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.