Robert Gregg IV, PhD, an assistant professor of bioengineering and mechanical engineering at The University of Texas at Dallas (UT Dallas), has received a five-year, $500,000 grant to support his work on control technology that would broaden the scope of activities available to users of powered lower-limb prostheses and orthoses. The grant was awarded by the National Science Foundation Faculty Early Career Development (CAREER) Program. In 2013, the year he arrived at the UT Dallas Erik Jonsson School of Engineering and Computer Science, Gregg received a $2.3 million grant from the National Institutes of Health for similar work. The university is also engaged in a licensing agreement with Bionik Laboratories, Toronto, Canada, which is seeking to commercialize the exoskeleton applications of Gregg’s control technology.
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. His devices would provide mobility for a continuously changing variety of tasks, with the ability to respond to unanticipated slope and footing changes.
“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. “When the user wants to change activity, the device has to somehow interpret his or her intent, and change its behavior,” Gregg said. “What I’m proposing is a prosthetic leg or exoskeleton that doesn’t actually have to interpret what the user is doing. 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 in the field from task-specific, kinematic control to task-invariant, energetic control. Gregg’s prosthetic leg design has a force sensor that detects weight automatically. Calibration would be a simple process.
“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. You’re not going to program jumping jacks into a prosthetic leg. 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.”
Editor’s note: This story was adapted from materials provided by UT Dallas.