, moving tactile strokes across a person's skin.
The video below from Disney Research provides a brief overview of the REVEL system.
Source: Disney Research