UT Dallas engineer applies robot control theory to improve prosthetic legs

December 04, 2014

A University of Texas at Dallas professor applied robot control theory to enable powered prosthetics to dynamically respond to the wearer's environment and help amputees walk.

In research available online and in an upcoming print issue of IEEE Transactions on Robotics, wearers of the robotic leg could walk on a moving treadmill almost as fast as an able-bodied person.

"We borrowed from robot control theory to create a simple, effective new way to analyze the human gait cycle," said Dr. Robert Gregg, a faculty member in the Erik Jonsson School of Engineering and Computer Science and lead author of the paper. "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."

Humanoid robots can walk, run, jump and climb stairs autonomously, but modern prosthetics limit similar actions in humans. While prosthetics have been made lighter and more flexible, they fail to mimic the power generated from human muscles in able-bodied individuals. Powered prostheses, or robotic legs, have motors to generate force, but lack the intelligence to stably respond to disturbances or changing terrain.

Control engineers view the human gait cycle through the lens of time -- the interval at which each movement in the walking cycle needs to occur. Gregg, an assistant professor of bioengineering and mechanical engineering, proposed a new way to view and study the process of human walking: measuring a single variable that represents the motion of the body. In this study, that variable was the center of pressure on the foot, which moves from heel to toe through the gait cycle.

"The gait cycle is a complicated phenomenon with lots of joints and muscles working together," Gregg said. "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 first tested his theory on computer models, and then with three above-knee amputee participants at the Rehabilitation Institute of Chicago, an affiliate of Northwestern University. He implemented his algorithms with sensors measuring the center of pressure on a powered prosthesis. Inputted with only the user's height, weight and dimension of the residual thigh into his algorithm, the prosthesis was configured for each subject in about 15 minutes. Subjects then walked on the ground and on a treadmill moving at increasing speeds.

"We did not tell the prosthesis that the treadmill speed was increasing. The prosthesis responded naturally just as the biological leg would do," Gregg said.

The participants were able to move at speeds of more than 1 meter per second; the typical walking speed of fully able-bodied people is about 1.3 meters per second, Gregg said. The participants also reported exerting less energy than with their traditional prostheses.

Gregg said current powered prosthetic devices require a team of physical rehabilitation specialists spending significant amounts of time tuning hundreds of knobs and training each powered leg to the individual wearer.

"Our approach unified multiple modes of operation into one and resulted in technology that could help people in the future," he said. "That and the feedback from participants were very rewarding."

Gregg said the next step in the research will be to compare results of experiments with robotic legs using both the time paradigm and center of pressure paradigm.
-end-
Researchers from the Rehabilitation Institute of Chicago, Northwestern University and the University of New Brunswick were also involved in the study.The work was funded by the United States Army Medical Research Acquisition Activity, the Burroughs Wellcome Fund and the National Institutes of Health through the National Institute of Child Health and Human Development.

University of Texas at Dallas

Related Engineering Articles from Brightsurf:

Re-engineering antibodies for COVID-19
Catholic University of America researcher uses 'in silico' analysis to fast-track passive immunity

Next frontier in bacterial engineering
A new technique overcomes a serious hurdle in the field of bacterial design and engineering.

COVID-19 and the role of tissue engineering
Tissue engineering has a unique set of tools and technologies for developing preventive strategies, diagnostics, and treatments that can play an important role during the ongoing COVID-19 pandemic.

Engineering the meniscus
Damage to the meniscus is common, but there remains an unmet need for improved restorative therapies that can overcome poor healing in the avascular regions.

Artificially engineering the intestine
Short bowel syndrome is a debilitating condition with few treatment options, and these treatments have limited efficacy.

Reverse engineering the fireworks of life
An interdisciplinary team of Princeton researchers has successfully reverse engineered the components and sequence of events that lead to microtubule branching.

New method for engineering metabolic pathways
Two approaches provide a faster way to create enzymes and analyze their reactions, leading to the design of more complex molecules.

Engineering for high-speed devices
A research team from the University of Delaware has developed cutting-edge technology for photonics devices that could enable faster communications between phones and computers.

Breakthrough in blood vessel engineering
Growing functional blood vessel networks is no easy task. Previously, other groups have made networks that span millimeters in size.

Next-gen batteries possible with new engineering approach
Dramatically longer-lasting, faster-charging and safer lithium metal batteries may be possible, according to Penn State research, recently published in Nature Energy.

Read More: Engineering News and Engineering Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.