Subject:
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Re: another comparison
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Newsgroups:
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lugnet.robotics
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Date:
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Sun, 21 Jan 2007 16:50:54 GMT
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Viewed:
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3199 times
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In lugnet.robotics, Chris Phillips wrote:
> In lugnet.robotics, Brian Davis wrote:
> > I'd love to make some other comparisions; actually, some of us have been trying
> > to figure out a good way to do this. Part of the problem is defineing specific
> > "goals" for a battery of tests.
> >
> > It's not a simple problem. As recent discussions have sometimes pointed out,
> > folks have very different viewpoints on what is or is not a good test, or what a
> > "good" comparision is... and if we want a speed comparison to be as useful as
> > possible to the community, it needs to be fairly generally agreed upon.
> >
> > So, ideas from the group?
>
> Perhaps a good benchmark would be to write a PID controller and measure the
> number of control loop iterations per second that can be achieved under each
> environment. This incorporates sensor input with motor output, and uses a
> moderate amount of computation in the middle. It is also a very useful
> "real-world" application in robotics. (Unfortunately, any sensor-input
> application is ultimately bounded by the maximum sampling rate of the sensors,
> although I think both RCX and NXT use a ~2ms sampling rate.)
>
> My gut tells me that the RCX (using BrickOS) would give the NXT (using anythng
> available so far) a good run for its money, though...
1. The DFT certainly may be considered as overkill for a toy robot kit. But I am
not sure that this forum considers the RCX or NXT only as toys. To say that NXT
or RCX are not made for this or that is like saying to the inventor of the
pencil that it is not thought for high arts, only for scribbling... and my best
puzzle is made of a pencil and a cord. OK, if we tell the pencil factory to
improve the quality, because we need sharp points in order to get a better
performence in bursting balloons, this would be absolutely crazy.
Now, what I want to say is that LEGO gave us the objects RCX and NXT, and we may
try out how to use them at their limits, how to extract the best performence,
how to create better robots than others. This is what FLL competitions and
comparable contests are for, aren't they? The history of the RCX told us, that
LEGO invented it on the base of MIT Papert's work. And Papert teaches us to
eagerly consider what he calls "bricolage", a kind of being creative with
things, using them unexpectedly. So, why not investigate the absolute limits of
the bricks.
2. Considering a ball, which is perhaps the most exciting object ever invented,
because you can make such diversity of things with it, you have to restrict
things, set up rules, if you want to compare human performence that use it in
soccer, basketball or baseball. FLL has trouble with fixing rules for their
contests: RCX-only, NXT-only, both allowed, software, firmware settings etc. And
those rules are essential for the fairness of the competitions. At least FLL
should know the possibilities what you can do with the devices.
3. I could have taken a simplier comparison, but the extreme performence ratio
appeared, because I wanted to do the DFT on NXT. (In fact, I was attracted by
the NXT display, in order to have small mobile scope for a special project I am
working on.) So, let's reduce the question to : "How fast can we do sensor-data
collection?" and "How fast can we replace a value in an array at a certain
index?" And I may argue that NXT, equipped with 2 microcontrollers should be
able to return better performence in those tasks compared to the RCX.
4. As to PID, a www.seattlerobotics.org/encoder/200108/using_a_pid.html Peeves
contest would be fine to find out, if NXT-Peeves can do better than RCX-Peeves.
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Message is in Reply To:
 | | Re: another comparison
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| (...) Perhaps a good benchmark would be to write a PID controller and measure the number of control loop iterations per second that can be achieved under each environment. This incorporates sensor input with motor output, and uses a moderate amount (...) (18 years ago, 21-Jan-07, to lugnet.robotics)
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