Mapping sensor activation time for typing tasks performed with a tongue controlled oral interface

Two tetraplegic subjects performed typing tasks on a computer in an experiment using a tongue controlled oral interface. This paper reports mapping of the sensor activation time for a full alphabet text input using 10 inductive sensors. A small cylindrical piece of soft ferromagnetic material activated the sensors when placed at or glided along the surface of the sensor. The activation unit was attached to the tongue as the upper ball of a piercing. The tasks consisted of typing characters according to ordered (rows and columns) or random test strings during 30 seconds, with and without deleting characters typed by mistake. Visual feedback assisted the subjects to perform the typing tasks. Average activation times were of 0.82+/-0.38 and 1.06 +/-0.27 seconds respectively for the two subjects. Analysis of activation times may be useful in characterization of the tongue ability to activate the interface as well as in design optimization of the layout of the sensors.