It’s not quite Robot Wars, but there’s a battle of the Cheetah bots going on in the robotics world. Back in 2012, Boston Dynamics unleashed its rather menacing looking Robo-Cheetah on the treadmill and it managed an impressive 28.3 miles per hour (45.5 kph) while tethered to a power supply, achieving the prestigious record of the world’s fastest mechanical mammal. Now, MIT researchers have unveiled their own version which managed 10 mph (16 kph) on an indoor track. Although that’s only a third of the speed of Boston Dynamics’ version, the new bot on the block managed to run that while untethered. Furthermore, it could even keep going after leaping over obstacles.
Why are researchers making Robo-Cheetahs, you ask? Well, cheetahs are the fastest land animal on Earth, so engineers are using them as inspiration to develop swift legged robots that don’t need to sacrifice speed for mobility on difficult terrains. Both projects were funded by the Defense Advanced Research Projects Agency (DARPA) and according to their website, these robots could one day be used in emergency response, humanitarian assistance and other defense missions.
While MIT’s version may look a little more like an ecstatic pig than a sleek cheetah, impressively it weighs around the same as its wild counterpart. Its ability to leap along the ground is thanks to MIT’s new algorithm for bounding that they plugged into the bot. When animals bound, their front legs hit the ground together, followed by the hind legs. Given that this gait is pretty simple, the researchers chose to model it first before eventually moving on to the more ambitious goal of galloping.
To achieve a bounding gait and maintain a constant speed, the researchers programmed each individual leg to exert a particular amount of force when it fleetingly touches the ground. In order to maintain momentum, that force needs to be sufficient enough for the robot to push against the opposing force of gravity. Generally speaking, the faster the speed, the greater the force that has to be exerted. According to Sangbae Kim, an MIT engineer, their approach is similar in principle to the way that many human sprinters race.
“Many sprinters, like Usain Bolt, don’t cycle their legs really fast,” Kim said in a news release. “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.”
It’s thanks to this force-based approach that Robo-Cheetah is able to maintain its speed on difficult terrain and even while clearing obstacles. The marriage of a high-torque-density electric motor and bio-inspired legs also allow force precision without the need for force sensors on the feet. Furthermore, this bot is much stealthier than robots equipped with gasoline powered engines. While they may be able to exert more force, they’re inefficient and noisy. MIT are hopeful that eventually, their model may reach speeds of 30 mph (48 kph).
Check out a video of Robo-Cheetah in action: