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Topic Name: Researchers at Carnegie Mellon University has Developed Magnetic levitation that Gives Computer Users Sense of Touch

Category: Mechanical

Research persons: Ralph Hollis

Location: Carnegie Mellon University, United States

Details

Computers, long used as tools to design and manipulate three-dimensional objects, may soon provide people with a way to sense the texture of those objects or feel how they fit together, thanks to a haptic, or touch-based, interface developed at Carnegie Mellon University.

Unlike most other haptic interfaces that rely on motors and mechanical linkages to provide some sense of touch or force feedback, the device developed by Ralph Hollis, research professor in Carnegie Mellon’s Robotics Institute, uses magnetic levitation and a single moving part to give users a highly realistic experience. Users can perceive textures, feel hard contacts and notice even slight changes in position while using an interface that responds rapidly to movements.

“We believe this device provides the most realistic sense of touch of any haptic interface in the world today,” said Hollis, whose research group built a working version of the device in 1997. With the help of a $300,000 National Science Foundation grant, however, he and his colleagues have improved its performance, enhanced its ergonomics and lowered its cost. The grant also enabled them to build 10 copies, six of which are being distributed to haptic researchers across the U.S. and Canada.

“We have gone from the prototype to a much more advanced system that other researchers can use,” Hollis said. Putting the instrument in the hands of other researchers is critical in a young, developing field such as haptic technology, he emphasized. Though haptic interfaces have uses in engineering design, entertainment, assembly, remote operation of robots, and in medical and dental training, their full potential has yet to be explored. That’s particularly the case for magnetic levitation haptic interfaces because so few have been available for use by researchers, he added.

“This is an affordable device that’s also practical,” said Hollis, who has started a spinoff company to build additional devices. “Now other people can have this technology, and this represents technology transfer in the very real sense.”

Six devices will be delivered to researchers at Harvard, Stanford, Purdue and Cornell, as well as to the universities of Utah and British Columbia. All are members of the Magnetic Levitation Haptic Consortium, an international group dedicated to fostering increased use of this technology.

Hong Tan, associate professor of electrical and computer engineering at Purdue University and a consortium member, studies human perception of fine surface textures — work that requires simulation resolution at the micron level. “This is beyond the capability of most commercially available haptic devices, but the maglev device developed by Dr. Hollis will make it possible for us to continue this research,” she said.

“The field of haptic research and development is expanding rapidly,” said Rob Conway, project manager in Carnegie Mellon’s Center for Technology Transfer. “Carnegie Mellon’s research opens new possibilities by joining the world of haptic feedback with a comfortable magnetic levitation interface. The magnetic levitation decouples the interface device from the mechanical world, eliminating friction, backlash, jump, sticking and other interfering effects, so that the user feels only the artificial environment in complete accuracy down to the micro scale.”

The system eliminates the bulky links, cables and general mechanical complexity of other haptic devices on the market today in favor of a single lightweight moving part that floats on magnetic fields.

At the heart of the maglev haptic interface is a bowl-shaped device called a flotor that is embedded with six coils of wire. Electric current flowing through the coils interacts with powerful permanent magnets underneath, causing the flotor to levitate. A control handle is attached to the flotor.

A user moves the handle much like a computer mouse, but in three dimensions with six degrees of freedom — up/down, side to side, back/forth, yaw, pitch and roll. Optical sensors measure the position and orientation of the flotor, and this information is used to control the position and orientation of a virtual object on the computer display. As this virtual object encounters other virtual surfaces and objects, corresponding signals are transmitted to the flotor’s electrical coils, resulting in haptic feedback to the user. Hollis and his colleagues will demonstrate the new maglev haptic interfaces at the IEEE 16th Symposium on Haptic Interfaces for Virtual Environments and Teleoperator Systems, March 13-14 in Reno, Nevada.

Note for Haptic
Haptic means pertaining to the sense of 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.
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 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 othere devices worldwide.

Note for Magnetic levitation
Magnetic levitation, maglev, or magnetic suspension is a method by which an object is suspended with no support other than magnetic fields. The electromagnetic force is used to counteract the effects of the gravitational force.
There are several methods to obtain magnetic levitation. The primary ones used in maglev trains are servo-stabilized electromagnetic suspension (EMS), electrodynamic suspension (EDS), and (in the future) Inductrack.
If two magnets are mechanically constrained along a single vertical axis (a piece of string, for example), and arranged to repel each other strongly, this will act to levitate one of the magnets above the other. This is considered pseudo-levitation.
A substance which is diamagnetic repels a magnetic field. Earnshaw's theorem does not apply to diamagnets; they behave in the opposite manner of a typical magnet due to their relative permeability of μr < 1. All materials have diamagnetic properties, but the effect is very weak, and usually overcome by the object's paramagnetic or ferromagnetic properties, which act in the opposite manner. Any material in which the diamagnetic component is strongest will be repelled by a magnet, though this force is not usually very large. Diamagnetic levitation can be used to levitate very light pieces of pyrolytic graphite or bismuth above a moderately strong permanent magnet. As water is predominantly diamagnetic, this technique has been used to levitate water droplets and even live animals, such as a grasshopper and a frog; however, the magnetic fields required for this are very high, typically in the range of 16 teslas, and therefore create significant problems if ferromagnetic materials are nearby.

In figure 1, Levitating pyrolytic carbon