Automatic waist airbag drowning prevention system based on underwater time-lapse and motion information measured by smartphone's pressure sensor and accelerometer

We propose an automatic airbag system helping evacuating swimmer who is motionless or spent abnormally long time underwater. The system is composed of a customized waist airbag and Smartphone equipped with pressure sensor and accelerometer. The Smartphone application will try to define accurately the position of the swimmer's head the whether underwater or not by comparing the real-time measured pressure to an estimated value of over the water surface pressure. If the time-lapse spent by the swimmer exceeds a predefined maximum threshold or the measured accelerometer information shows that he has been motionless for long time period underwater, an on device alarm is triggered and a signal is sent to the servomotor connected to the deflation system of the airbag to trigger it and evacuate the swimmer.