Dont think thay will catch on but stil cool..

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gummidge
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Re: Dont think thay will catch on but stil cool..

Postby gummidge » Tue Jan 17, 2012 9:38 pm

Mick wrote:
gummidge wrote:I'm not sure I agree with that. If your skate only accelerated when you weren't pushing then wouldn't that mean that all of your acceleration came from pushing off from the skate rather than from pushing sideways?

Well, there are two ways of looking at the acceleration of the skater, either as the actual acceleration of the skater's centre of mass during a single stroke, or else as the average acceleration in the overall direction of travel. The actual acceleration will always be very close to 90 degrees to the fore/aft axis of the skate, so there can be no acceleration of the skate in the same direction as the momentary acceleration of the skaters centre of mass.

However it is possible to accelerate the skate in the average direction of travel by using a purely sideways stroke, but it's not necessary and it will vary depending on how far you let your foot fall behind you during a stroke. Because it's variable I don't think it's a useful measure of how much power assistance to supply.

If you did use just that acceleration to decide how much power assistance to provide then it might be possible to learn to control it, but you would no longer just be skating normally but more powerfully, you would need to learn a special technique. And I have a suspicion that it might be unstable. If you accidentally let a skate shoot out a bit too much the power assistance would try to accelerate it even more.

Yeah, what we really want is to somehow measure the force the stride is producing.

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Re: Dont think thay will catch on but stil cool..

Postby Stoo » Wed Jan 18, 2012 12:27 am

Looks like you'd need to discover a set of "assisted skating parameters" - probably with at least three multi-axis accelerometers attached to a datalogger - one on each skate and another on a fairly stable area of the body - probably the head or waist? Although adding in electronic gyro's might negate that part..

The third sensor and or gyro would provide the general direction of travel, which you could then use to subtract from the stroke data to discount the general momentum?

Repeat for a range of people and a range of skating styles, then you'd need to crunch a lot of data to discover the required pattern. Then once the incoming data matched the required patterns, provide rotation assist to the wheels, and cut it when it doesn't match, that way you should emulate a more powerful stroke?

I'm sure at least some of this already exists for other areas of sports science (calculating stroke/stride forces etc), so you might be able to ride of the coat-tails a little for some parts of the calculation/pattern matching.. Or something..

Or I'm talking a load of crap so feel free to ignore me (It's getting late and I'm getting sleepy), lol :D

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Re: Dont think thay will catch on but stil cool..

Postby Mick » Wed Jan 18, 2012 12:41 am

I agree, Stoo. Can't see any other way of doing it unless you go the powered exoskeleton route.

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Re: Dont think thay will catch on but stil cool..

Postby lurch » Wed Jan 18, 2012 12:57 am

gummidge wrote:Nah, I'd only like it if it works like we're discussing, like your skating on ABEC 10,000s (i.e. it just makes it feel like you have more strength and energy while skating completely naturally).

I don't think it could work that effortlessly - not 'completely naturally'.

Just consider a regular stride - assuming you're doing it right - you push laterally outward and a teeny bit forward. The angle of the frame to the direction of travel determines the 'gearing' of the motion. The force is from your centre of gravity more or less directly to your (say) right.

If I get what you're saying, the wheels on the skate should detect this and spontaneously drive forward in this scenario. But if I'm not mistaken, it's just going to feel like someone is shoving your foot out from under you. If you don't stiffen up your leg and lean into it your foot will shoot ahead leaving your centre of gravity behind ... and a second or two later, you, landing *on* your behind.

Except in *one* circumstance: Rough surfaces are harder to roll over. It feels like the skate is being pulled back by the surface. You have to stiffen and bend your knees to keep your skates underneath you and prevent yourself from toppling forwards. A motorized wheel that compensated for the resistance effect of a rough surface could neutralize things and make it feel as effortful as a smooth surface, so you don't notice the slow down.

On a smooth surface though, you're going to have to adjust your stride somehow. If nothing else you'll probably need to use a different frame angle (gearing) because you're going to be moving faster.

