9 Conclusion
This report presents results that shows that is it possible to build a Brain-Computer
Interface system that allow users to play a game and controlling it with their brain
waves. This have been accomplished by using the NeuroSky mindset EEG equipment featuring only one electrode on the forehead. EEG signals from the user are
sent to the computer via bluetooth. The signal is then processed and the waves
band power is calculated using the Fourier transform. This information is used
as input to a neural network that is trained to classify two different mental tasks.
Then this classification is used to control the movements (left and right turn) of a
character in a custom built PC game, successfully.
The biggest challenge and time-consumption in the project was not the implementation itself, but testing it with the use of real-time EEG input. Three major test
steps is outlined with results that have given insights in the workings of EEG and
difficulties with BCI systems. The first step was to implement all the components
of the system and make them communicate with each other, then enable the system to classify blinks in the incoming EEG signal samples. This was done with
a success rate close to 99%. The solution worked, indeed, but was not adequate
to classify mental tasks. This was improved in step two, were a new method was
discovered that required ten times as many samples and thus effort from the user.
Still, it became possible to classify two mental states: baseline (relaxed, calm and
not thinking of anything in particular), and mental counting. The first results
only gave 60% probability of correct classification, but this was further increased
to greater than 90%. This high rate was only attainable when eye states (eyes open
and closed) were used actively by the user in addition to the tasks. However, this
enabled the realization of step 3, were a version of the game Snake was designed
and implemented to work with the EEG input. Results from user tests show that
the snakes movements were correctly controlled with an accuracy of 90 to 100%.