The robot’s feedback control algorithms should be able to help other two-legged robots as well as powered prosthetic legs gain similar capabilities.

MARLO, the 3D bipedal robot that belongs to electrical engineering professor Jessy Grizzle and his team of students, is starting to really figure out this walking thing. Here, robotics PhD student Ross Hartley watches as MARLO demonstrate's her ability to conquer tough terrain. Image credit: Evan Dougherty, Michigan Engineering

A free-standing bipedal robot at the University of Michigan can now walk down steep slopes, through a thin layer of snow, and over uneven and unstable ground. The robot’s feedback control algorithms should be able to help other two-legged robots as well as powered prosthetic legs gain similar capabilities.

“The robot has no feeling in her tiny feet, but she senses the angles of her joints— for instance, her knee angles, hip angles and the rotation angle of her torso,” said Jessy Grizzle, the Elmer G. Gilbert Distinguished University Professor of Engineering and the Jerry W. and Carol L. Levin Professor of Engineering. “It’s like walking blindfolded and on stilts.”

MARLO is Grizzle’s first robot that can walk (and fall) in any direction, known as 3D walking. With their previous robot, MABEL, Grizzle’s team produced leading control algorithms for robots that need to move in only two dimensions. MABEL was attached to a boom that gave her sideways stability.

“Getting a robot to walk well in 3D can be a very frustrating process,” said Xingye (Dennis) Da, a doctoral student in mechanical engineering.

Taking a hint from Grizzle’s long-time collaborator Jonathan Hurst at Oregon State University, who built MARLO, Da developed a way to control the robot with two 2D algorithms. This approach takes advantage of what the team learned by working with MABEL.

“The method could help many researchers speed up the process of achieving stable walking on their robots,” said Da, who designed this control algorithm.