Can fluid power play a role in wearable exoskeletons?

power-loaderPopular movies have long imagined robotic assist type machinery, from the Power Loader exoskeleton that Ripley wore in Aliens to the military weaponry showcased in Starship Troopers and Avatar—not to mention basically the entire premise of the Iron Man movies. But, as so often happens, the real world is catching up to the imaginations of so many science fiction writers.

At this week’s Fluid Power Innovation and Research Conference, held at the Hyatt Regency Minneapolis, Professor Thomas G. Sugar (pictured, below left) of Arizona State University discussed the trends in wearable robots, and what opportunities these devices held for fluid power technology.

The key to these devices, Sugar argued, is that more and more humans are simply dying of decay—we’re getting older as medicine has improved. And even for those with disease—say, cancer, heart disease, or diabetes—it’s often harder to walk, to get up and down, to lift objects.

“People are getting older and they still want to walk, they still want to be agile,” Sugar said, noting that sitting is believed to contribute to diabetes, cardiovascular disease, and greater risks of other types of mortality. “We need to walk, so that why wearable systems [are needed]. We need to walk.”

sugarSugar said that the foundation of technologies for wearables are here now.

“We’re got batteries, microprocessors. You’ll always need better actuators, but there’s systems out there. Wearable robots are key for the health market, assisted market, manufacturers, military, and recreation.”

Whether working on exoskeletons, orthoses, or prostheses, he said that designers need to build devices that seamlessly interact with the user; you cannot force them into some type of motion. The person has to be able to walk and have the robot “follow” them—you can’t disrupt the gait cycles or normal movement. People want to be able to move comfortably. And the massive exoskeletons that many people envision aren’t the reality in the near future, smaller units–ideally 10 lb or less in weight—are ideal. Sugar said that in testing, people who wore larger devices, in the 16-lb range, felt like they were walking through a swimming pool or that it was like a piece of exercise equipment.

Sugar’s team has created a hip exoskeleton, with 10% metabolic augmentation. He said that it’s actually 10% easier to run with the device than no device at all. They had people running fast, too—12.8 miles per hour. They have been focusing on phase angles to assist with delivering power to the user, looking at the velocity and position of the limbs.

Sugar detailed some of the numerous aspects to wearables that are currently in development, including:

• Devices that power the hips and knees, forcing people to follow a pattern of walking
• Prosthetics that can test for stiffness in an individual user and tune for it
• Devices specifically for amputees (large number of amputees from military veterans and diabetics)
• Rehabilitation exoskeletons attached to treadmills to allow people to walk
• Devices that allow stroke victims to practice repetitive tasks and build up those neural pathways
• Gravity-compensation devices that are used with muscular dystrophy patients
• Wearables that allow the elderly to successfully get up out of chairs
• Pneumatic muscle systems for a variety of assistive uses
• Hydraulic systems for picking up huge weights, suitable for warehousing uses
• Devices that tie into work tools and reduce the load on the user, such as a rake that is used to lay down asphalt
• Hand-assist devices that allow the user to better grip objects
• So-called chairless chairs, which allow the user to squat—they then lock in place, so the user can work in an otherwise uncomfortable position
• Recreational devices, which assist in skiing—using pneumatic or hydraulic damming devices for the knees, and
• Assist devices to let recreational runners run faster

Sugar stressed that battery life and component durability are key concerns.

“The army said that they wanted a soldier to walk an eight-hour march, so that’s about 5,000 to 8,000 steps. With a 5-amp, 24-V lithium ion battery, we do eight hours of marching. You can only do that if you store energy properly,” he said. “We typically use about a 1-lb battery, that gives you about three hours of life, of just continuous walking, and the idea is that you swap out. That’s not the problem. The bigger problem is [in the private sector], Medicare will only pay for one ankle every five years, so you need a device that can do about ten gigs, motor and bearings need to do about 10 gig cycles—so life cycle is the biggest concern.”

Both hydraulics and pneumatics can find niches in wearable devices in the coming years, and Sugar stressed that the industry should consider looking more at soft robotics, where pneumatics is obviously a critical player.

“There’s a big push into this, to get away from big, clunky devices,” he said.

And for hydraulics, where it may be more well-suited to handling loads?

“There still is this need for people to load and unload things. I met the CEO of Walmart at a conference two weeks ago, and he said, ‘Well, we have all these robots at the distribution centers, its perfect—and distribution centers are lights-out robotics, and that’s definitely where we’re going. But I’ve got 11,000 stores, and on average, two trucks go to each store each night, so we have got to unload 22,000 trucks every night—there’s still a need for humans there.’”

Pneumatic Tips