Design of a Brazilian Portuguese virtual keyboard for people with severe motor disability

Virtual keyboards represent an important tool in the Assistive Technology area as they can assist in computer interaction by people with severe motor disability. Depending on the interaction method used, a differentiated arrangement of keys can speed up the task of typing a text. This work proposes a virtual keyboard layout which allows people with disabilities to write texts in Brazilian Portuguese language efficiently. The method of human-computer interaction used is a webcam-based cursor controller limited by continuum vertical and horizontal movements. Keys arrangement is based on digraphs frequency of occurrence in a corpus of Portuguese language. The performance of the virtual keyboard was evaluated by two tests. Firstly, a function which estimates the movement efficiency when typing a key is used to compare the layout with other solutions. Proposed layout presented typing speed faster than QWERTY (41%), OPTI (4%) and FITALY (3%). In user evaluation, users have performed the tasks significantly faster with the proposed keyboard layout.