MIT Researchers developed an algorithm four bounding and applied it to a robotic cheetah.
The robot proved to be able to silently sprint at 10 miles per hour and clear a hurdle; it could eventually reach speeds of 30 mph. The key to the algorithm is programming each of the robot's legs to exert a certain amount of force in a split second once it hits the ground. This allows the robot to maintain a given speed.
"Many sprinters, like Usain Bolt, don't cycle their legs really fast," said Sangbae Kim, an associate professor of mechanical engineering at MIT. "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."
The adapted force-based approach allowed the cheetah-bot to handle rougher terrain, such as a grassy field.
"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."
The robot possesses a high-torque-density electric motor controlled by amplifies as well as bio-inspired legs allowing it to bound across bumpy terrains.
"Bounding is like an entry-level high-speed gait, and galloping is the ultimate gait," Kim said. "Once you get bounding, you can easily split the two legs and get galloping."
The algorithm allowed them to determine how much force each leg should exert in the short period cycle that it spends on the ground.
"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," Kim said. "Now we're able to control bounding at many speeds. And to jump, we can, say, triple the force, and it jumps over obstacles."
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