An Autonomous Water-Dropping Method with High Precision using Unmanned Aerial Firefighting Vehicles

The water-dropping method is crucial for the aerial firefighting using either fixed-wing or rotary-wing aircraft. When a wildfire occurs, aerial firefighters need to cross the wildfire and extinguish it by dropping water/retardant based on their experiences. It is extremely dangerous for aerial firefighters to carry out such a mission with also the lack of water-dropping accuracy while mainly based on pilot’s experience. In order to improve the precision of water-dropping and reduce the risk to firefighters in aerial firefighting missions, an autonomous water-dropping method with high precision has been proposed for fire spot suppression using unmanned rotarywing aerial firefighting vehicles. Once a fire spot location is determined, the unmanned aerial firefighting vehicle will fly to and hover above the fire spot based on GPS navigation information autonomously. Then a feedback controller drives the unmanned aerial firefighting vehicle to approach the fire spot quickly based on the relative distance difference perceived by an infrared thermal camera. Meanwhile, a wireless trigger is utilized to execute the drop action when the precision or time conditions for water-dropping are met. Finally, the unmanned aerial firefighting vehicle returns to the ground station safely. The designed method implemented and tested in the outdoor field with a DJI M300 quadrotor unmanned aerial vehicle equipped with an onboard H20T payload. The experiment results have demonstrated the effectiveness of the designed method.