

Ask HN: Powered Exoskeletons; What's stopping us? - tocomment

Why hasn't anyone invented an exoskeleton that handicapped people could wear to help them walk?  It seems like it would just be some motors on a frame.  Are there challenges that make this kind of technology infeasible?
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jws
Efficiency: It is hard to beat wheels on hard surfaces for efficiency. Battery
life.

Stability: Wheelchairs are inherently stable. There are a 1000 ways to fall
from a standing position.

Cost: Two small motors in a wheelchair. A dozen powerful actuators in a legs
only exoskeleton. Simple tubing suffices for a wheelchair, an exoskeleton will
be pushed to more exotic materials and forms because any additional weight
will raise the cost of the actuators and reduce the already sad battery life.

Ask this question again when you see recreational exoskeletons for wealthy
people.

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mbrubeck
Control: You can move and turn a wheelchair with your hands (or someone's
help), or with a very simple joystick. An exoskeleton would need an elaborate
control system to coordinate its movements with your legs.

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krschultz
Research on this is ongoing at my college and I've taken a grad class on
it/looked into a lot of research on it so I feel like I can comment.

It is EXTREMELY difficult. I am in the last semester of undergrad degrees in
computer science & mechanical engineering. I have worked on path finding, AI,
computer vision and a bunch of mech engineering stuff. This was the hardest
topic I've ever covered, by far.

At my college the professor in charge of research and his grad students have
had success for lower body exoskeletons and are just now starting to work on
upper body ones.

It is not just some motors on a frame. Realize the person inside the frame has
limits on their joint motion and a certain gait, if the motors do not
correctly follow the prescribed gait you could seriously injure the person
wearing it. The human body has many more degrees of freedom than you would
expect, it is not simple hinge joints.

Plus there is the density issue, batteries, motors, computers, frames must be
made light but strong and durable etc.

And then there is the interface, how does the exoskeleton know when you want
to move your arm/leg down. Is it pushing down on the exoskelton because you
have no strength and gravity is pulling? Or do you want to put down the glass
you are holding or take a step forward?

So people out there are trying, it is just really hard.

Note that the goal is to rehabilitate people, not replace wheel chairs. After
enough time with a lower body exoskeleton and continually lowering the help
the skeleton provides until there is basically none, the person slowly regains
the ability to walk (in the case of a stroke victim).

For the upper body exoskeleton the goal is to provide help for those with
muscular dystrophy or the like, i.e. where there is no solution today.

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tokenadult
_Realize the person inside the frame has limits on their joint motion and a
certain gait, if the motors do not correctly follow the prescribed gait you
could seriously injure the person wearing it._

That's a very good point. Muscle stiffness or spasms are a persistent problem
for people with paralyzing injuries.

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tokenadult
_It seems like it would just be some motors on a frame._

My dad was paralyzed for the last six years of his life with a slip-and-fall
injury to his second cervical vertebra. He underwent a great deal of expensive
physical therapy (illustrating starkly what Medicare DOESN'T cover) and tried
out several models of motorized wheelchairs. Sometimes he attempted standing
in standing frames. An effective motorized exoskeleton would have to have a
very sophisticated balance system, and it would have to have a very sensitive
and delicate control system to respond to inputs from people who often don't
have much other control of voluntary muscle movements. What would its default
(at rest) position be? How much would it allow connecting gastric tubes
(something my dad used) or intravenous tubes or emergency airway tubes or
other medical devices?

 _Are there challenges that make this kind of technology infeasible?_

My list of areas to ask questions about above is not exhaustive. If the
proposed treatment is more technically complicated (that is, more expensive)
than some existing treatment, and few people can afford the existing
treatments to begin with, there isn't a lot of market push to develop the new
treatment.

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notaddicted
(answering without research)

Power supplies, i.e. the battery problem. Wheeled vehicles are much more
efficient than walking/running.

So for an exoskeleton you need more motors, you need big joints, AND you need
a bigger energy source, whatever that may be. My guess is that batteries can't
meet the cost and weight requirements, and there is no market for a 1000 lb.
V8 powered wheelchair that would probably kill 3 people if it fell down the
stairs, negating the benefit of the extra mobility.

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kevinherron
The Raytheon Sarcos exoskeleton looks promising:

<http://www.youtube.com/watch?v=Nhj3Z9o6t0g> and
[http://www.raytheon.com/newsroom/technology/rtn08_exoskeleto...](http://www.raytheon.com/newsroom/technology/rtn08_exoskeleton/)

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noodle
iirc, they have. i can't find a link on it though.

i imagine the problem is cost. handicapped people can afford a wheelchair, but
not an exoskeleton.

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tocomment
I wonder why it should be more expensive than a motorized wheelchair?

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noodle
i imagine the engineering backing it. wheelchair is wheels on a chair. we've
got the wheels-powered-by-a-motor technology down. exoskeleton is full of more
intricately complex systems (assuming we're talking about the same thing here)

