Subject:
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Re: Not totally satisfied with the Lego Mindstorm concept: Mathematical variables and direct connection PC/mechanical device
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Newsgroups:
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lugnet.robotics
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Date:
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Wed, 24 Apr 2002 14:41:47 GMT
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Original-From:
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Steve Baker <{sjbaker1@airmail.}IHateSpam{net}>
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Reply-To:
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sjbaker1@^saynotospam^airmail.net
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Viewed:
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615 times
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Andrew Burton wrote:
>
> You need to look up pbForth (or is it pBrick?) and NQC. Those are two
> languages for the rcx that have variables -- specifically math, as I'm
> not sure if there are strings for the RCX. But I digress, those have
> variables. My guess, and I am taking a LEAP here, is that you're using
> the Mindstorms's software which does not have variables.
>
> Now, specifying a language you might prefer, and I say this having very
> little experience with any of the languages -- there's a reason I lurk
> -- pbForth allows you to terminal to the RCX and issue direct, real-time
> commands through the infrared port. I've thought about a similar
> project, using the full force of my computer to act as the brains.
That's OK so long as the RCX doesn't get out of IR contact with the PC - as
can *EASILY* happen. You need to have at least some autonomous code inside
the robot that will enable it to regain contact with the PC by (for example)
backtracking over it's last couple of manouvers in the event that it loses
the IR signal.
Rather than have a language that works in the way you describe, I'd suggest
writing a simple program (in NQC for example) that takes movement commands
from the PC and relays back sensor outputs - but which has enough on-board
intelligence to remember how to backtrack when it loses contact *AND* what
immediate action to take if (for example) a collision sensor reports a
'furniture impact event'. The round-trip time to the PC and back again
can be pretty slow - so you'll want something like:
if I collide with something
{
stop ;
tell the PC we collided ;
sit still until the PC tells me what to do ;
}
> You may also seriously want to look into PalmPilot programming in
> regards to the RCX. One idea that's danced through my head, but I'm ill
> prepared to work with yet, was attaching a PalmPilot to a LEGO creation.
> The infrared on the PalmPilot allows communication (as people have
> shown) and with a direct "connection" to the creation it could function
> as the brains since it has more memory.
Yes - that at least eliminates the "loss of IR signal" problem. However,
I think you still need to consider the long-ish latency between the RCX
detecting some onboard condition, sending it over IR, then the PDA detecting
the signal, acting on it, sending the command back to the RCX and then finally
having the RCX react to it.
That sort of round-trip can easily take a half second or more - which can
be a long time if you are rammed against the refrigerator with your motors
stalled (or your 'MegaDeath Killomatic Blastotron' machine is dismembering
your cat).
----------------------------- Steve Baker -------------------------------
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URLs : http://www.sjbaker.org
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