New research aims to build lower limb prostheses with human-like reflexes

Researchers at Carnegie Mellon University are developing a lower limb prosthesis based on features of the human reflex, which they hope can increase users’ balance and improve current prostheses.

“Powered prostheses can help compensate for missing leg muscles, but if amputees are afraid of falling down, they will not use them,” Hartmut Geyer, PhD, assistant professor of robotics at the university, said in a press release. “Today’s prosthe[ses] try to mimic natural leg motion, yet they cannot respond like a healthy human leg would to trips, stumbles and pushes. Our work is motivated by the idea that if we understand how humans control their limbs, we can use those principles to control robotic limbs.”

Researchers evaluated a neuromuscular model using the Robotic Neuromuscular Leg 2, a computer-simulated, cable-driven device about half the size of a human leg. Funding for the test was provided by the Eunice Kennedy Shriver National Institute of Child Health & Human Development.

Findings showed that much like force feedback from leg extensor muscles, which respond to ground disturbances and automatically slow or extend the leg as necessary, the neuromuscular control method can produce normal walking patterns and respond to disturbances as the leg begins to swing forward as well as late in the swing phase.

As the control scheme does not yet respond to disturbances at mid-swing, more testing will be necessary, Geyer said. However, a control strategy based on human reflexes and other neuromuscular control systems has shown promise in simulation and in laboratory testing, producing stable walking gaits over uneven terrain and better recovery from trips and shoves. These principles could also aid legged robots, according to the release.

During the next 3 years, as part of a $900,000 National Robotics Initiative study funded through the National Science Foundation, the neuromuscular control method will be further tested using volunteers with above-the-knee amputations.

Geyer’s findings were recently presented at the Institute of Electrical and Electronics Engineers (IEEE) International Conference on Intelligent Robots and Systems in Hamburg, Germany. An upcoming paper in IEEE Transactions on Biomedical Engineering will focus specifically on how this method could improve balance recovery.


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