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Device Improves Wheelchair Control for Spinal Cord Injured

Intraoral tongue drive device (Georgia Tech)

Intraoral tongue drive device (Georgia Tech)

A system designed at Georgia Institute of Technology enables people with high-level spinal cord injuries to operate a computer and electrically powered wheelchair by moving their tongues. The Tongue Drive, as the system is called, is scheduled for demonstration today by electrical and computer engineering professor Maysam Ghovanloo and colleagues at the IEEE International Solid-State Circuits Conference in San Francisco.

The new version of the Tongue Drive, now in prototype, allows a user to wear a dental retainer completely inside the mouth embedded with sensors to control the system (pictured right). The sensors track the location of a tiny magnet attached to the user’s tongue.

Earlier versions of the device used sensors on a headset worn by the user. “By moving the sensors inside the mouth, we have created a Tongue Drive system with increased mechanical stability and comfort that is nearly unnoticeable,” says Ghovanloo.

The new device has magnetic field sensors mounted on its four corners that detect movement of a tiny magnet attached to a tongue stud implanted by piercing. The system also has a lithium-ion battery and an induction coil to recharge the battery.

The circuitry fits on the retainer, which sits against the roof of the mouth and is covered with an insulating, water-resistant material and vacuum-molded inside standard dental acrylic. The appliance is molded from dental impressions to fit tightly around an individual’s teeth. The earlier version using a headset could shift on a user’s head and the system would then need to be recalibrated.

Signals from the sensors on the dental plate are wirelessly transmitted to an iPod or iPhone, with software that interprets the user’s tongue commands by determining the real-time position of the magnet relative to the sensors. These data control the movements of a cursor on a computer screen or work like a joystick on a powered wheelchair. The Georgia Tech team also designed a utility module that holds the iPhone or iPod, receives data from the sensors, connects the iPhone/iPod to the wheelchair, recharges the iPhone/iPod, and holds the dental retainer overnight for charging.

Preliminary tests showed the device exhibited an increased signal-to-noise ratio that offers more sensitivity — even with a smaller tongue magnet — which will allow more commands to be programmed into the system. Providing more commands in the basic system, plus the ability to train the system with additional commands, are considered improvements over the previous headset version of the Tongue Drive with limited built-in commands and current sip-and-puff devices that act as a simple switch controlled by sucking or blowing through a straw.

Ghovanloo’s team has tested the headset version of the Tongue Drive in a clinical trial at the Shepherd Center in Atlanta and Rehabilitation Institute of Chicago. The researchers expect usability tests of the intraoral Tongue Drive System by able-bodied individuals to begin soon, followed by clinical trials by people with high-level spinal cord injuries.

Read more: Utah Engineering Program Develops Paraglider for Disabled

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