Flame extinguishment by cooperation of two aerial extinguishers

Fire extinguishment approaches with inert gas such as carbon dioxide (CO2) or nitrogen (N2) have several advantages compared with ones with water. On the other hand, they have low extinguishment performance and put lives at risk. To enhance the extinguishment performance and to reduce risk to life, the authors have proposed a robotic fire extinguishment approach with massive aerial extinguishers with inert gas. This paper proposes a control algorithm for multiple aerial extinguishers without any markers, while a single extinguisher with an easily extracted marker has been controlled in our previous work. This paper also demonstrates flight control of two extinguishers and flame extinguishment by cooperation with two extinguishers. The cooperative behavior in the flame extinguishment experiment is not explicitly programmed, and the two extinguishers are simply controlled by trajectory tracking using PID controllers.