Why Animals Run Faster than Robots

M ore than a decade ago a skinny-legged knee-less robot named Ranger completed an ultramarathon on foot. Donning a fetching red baseball cap with “Cornell” stitched on the front, and striding along at a leisurely pace, Ranger walked 40.5 miles, or 65 kilometers, on a single battery charge.

Ranger broke a record that day, walking farther than any robot before it—and that record remains unbeaten among robots. But Ranger’s pace was surprisingly pokey: It took 30 hours and 49 minutes to cover the distance, equivalent to a mile every 45 minutes. By comparison, the average human can walk at a speed of about 3 miles per hour, and marathon runners average a mile every 10 to 12 minutes.

It turns out that building robots that can walk and run as speedily and fluidly as humans and other animals, over both short and long distances, is extraordinarily complex. Even though the physical materials used in the construction of robots are often more resilient and powerful on a part-by-part comparison, the coordination of the parts seems to matter more for speed and agility. That’s where biological creatures have a leg up, according to new research led by Samuel Burden, robotics professor at the University of Washington.

To answer the question “Why do animals outrun robots?” Burden and his team decided to break down running into its major component systems and then compare the biological version to the engineered. They took this approach rather than compare specific robots to individual animal species because “we didn’t want to tear down any particular robot,” says Burden. This way, they reasoned, the comparison would also be at its purest, since no robot or animal is designed exclusively for running, per se.

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