MIT's robot cheetah is apparently able to run with less effort than an actual cheetah, wasting little energy as it trots for 90 minutes on a treadmill (note that this is a different device than Boston Dynamic's cheetah robot).
(MIT's relaxed cheetah robot trots effortlessly)
The key to the robot’s streamlined stride: lightweight electric motors, set into its shoulders, that produce high torque with very little heat wasted.
The motors can be programmed to quickly adjust the robot’s leg stiffness and damping ratio — or cushioning — in response to outside forces such as a push, or a change in terrain. The researchers will present the efficiency results and design principles for their electric motor at the International Conference on Robotics and Automation in May.
Sangbae Kim, the Esther and Harold E. Edgerton Assistant Professor in MIT’s Department of Mechanical Engineering, says achieving energy-efficiency in legged robots has proven extremely difficult.
To understand how an electrically powered system might waste little energy while running, the researchers first looked at general sources of energy loss in running robots. They found that most wasted energy comes from three sources: heat given off by a motor; energy dissipated through mechanical transmission, such as losses to friction through multiple gear trains; and inefficient control, such as energy lost through a heavy-footed step, as opposed to a smoother and more gentle gait.
The group then came up with design principles to minimize such energy waste...
... The cheetah robot, according to Kim’s calculations, falls around the efficiency range of humans, cheetahs and hunting dogs.
Currently the team is assembling a set of new motors, designed by Jeffrey Lang, a professor of electrical engineering at MIT. Kim expects that once the group outfits the robot with improved motors, the cheetah robot will be able to gallop at speeds of up to 35 mph, with an efficiency that rivals even fliers. The researchers are convinced that this approach can exceed biological muscle in many aspects, including power, torque and responsiveness.
Fans of Neal Stephenson's 1992 novel Snow Crash may recall the Rat Thing:
The body is Rottweiler-sized, segmented into overlapping hard plates like those of a rhinoceros. The legs are long, curled way up to deliver power, like a cheetah's. It must be the tail that makes people refer to it as a Rat Thing, because that's the only ratlike part - incredibly long and flexible.
(Read more about Stephenson's Rat Thing)