Mag-lev interface offers sense of touch

Most haptic interfaces rely on motors and mechanical links to provide some sense of touch or force feedback.

But the device developed by Ralph Hollis, a research professor at Carnegie Mellon's Robotics Institute, uses magnetic levitation and a single moving part to give users a "highly realistic" experience.

Professor Hollis said that 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 Professor Hollis, whose research group built a working version of the device in 1997.

At the heart of the maglev haptic interface is a bowl-shaped device called a flotor 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.

Professor Hollis and his colleagues have improved the interface's performance, enhanced its ergonomics and lowered its cost with the help of a US$300,000 National Science Foundation grant.

The grant also enabled the team to build 10 copies of the device, six of which are being distributed to haptic researchers across the US and Canada.

"We have gone from the prototype to a much more advanced system that other researchers can use," said Professor Hollis.

"Putting the instrument in the hands of other researchers is critical in a young, developing field such as haptic technology."

Devices will be delivered to researchers at the universities of Harvard, Stanford, Purdue, Cornell, Utah and British Columbia.

The academic institutions are members of the Magnetic Levitation Haptic Consortium, an international group dedicated to fostering increased use of the technology.

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