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Re: Dont think thay will catch on but stil cool..

Postby gummidge » Wed Jan 18, 2012 10:25 am

Yeah, if it worked as I image then you'd have to adjust your gait / gearing just as you would if you, say, found your muscles not working as well as they used to. But the adjustment should be the same as it would be if you did actually have the extra strength naturally.

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Re: Dont think thay will catch on but stil cool..

Postby Mick » Wed Jan 18, 2012 12:33 pm

gummidge wrote:Yeah, what we really want is to somehow measure the force the stride is producing.

The force of the stride is acting between the skater's centre of mass and the sideways resistance of the skate. The skater automatically adjusts the angle and position of the skates to translate that force into forward motion, braking or cornering using the natural sensors we have built into our bodies which monitor force, position and acceleration of the various parts of the system. That's not a problem with the exoskeleton because you're just amplifying an existing force and the skater can adjust for it in a natural manner as you pointed out. However the force produced by powered wheels acts perpendicular to the natural skating force, so to mimic the effect of an increased natural skating force you need a processor to reverse engineer those calculations we are automatically doing in our heads, to match the power assistance to a notional increase in leg power. To do that the processor must have the same information that our brains have about force, position and acceleration so we need to provide it with equivalent sensors.

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Re: Dont think thay will catch on but stil cool..

Postby ManicStar » Wed Jan 18, 2012 1:56 pm

Why bother doing it with sensors trying to work out the forces that are acting on the skates and instead use technology that reads brains waves? That way the additional force is applied where is is needed according to your thoughts and desires. Your brain knows when you're skating forwards, transitioning to backwards, braking, sliding, etc.

If you can drive a car completely with brainwaves, (http://news.discovery.com/autos/the-car ... drive.html) then skates shouldn't be a problem. It would take some mental conditioning and some 'learning;' on the part of the computer, but I don't see why it wouldn't be feasible.

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Re: Dont think thay will catch on but stil cool..

Postby Mick » Wed Jan 18, 2012 2:26 pm

You're absolutely right, Rob! Accelerometers are so 20th century. Direct mind control is the way forward! It would be a lot simpler too because all you'd need to do is think "forwards" or "backwards" (I think) as long as you can modulate it.

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Re: Dont think thay will catch on but stil cool..

Postby Dan B » Wed Jan 18, 2012 9:16 pm

lurch wrote:If I get what you're saying, the wheels on the skate should detect this and spontaneously drive forward in this scenario. But if I'm not mistaken, it's just going to feel like someone is shoving your foot out from under you. If you don't stiffen up your leg and lean into it your foot will shoot ahead leaving your centre of gravity behind ...

This was my objection, but your example of rough surfaces leads me to think it's not actually a problem. We don't fall over backwards when we put new bearings in our skates, nor forwards when we have old crappy ones. Imagine a power-assisted system where the driving force was exactly sufficient to balance the losses due to bearing friction: it would "feel like we're skating on abec 1000s" but I don't think it would make us fall over. Having imagined that system, imagine one with driving force equal to friction losses plus delta: how big would delta have to be before it occasioned arse-ground interface?

I agree with you that you'd be skating differently to compensate for the extra force. I don't think however that you'd be conscious of it - at least after the initial getting-used-to-it bit

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Re: Dont think thay will catch on but stil cool..

Postby Dan B » Wed Jan 18, 2012 9:18 pm

Mick wrote:You're absolutely right, Rob! Accelerometers are so 20th century. Direct mind control is the way forward! It would be a lot simpler too because all you'd need to do is think "forwards" or "backwards" (I think) as long as you can modulate it.

You'd have to learn Russian, though

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Re: Dont think thay will catch on but stil cool..

Postby ld50 » Fri Feb 10, 2012 2:06 am

I've seen both motorized skates (attachments/mods) and strap on skates for your shoes. This seems inferior to both. New/silly inventions are still rad though.

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Re: Dont think thay will catch on but stil cool..

Postby greggplatt » Tue Mar 20, 2012 7:54 am

Glad I came across this one.


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