Subject:
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Re: Very Newbie Question regarding remote control
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Newsgroups:
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lugnet.robotics
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Date:
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Tue, 23 Jan 2001 02:13:09 GMT
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Original-From:
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Steve Baker <SJBAKER1@AIRMAILspamcake.NET>
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Reply-To:
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SJBAKER1@AIRMAIL.NETihatespam
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Viewed:
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659 times
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Jake Baker wrote:
> What I want to do is establish a system where the agent AI is hosted by a PC
> (so I can write it in ruby or whatever without limitations); the robot
> communicates remotely (no wires) it's sensory information to the PC, and
> then the PC sends remote commands to control the robot.
Well, the RCX (the computer "brick" that comes with the $200 Mindstorms set)
has Infrared communications with the PC. The amount of RAM in the RCX is
rather limited for fancy AI stuff - but plenty for taking simple commands
*from* the AI running on the PC and having enough autonomy to be able to
cope with short term panics that the AI may not be able to help with.
So this is pretty much perfect for your needs.
If there is any problems at all, they relate to the IR link. Just like
a TV remote, it's somewhat directional - and if the robot is facing the
wrong way, it won't be able to talk to the PC. Depending on what your robot
has to do (and in what sort of environment it has to do it), you can probably
fix that by having the robot do a little 360 degree spin if it hasn't heard
from the PC for a while...but if it drives under a table, you are screwed.
I've also found the IR to be *VERY* slow. Don't count on transmitting
more than a handful of bytes per second.
There are some other attractive alternatives - one is to use a small (but
more powerful) computer on the robot itself. There has been some discussion
of that on this list - which has largely ignored the best (IMHO) machine for
that job.
I'm using an Agenda Palmtop (www.agendacomputing.com) which runs Linux and
can *easily* be programmed much like a desktop computer. It weighs just
a few ounces and is the ame size as the RCX but less than a half inch thick.
It can communicate with the RCX quite easily over IR - and since you can design
the robot such that the two IR sensors are facing each other, you won't have
communications problems.
> Therefore, my question is: Is this possible to set up? If so, is it
> relatively easy? I'm good with software, so its mainly the hw issue I have
> questions about.
Yes - I got my RCX about six months ago - and just like you, had no prior
experience with hardware, mechnical or electrical. This is *definitely*
an ideal robotics set for us software geeks.
Apart from the problem of the IR link, the mechanical issues aren't too hard
and the electrical issues are non-existant. Lego makes it remarkably easy
to build the most wonderful contraptions in just a couple of hours.
I'd advise you to start off by building the basic robot chassis whose build
instructions come with the Mindstorms set - it's not *great* but it's reliable
and a good starting point.
Once you have a better idea of what missions your robot has to fulfil, you can
get deeper into the mechanical side of things - but the basic robot is pretty
good for us software types.
I'd advise you to start working with NQC (Not Quite C) rather than the software
that Lego supply. NQC is freeware and sufficiently similar to C that you can
be writing programs within an hour of getting your Lego unpacked.
Later on, you'll probably want to progress to "LegOS" - which is another freeware
package that provides a much more professional Operating system than the stuff
that Lego provides for the RCX. With LegOS, you can use 'gcc' to compile *FULL*
C programs (where NQC is an interpreted "byte code" kind of idea) - so you get
much more speed and better access to the hardware.
Both LegOS and NQC work nicely with either Windoze or Linux.
In addition to the hardware that comes in the $200 set, you'll *CERTAINLY*
want to go out and buy a couple of rotation sensors - these don't come with
the set - but for serious robotics, they are *ESSENTIAL*. IIRC, they cost
about $15 each - but without them, you won't have a prayer of even getting
the robot to drive in a straight line! You may want to buy an additional
motor too. The set only comes with two - and for most mobile robots, you
need both of them just to drive you around - hence if your robot is going
to actually *do* something, you'll need a third motor. Since the RCX can
essentially only drive 3 motors and read 3 sensors, that's about all you'll
need!
One other thing I bought recently that I'm a *GREAT* fan of is the Lego
Remote controller. It's just like a TV remote - but it has controls to
drive the motors in the RCX (overriding the internal software) and to
send up to four pre-programmed commands to it (that your software can
decide what to do with). I've found this invaluable for debugging and
for testing out the robot *before* I go and write the software for it.
Just stupid things like knowing which way round I wired the motor - or
which way it has to be driven (through a half dozen gear wheels) to make
it go forwards.
It's also *very* useful to be able to turn the RCX *off* remotely so that
when your robot is grinding it's gears into dust - or hurtling at a wall
at high speed, you have an emergency cut-off switch!
--
Steve Baker HomeEmail: <sjbaker1@airmail.net>
WorkEmail: <sjbaker@link.com>
HomePage : http://web2.airmail.net/sjbaker1
Projects : http://plib.sourceforge.net
http://tuxaqfh.sourceforge.net
http://tuxkart.sourceforge.net
http://prettypoly.sourceforge.net
http://freeglut.sourceforge.net
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Message has 1 Reply:
Message is in Reply To:
 | | Very Newbie Question regarding remote control
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| Greetings all, I am persuing a grad level course in AI agents, and the course requires that I to do a project. One idea I have is to create a robot and have it do something AI-ish. Since I'm not very adept with hardware, using a Mindstorms robot for (...) (24 years ago, 22-Jan-01, to lugnet.robotics)
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