Dr. Robert Gregg has devoted years of research to helping lower-limb amputees and stroke survivors walk again. A new grant from the National Science Foundation (NSF) has given that effort a significant boost.
The UT Dallas assistant professor ofbioengineering and mechanical engineering has received a five-year, $500,000 NSF Faculty Early Career Development (CAREER) award to support his work on broadening the scope of activities available to users of powered lower-body prosthetics and orthotics. In 2013, the year he arrived at the Erik Jonsson School of Engineering and Computer Science, Gregg received a $2.3 million grantfrom the National Institutes of Health for similar work.
“The goal is to produce technologies that allow better mobility in changing environments and scenarios, which is important to regaining independence and quality of life,” Gregg said.
Most current advanced control methods are specialized to a limited set of specific predefined motions, like walking on a specific slope, and ascending or descending stairs.
Gregg’s devices would provide mobility for a continuously changing variety of tasks, with the ability to respond to unanticipated slope and footing changes.
“What I’m proposing is a prosthetic leg or exoskeleton that doesn’t actually have to interpret what the user is doing,” Gregg said. “It’s synchronizing to the motion of the user in real time instead of choosing from a set of options.”
This difference represents a paradigm shift under way in the field from task-specific, kinematic control to task-invariant, energetic control.
“In this new approach, the amputee would be using his or her hips to coordinate the control of the knee and the ankle,” Gregg said. “We’re controlling energy rather than specific joint patterns, so we don’t have to estimate intent. By injecting energy into the gait cycle, then removing it at the right times, it will produce the correct joint trajectories.”
Gregg’s prosthetic leg design has a force sensor that detects the weight automatically. Calibration would be a simple process.
“Our approach is very different in that we have a very small set of parameters that can be automatically calibrated,” Gregg said. “We’re getting closer to what I’d call plug-and-play robotic legs and exoskeletons that require very minimal tuning. That’s our vision.”
This would differ greatly from current state-of-the-art powered prosthetics, which “have dozens, perhaps hundreds of different parameters and coefficients that would need to be tuned for every individual patient over a period of several hours if not multiple days.”
Gregg said that the long-term goal of his research is to create a powered prosthetic leg that can perform a wide range of activities as opposed to a limited set of preprogrammed responses.
“You’re not going to program jumping jacks into a prosthetic leg,” Gregg said. “But if we’re able to control such a continuum of activities, then maybe the leg can actually help you perform that, or any other activity you need to do.”
Like all NSF CAREER awards, Gregg’s grant comes with an educational component. His plan focuses on both research and awareness, involving both the UT Dallas engineering school and the prosthetics-orthotics program at the UT Southwestern School of Health Professions.
“Our plan spans multiple levels of education, from K-12 up to prosthetics medical training,” Gregg said. “For the younger group, we’ll be doing outreach activities — engineering camps and exhibits at local libraries. We’ll work with college senior design projects through UTDesign, and I’m helping add new curriculum for the prosthetics program at UT Southwestern Medical Center. I’m very passionate about the educational aspect of this.”
Though powered multi-joint prosthetics have been confined to the research world, Gregg has gained support from a robotics company that envisions future applications for his exoskeleton work.
“We’re engaged in an option agreement with Bionik Laboratories and are collaborating with them as they seek to commercialize the exoskeleton applications of this control technology,” Gregg said.