Friday, July 21, 2017
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Building a Better Robotic Leg by Considering Pressure

Dr. Robert Gregg stands next to a robotic leg that was designed by UTDesign students and is similar to the one reported in his research. Photo courtesy of University of Texas, Dallas.
Robert Gregg stands next to a robotic leg that was designed by UTDesign students and is similar to the one reported in his research. Photo courtesy of University of Texas, Dallas.

Researchers have developed a new way of analyzing walking, with the hope of improving robotic legs.

Usually, researchers look at time as the all-important variable when trying to develop models for robotic legs. But a team at the University of Texas, Dallas, decided to focus on a different variable: the center of pressure on the foot. It’s a spot that moves from heel to toe as we walk.

“The gait cycle is a complicated phenomenon with lots of joints and muscles working together,” says Robert Gregg, lead author of a paper about the work that was published in IEEE Transactions on Robotics. “We used advanced mathematical theorems to simplify the entire gait cycle down to one variable. If you measure that variable, you know exactly where you are in the gait cycle and exactly what you should be doing.”

Gregg measured the location of that moving target on three subjects with above-the-knee amputations. By inputting the wearer’s height, weight and dimension of the residual thigh into his algorithm, he was able to quickly configure the robotic leg to each person is about 15 minutes. (Normally, this process takes a lot more time and involves a team of physical rehabilitation specialists.)

Once the leg was properly configured, the subjects walked on a treadmill and the speed was increased, without their prior knowledge. The subjects were able to walk about 1 meter per second, which is almost as fast the 1.3 meters able-bodied individuals are typical able to walk. Importantly, the subjects said they didn’t have to exert as much energy as they normally did when walking.

“Our approach resulted in a method for controlling powered prostheses for amputees to help them move in a more stable, natural way than current prostheses,” Gregg says.

Next, Gregg hopes to compare results of experiments on robotic legs using both time and center of pressure models.

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