Hi Luighi,
I don't know myself the modular EEG, but if you have only two bipolar channels, it will be difficult to create a multi-class (i.e., at least 3-class) motor imagery BCI.
For instance, to classify left hand, right hand and foot movements you would need a minimum of 3 channels, over C3 (for right hand), Cz (for foot) and C4 (for left hand) electrode positions.
This being said, with only two classes, e.g., left and right hand imagined movements (which you can do with only 2 channels), you can still send more than 2 commands to your robot, using scanning principles (i.e., different commands would be sequentially highlighted to be potentially selected. In other words, the command you will issue depends on when you performed the selected mental task), see, e.g., the following recent paper (and the other works from the same authors) :
http://www.sciencedirect.com/science/ar ... 1213001525
Hope this helps,
Best regards,
Fabien