Speed and agility are hallmarks of the cheetah: The big predator is the fastest land animal on Earth, able to accelerate to 60 mph in just a few seconds. As it ramps up to top speed, a cheetah pumps its legs in tandem, bounding until it reaches a full gallop.
Now MIT researchers have developed an algorithm for bounding that they’ve successfully implemented in a robotic cheetah — a sleek, four-legged assemblage of gears, batteries, and electric motors that weighs about as much as its feline counterpart.
The team recently took the robot for a test run on MIT’s Killian Court, where it bounded across the grass at a steady clip. In experiments on an indoor track, the robot sprinted up to 10 mph, even continuing to run after clearing a hurdle. The MIT researchers estimate that the current version of the robot may eventually reach speeds of up to 30 mph.
The key to the bounding algorithm is in programming each of the robot’s legs to exert a certain amount of force in the split second during which it hits the ground, in order to maintain a given speed: In general, the faster the desired speed, the more force must be applied to propel the robot forward.
In experiments, the team ran the robot at progressively smaller duty cycles, finding that, following the algorithm’s force prescriptions, the robot was able to run at higher speeds without falling. Sangbae Kim, an associate professor of mechanical engineering at MIT, says the team’s algorithm enables precise control over the forces a robot can exert while running.
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Transcript
00:00:15 The general goal of our lab is to understand the locomotion aspect of animals. Recently we are focusing on quadrupeds, or four-legged animals and we try to understand how they efficiently run in the field and nature so that we can take that inspiration and then use it in our engineering world. So for example we can create prosthetic legs out of that technology and you could even make new transportation replacing cars so that you don't need the road in our world. The cheetah is the fastest four-legged animal in the world
00:00:51 and we would like to make out robot run fast like a cheetah. When we started with our robot, we started to look at cheetahs' motion and applied its principles to our mechanical version of a cheetah. Currently our robot cheetah can run up to 10 mph and jump over a 33 cm high obstacle. So previously, most legged robots are powered by internal combustion engines and then hydraulic transmissions, and those are very noisy and very inefficient. But people believe that
00:01:33 internal combustion engines and hydraulics are the only way to make a legged robot run and support itself. People believe that electric motors are not powerful enough, so this is the first time we show that an electrically powered robot can run and jump over a foot high obstacle. In order to build a dynamic robot like Cheetah we had to develop everything on the robot including motors, control system and control algorithms. Because previous robotic technology is focused on controlling static motion over the robot.
00:02:09 I think this is a really exciting future where robots can be quiet and efficient and also powerful and then we might exceed the muscles' performance in the future.
