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Ankle Exoskeleton Takes a Load Off Calf Muscles To Boost Walking Efficiency
Zothecula writes We might have started off in the water, but humans have evolved to be extremely efficient walkers, with a walk in the park being, well, a walk in the park. Human locomotion is so efficient that many wondered whether it was possible to reduce the energy cost of walking without the use of an external energy source. Now researchers at Carnegie Mellon and North Carolina State have provided an answer in the affirmative with the development of an unpowered ankle exoskeleton."
The energy to load the spring comes from the user as part of the normal operation cycle. That makes it unpowered.It does not bring extra energy to the operation (user walking by converting chemical energy to muscle contraction), it only changes how the energy is used.
The trick is to define the system and timeframe you are looking at sensibly. In this case you have the braces and the user taking a number of steps. The user generates the power, the braces are unpowered. If you looked at the braces for one unloading of the spring, you could say the frame is powered by the spring, but that is not very useful choice in most contexts outside design of the device.
Indeed, I thought modern humans evolved in Olduvai Gorge
The Omo River site in Ethiopia is the current frontrunner, I believe.
https://en.wikipedia.org/wiki/...
rage, rage against the dying of the light
It might help with people who have injured calf muscles where that extra 10lbs can help out a bit.
But effenancy isn't good for exercise as we want to burn calories and build up muscles.
However it could be used for jobs where there is a lot of walking where the effenancy can allow you to have enough energy at the end of your shift to be more effective.
If something is so important that you feel the need to post it on the internet... It probably isn't that important.
Don't be obtuse. It's clear that what they're getting at is that it isn't externally powered when they say it's "unpowered".
Moreover, you've failed to consider how different efficiencies can affect the situation (i.e. the real world is not a frictionless vacuum). Yes, moving more mass means requiring more energy...output energy. But what we're concerned with here are inputs, since that's what we're expending.
Just to drive home the importance of the distinction between inputs and outputs (and also to toss in an obligatory car analogy), consider the Tesla Model S. It weighs about 50% more than a Toyota Camry, which means it'll take a greater energy output to move than the Camry. That said, the Camry's engine is only about 1/3 the efficiency of the Tesla's, which means that despite its lighter weight you'll still have to put more energy into it than the Tesla to get it to move the same distance.
The same applies here. Yes, adding an extra mechanism adds more weight, which means that the necessary energy output is greater. That said, your calf is inefficient at locking up during the downward part of your step, whereas a mechanical clutch is quite efficient at locking up, so by relying on simple machines to divert those forces to the clutch instead of your calf, you can reduce your dependency on an inefficient system (i.e. your calf), thus reducing the amount of input energy necessary, to the tune of 7%.
Or, hey, it's impossible. Because efficiency isn't a thing. How do you breathe in a frictionless vacuum, anyway? :P
According to the article in Nature at http://www.nature.com/news/exo... , it only improves normal walking speed on level ground.
Which is too bad. My sister in law's right side was mostly paralyzed by a stroke. She shuffles around, swinging her body weight on her good leg, and is quite the effort. I was hoping this could help her, but given her gait it's unlikely.
John