In this paper, an asynchronous brain-computer interface is presented that enables
the control of a wheelchair in virtual environments using only one motor imagery
task. The control is achieved through a graphical intentional control interface with
three navigation commands (move forward, turn right, and turn left) which are displayed
surrounding a circle. A bar is rotating in the center of the circle, so it points
successively to the three possible commands. The user can, by motor imagery, ex-
tend this bar length to select the command at which the bar is pointing. Once a
command is selected, the virtual wheelchair moves in a continuous way, so the user
controls the length of the advance or the amplitude of the turns. Users can volun-
tarily switch from this interface to a noncontrol interface (and vice versa) when
they do not want to generate any command. After performing a cue-based feed-
back training, three subjects carried out an experiment in which they had to navi-
gate through the same fixed path to reach an objective. The results obtained sup-
port the viability of the system.
