A Novel Semi-Dry Electrode Suitable for Collecting EEG Data for Detecting Driving Fatigue in Long-Period Driving Case

To address issues with the conventional wet electrode during long-period experiments, which include signal acquisition distortion caused by conductive liquid volatilization and drying, as well as time-consuming conductive liquid refilling, this study introduced a portable semi-dry electrode that allows for convenient conductive liquid replenishment at any time. The new semi-dry electrode combines the advantages of the small impedance value of wet electrodes and the convenient installation and disassembly of dry electrodes. And this electrode is suitable for collecting human electroencephalogram (EEG) for a long time, such as detecting the EEG characteristics of drivers who drive vehicles for a long time. In addition, since the order recurrence plot (ORP) does not require signal stability, data length, and signal-to-noise ratio, this article used the method to analyze the driving fatigue characteristics of the subjects. First, the ORP method was used to map EEG signals collected by the two types of electrodes, and the ORP was performed by recurrence quantitative analysis (RQA). Then, two quantitative parameters, determinism (DET) and average diagonal line length (DLL), were selected to analyze the fatigue-driving characteristics of the subjects. The results showed that with the increase of fatigue degree of the subjects, the blue and white squares in ORP from EEG signals collected by the two kinds of electrodes gradually increased, with a clearer texture and a more organized arrangement. Meanwhile, the quantization parameters DET and DLL increase gradually as well, which can effectively express the law of driving fatigue change. The results of this study are helpful to address the problems such as the difficulty of supplementing conductive fluid with traditional wet electrodes and to address the problem of easy interference in EEG acquisition experiments in complex environments.