Cheetah, the robot inspired by the fastest land animal on the planet, has been tested without a tether for the first time by researchers from the Massachusetts Institute of Technology (MIT) developing it. The mechanical feline was able to walk, run and jump as it scurried across a grass field.
Cheetahs in the wild reach top speeds of 60 miles an hour for short sprints. The speedy mammal accomplishes this by moving its legs in tandem, until the creature has reached its desired speed.
A new algorithm was designed by the MIT researchers, allowing the robotic device to accomplish the same task as its animal namesake. Central to this development is the amount of force applied to the feet of the animal when they touch the ground. Pushing off with greater force results in a faster run, according to the researchers. They believe this process may be similar to the method used by the world's fastest human runners.
"Many sprinters, like Usain Bolt, don't cycle their legs really fast. 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," Sangbae Kim, associate professor of mechanical engineering at MIT, said.
This is accomplished in the robot using a high-torque-density electric motor. These are connected to specially designed amplifiers, allowing the mechanism to sprint over rough terrain without the use of sensors on the feet of the device.
Controlling speed by directing the amount of force applied to the ground not only allows greater speed than trying to increase the frequency of strokes, but also provides greater stability to the robot. During tests, Cheetah maintained its speed, even when passing over foam barriers placed in its path.
Bounding in animals involves the creature touching their front legs together on the ground for a fraction of a second, followed by a similar motion with their rear legs. Time spent with paws on the ground is referred to as the duty cycle. Faster animals have shorter duty cycles than slower species, according to the research.
"Bounding is like an entry-level high-speed gait, and galloping is the ultimate gait. Once you get bounding, you can easily split the two legs and get galloping," Kim told the press.
Cheetah weighs roughly the same amount as the large cat.
The test was carried out at Killian Court on the MIT campus. During indoor tests, the robotic Cheetah was able to reach speeds of around 10 MPH, although developers hope to improve that speed in future runs.
Hae-Won Park and graduate student Meng Yee Chuah of MIT, developers on the project, will detail the new bounding algorithm later in Septemeber at the IEEE/RSJ International Conference on Intelligent Robots and Systems, to be held in Chicago.
A video showing the Cheetah in action was released on the MIT YouTube page.
