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UMass Project Will Develop Next Generation of Robotic Lower Limbs for Amputees

Frank Sup

Frank Sup

Brian Umberger

Brian Umberger

Two researchers at the University of Massachusetts Amherst are aiming to create better fitting, more functional, and comfortable robotic lower limbs for amputees, especially those over 65. Principal investigator Frank Sup of the Mechanical and Industrial Engineering Department and Brian Umberger of the Kinesiology Department have received a $630,331 grant over three years from the National Science Foundation (NSF) to develop these revolutionary robotic prostheses for below-knee amputees.

The title of the UMass project is “Simulation Guided Design to Optimize the Performance of Robotic Lower Limb Prostheses.” The project is funded through the National Robotics Initiative, which is supported by the NSF, National Institutes of Health, United States Department of Agriculture, National Aeronautics and Space Administration, and Defense Advanced Research Projects Agency. The aim of the National Robotics Initiative is “to accelerate the development and use of robots in the U.S. that work beside or cooperatively with people.”

Sup and Umberger will design their new kind of robotic limb to relieve the commonly experienced pressure and discomfort that many amputees currently suffer in their residual limbs from ill-fitting or poorly functioning prostheses, which often cause pressure ulcers and deep tissue injury. Such injuries frequently lead amputees to abandon their prostheses and settle for a more sedentary lifestyle that can have serious negative health consequences.

A key to the project is the collaboration between Sup, the director of the Mechatronics and Robotics Research Laboratory in the MIE department, and Umberger, co-director of the Biomechanics Laboratory in the Kinesiology Department. To achieve the project goals they will use sophisticated computer simulation models of the human body to help design the next generation of robotic prosthetic technologies that maximize mobility for lower-limb amputees.

Sup and Umberger say that “The major outcome of this project will be an improved approach for designing prosthetic devices that reduce loading on the body and make walking easier.”

The NSF project is intended to upgrade the current generation of robotic prostheses, which might improve functional performance in a lower-limb amputee by restoring natural joint powers, but which fail to optimize the loading conditions on the residual limb.

The two researchers observe that the proposed research is especially relevant for older amputees, whose residual limbs cannot tolerate significant loading. Currently, 42 percent of persons living with limb loss are 65 years or older in the United States, and that figure is expected to jump to 62 percent by 2050.

“People will optimize gait based on energy, stability, and comfort,” as Sup and Umberger explain. “Stated more simply, people will do the best they can with what they have to work with.”

According to the two researchers, the performance of a lower-limb amputee is limited by the physical anatomy of the residual limb, the prosthesis, and the socket connecting them. Current lower-limb prostheses, both active (robotic) and passive (non-robotic), are focused on recreating the biomechanics of intact limbs. This mimic-type approach assumes that the socket, connecting wearer to prosthesis, is “a perfect mirror of the intact limb.”

However, as Sup and Umberger add, the amputee’s soft tissue at the socket interface is not designed to bear the loads to which it is subjected. Neglecting the unique anatomy and capabilities of an amputee results in “a human-machine system unable to achieve its maximum potential.” As a result, an amputee will often suffer high pressure on the residual limb, thereby amplifying discomfort. This problem can result in pressure ulcers or deep tissue injury to the residual limb and potentially overload other parts of the body as the user adapts to the device.

The researchers say that an amputee’s dissatisfaction with a prosthesis will often lead to disuse of the artificial limb, a more sedentary lifestyle, and greatly inhibited mobility. Without the independent mobility enabled by a prosthesis, an amputee needs more assistance and thus experiences a poorer quality of life.

The research project is focused on creating a new design process for assistive robotic devices that aid people with mobility impairments. Sup and Umberger will use detailed musculoskeletal models and optimal control simulations to optimize loading conditions in amputees while minimizing their metabolic energy consumption.

In the process, the researchers will generate optimal prosthesis forms through predictive simulations. Then Sup and Umberger will reverse-engineer the results to develop robotic ankle prostheses that allow the best possible gait performance for below-knee amputees. Each participant in the research will undergo a whole-body, computerized, gait analysis, first while walking in a passive, daily-use prosthesis, then while walking in a custom-designed robotic prosthesis, created from computer models and simulations of walking patterns.

The collaboration between Sup and Umberger is the critical factor in the success of the NSF project. Sup’s Mechatronics and Robotics Research Laboratory focuses on the advancement of physical human-machine interaction. The core of the lab’s research is on human-centered mechatronic design in the development of rehabilitative technologies. The goal of Umberger’s research in the Biomechanics Laboratory is to advance our understanding of the mechanics, energetics, and control of bipedal locomotion. He studies basic and clinical aspects of locomotion in humans and other bipeds, using a combination of experimental and computer modeling techniques. Much of his research is focused specifically on how the mechanical and energetic properties of skeletal muscles influence human movement.