Modular Exoskeleton Set
for Commercialization


Parker Hannifin Corp. plans to commercialize an exoskeleton in 2014. The device, developed at Vanderbilt University's Center for Intelligent Mechatronics, enables people with severe spinal cord injuries to stand, walk, sit, and climb stairs. Its combination of slim profile, modular design, and low weight — 40-50 percent lighter than competing exoskeletons — makes it easier to use and transport.

Exoskeletons strap tightly around the torso and legs to provide support. They also contain electric motors to flex the device's hip and knee joints. Patients use walkers or forearm crutches to maintain their balance. "If the person wearing it leans forward, he moves forward. If he leans back and holds that position for a few seconds, he sits down. When he is sitting down, if he leans forward and holds that position for a few seconds, then he stands up," said Michael Goldfarb, the Vanderbilt mechanical engineer who led the development effort.

This newly developed exoskeleton helps strengthen the leg muscles of its users.





Over the past decade, advances in robotics, control systems, batteries, and servomotors have made exoskeletons practical. Two companies, Argo Medical Technologies in Israel and Ekso Bionics in Berkeley, CA, are already marketing commercial products in the U.S. The Vanderbilt exoskeleton has several advantages over competing models, according to Goldfarb. It weighs 27 pounds, compared with roughly 45 pounds for other systems.

It also does away with the bulky backpacks used to hold batteries and control electronics. Equally impressive, the device automatically adjusts the amount of robotic assistance to compensate for users who have some muscle control in their legs. It also uses a technology called functional electrical stimulation to contract and relax leg muscles, which can improve the strength of people with incomplete paraplegia.

"This is an extremely exciting new technology," said Clare Hartigan, a physical therapist at Shepherd Center, a spinal cord injury rehabilitation hospital. Hartigan worked with Argo, Ekso, and Vanderbilt devices. "All three models get people up and walking," she said. This significantly reduces the likelihood of urinary, respiratory, cardiovascular, and digestive problems associated with lack of mobility.

She also noted that exoskeletons are not yet a cure-all: "A person has to be physically fit to use them. They have to keep their weight below 220 pounds, develop adequate upper body strength to use a walker or forearm crutches, and maintain flexibility in their shoulder, hip,knee, and ankle joints." This is not easy for someone who has relied on a wheelchair for months or even years, she added.

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This is an extremely exciting new technology. All three models get people up and walking.

Clare Hartigan, physical therapist, Shepherd Center


January 2013

by Alan Brown, Associate Editor, Mechanical Engineering Magazine