Tuesday, June 02, 2015

Cheetah Robot Sees, Runs, and Now Leaps Over Hurdles

A cheetah-inspired robot can now spot and jump over hurdles all while running autonomously at 5 miles per hour.

Researchers at the MIT Biomimetic Robotics Lab have been developing this four-legged robot, named MIT Cheetah, for the past three years. First it could run on a treadmill, then it could gallop at speeds of 14 miles per hour, then it could run untethered outside. Now the group has released a video showing MIT Cheetah running untethered on an indoor track and leaping over random hurdles without breaking a stride.

Adaptive Leg "Muscles"

The key to MIT Cheetah's agility is a set of custom-built motors that precisely control how much force is delivered to each leg as it touches the ground. To gain speed, the legs push off the ground with more force so that the robot spends a greater fraction of the time flying through the air. The robot continually monitors its gait and the length of time its feet touch the ground in order to adjust its leg force to match.

"Once I know how long my leg is on the ground and how long my body is in the air, I know how much force I need to apply to compensate for the gravitational force," said group leader Sangbae Kim in a press release last September announcing MIT Cheetah's untethered running.

"Now we’re able to control bounding at many speeds. And to jump, we can, say, triple the force, and it jumps over obstacles."

Kim believes this force control is similar to how four-legged animals and human sprinters speed up.

"Many sprinters, like Usain Bolt, don’t cycle their legs really fast,” said Kim. “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."

Controlling the force in each leg also helps MIT Cheetah adapt to softer, bumpier terrain, and to leap over obstacles.

See, Run, Jump, Repeat

The robot's onboard vision system uses laser reflection to map the terrain and estimate the height and distance of obstacles in its path. This information is fed to an onboard computer program that finds the right speed and distance from the hurdle at which to jump, all in the space of about 100 milliseconds. By calculating backwards, MIT Cheetah's leg motors gradually adjust the force applied to the ground in order to prepare the robot for the leap.

On an indoor track scattered with randomly-sized hurdles, MIT Cheetah recently cleared 90 percent of the hurdles up to 18 inches tall (more than half the height of the robot).

MIT Biomimetic Robotics Lab with their cheetah-inspired robot. Credit: MIT
This research is funded in part by the Defense Advanced Research Projects Agency (DARPA), but the MIT researchers say their robot has a wide range of applications in disaster-relief efforts.

"Our goal is to use this kind of robot to save lives in a disaster situation. It could be used to help fire fighters or police in a dangerous situation," said Kim in an interview with Fox News.

The group will present their hurdle-loving robot at the DARPA Robotics Challenge in Los Angeles at the end of this week.

--
By Tamela Maciel, also known as "pendulum"

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