Investigation on thermal comfort using driver's bio-signals depend on vehicle cabin and vent exit air temperature

In this study, the brain and pulse waves of test subjects were measured when the cabin temperature of a vehicle was changed from an uncomfortable range to a comfortable range. In addition, questionnaires on the thermal comfort level of subjects were distributed and the results were analyzed. In the cooling condition, the stress index and ratio between low frequency and high frequency (LF/HF) did not clearly indicate an uncomfortable condition, except when the cabin and vent exit temperatures were 30 degrees C and 16.5 degrees C, respectively. When the air temperature from the vent exit was very low, the thermal sensation temperature of test subjects became lower, which could be inferred from the activation of high beta wave owing. The subjects also felt uncomfortable because of increasing visual fatigue, which became evident after long periods of driving. In the heating condition, subjects felt great satisfaction because of the warm air flow from the vent exit during the initial test. After the cabin and vent exit temperatures reached 17.5 degrees C and 37.5 degrees C, respectively, the subjects remained in the wakefulness state, while simultaneously feeling bored and uncomfortable because of the long driving time.