Portable engine powers artificial muscles in

Scientists have developed a lightweight fluidic motor to power soft, muscle-like robots for use in assistive devices. The new motor’s distinguishing feature is its ability to generate significant force without the need for an external power source.

“Soft robots powered by fluid motors—such as hydraulic or pneumatic motors—can be used to mimic muscle behavior in ways that rigid robots can’t,” says Hao Su, corresponding author of the paper and an associate professor of mechanical and aerospace engineering at North Carolina State University. “This makes these robots particularly attractive for use in assistive devices that improve humans’ ability to move their upper or lower limbs.”

However, most liquid engines are physically connected to an external power source, such as a large air compressor. This greatly limits their usefulness. And previous liquid engines that were not connected to external power sources were not able to generate much force, which also limited their usefulness.

“Our work here solves both of those problems,” Su says. “Our fluidic engine is not tethered to an external source but can still generate up to 580 newtons of force.”

The new motor works by pumping oil into and out of a chamber in the soft robot, causing the soft robot to act like an artificial muscle that flexes and relaxes. The fluidic motor pump is powered by a battery-powered, high-torque motor that allows it to generate significant pressure, allowing the artificial muscle to exert significant force. A video of the untethered motor can be found at https://www.youtube.com/watch?v=csVBpZIS_is.

In the concept tests, scientists evaluated not only the force the new engine could generate, but also how efficiently it converted electrical energy into jet energy.

“We found that we could generate an unprecedented amount of force for a tetherless motor while keeping the fluidic motor’s weight down,” says Antonio Di Lallo, the paper’s first author and a postdoctoral researcher at NC State. “And our fluidic motor’s peak efficiency is higher than previous portable tetherless motors.”

The article entitled “Untethered Fluidic Engine for High-Force Soft Wearable Robots” has been published in open access in the journal Advanced intelligent systemsCo-authors on the paper were Shuangyue Yu, a former postdoctoral researcher at NC State; Jie Yin, associate professor of mechanical and aerospace engineering at NC State; Jonathon Slightam of Sandia National Laboratories; and Grace Gu of the University of California, Berkeley.

This work was supported by the National Science Foundation under Grants 2026622 and 1944655; the National Institute on Disability, Independent Living, and Rehabilitation Research under Grant 90DPGE0011; and Amazon Robotics.