Cornell robot sets a record for distance walking

The Cornell Ranger robot on 3 April set an unofficial world record
by walking nonstop for 45 laps — a little over 9 kilometers or 5.6 miles —
around the Barton Hall running track on the Cornell University campus. Developed by a team of students working with Andy Ruina, Cornell professor of theoretical
and applied mechanics, the robot walked until it finally stopped and fell
backward, perhaps because its battery ran down. “We need to do some
careful analysis to find out for sure,” said Greg Stiesberg, a graduate
student on the team. An
earlier version of the same robot had already set a record by free-walking a
bit over one kilometer, about .62 miles. Another robot has walked 2.5
kilometers [1.55 miles] on a treadmill, Ruina noted. A six-legged robot has
walked a bit more than 2 kilometers, and there’s some debate over whether or
not that counts. There are no rules for such records, Ruina admits, and the
Guinness people were not involved. “There’s a lot of rigmarole with
that,” he explained. The event, he said, was to show off the machine’s energy
efficiency. Unlike other walking robots that use motors to control every
movement, the Ranger emulates human walking, using gravity to help swing its
legs forward.

Standing still, the robot looks a bit like a tall sawhorse; walking, it
suggests a human on crutches, alternately swinging forward two outside legs and
then two inside ones. There are no knees, but at the ends of the legs are feet
that can be tipped up and down, so that the robot pushes off with its toes,
then tilts its feet upward to land on the heels as it brings its legs forward.
The goal of the research, Ruina said, is not only to advance robotics but also
to learn more about the mechanics of walking. The information could be applied
to rehabilitation and prosthetics for humans and even to improving athletic
performance. Ruina’s lab has built several walking robots of various designs. A
model with flexible knees, designed to closely imitate human walking, consumed
energy per unit weight and distance comparable to a human walker. In contrast,
Ruina estimates that the well-known Honda Asimo uses at least ten times as much
energy as a human when walking. As it happens, Ruina was not present to witness
the record-breaking event. By phone, from a conference on locomotion in Columbus, Ohio, he commented, “We’ve just
moved into this world of electromechanical devices, and to make something this
robust is a big achievement. We’ve learned tons about what it takes to make
walking work.”