These Energy-Recycling Actuators Can Cut a Robot's Power Consumption By Up to 97 Percent

Researchers at Stanford University have come up with an alternative to classic motors, designed to deliver more energy-efficient next-generation robots — by recycling energy using a series of springs and clutches.

"Rather than wasting lots of electricity to just sit there humming away and generating heat," professor of mechanical engineering Steve Collins says of the technology detailed in the paper on which he is senior author, "our actuator uses these clutches to achieve the very high levels of efficiency that we see from electric motors in continuous processes, without giving up on controllability and other features that make electric motors attractive."

"They're lightweight, they're small, they're really energy efficient, and they can be turned on and off rapidly," adds lead author Erez Krimsky, PhD, of the resulting actuators, designed to deliver dynamic movements considerably more efficiently than traditional motors. "And if you have lots of clutched springs, it opens up all these exciting possibilities for how you can configure and control them to achieve interesting outcomes."

The team's prototype actuator works by harvesting energy and storing it in the stretched rubber springs, which are sandwiched between two clutches. When the robot is, for instance, lowering something heavy, the springs can take some of the load away from other traditional motors in the system — then lock in the stretched position to store the harvested energy, delivering it at effectively zero cost when required.

The prototype, built using one traditional motor and six clutched springs, showed real promise in testing with a 50 percent reducing in power required by the augmented motor compared to an unaugmented version — peaking at a whopping 97 pe cent drop in power consumption in the best-case scenario.

"This has implications for assistive devices like prosthetics or exoskeletons as well," Krimsky notes. "If you don't need to constantly recharge them, they can have a more significant impact for the people that use them."

The team's work has been published under free access terms in the journal Science Robotics; Collins claims that "the technology is really at a place where it's ready for commercial translation," though admits that there are "a bunch of little control and design tweaks we'd like to make" — including reducing the time it takes for the controller to work out how best to apply the actuators for a given task.

Main article image courtesy of Erez Krimsky.