A robot learns to ice skate


‘RHex,’ started over a decade ago for search-and-rescue, is learning to walk on ice


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RHex is a six-legged robot whose team hopes to one day use it for search-and-rescue missions or data collection. The decade-old project began to move on ice eight weeks ago.



A six-legged robot is a new weekly skater at Penn’s ice rink.

RHex, a research project created over a decade ago by engineering professor Daniel Koditschek, is a robot designed to handle a variety of terrains, including desert, rocks and, most recently, ice. The team hopes that the robot can one day be used for search-and-rescue missions as well as data collection.

Anna Brill, an Engineering sophomore who worked as an undergraduate mechanical engineer in Kod*lab during the summer, came up with the idea of running RHex on ice. She was encouraged by both Koditschek and her mentor, who also works on the project, to pursue her own personal research project.

“As someone who is also interested in the artistic aspect of robotics, the idea of a robot that could elegantly ice skate seemed both an artistic and a scientific goal,” she said.

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“The idea of having RHex run on ice is to study the phenomenon and see what goes on,” said David Isele, a third year graduate student in the school of Engineering and Applied Science and main researcher for the ice trial. “Exploring its behavior on ice expands the breadth of what the robot is able to handle.”

According to Isele, the goal of these weekly ice trials, which started eight weeks ago, is to try out a row of physical models and optimize parameters for changing speed and angles in a low friction environment.

“Currently we’ve been running a stochastic search to find an optimal gait,” Brill added. “The lab has previously done similar searches on various terrains and we hope to compare the optimal low-friction gait with others to provide some insight into whether this research could be productive in the future.”

Though RHex has just started its journey on a low friction surface, it has performed impressively in other harsh environments before.

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“I’ve taken the robot to the Mojave Desert several times to see how it works on sand and rocks,” Aaron Johnson, a sixth year graduate student in charge of the project, said. “The desert has a lot of variety in the terrain, but the legs help the robots to bounce around different types of rocks.”

“One nice thing about RHex is that the body is made of carbon fiber,” he added. “Even in the jumps and flips, it can keep going.”

According to Isele, RHex’s autonomy and resilience to adjust to different terrains makes it “a candidate for search and rescue robotics to places where wheeled vehicles can’t get to.” It can also be used to go into remote environments to collect scientific data. With a standard computer inside, RHex can use any common network or more advanced radio to communicate.

“The base robot is about getting to a location, but we have a modular interface for different sensors,” Johnson said. “We’ve done experiments to let it climb a hill completely autonomously. It needs to use outward looking sensors to avoid trees.”

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“Robotics is a hands-on way of seeing science,” Isele said.

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