Published: Sept. 24, 2021 By

Banner image: CU Boulder engineers prep robots for the final event of the DARPA Subterranean Callenge. (Credit: MARBLE)

A CU Boulder team has taken home third place and $500,000 in prize money in an international competition that sends teams of robots deep underground to conduct search-and-rescue operations.

The CU Boulder group, made up of engineers from across the university, took part in the final event of the Defense Advanced Research Projects Agency (DARPA) Subterranean Challenge from Sept. 21-24 in Louisville, Kentucky. The competition, now in its third year, has pushed the bounds of what autonomous vehicles are capable of: Over three tense challenges, teams from around the world launched fleets of drones into underground caves, mines, subway tunnels and more to complete a high-tech game of hide-and-seek—searching for lost “artifacts” amid hazards like dust and mud and steep drops.

The competition strives to develop new technologies that could one day safely locate the human survivors of disasters like mine and cave collapses. 

“I couldn’t be prouder of all of our brilliant and talented graduate and undergraduate students that earned this award and international recognition,” said Sean Humbert, a professor in the Paul M. Rady Department of Mechanical Engineering who leads the CU Boulder team. 

DARPA recognized the CU Boulder group, named Multi-agent Autonomy with Radar-Based Localization for Exploration (MARBLE), Friday, Sept. 24, at a prize ceremony in Kentucky. 

MARBLE includes researchers from CU Denver, the University of California, Santa Cruz and the Massachusetts-based Scientific Systems Company, Inc. Researchers from CU Boulder also hailed from the Department of Computer Science and Ann and H.J. Smead Department of Aerospace Engineering Sciences. In 2018, the group received $4.5 million to join in the challenge and competed in a cohort of six funded teams. 

Stefanie Tompkins, director of DARPA, addressed the competitors at the awards ceremony: “I have heard some of you say off to the side and some of you say directly to my face that when they first heard about this, they were absolutely positive it was impossible,” she said. “So thank you for ignoring your gut feelings and diving into this competition and proving to all of us that it’s not impossible.”

For the final event, eight teams, including several un-funded groups, traveled to Kentucky’s famed Louisville Mega Cavern. Spanning nearly 100 acres, this former mine ranks as the biggest building in the state. It includes warehouses, tunnels and natural caverns—complete with dangers like stairs, rough pathways and DARPA-installed “dynamic” obstacles like falling debris. 

To nab third place, MARBLE sent a group of four robots into this perilous environment, including two rolling vehicles and two dog-like robots manufactured by the company Boston Dynamics. The robots worked on their own to earn points by finding series of targets, such as backpacks, cellphones, gas leaks and lost helmets.

And the group was able to adjust its strategy as it went.

“Early on at the final event, our team’s perspective began to shift to thinking about our system less as an autonomy experiment and more as a tool to interrogate subterranean environments,” Humbert said. “We started to incorporate additional human-robot interaction elements that resulted in an additional five to seven points in the final round, and ultimately a third-place finish.”

MARBLE earned 18 points, placing behind second-place finisher CSIRO Data61, led by the Commonwealth Scientific and Industrial Research Organization in Australia, with 23 points. First place and $2 million went to CERBERUS, led by ETH Zurich. MARBLE also earned a special recognition for finding an artifact, a red power drill, before any other team—just 68 seconds into the competition.