A professor from the University of Texas at Dallas designed a robotic leg that could adapt to the wearer’s environment, make walking easier and look and feel more natural. The scientists aimed to integrate the vast improvements made in humanoid robots in robotic legs for amputees. The powered prosthesis has been featured in a number of online reports and in print in an upcoming issue of IEEE Transactions on Robotics, and is 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.
Lead author Dr. Robert Gregg, an assistant professor of bioengineering and mechanical engineering in the Erik Jonsson School of Engineering and Computer Science, said their application of robot control theory resulted in a breakthrough method for dynamically controlling powered prosthesis for amputees, giving them enhanced stability and comfort. Today’s robotic prostheses have succeeded in becoming lighter and more flexible, but still fail in having the adaptive intelligence required for natural mobility in changing terrain.
Control engineers’ traditional approach to understanding the cycle of human gait is viewed chronologically, based on the intervals at which each movement occurs during walking. Dr. Gregg adopted a novel view of human walking by measuring a single variable, representative of the body’s motion; and in this study, making it the center of pressure on the foot, which travels from heel to toe across the cycle. He explains, “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.”
What is notable about Dr. Gregg’s demonstration of the redesigned powered prosthesis at the Rehabilitation Institute of Chicago, is the above-knee amputee wearers were not informed the treadmill speed was increasing, but the robotic legs were able to intelligently adapt to the changing requirements without making the wearer feel awkward or unstable. The only information Dr. Gregg needed to program the robotic legs were the wearer’s height, weight and measurements of the residual thigh, and they were ready to be worn in 15 minutes. Additionally, the enhanced robotic legs have the potential to reduce the need for intensive conditioning and gait training from professionals.
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.