Dark and disorientating, prone to rockfalls and flooding, and often filled with toxic gases: caves are not a safe place for humans.
When people get stuck – and they often do – rescue teams face an often uncharted and always unpredictable environment.
“One of the main limitations facing warfighters and emergency responders in subterranean environments is a lack of situational awareness; we often don’t know what lies beneath us,” says Timothy Chung, from the US Defense Advanced Research Projects Agency (DARPA).
The agency, which sits within the United States Department of Defense, believes that instead of sending humans into the underground unknown, it would be safer for robot systems to serve as surrogates.
Advances in associated technologies have a reached a “crucial point” the agency says, and bots are on the brink of “permitting us to explore and exploit underground environments that are too dangerous for humans”.
As well as for civilian cave rescues, DARPA is also considering robots in military and national security settings, say the Taliban hideout Tora Bora, underground enemy military complexes and the drug smuggling tunnels that run into the US from Mexico.
“The hazards vary drastically across domains that can degrade or change over time and are often too high-risk for personnel to enter,” Chung adds.
To accelerate the field, late last year the agency announced a ‘Subterranean Challenge’ or ‘SubT’ in which teams are tasked with quickly and remotely mapping, navigating and searching for items in perilous underground environments.
This month a team from CSIRO’s Data61 Robotics and Autonomous Systems group was named as one of only seven teams globally to receive up to US$4.5 million from DARPA to compete in the three year contest.
CSIRO has a head start on many of the participants. It already has a fleet of legged robots – including the world’s first large scale ultra-light hexapod MAX and another which is capable of crossing tricky terrain like the Amazon Rainforest floor. The organisation has also refined a LIDAR mapping and autonomy product – Hovermap – which can generate highly accurate 3D maps.
But there are still major hurdles to overcome. Just as underground depths test human survival, they are incredibly tough territory for robots too. And in most cases, once down there, they’ll be going it alone.
Garden hose comms
Last year, CSIRO sent a drone fitted with its Hovermap payload 600 metres underground, down a mine in Western Australia.
Hovermap is a self-contained unit consisting of a small processor and a spinning cylinder, about the size of a can of beans, which emits 300,000 laser beams a second.
The LIDAR system creates a ‘3D point cloud’ of any space – even a dusty and lightless underground cavern – which allows the drone or robot it is mounted on to move around without GPS and not crash. Typically, after a flight around a space, the data is uploaded to a server for processing and a map is created.
For the DARPA challenge – which consists of three domains: tunnel systems, urban underground and cave networks – analysis after the fact won’t be sufficient.
But since there is no GPS, 3G coverage or Wi-Fi deep underground, it’s not feasible for a human operator on the surface to make decisions for the robots and look out for objects.
“You could have a camera running continually looking for things of interest but that strategy where you send a video stream back up and a human says ‘that’s interesting’ is not viable. Even if you send back every single laser point, each one of those takes a few bytes to encode, so sending all of that back is huge, a big firehose of data,” says Fred Pauling, Data61’s Robotics and Autonomous Systems group leader.
“You might only have a garden hose link back up, so you need to be really smart about how you compress that or send the most important information, and do as much as you can on board the robot to do processing and detecting things of interest,” Pauling, part of a 30-strong team featuring recruits from QUT, the University of Queensland and Georgia Institute of Technology assembled for the challenge, explains.