A volunteer tests gait patterns using the neuromuscular prosthetic leg. Photograph courtesy of CMU.
A robotic leg prosthesis being developed at Carnegie Mellon University (CMU) uses techniques based on the control mechanisms of the human leg to help prosthesis users avoid stumbles and reduce the risk of a fall. The control strategy, devised after the research team studied human reflexes and other neuromuscular control systems, has shown promise in simulation and in laboratory testing, where it has produced stable gaits over uneven terrain and better recovery from trips and shoves.
The researchers found that the neuromuscular control method can reproduce normal walking patterns and that it effectively responds to disturbances as the leg begins to swing forward and late in the swing. More work is necessary, however, because the control scheme doesn’t yet respond effectively to disturbances at mid-swing, according to the team.
The researchers studied the role of the leg extensor muscles because the force feedback from these muscles automatically responds to ground disturbances, quickly slowing or extending leg movement, as necessary. The team-Hartmut Geyer, PhD, assistant professor of robotics; Steve Collins, PhD, associate professor of mechanical engineering and robotics; and Santiago Munoz, CPO, instructor in the department of rehabilitation science and technology at the University of Pittsburg-evaluated the neuromuscular model by using computer simulations and a cable-driven device about half the size of a human leg, called the Robotic Neuromuscular Leg 2. Over the next three years, as part of a $900,000 National Robotics Initiative study funded through the National Science Foundation, the technology will be further developed and tested using volunteers with transfemoral amputations.
“Today’s prosthetics try to mimic natural leg motion, yet they can’t respond like a healthy human leg would to trips, stumbles, and pushes,” said Geyer. “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.”
Geyer’s latest findings applying the neuromuscular control scheme to prosthetic legs and, in simulation, to full-size walking robots, were presented at the IEEE International Conference on Intelligent Robots and Systems in Hamburg, Germany. An upcoming paper in IEEE Transactions in Biomedical Engineering focuses specifically on how this control scheme can improve balance recovery.
Editor’s note: This story was adapted from materials provided by CMU.
