Portable engine could power artificial muscles in assistive devices

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 – hydraulic or pneumatic, for example – can be used to mimic muscle behavior in ways that rigid robots cannot,” says Hao Su, a corresponding article on this work and an associate professor of mechanical engineering and Aerospace from North Carolina State University.

“This makes these robots particularly attractive for use in assistive devices that improve people’s ability to move their upper and lower limbs.”

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

“Our work addresses both of these challenges,” Su says. “Our thruster is not connected to an external source, but it can still generate up to 580 newtons of force.”

The new motor works by pumping oil in 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 driven by a battery-powered, high-torque motor that allows it to generate significant pressure, enabling the artificial muscle to exert significant force.

As part of the proof-of-concept testing, scientists not only evaluated the force the new engine could generate, but also how efficiently the engine converted electrical energy into liquid power.

“We found that we were able to generate unprecedented force for the standalone engine while keeping the mass of the ramjet low,” says Antonio Di Lallo, first author of the paper and a postdoctoral researcher at NC State.

“The maximum efficiency of our fluid engine is higher than that of previous portable, tetherless engines.”

The article “Untethered Fluidic Engine for High-Force Soft Wearable Robots” was published in an open access journal Advanced intelligent systems.