Alt-BEAM Archive
Message #03908
To: beam@sgiblab.sgi.com
From: Richard Piotter richfile@rconnect.com
Date: Fri, 28 May 1999 19:23:43 -0500
Subject: [alt-beam] Re: Efficiency and Good Old Stryder
I see efficiency as the best use of what you put into something.
Efficient motor:
Low current in with useful mechanical output.
Efficient Walking gait:
1: The ability to sustain a useful gait with low current consumtion
2: The ability to make the best use of mechanical output for a gait that
does not waste much mechanical energy (it doesn't slip around or move
back during part of a step while walking forward)
Efficient Circuit: A circuit that uses little power for it's given task.
Efficient motors and circuits, and gait efficiency definition 1 are
measurable, by measuring the current consumtion.
The second gait definition may not be so measurable.
Well, that's what I think any way.
"John A. deVries II" wrote:
>
> At 11:49 AM 5/25/99 , Dave Hrynkiw wrote:
> >I look at Stryder and see a working example of
> >something I thought wasn't possible - a 4 legged, fixed motor position
> >walker capable of very efficient walking gait (not lifting legs very high
> >saves power).
>
> I no longer have a clue what any of the readership of the BEAM emailing
> list means by the term "efficient" or "efficiency". I had always been led
> to believe that "efficiency" was a ratio of what you got out of something
> for how much you put into it. In other words, if one was talking about
> useful work efficiency, you'd want to look at W(useful)/W(total).
>
> I've read about the "efficiency" of motors and of circuits and of walking
> gaits and the like, but in so many different ways and so loosely and so
> without any measurement or evidence that I can hardly believe that those
> meanings have much to do with the most commonly accepted version. I mean,
> nobody seems to figure out how much energy is being put into a system and
> how much energy generates useful work (after all, work and energy use the
> same units: it is just that "useful" work is less than "total" work or
> else we'd be violating one of the laws of thermodynamics.) No one ever
> _measures_ anything, ever calculates the ratio, ever compares the ratios
> (i.e. efficiency) of one system with another. It seems to me that the word
> "efficient" is used as a synonym for "good" and the word is used for hype
> like "new" and "improved" in ads.
>
> I wish that people would measure the useful work produced by these robots
> and compare it to the amount of energy that was put in. In other words,
> determine the amount of energy that is required to move a robot of a given
> mass a given distance (or use Watt's method and have the robot lift a
> weight) and compare that to the total amount of electrical energy it
> consumed doing so. Then you'd have a meaningful "efficiency" you could
> compare to another robot's in a meaningful way.
>
> Until then, "efficiency" and "efficient" are meaningless buzzwords.
>
> Zoz
>
> p.s. anyone want to bet whether or not the Beamant 6.x is more efficient
> than Stryder???
>
> ---------------------------------------------------------------
> John A. deVries II
> zozzles@lanl.gov
--
Richard Piotter
richfile@rconnect.com
The Richfiles Robotics & TI web page:
http://richfiles.calc.org
For the BEAM Robotics list:
BEAM Robotics Tek FAQ
http://people.ne.mediaone.net/bushbo/beam/FAQ.html
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