In partnership with the Tokyo Institute of Technology, SoftBank Corp. (TOKYO: 9434) has been researching and developing drone systems to locate people lost in the mountains or buried under rubble caused by natural disasters like earthquakes and typhoons.
As part of this initiative, SoftBank and the Tokyo Institute of Technology jointly developed a “Drone Wireless Relay System” with Futaba Corporation in 2020 to locate stranded people. The system made it possible to provide search parties with the locations of smartphones held by people in distress buried under sand or rubble, even in mountainous areas without network coverage. The Drone Wireless Relay System did this by providing temporary wireless connectivity and utilizing the GPS functions of smartphones.
After demonstrating the solution in 2020, the system was chosen by Japan’s Fire and Disaster Management Agency as a research topic for its “Fire and Disaster Management Science and Technology Research Promotion Program.”
Despite the strengths of the solution, significant challenges for finding smartphones buried deep under sand or rubble remained. Specifically:
- The difficulty of providing prompt rescue assistance in large search areas
Conventional drone systems only have maximum flight times of about 30 minutes per flight, making it difficult to provide prompt rescue assistance in large areas
- Drone systems that use a wired power feed can get tangled up with obstacles
The wired power cable that powers the drone can get tangled up with debris, trees, and other obstacles, interfering with search and rescue
New drone system can avoid obstacles and fly longer
To solve these issues, SoftBank, the Tokyo Institute of Technology and Futaba developed a new "Wired Power Feed Drone Wireless Relay System" that uses a main drone to provide a conventional radio relay system and an auxiliary drone that controls the power cable, which powers both drones. The ground-based wired power supply enables more than 100 hours of continuous flight, and the power cable can be lifted by the auxiliary drone to avoid obstacles.
The two-drone system makes it possible to search an area of approximately 200 meters, even when there are obstacles like collapsed houses or fallen trees between the two drones and the search area.
The new system was put to the test in November 2022 on the grounds of Futaba’s Chosei Factory in Chiba Prefecture, just east of Tokyo. When a pile of earth was prepared to bury smartphones, making them inaccessible to cellular and GPS signals, the system succeeded in locating smartphones buried up to 5 meters under sand.
The distance between the pile of sand and the power supply on the ground was about 200 meters, and trees about 10 meters high and a fence about 3 meters high stood between them. The main drone could not search the area on its own because the power cable would get caught on the trees. The auxiliary drone, however, controlled the power cable’s position so the main drone could fly directly above the sand pile.
The newly developed system was able to pinpoint the location of the smartphone, even though it was buried deep under sand, out of communication range, and unable to receive GPS signals.
How can the drone system locate the buried smartphone? The main drone emits radio waves with a highly directional antenna that can penetrate deep into sediment, which brings the smartphone into range. Data on the radio wave strength received by the smartphone is then transmitted to a location information identification server. Also, by simultaneously transmitting the location information of the main drone itself—which is receiving the GPS signal—to the location-specific server, the system identifies the location of the buried smartphone, which lies directly below the drone's location at the point where the strongest radio signal is detected.
This research initiative is expected to contribute to rapid rescue efforts in the event of typhoons, earthquakes, landslides, avalanches, and other natural disasters.
(Posted on February 10, 2023)
by SoftBank News Editors