The short-time fractal scaling of heart rate variability to estimate the mental stress of driver

Traffic accidents happen everywhere, especially if the car driver cannot concentrate when he/she is under mental stress. The main purpose of this research is to utilize the method of the nonlinear dynamic system for analyzing the driver´s mental stress. In physiology, the autonomic nervous system, including sympathetic and parasympathetic nervous systems, controls the cardiovascular system. Human´s heart rate and blood pressure violently fluctuate while under mental stress. Therefore, the short-time fractal scaling of the heart rate variability (HRV) is analyzed to estimate the driver´s mental stress. In our virtual-reality lab, a subject sat on a 6-D motion platform designed to emulate a driver-vehicle environment. The electrocardiogram of the subject was recorded. It was found that the Lyapunov exponent could effectively represent the HRV. Therefore, we conclude that the nonlinear dynamic system can be applied to analyze the driver´s HRV under mental stress.