Tongue Drive System’s Dental Appliance

The Tongue Drive System is getting less conspicuous and more capable. Tongue Drive is a wireless device that enables people with high-level spinal cord injuries to operate a computer and maneuver an electrically powered wheelchair simply by moving their tongues.

The newest prototype of the system allows users to wear an inconspicuous dental retainer embedded with sensors to control the system. The sensors track the location of a tiny magnet attached to the tongues of users. In earlier versions of the Tongue Drive System, the sensors that track the movement of the magnet on the tongue mounted 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 Maysam Ghovanloo, an associate professor in the School of Electrical and Computer Engineering at the Georgia Institute of Technology.

The new dental appliance contains magnetic field sensors mounted on its four corners that detect movement of a tiny magnet attached to the tongue. It also includes a rechargeable lithium-ion battery and an induction coil to charge the battery. The circuitry fits in the space available 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.

“One of the problems we encountered with the earlier headset was that it could shift on a user’s head and the system would need to be recalibrated,” Ghovanloo explains. “Because the dental appliance is worn inside the mouth and molded from dental impressions to fit tightly around an individual’s teeth with clasps, it is protected from these types of disturbances.”

When in use, the output signals from the sensors wirelessly transmit to an iPod or iPhone. Software installed on the iPod interprets the user’s tongue commands by determining the relative position of the magnet with respect to the array of sensors in real-time. This information controls the movements of a cursor on the computer screen, substituting for the joystick function in a powered wheelchair.

Ghovanloo and his team have also created a universal interface for the intraoral Tongue Drive System that attaches directly to a standard electric wheelchair. The interface boasts multiple functions: it not only holds the iPod, but also wirelessly receives the sensor data and delivers it to the iPod, connects the iPod to the wheelchair, charges the iPod, and includes a container where the dental retainer charging during the night.

In preliminary tests, the intraoral device exhibited an increased signal-to-noise ratio, even when placing a smaller magnet on the tongue. That improved sensitivity could allow programming of additional commands into the system. The existing Tongue Drive System that uses a headset interprets commands from seven different tongue movements.

The ability to train the system with additional commands – as many commands as an individual can comfortably remember – and having all of the commands available to the user at the same time are significant advantages over the common sip-n-puff device that acts as a simple switch controlled by sucking or blowing through a straw.

Georgia Tech graduate students Abner Ayala-Acevedo, Xueliang Huo, Jeonghee Kim, Hangue Park and Xueli Xiao, and former postdoctoral fellow Benoit Gosselin also contributed to this work.

All Photos courtesy of Georgia Institute of Technology.
 

Georgia Institute of Technology
Atlanta, Georgia
gatech.edu