1. Overview

In a large-scale oil tank fire, people are not allowed to approach the area near the facility where the fire started because of the danger of intense radiant heat from the flame (estimated to be up to 20 [kW/m²]) and explosions.  We have developed an innovative robot system that can monitor fire scenes and perform firefighting activities, such as discharging water on flames in such an environment without human intervention (Fig. 1).

Fig.1  Firefighting robot system

This robot system consists of a flying reconnaissance robot, a traveling reconnaissance robot, a water cannon robot, a hose-laying robot (Fig. 1, from front right to left), and a vehicle carrying these robots to the fire site (Fig. 1, back). The inside of the vehicle where the robot is mounted becomes a robot control room when the robot is unloaded. It is equipped with a command system that plans the moving route of all the robots and the action plan of the water cannon robot, such as the position and angle of water discharge, and proposes it to the operator (fire crew). The operator can operate the entire robot by selecting the proposed plan. The robot operates autonomously, moving, laying water hoses, and adjusting the angle of water discharge considering the wind direction.

The procedure for discharging water to the flame using a water cannon robot and a hose-laying robot is explained. The water hose mounted on the hose-laying robot is connected to the water cannon robot in advance. The water cannon robot is moved to the water cannon position by autonomous or remote control, and the hose-laying robot automatically follows behind it, maintaining a distance between vehicles (Fig. 2 (1)). After arriving at the water discharge position, the water cannon robot stays there. And the hose-laying robot sends out and lays the water supply hose while moving back to the water source, autonomously or by remote control (Fig. 2 (2)). Firefighters connect the pumps and water hoses at the water source where the radiant heat is low enough because it is far away from the facility of fire started (Figure 2(3)). And discharges 4000 L/min of water at a water pressure of 1 MPa (Fig. 2 (4)).

2. The development of new technological

2.1 Development of a Hose Laying Robot for Completely Unmanned Water Discharge Operation

Water discharging stations near disaster facilities are dangerous, and there are many examples of the development of water cannon robots that perform water discharging operations on behalf of people. However, installing water hoses from water sources and connecting them to water cannons required human labor, so there was a need without human operation. Although there are some cases where a water hose connected to a water cannon robot in advance is towed and moved, the possibility that the water hose is caught at a bend and can’t be hauled and the damage caused by dragging becomes a problem. We also examined a method to mount a water hose on a water cannon robot and move it to a fire site while placing it on the ground. Still, there was a problem: water could not be sent if the water hose mounted inside the robot remained after arriving at the destination due to crushing and flattening or other reasons. In response, we developed a new hose-laying robot that automatically follows the preceding robot and automatically lays water hoses. The hose-laying robot is mounted with six water hoses (300 m in total) with an inner diameter of 150 mm with connection fittings on both ends wound around the hose drum. To properly discharge water, it is necessary to lay a water hose on the ground without twisting at a certain curvature or more. In order to realize the automatic laying of water hoses, we have developed a route planning method for autonomous robot movement and an appropriate sending control technology for water hoses. By combining this with the automatic tracking technology of the preceding robot, the water discharge work, including the water hose handling, is completely unmanned.

Fig.2  Water discharging to the flame using a water cannon robot and a hose-laying robot

2.2 Countermeasure against radiant heat from flame equipped on the robot

There was a need for robots to withstand the intense radiant heat from flames as they sprayed water at large-scale fire sites. Some fire engines and firefighting robots have a self-defense water spray function that cools them by pouring water on them as equipment that can cope with radiant heat. The problem was that water could not be sprayed during the robot movement because the water for discharging sent from the water source was used by diversion. There is also a method to load the tank with water necessary for sprinkling, but a large amount of water is needed, and the robot’s enlargement is a problem.

We solved this problem by developing an innovative exterior that reflects most of the radiant heat at the surface and suppresses the temperature rise by vaporizing heat cooling with a small amount of water spray on the back fibers and by replacing the air with natural convection inside the robot (Fig. 3). Because the amount of water sprayed is small, the tank that holds the water used while there is no water supply from the water source can be miniaturized, enabling the development of a robot large enough to be mounted on a transport vehicle.

Fig.3  Radiation-resistant exterior using radiant heat reflection and vaporization heat

3. Summary

We have completed a robot system that can perform water discharge activities, including handling water hoses near disaster-stricken facilities, which are dangerous places inaccessible to humans without human intervention. This is the first robot with this performance in Japan and has yet to be confirmed anywhere in the world. The system is expected to be in petroleum complexes as firefighting equipment that can extinguish fires and gather information unmanned close to the facility where the fire occurred, which was previously impossible. This robot system has been deployed to the Ichihara City Fire Department in Chiba Prefecture and operates in case of a disaster. Completing the firefighting robot system, which can be considered for deployment by local fire departments and complex petroleum operators in preparation for large-scale fires and explosions, is an excellent achievement that will strengthen firefighting capabilities.

*This robot system is the result of the “Research and Development of Firefighting Robot System for Energy and Industrial Infrastructure Disaster Response,” a publicly solicited project conducted by the Fire and Disaster Management Agency of the Ministry of Internal Affairs and Communications from FY2014 to FY2020.

Jun Fujita
Member, Mitsubishi Heavy Industries, Ltd.

Hisanori Amano
Member, National Research Institute of Fire and Disaster

Kenichi Murasumi
Corporate Member, Mitsubishi Heavy Industries, Ltd.

Kazunori Ohon
Member, Tohoku University

Shotaro Kojima
Member, Tohoku University