Bio-Inspired Prosthetic Limbs

I am pretty lucky to work on some cool projects. I am currently working on a project to improve the function of a remarkable Bionic ankle-foot prosthesis (BiOM). If you want to see what science is capable of today, watch this video.

Advances in prosthesis development have been driven largely by technology (e.g., light-weight materials, long-life lithium batteries, programmable electronics, and wireless communication), rather than by advances in our understanding of the underlying biological principles of movement. The BiOM can adapt to changes in walking speed on level ground. The main problem is that the control approach exhibits no inherent adaptation to varying environmental conditions. Instead, algorithms are required to generate particular torque control for all intended activities and variations of terrain, along with an appropriate means to select among them. Even with the power of AI, this is still an impossible task.

Perhaps we show look towards biology: muscles behave as non-linear, self-stabilizing springs and play an important role in the control of movement, particularly in response to unexpected perturbations. To maintain stability while navigating the environment, ankle plantar flexors and dorsiflexors instantaneously adjust their force output to meet the needs required for stability the muscles in our body are able to adapt instantaneously to changes in load without requiring sensory feedback, a property that has remain unexplained for decades. We have developed control algorithms for the BiOM based on the novel winding filament hypothesis (WFH), which builds on the sliding filament theory by incorporating a role for titin.

Is it any good? Check out this presentation by my long-time colleague, Dr. Uzma Tahir.

 

And the corresponding research paper from this study.

Future work: we are continuing to study our prostheses, and also moving into user safety and stability.

This is where I would like to explain something important: It took us almost 5 years to get to this point. We iteratively changed the controller as we tested the BiOM, making some major and minor adjustments as we went. Is it better to publish with your best foot forward, rather than several reports of small advances? Dissertations could be written on this topic!

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