The causes of deaths in traffic accidents are predominantly
human factors such as careless or "heedlessness" driving;
recently, accidents that are believed to be due to deteriorated
physical conditions, such as heart attacks, have been reported.
Non-contact electrocardiography (ECG) monitor for continuous ECG
detection while driving is needed to reduce a number of fatal
accident by human error like this. Recently there are a lot of
papers to detect cardiac electricity using capacitance coupling
between human body and electrode. This sensor system must be
adopted appropriate high input impedance circuit and noise
reduction technique as a function of source impedance value
especially for a seat mounted sensor.
We investigated the impedances of the intermediary materials
such as a seat cover and clothing for installing vehicle use by
dielectrics measurement system can measure extra-high impedance
(100TΩ), and designed an effective circuit configuration for common
noise resistance, considering the effect of the sitting posture
according to their results. The sensor system employed the DRL
(Driven Right Leg) circuit is composed of two sensor head mounted
into the seat cover and a electrode mounted on a steering wheel for
reducing well common mode noise in cardiac electricity
frequency.
We have succeeded in attaining stable detection of cardiac
electrical impulses during two driving conditions, stable driving
at the average speed of 70km/h and driving with frequent changes
at the speed of 0-30km/h, operations of the accelerator, brake,
steering wheel, and direction indicator.
