Engineering and Earth profs unite to fight desertification

Kieran Dunne, a Penn grad student, remembers his first trip last year to White Sands National Monument, a desert in New Mexico, as part of Earth & Environmental Science (EES) professor Douglas Jerolmack’s annual course in geomorphology.

“It’s almost an alien-looking place,” says Dunne, who is now a teaching assistant for the class. “You can stand on top of a dune and in all directions you’re surrounded by a sea of white sand. When the wind picks up and you feel the sand hitting you, you realize that the environment is changing around you.”

Although Jerolmack, an associate professor and graduate chair at EES, has been conducting the trips with his undergraduates and doctoral advisees for nine years, this past March was the first time he was joined by Penn engineers and roboticists as part of a National Science Foundation grant to develop robots capable of traversing through desert sand to take measurements.

The principal investigator on the grant is Daniel Koditschek, the Alfred Fitler Moore Professor in the Department of Electrical & Systems Engineering in the School of Engineering and Applied Science. He is collaborating with Jerolmack and other desert scientists to supply RHex, a six-legged robot inspired by the movement of cockroaches, with the skills and tools needed to make measurements in the field of aeolian science—the study of windborne erosion and sediment deposition.

“We hope to give the aeolian scientists a new instrument in their fight against desertification around the globe,” Koditschek says. “The most immediate goal is to provide a mobile base for presently available instruments that would otherwise be stationary or have to be ported around by people. In the long run, the benefit for humanity would be if we can really equip the scientists who are studying these changes with much more pervasive means of instrumenting events that are just too uncomfortable or dangerous for humans to be there at all.”

In addition to trying to perfect the locomotion of the robots on steep, sandy slopes, which even humans have trouble walking through, the researchers are strapping RHex with scientific equipment to gather data such as wind velocity and sediment flux rate.

Typically in aeolian science, instruments are housed in stationary meteorological towers. The problems with these towers are that they’re expensive, take a long time to build, and can only take data in one specific spot.

“If we can turn a robot into an automated outdoor lab, then it gives us so much more capability to go out there and take data in real environmental settings," says Feifei Qian, a postdoctoral student working on the project.

One particular technology Qian and Jerolmack were testing on the trip was the ability to use the robot’s legs and the resistance they encounter as they drag through the dune surface to measure the erodibility of the sand beneath them. With this technique, they found a very strong correlation between mechanical shear strength and erodibility.

Other researchers working on the project were studying the decision-making process of the Earth scientists on the trip with the longer term hope of developing algorithms that would allow the robot to act semi-autonomously and make decisions about how to best take measurements of its surroundings.

In the future, Koditschek says, this technology could even be used to improve robotic locomotion in Martian sands or other extraterrestrial environments.

“I think this could be a great example to show people how a legged machine can generate scientific data and work with human beings,” Qian says. “As a roboticist, I would say that’s something I’m really excited about: Not just having the robot for basic research, but showing that it can actually be helpful to society.”

Jerolmack hopes that by exposing his students to real fieldwork and cutting-edge collaborations across different disciplines, they can get an appreciation for the scientific process and the sheer amount of work that goes into producing data.

“When we’re all there working to solve problems together in the field, the boundaries between teacher and student, or geologist and engineer kind of dissolve away,” Jerolmack says. “In the evening when we’re all eating dinner, I see spontaneous conversations happening between engineering postdocs really heavily invested in the instrument and undergrads in Earth science just curious about how it works. That effect lasts beyond the time we’re in the field. People carry it home with them.”