Targeting a specific set of applications where a wearer needs some partial assistance from a robot, Wyss Institute researchers are pursuing a new paradigm: the use of soft clothing-like “exosuits.” An exosuit does not contain any rigid elements, so the wearer’s bone structure must sustain all the compressive forces normally encountered by the body — plus the forces generated by the exosuit. The suit, which is composed primarily of specially designed fabrics, can be significantly lighter than an exoskeleton since it does not contain a rigid structure. It also provides minimal restrictions to the wearer’s motions, avoiding problems relating to joint misalignment. Ongoing work to optimize the suit design and make it portable is funded by DARPA’s Warrior Web Program.
A soft robotic exoskeleton, pulled on like a pair of pants, could one day give athletes an extra kick or soldiers the strength to lift heavier loads than their muscles alone could bear.
The soft suit is much lighter than the hard prosthetic exoskeletons, weighing just 7.5 kilograms (not including the air supply that drives the artificial “muscles”). Also, the suit relies on the existing movement of the legs as a person walks — its talent is adding a crucial nudge at the just right moment.
The suit’s performance was tested by five healthy members of the Wyss lab — all male — after they trained to use it for about three days. It’s confusing to react to the suit at first, but once a person adjusts to the push-and-pull of the suit, you feel the difference, Walsh said. “When you wear it, you feel like you’re getting a bit of a boost. After you stop wearing it, you notice that you don’t have that extra assist any more.”
Getting that timing right is important for the suit to work efficiently, sort of like how finding just the right moment to push a person on a swing set can keep them going fairly efficiently for a long time, Walsh explained. This means the suit needs to be an active sensor of a person’s gait as well. “If that timing is off it can actually make it harder for people to walk.”
Harvard Biodesign Lab – The suit includes sensors that are fitted on the knee, hip and ankle, to sense a person’s gait and gives them an extra push at just the right time.
The suit would need to be custom-fit to a person’s frame and gait, but that’s a one-time thing, Walsh says, “If you buy a bicycle you have to adjust the handlebars and then it’s set.” After that, “Every time they want to wear it, they [can] pull it on like a piece of clothing.”
Though applications and manufacture are years away, Walsh says the suit will see development in three main areas: in military applications, to help soldiers walk farther and carry heavier loads; as performance enhancers for athletes; and in rehabilitation medicine as an assistive technology for people who’ve retained the ability to walk, but find it difficult because their muscles are weakened or seen minor damage.
Considering the lifting applications that the suit might one day be used for: “Your muscles are three times as strong, but your bones aren’t any stronger,” he explained.
The “muscles” — or actuators, as roboticists like to refer to them — are powered by compressed air (you can hear the hissing in the YouTube video). The goal is to switch to an electrical, battery-operated system instead.