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Vision system added to prosthetic leg to improve function

Engineers from Michigan Technological University (MTU) in the United States have integrated a vision system onto a prosthetic leg in order to adjust how it moves depending on whether a person is walking, striding, or climbing.

The MTU team’s prototype can already provide a range of motion that rivals a natural gait, but engineer Mo Rastgaar and his colleagues wanted to add a pair of ‘eyes’ to the robotic ankle.

The key components consist of a low-cost camera and a computer-controlled actuator, which adjusts the ankle’s position through a system of cables.

‘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,’ explained Rastgaar, who is an assistant professor of mechanical engineering-engineering mechanics. ‘Then the computer analyses 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.’

Thus, the ankle could adapt precisely, whether the user is climbing stairs or striding over a pothole, for example.

Rastgaar’s team has also refined the actuator’s design, making it lighter and more streamlined. Because the foot is moved by lines similar to bicycle brake cables, the actuator does not have to be mounted on the prosthesis, where the user must to move it with every step. Instead, it could be carried in a pocket, for example.

He hopes that eventually the robotic ankle will find its way out of the lab and onto the sidewalk. ‘One of these days, we hope this can be brought to market, where it could really help people,’ he said.

The research is being partially supported by a five-year Faculty Early Career Development (CAREER) Award from the National Science Foundation (NSF), and a provisional patent has been issued for the technology.

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