Tongue drive sounds at first like a strange sexual fetish. That may well be true, but it is also a disability-overcoming interface that has been developed over the past year by the Georgia Institute of Technology. Initial linical trial results are now out, as the system, which allows those with limited general muscle control, or nerve damage to operate wheelchairs and other devices, is unleashed on the general wheelchair user population outside of the lab.

The results were presented by Maysam Ghovanloo, an assistant professor in the School of Electrical and Computer Engineering at the annual meeting of the Rehabilitation Engineering and Assistive Technology Society of North America (RESNA). One of the features highlighted, which may make it suitable for virtual applications as well, is it is highly intuative and participants became accustomed to it in a short space of time.

A tongue-drive user controls an electric wheelchair's speed and direction through a winding assault course, purely with their tongue movements.

Maysam stated, "Trial participants were able to easily remember and correctly issue tongue commands to play computer games and drive a powered wheelchair around an obstacle course with very little prior training."

At the beginning of each trial, Maysam and graduate students Xueliang Huo and Chih-wen Cheng attached an electromagnet the size of a single grain of rice to the participant's tongue. The position of this magnet was then tracked in real-time and in six degrees of freedom by an array of magnetic field sensors positioned on a headpiece the participant wore.

The result was something akin to old-style HMD and CAVE hear tracking, but with a high degree of precision. No studies as to the mental effects of a powerful magnetic field directly under the brain were carried out.

The positional information gathered by the sensors were transmitted to a small palmtop PC embedded into the wheelchair itself. This served as the co-ordination centre, putting the signals together, and passing the result on to the wheelchair's own subprocessor.

This information was then used to control the movements of the cursor on a computer screen or to substitute for the joystick function in a powered wheelchair. In theory, it could be used relatively easily as the control system for a virtual environment by supplanting the mouse itself, or through custom input channels.

Before using the Tongue Drive system, the subjects trained the computer to understand how they would like to move their tongues to indicate different commands. A unique set of specific tongue movements was tailored for each individual based on the user's abilities, oral anatomy and personal preferences. Because all of this is handled by the palm top, the external output is the same across users. This makes it much easier to integrate into existing systems.

While this initial performance trial only required six tongue commands, the Tongue Drive system can potentially capture a large number of tongue movements, each of which can represent a different user command. Indeed, the possibilities are as great as any macro/trigger command system.

A future system upgrade will be to move the sensors inside the user's mouth, using something akin to a tooth guard to position the sensors. This will lower the intensity of the electromagnet, and potentially increase both fidelity and response time.

References

Clinical Trial Shows Quadriplegic Individuals Can Operate Powered Wheelchairs and Computers with Tongue Drive System

Using Unconstrained Tongue Motion as an Alternative Control Mechanism for Wheeled Mobility (PDF)

WMV Video of Trial