The Voice interface will use the serial data [a byte per recognized message] from the voice recognition module, and drive an LCD display [20 char x 4 lines] to show what it has understood from the user's commands, and will either use the commands to move the wheel chair, or forward it on a rs232 type serial bus so that add-on devices such as a TV remote, cell phone, gripper hand, etc can make use of the interface.
The controller would list for selection type commands such as: CHAIR, TV, PHONE, ARM, and if the command sequence is not idle, ignore command sets that do not have the 'prefix' of "CHAIR", and ignore "CHAIR" until the 'deselect' command of 'FINISH' is detected.
I envision a command set for the wheel chair consisting of words such as: CHAIR, FORWARD, BACKWARD, LEFT, RIGHT, STOP, FASTER, SLOWER, MORE, NUDGE, STOP, FINISH, etc.
The first pass of the software will recognize a sequence such a: CHAIR FORWARD MORE MORE STOP LEFT MORE NUDGE NUDGE FINISH.