Subject:
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Re: Rack-and-pinion steering line tracker
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Newsgroups:
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lugnet.robotics
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Date:
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Sun, 9 Jan 2000 18:10:56 GMT
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Viewed:
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2495 times
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I'm working on my first original robot, having built the 3 in the
Constructopedia and modified them a bit. I'm currently on my 4th R&P design:
the first two just didn't work, and the 3rd had a turning circle larger than
my living room. It incorporates a light sensor by running a second set of
gears off the motor drive, and attaching a 2x12 plank to a large cog (40
tooth?). The light sensor is mounted on this, currently using an L-bend to
point it at the floor, but it will also point forwards when I have a go at
proximity detection.
Again, it's stunningly clunky. If anyone knows of or has a LEdit file of an
elegant R&P system I'd love to see it!
--
Mark R
www.markrendle.co.uk
Tilman Sporkert <lego-robotics@crynwr.com> wrote in message
news:NCBBKPAJLICLDDABDHAMAEEADGAA.tilman@activesw.com...
> I too spent quite some time trying to build a steering mechanism from • standard
> Mindstorms parts. After many rebuilds I still wasn't quite satisfied. The • final
> version actually worked pretty well, but was much too bulky (not as bulky • as
> Doug's version however :-) ), and the wheels were tilted inward too much • for my
> taste. So I decided to see what I could do with some more specialized Lego
> parts. I could have just bought the service pack with the various Lego • steering
> mechanism parts from S@H. But no, I decided to use it as an excuse to buy • all
> sorts of Technic sets. Along the way I learned that Lego can't make up • their
> mind about how to build a steering mechanism either. There are so many
> variations!
>
> About the return to center problem: My solution is to incorporate the • light
> sensor into the steering mechanism. Mount it at the end of a short arm • pointing
> forward, ahead of your wheels. This has two advantages:
> - You will get a much smoother steering vehicle, with gradual steering
> movements.
> - You don't have to worry about centering the steering mechanism.
>
> With the traditional approach, you will be sensing that you are off the • track.
> But you don't really know how far to turn the wheels to stay on the track. • So
> you make a best guess, turn too far, until you are back on center. Now you • have
> to figure out how to go straight again.
>
> With my approach, you keep the light sensor on the track all the time, and • the
> vehicle sort of follows it. As soon as the sensor moves off center, you • start
> steering to keep the sensor on the track. The steering system is now part • of a
> direct feedback loop, and will always point in the right direction.
>
> This of course doesn't make the steering system any easier. You now have • to turn
> three things - the two wheels, and the arm that holds the sensor.
>
> Tilman
>
>
> > I spent a _lot_ of time trying to get a non-sensored R&P steering system • to
> > work, using pulleys, rubber bands (both as drives and springs), and
> > you-name-it! I finally gave up, but did manage to build one with only • _one_
> > sensor that was very effective.
> >
> > See http://www.wordsmithdigital.com/mindstorms/ for a scan and my • described
> > history of running my head into the wall. Should get you started in the
> > right direction--or avoid getting you started in the wrong direction.
> >
> > Ironically, I've started playing with roboticizing the 8479 as well!
> >
> > --Doug Wilcox
>
>
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Message is in Reply To:
 | | RE: Rack-and-pinion steering line tracker
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| I too spent quite some time trying to build a steering mechanism from standard Mindstorms parts. After many rebuilds I still wasn't quite satisfied. The final version actually worked pretty well, but was much too bulky (not as bulky as Doug's (...) (27 years ago, 8-Jan-00, to lugnet.robotics)
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