Abstract:
Drowning remains a critical socio-technical challenge in Sri Lanka, intensified
by monsoon-driven flooding, hazardous currents in inland reservoirs, and a lack
of lifeguard infrastructure in rural coastal regions. This research presents the
engineering design, fabrication, and experimental validation of a low-cost, GPSassisted
Unmanned Surface Rescue Vehicle (USRV) integrated with a preventative
geofencing wireless signaling system. The vessel utilizes a catamaran architecture
for enhanced lateral stability, locally fabricated using a fiberglass-reinforced plastic
(FRP) matrix over a medium-density fiberboard (MDF) core to ensure both
affordability and watertight integrity. Propulsion is achieved via dual water-jet
thrusters powered by two nickel-metal hydride (NiMH) battery modules, strategically
placed to optimize stabilizing mass and vessel balance. Experimental validation
confirmed a vessel mass of 16.50 kg and a static draft of 6.60 cm, aligning with
theoretical hydrostatic predictions within a 10.00% margin. Hydrodynamic analysis
demonstrated efficient hull-water interaction, overcoming a calculated drag
force of 2.41 N at operational speeds. A core innovation is the integration of a
swimmer-worn GPS wristband featuring geofencing logic. Unlike reactive visionbased
systems, this preventative trigger transmits an SMS alert with real-time
coordinates via a Global System for Mobile Communications (GSM) link upon
boundary violation. Field testing confirmed a notification latency of less than
5.00 seconds, effectively mitigating manual detection delays. This study provides
a scalable, locally manufacturable solution for improving search-and-rescue (SAR)
efficiency in diverse aquatic environments.
