Robotic exoskeletons could prevent falls in older people

Researchers in Italy and Switzerland have developed a prototype robotic exoskeleton that can detect a slip in progress and help its wearer avoid falling (Science, 2017). If perfected, a system like this could one day help millions of older people and amputees maintain balance and avoid serious falls.

Some researchers are trying to take preventive action for falls with powered exoskeletons using braces for the legs with motorised joints that assist wearers while walking. But the braces are usually bulky and slow, and most people don’t need their assistance with every step. So the researchers set out to solve that problem with a device that would take action only when needed.

“It’s the first time that someone has rationally dealt with falls by having the robot collaborate with the person” said David Reinkensmeyer, a biomechanical engineer at the University of California, Irvine, who was not involved in the research. “It’s supercool.”

The new Active Pelvis Orthosis (APO) consists of a waist brace holding motors on the hips that move lightweight carbon fibre links connected to thigh braces. It uses an algorithm that monitors leg movement. If the legs diverge from a natural gait in a way that suggests a slip, the motors apply force to help the legs counteract the slippage.

To find out how it would work in people, its developers at the Sant’Anna School of Advanced Studies in Pisa and the Swiss Federal Institute of Technology in Lausanne outfitted eight older people and two above the knee amputees, who wore prosthetic legs with the device. The device testers walked on a custom treadmill split in two. Once in a while, the right or left half would jolt forward, simulating a foot slipping on ice or a loose rug. Sometimes the APO was on, sometimes it was off, and sometimes the study participants didn’t wear the APO at all. Motion capture cameras recorded their limb positions, creating stick figure animations for analysis.

After the start of a slip, the APO reacted within a third of a second, correcting a person’s gait for a quarter of a second. The study, published in Scientific Reports, shows that stick figure analysis showed that without the help of an additional restraining harness to prevent real falls they would have fallen. What’s more, during normal walking, the APO, which weighs about 5kg, had no effect on gait. “It’s a great example of trying a unique approach to exoskeleton control that’s having real results” said Daniel Ferris, a biomedical engineer at the University of Michigan in Ann Arbor who was not involved in the research. “I’m very excited about it.”

The device doesn’t require much customisation. After a user straps in, they programme in their weight and take three steps. The device forms an internal model of their normal walking movement in just a couple of minutes. The device doesn’t completely replace a user’s reflexes, but merely amplifies their leg force by 20% or 30%. “It’s a nice example of a robot being synergistic with a person in an emergency situation” said David Reinkensmeyer.

Daniel Ferris said the reason why no one has done this before is because there’s no universal hardware on which to test control systems, so each lab has to build its own. Also research will require experts in electronics, mechanical engineering, control algorithms, and biomechanics. In addition researchers have previously focused on the “low-hanging fruit” of helping users walk steadily, without worrying about recovery from falls.

Daniel Ferris thinks a device will be ready for the market in ten years, whereas David Reinkensmeyer thinks it’ll be ready in one or two years. As part of the needed development to reach that goal, Silvestro Micera, one of the study authors, hopes to make the APO less bulky and untether it from the external computer that controls it. He said future iterations will also include algorithms and motors to help with different types of falls, such as stumbling sideways.

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