Figure 5 shows the EEG measurement system (Geodesic
Sensor Nets, Electrical Geodesics, Inc.) used in this study. This
sensor system can measure EEG signals of 256 channels. By
using this system, EEG signals are measured with the sampling
frequency of 1 kHz.
As same as EMG signals, the measured raw EEG signals
are not suitable for input signals for the robots. At first, to
remove the influence of the noise that is generated among
whole electrodes, Common Average Reference (CAR) is
carried out to the measured raw EEG signals as follows.