Bionic Human Limbs and Humanoid Robots

Medical Design Briefs INSIDER

Hugh Herr, an associate professor of media arts and sciences at the MIT Media Lab, who designs, creates, and wears bionic prosthetic lower limbs, has become somewhat of a celebrity in this field, and has inspired students to learn more about the technology. “It’s always good to design something people will use. It’s great to do the science, yes, but it’s also great to see humanity using something that one has invented,” Herr says. “Translating technology out of the lab keeps engineers honest.”

Using battery-powered “bionic propulsion,” two microprocessors and six environmental sensors adjust ankle stiffness, power, position, and damping thousands of times per second, at two major positions: First, at heel strike, the system controls the ankle’s stiffness to absorb shock and thrust the tibia forward. Then, algorithms generate fluctuating power, depending on terrain, to propel a wearer up and forward.

When fitting the prosthesis to patients, prosthetists can program appropriate stiffness and power throughout all the stages of a gait, using software created by Herr’s group, which they call “Personal Bionic Tuning.”

Among other things, the system restores natural gait, balance, and speed; lowers joint stress; and drastically lowers the time required to acclimate to the prosthesis. The system, Herr says, could also help prevent osteoarthritis, a joint condition caused by age and leg strain, by providing calf and ankle power and support even in old age.

Since 2003, the group has designed and fabricated many prosthetic prototypes to test hypotheses on human-machine interaction. By advancing prostheses, Herr says, the technology could also lead to innovation in a closely related field: humanoid robotics.

But ultimately, his work aims to help revolutionize the idea of “personal bionics,” which is blurring the lines between electromechanics and the human body. For instance, his MIT group is working, among other things, on bionic limbs that can be controlled by the mind and attached to the body.

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