Prosthetic ankle scans the ground ahead and adjusts accordingly

MTU researchers are hopeful that the all-seeing prosthetic foot will be pounding the pavement some time in the future (Photo: Michigan Tech)

Computer-controlled artificial legs have aided in improving amputees' freedom of movement by mimicking the natural motion of their missing limbs. Now, a new robotic ankle promises to make this motion even more precise by using a camera to scan the ground ahead and dynamically adjusting to the terrain underfoot.

A team of engineers at Michigan Technological University developed the prototype with the aim of providing a medical device that would help provide a natural gait. The same researchers were behind a microprocessor-controlled leg unveiled in 2013 that allows the foot sideways movement, and are one of a number of teams working at providing prostheses that rely on computing power to provide more natural movement.

Led by assistant professor of mechanical engineering Mo Rastgaar, the team produced a system comprising a prosthetic ankle, a low-cost camera and a separate computer-controlled actuator. As the user walks around, the camera scans the ground and a computer-controlled actuator readies the prosthetic foot to take its next step.

"The camera can identify the profile of the ground, while the computer knows where the next footstep will be, based on how the user is moving the leg,” says Rastgaar. "Then the computer analyzes the information from the camera and applies the correct angle and stiffness to the ankle, just as you would with your biological foot and ankle."

With the foot's movement dictated by a system of cables similar to a bicycle's brake cables, the actuator need not be fixed to the prosthetic and could instead be slipped inside the user's pocket or fanny pack. Rastgaar says this will allow greater flexibility and also give wearer's the ability to remove the actuator if need be. He is hopeful that the all-seeing prosthetic foot will hit the pavement at some time in the future.

"One of these days, we hope this can be brought to market, where it could really help people," he says.

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