University of Michigan First in Line to Receive Improved Biped Robot


Cassie, a third-generation biped robot designed to walk through extreme terrain, will be coming to professor Jessy Grizzle’s lab at the University of Michigan’s College of Engineering in Ann Arbor. Cassie is the first offering form new robotics startup Agility Robotics, spun out of the lab of Oregon State University’s Jonathan Hurst, a longtime collaborator of Grizzle’s.

Cassie is loosely modeled on the cassowary, a flightless bird similar to an ostrich, with backwards-facing knees attached to a short torso that holds batteries, motors, and a pair of computers. The University will be receiving the first unit, scheduled to arrive in Ann Arbor in five to seven weeks.

“Cassie is tough. It is designed for the rough-and-tumble life of an experimental robot. In principle, we should not have to use a safety gantry of any kind,” says Grizzle, the Elmer G. Gilbert Distinguished University Professor and Jerry W. and Carol L. Levin Professor of Engineering. “This will allow us to take the robot in wild places.”

Grizzle pushes his current robot, MARLO, to its limits on the University’s North Campus Wave Field, an earthen art installation near his lab, and on off-the-path treks in the woods. He plans to find new challenges for Cassie to overcome, because the improved robot won’t have some of the technical limitations and sensitivities that MARLO does. MARLO needs to be tethered to a support beam to prevent stumbles from being catastrophic falls, which has made navigating the Wave Field’s rugged terrain difficult. Cassie also features a full range of motion through the hips, allowing the robot to maintain and change direction. Grizzle’s team is already testing algorithms on a simulated version of Cassie.

Grizzle says Cassie’s “compact and robust frame” makes falls survivable for the robot, as does being 40 percent lighter. Unlike MARLO, Cassie also has powered ankles, allowing it to stand still unassisted. These improvements accompany additional computing power and onboard battery power, allowing Grizzle to integrate a perception system into the robot.

Grizzle’s robots typically operate as though they are blindfolded, but Cassie’s perception will help the new robot handle more extreme terrain, in addition to feeling changes in topography as it encounters them. Eventually, robots with Cassie’s capabilities could be used for rescues in smoke-filled buildings, among other things.

Grizzle is optimistic about Cassie’s potential, with the help of modifications and algorithms developed by his team. Previously, his lab debuted the fasted two-legged robot, which ran a nine-minute mile pace on a circular track, while attached to a boom for stability. Grizzle says Cassie might be capable of running faster than an eight-minute mile across an uneven field.

“We can still develop and test cool ideas around the ATRIAS platform,” adds Grizzle. “While their realization on the Cassie platform will be more spectacular, you can never have too many functioning robots.”

The University’s purchase of Cassie was funded by the National Science Foundation and the Toyota Research Institute. Grizzle is also a professor of electrical engineering, computer science, and mechanical engineering.

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