The MouthPad - a Tongue Interface for Hands-Free Computer Control

Abstract

Tongue-computer interfaces allow people with upper limb disability to control a computer with their tongue. A number of assistive devices, that make use of this technology, have been developed in the last two decades: some employ contact impedance, membrane switches, or miniature joysticks, while others use magnetic or piezoelectric sensors. This thesis proposes a new tongue-computer interface, which was designed to enable users to manipulate a computer pointer by moving the tip of their tongue over an intraoral electrode array. The system maps the contact between the tongue and the electrodes, detects the movements of the tongue, and translates it into pointer movements. Compared to similar devices, the MouthPad does not require any head gear or sensors, and does not employ heavy signal processing. The hardware is simplified by using a small number of electrodes and only one output channel, multiplexed over the electrode array. A low power footprint allows the potential miniaturization of the system, so that it could fit on palatal retainer, and allow for permanent unobtrusive usage. The performance of the device was evaluated by measuring the throughput and the accuracy as defined in ISO 9241-9 standard. Two extra measures proposed in the literature, target re-entry and movement offset, were used for the evaluation of the accuracy. The measured throughput values were situated between 78% and 88% of the throughput rates of regular computer joysticks.