Portable engine powers artificial muscles in assistive devices

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Researchers have developed a lightweight fluidic engine to power muscle-mimicking soft robots for use in upper or lower limb assistive devices.

Left: Evaluation of the effect of the assistance on the activity of the biceps muscle while lifting a weight of 5kg. Results showed that on average the muscle activity was reduced by 39 per cent with assistance compared to the condition without wearing the device. Middle: Demonstration of high assistive force: the muscle can lift a 20kg object 18mm off the ground. Right: Proof-of-concept demonstration of wearable robot application to assist ankle plantar flexion
Left: Evaluation of the effect of the assistance on the activity of the biceps muscle while lifting a weight of 5kg. Results showed that on average the muscle activity was reduced by 39 per cent with assistance compared to the condition without wearing the device. Middle: Demonstration of high assistive force: the muscle can lift a 20kg object 18mm off the ground. Right: Proof-of-concept demonstration of wearable robot application to assist ankle plantar flexion - Antonio Di Lallo, NC State University

The solution from researchers at North Carolina State University, Sandia National Laboratories, and UC Berkeley is said to generate significant force without being tethered to an external power source.

In a statement, Hao Su, corresponding author of a paper on the work, said: “Soft robots that are powered by fluid engines – such as hydraulic or pneumatic action – can be used to mimic the behaviour of muscle in ways that rigid robots cannot.

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

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

“Our work here addresses both of those challenges,” said Su, an associate professor of mechanical and aerospace engineering at NC State. “Our fluidic engine is not tethered to an external source but can still generate up to 580 Newtons of force.”

According to NC State, the new engine works by pumping oil into and out of a chamber in a soft robot, causing the soft robot to act as an artificial muscle that is flexing and relaxing.

The fluidic engine’s 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.

In proof-of-concept testing, the researchers assessed the amount of force the new engine can generate, and how efficiently the engine converts electrical power into fluidic power.

“We found that we were able to generate an unprecedented amount of force for an untethered engine, while still keeping the weight of the fluidic engine low,” said Antonio Di Lallo, first author of the paper and a postdoctoral researcher at NC State. “And the maximum efficiency of our fluidic engine is higher than previous portable, untethered engines.”

The paper, “Untethered Fluidic Engine for High-Force Soft Wearable Robots,” is published in Advanced Intelligent Systems.

This work was done with support from the US National Science Foundation, the National Institute on Disability, Independent Living, and Rehabilitation Research, and Amazon Robotics.

portable engine for assistive devices