The dark, cavernous depths of an old Pittsburgh mine will test the performance of autonomous robot drones and the engineering prowess of their creators at the DARPA Subterranean Challenge Tunnel Circuit event, underway Aug. 15-22.

CU Denver engineers designed the power and communications systems for MARBLE, the interdisciplinary engineering team from CU Denver and CU Boulder that won a $4.5 million DARPA Subterranean Challenge grant to prove their system design innovations in four underground circuit events through 2021.

DARPA’s stated objective is to “find novel approaches to rapidly map, navigate, and search underground environments during time-sensitive combat operations or disaster response scenarios.”

A novel communications network

MARBLE created a small fleet of autonomous robotic drones equipped to deploy a temporary, highly adaptable wireless mesh network and use it to simultaneously map, navigate and search the mine’s tunnels, identify artifacts and communicate information to an above-ground relay station.

“We were tasked to design a new, robust and reliable communication system that could transfer significant amounts of data in real-time,” said Mark Golkowski, professor of electrical engineering at CU Denver and co-PI on the MARBLE award.

Overcoming underground obstacles

Existing satellite and cellular networks aren’t available underground; the signals cannot reliably penetrate the meters-thick to miles-thick mass of rock, earth, metal and concrete between the earth’s surface and the tunnel’s interior.

Tunnel are the nemesis of legacy radio frequency communication. Limited line-of-sight, sharp turns, narrow passages and airborne debris can cause signal loss, reverberation and interference.

“Underground communication is cutting edge. Nobody’s solved the problem yet, and there are many unique challenges,” said Chad Renick, in Pittsburgh for the Tunnel Circuit prior to starting a new job in deep-space satellite communication at Lockheed Martin later this month.

Finding advanced radio hardware

The CU Denver engineers tested and rejected several iterations of radio technology until they discovered radio hardware from Doodle Labs that met all of their requirements:

• As small as possible
• As powerful as possible
• Software compatible with the computer software and protocols used in robotics
• Multi-frequency capability

“In the testing we did, Doodle Labs outperformed the other radios we considered and achieved greater connectivity with fewer nodes,” said Renick, who served as one of two full-time graduate researchers on the CU Denver team while completing his master’s degree in electrical engineering earlier this year.

In conversations with Golkowski, leaders at Doodle Labs became excited about the solution the team devised and wanted to help the team be competitive in the SubT Challenge. Doodle Labs agreed to become a sponsor, which enabled the CU Denver engineers to build the cutting-edge, drone-portable, subterranean communication system they envisioned.

“We designed our radios to enable cutting edge IoT applications in challenging environments, like the system CU Denver designed for the DARPA SubT Challenge. This is the deepest and furthest underground network deployed exclusively with Doodle Labs hardware. We’ve been happy collaborating with CU Denver to see how the mesh network overcomes many of the communications challenge,” said Nimesh Parikh, CEO of Doodle Labs.

Engineering for the future

The DARPA Tunnel Circuit is an example of a real-world challenge that demands interdisciplinary engineering collaboration, for which there is an increasing need, and a focus of the CU Denver College of Engineering, Design and Computing.

DARPA will announce final results of the Tunnel Circuit on August 22.

The engineering world will be watching for breakthroughs in the autonomy, perception, networking and mobility technologies and systems needed to map unpredictable and often hazardous conditions underground.