SERVO 07.2014 69
RUN, RAPTOR, RUN
Researchers have long been interested in fast running robots with
powerful agile legs. In particular, several groups have focused on bioinspired designs based on cheetahs. But when a team at the Korea
Advanced Institute of Science and Technology (KAIST) set out to create
a new sprinting robot, they didn't look at big cats. Instead, they found
inspiration in a completely different kind of creature: a
The robot — called Raptor — has two nimble legs and a
mechanism that mimics a tail. In a recent experiment, it
achieved an impressive speed of 46 kilometers per hour on a
treadmill. That's faster than the fastest human — the Olympic
sprinter Usain Bolt, whose top speed has been estimated at
Raptor is almost as fast as the world's fastest legged
robot, Cheetah (built by Boston Dynamics), which reached
47 km/h in a trial two years ago — also on a treadmill.
Now, before you suggest a robot race between the two
machines, note that both Raptor and Cheetah are attached
to beams that keep them steady and prevent them from running off the treadmill — and crashing
through a wall.
Despite their similar speeds, the two robots are very different. Cheetah is a hefty quadruped,
powered by hydraulic actuators. Raptor is a compact 3 kilogram machine with two legs made of
lightweight composite material.
Another difference is that Raptor has a tail. Although it looks nothing like a real velociraptor's tail,
it works like one, moving rapidly to help the robot maintain its stability while stepping over obstacles,
says Jongwon Park, a PhD student at KAIST's Mechatronics, Systems, and Control Laboratory.
Park developed Raptor along with colleagues Jinyi Lee, Jinwoo Lee, Kyung-Soo Kim, and Professor
Using a tail for stability is not a new idea in robotics. MIT's cheetah-inspired quadruped has a
mechanical tail, and a UC Berkeley wheeled robot features a tail that is also based on a velociraptor's.
Raptor is not the first robot to sport legs with prosthetic blades, either. The biped running robot,
Athlete (built several years ago), also used carbon-fiber running blades. Still, Raptor stands out for its
simplicity, showing that it's possible to achieve significant speeds with an uncomplicated design.
Unlike other legged robots that rely on multiple actuators, Raptor uses just one motor per leg
which consists of a nine-bar linkage. To recover part of the energy used to make the robot move,
researchers added Achilles tendons that work as springs, absorbing and restoring energy with every
The robot's control system is also simple. Raptor runs a computer program known as a running
pattern generator which controls gait and speed.
The KAIST team is currently working to optimize their robot. They're interested not only in
achieving even greater speeds, but also improving control and stability.