Subject:
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Re: How can we make TINAH peck ? (long)
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Newsgroups:
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lugnet.robotics
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Date:
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Thu, 29 Aug 2002 02:10:02 GMT
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Original-From:
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Steve Baker <sjbaker1@airmail#StopSpammers#.net>
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Roul Sebastian John wrote:
> (1) TINAH has to peck at so-called pecking disks, which are small round
> plates...
> So, what we rather look for is a mechanism which
> turns the circular movement of an RCX motor into a back and forth (but
> not up and down) movement in a stable way. Has anybody of you any
> experiences or any suggestions how such a mechanism should be built with
> LEGO ?
It rather depends on how fast it has to go - and how much power it has to
deliver (eg how heavy is TINAH's beak?).
One way is to use a worm gear (one of those black spiral-shaped things) and
a linear 'rack' gear (a 1x4 plate with gear teeth on one side). meshing the
rack with the worm gear makes the rack move one tooth forwards for every
revolution of the motor - which is slow - but capable of delivering a lot of
power.
Another way is to think of the piston of a steam engine sliding back and
forth with linear motion driving a connecting rod that turns a wheel...but
backwards...so the wheel drives the piston.
There are a bunch of other rotary-to-linear mechanisms here:
http://www.dtonline.org/apps/infopage/app.exe?1&6&1&22&1&0
> (2) It turned out that we will need more than one RCX to be able to use
> more than those three sensors, and possibly also more than three motors.
That's possible.
> In the robot model we have built until now, we combined two RCXs. But
> unfortunately, there seems to be surprisingly little information on
> using more than one RCX for building LEGO robots.
There isn't really a lot to say. If you use NQC or something like it,
you can send single byte messages between two RCX's via infra-red - so
just make them face each other and they can talk.
Ideally, you need to make them take it in turns to send IR messages
because they can't transmit and recieve at the same time without seeing
garbled versions of their own messages reflected back at themselves.
It's better to have one of them sit and passively listen - or if it
must return information, to do it only when requested to by the 'master'
RCX. I've made this work with four Lego computers at the same time.
http://www.sjbaker.org/steve/lego/master_slave/
(I used one RCX and a bunch of the cheaper 'Scout' computers - but it
would work with multiple RCX's too.)
In the many books on
> Mindstorms I have, I only found some information on this in the last
> chapter of the new Ferrari et al. book (about which I learned from this
> list -- thanks a lot !). But even there, the RCXs have to be built into
> two separate robots, separated by a wall, so this is also not applicable
> in our case. What we would really need is a way to write to and read
> from two RCXs which are controlling different parts of *one* robot.
There is complete NQC source code on my web page.
> Currently, our programming gurus are struggling with this and try to
> define their own protocol etc.. But is there really nobody out there,
> who already dealt with this problem and could help us, at least with
> part of a solution ?
Yes - there is...*ME*! :-)
> (3) In her environment, TINAH would have to move left and right. She
> should best also be able to move forward and backward, but *without*
> turning. Is there any mechanism implementable in LEGO which can move in
> such a way ?
Since you said you have the (excellent) Ferrari book - you'll see instructions
for building a 'Syncro Drive' on p146 onwards. That does exactly what you want.
These things look *really* cool when they are driving around. I had endless fun
with the Lego remote controller driving one in and out of the legs of chairs.
> (4) Our vision experts wonder if there is a stable Linux driver for the
> LEGO camera (which best should work with the Video for Linux standard)
> or if we have to use a different camera. Does anybody of you have
> experience with using the LEGO camera under Linux and could give us a
> recommendation ?
I use Lego (with NQC and occasionally LegOS) under Linux - but I don't think
the Camera works. It's supposedly just a standard commercial camera that
Lego have re-packaged - but for the moment, I don't recall which one it
really is...someone here will know.
There is *hope* that you might find a driver - but don't bet the farm on
it! You might need to find a non-Lego camera for that part.
> We (i.e. the members of the EROSAL workgroup) thank you in advance for
> any hints and tips on these issues,
No problem - just be sure to post photo's when it's working!
----------------------------- Steve Baker -------------------------------
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Message is in Reply To:
 | | How can we make TINAH peck ? (long)
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| Dear LEGO experts, we are currently running a research project using a LEGO robot and we have some questions for which we would very much appreciate any help ! Let me first sketch the background: I am a Ph.D. student in the first international (...) (22 years ago, 28-Aug-02, to lugnet.robotics)
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