According to the British Royal Society for the Prevention of Accidents, research shows that driver fatigue may be a contributory factor in up to 20% of road accidents and up to a quarter of fatal and serious accidents.
Until recently, measuring ECG in a car meant the driver having a set of electrodes attached to his/her bare chest using gel. Plessey, however, has developed a solution to monitor driver fatigue that is based on its multi-award winning EPIC sensor technology.
Because the EPIC sensor utilises capacitive coupling, it doesn’t rely on good skin contact and can measure ECG through normal clothing and seat cover fabric. By monitoring a parameter called Heart Rate Variability (HRV) – which is a measure of how stable the heart rate is from beat to beat – it is possible to tell when the driver is starting to become sleepy.
The company recommend an array of sensors built into the seat back, so that the optimal sensing location can be chosen, regardless of the driver’s height and build. Movement noise is minimised by placing the sensors away from the shoulders on the lower part of the seat back. The system uses a capacitive driven ground plane, which can also be placed under the seat cover fabric on the base of the seat, to produce a completely hidden system. Further noise reduction can be achieved by coupling this driven ground to the steering wheel. The system has been shown to be completely immune to electrical noise sources within the car.
Plessey now has available evaluation kits for car manufacturers and suppliers, which takes the form of a seat pad containing a six sensor array on the seat back and a ground plane on the base. The demonstration kit also includes an interface box with a USB output to the display and recording software. Plessey’s own tests show that more than 95% of heart beat peaks were detected during a ten minute trial over a variety of driving conditions.