Robotic cheetah runs and jumps untethered

The agility and speed of the cheetah -- the fastest land animal on earth -- inspired the design of a robot that can run and jump across grassy terrain.

The robotic cheetah, created by a team at MIT, is a four-legged creation made of gears, batteries and electric motors, weighing about as much as the actual animal.

In a recent field test, the robot sprinted across a field of grass at the speed of up to 10 mph, and was even able to continue running after clearing a small hurdle. The investigators estimate that the current version of the robotic feline may eventually be able to reach speeds of up to 30 mph -- though that's still only half the speed of 60 mph that a real cheetah can accelerate to in a matter of seconds.

Just like its feline prototype, the robot can move in a gait pattern called bounding, in which its front legs hit the ground together and so do its hind legs.

Here is a video of the robot in action:

To optimize the cheetah-bot's speed and efficiency, the researchers developed a special bounding algorithm, which makes each of the robot's legs exert a specific amount of force when it hits the ground to maintain a particular speed. The general rule is that the faster the robot moves, the more force needs to be applied to propel the robotic "animal" forward. Sangbae Kim, an associate professor of mechanical engineering at MIT, noted a similarity between this force-control approach to robotic running and the way world-class sprinters race.

"Many sprinters, like Usain Bolt, don't cycle their legs really fast," Kim said in a statement. "They actually increase their stride length by pushing downward harder and increasing their ground force, so they can fly more while keeping the same frequency."

Thanks to the special algorithm, the cheetah-bot can also run across rougher terrain, such as a grassy field, and can even handle slight bumps and hurdles without losing speed. It leaped over an approximately 1-foot-tall foam obstacle during a test and kept on running.

"Most robots are sluggish and heavy, and thus they cannot control force in high-speed situations," Kim said. "That's what makes the MIT cheetah so special: You can actually control the force profile for a very short period of time, followed by a hefty impact with the ground, which makes it more stable, agile, and dynamic."

Unlike some other quadruped robots, which run on gasoline and are powered by a gasoline engine to generate high force, this electric-powered cheetah-bot moves much more quietly, Kim said.

"Our robot can be silent and as efficient as animals," he added.

The researchers will present details of the bounding algorithm this month at the IEEE/RSJ International Conference on Intelligent Robots and Systems in Chicago.