Exosuit Designed for Personalized Walking Help

Military version of exosuit (Biodesign Lab, Harvard University)

17 September 2018. A wearable robotic exoskeleton designed into textiles to provide personalized assistance is shown in lab and field tests to reduce the amount effort needed to walk long distances. A team from the Wyss Institute at Harvard University recently reported on these developments at the IEEE International Conference on Robotics and Automation in Brisbane, Australia and in the Journal of NeuroEngineering and Rehabilitation.

Exoskeletons are lightweight motorized frames worn like a brace over the legs that offer help in walking for people with limited or no mobility, such as those with a spinal cord injuries or a stroke. Advances in the technology enable the functions of the once-rigid frame to be integrated with textiles and worn like apparel, called exosuits, but still connected to motors and electronic controllers. While the devices were initially designed for people with disabilities, the U.S. Defense Advanced Research Projects Agency, or Darpa, is also interested in the technology to help soldiers expend less effort and remain alert when marching long distances in hostile territory.

A Wyss Institute team led by Harvard bioengineering professor Conor Walsh is developing exosuit technology in partnership with the Israeli exoskeleton company ReWalk Robotics Ltd., as reported in May 2016 by Science & Enterprise. To help individuals with limited mobility, the exosuit requires a more complex system than an exoskeleton helping someone with full paralysis, since a person with a stroke or multiple sclerosis can still perform some walking functions. In this case, the exosuit needs to sense where joints in the legs need help and provide that help when needed.

The exosuit designed by Walsh and colleagues for people with disabilities has an electronic controller and motors worn in a self-contained unit on a belt around the waist. In the military version, the controller and motor unit attaches to the bottom of a standard rucksack. The controller and motor unit is connected to sensors and support units on the ankles and hips with Bowden cables that capture and transfer push-pull energy, often used in remote-controlled systems. The system also has sensors connected to the thigh and calf. The power transferred to the hip and ankle joints helps the wearer walk by assisting the weakened joints.

In the IEEE paper, the Wyss Institute team field tested the military version of the exosuit with two volunteers. The researchers first manually tuned the system in the lab to the individual walking styles of each participant, having the volunteers walk over bumps and then for brief walks outside the lab. The two participants then wore the exosuits for extended walks through a park in Medford, Massachusetts encountering mud, rocks, and tree routes along the way. The participants first walked the 1 kilometer course with a 7 kilogram (15.4 lb.) rucksack but without the exosuit, then wearing the system, with caloric measurements of metabolic rate showing 7 and 17 percent less energy expended by the respective volunteers when wearing the exosuit.

In the journal paper, the team refined the system with an automated tuning algorithm that customizes the energy provided to the ankles. Tests with 7 volunteers walking on a treadmill and wearing the military version of the system for 15 minutes with a rucksack show the device enabled participants to expend 15 percent less energy, compared to walking without the system, and 22 percent less energy when walking with device unpowered.

“We are now continuing to optimize the technology for specific uses in the Army where dynamic movements are important,” says Walsh in a Wyss Institute statement, “and we are exploring it for assisting workers in factories performing strenuous physical tasks.” The following video demonstrates the military exosuit.

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